BB compatibilty advice please

Why are you looking at STA?

It's one of the least useful dimensions on a bike as there is so much adjustment on the saddle rails. Also, trying to compare a road/cx fit with an MTB fit, especially on an MTB that's not hardcore XC, is a bit of an exercise in futility.

You actually need to check the frame to see what standard bottom bracket it is (other than the old road bike, that'll almost certainly be BSA threaded). HTII is a crank standard and could have one of several types of bottom bracket. BB30 is likely press fit, but the ragley is listed with a BSA threaded shell.

As Mert has alluded to, the crank type doesn't determine the type of bottom bracket shell.

The Ragley Marley is listed as having a BSA (threaded) bottom bracket shell, so if your cranks are BB30 (is that what you meant?), that means it will have a threaded, external cup bb something like this

https://www.hopetech.com/products/drivetrain/bottom-bracket/bottom-bracket-30mm-threaded/

Your old road bike should be BSA if it's got spare tapered cranks. I guess there's a chance it could have Italian (reverse) threads. I could be wrong about that

I'm not sure what bb shell your RX has. Google seems to say it varies with model year. Can you see external splines on the RX's bb? Or does it look like the bearing cups have been pressed in?

So, it sounds like you may be able to swap the cranks and bb from your road to mtb bike (prob not a good idea, I'm guessing the road cranks won't be very tough). But your CX bb and cranks may or may not be compatible with the other two bikes, potentially depends on the model year of the RX

Ah, I see.... I think.
OK, @Mert , a sort of skim over the top of the STA thing.
Basically I have never worked out what to do.
I have never seemed to fit any bikes I have tried. I did some calcs a few years ago and realised most geometries are set to fit the same shape person, right?
Basically I always thought everyone was harder than me, because i am in quite a lot of discomfort after just a couple of miles. Also, I didn't realise everyone else's feet didn't go numb. when I stood up I could feel the blood flowing back in lol.
This eventually got solved with flat saddles.
The reason I have the different STAs is because I don't know what I am doing. I can't stop myself sliding forward. All my cycling is done basically holding myself back on the saddle. I wedge myself against the bars to hold myself back and tilt my feet to push myself back.
So, reading stuff on getting balanced first on the saddle, i tried pushing myself back. saddle etc. Tried moving feet further forward. Set back seat post. Then a 67 degree frame (it isn't really that cos it has a bit of a bend in it).
So, eventually, I am almost a bit more able to hold myself back. blocks of wood at front of pedals, 67 degree (ish) frame inch setback seat post and saddle as far back as it can go. So, that makes no sense, but that is that theory tested. That is how much it took.

Anyway, becuase I have shorter arms, I thought a shorter top tube might help me reach the bars (drops have always been a stretch.... well so have hoods and I just push back on them anyway.) So, a short arm thing needs closer bars, a cx bike has a shorter top tube. Possibly, as well, I might have looked to raise them and use flat bars. Added to it, you see, I am not looking to race or anything, just a casual cyclist. I have a longer body, so, short arms makes the bars further away. Longer body lifts the shoulders up, making the bars further away.

MTB is just my sort of medium bike. I am pretty sure the 67 degree frame is wrong, (too long a top tube for sure)but it is what i have and better than any other frame i have used. Although, I think the MTB is slightly better.

So, to bring the reach of the 'road' bike, I have very adjustable bars and bring the bars higher than the saddle so I can reach them and they are basically level with the headset i think. But still all very wrong.

So.
having tested that theory, and found it wanting, because I am so far back, it is nuts. (Oh, I Ialso have quite a boney bum (sit bones) I think).
Need to try something else, hence the shorter TT and steeper STA to test vs the Marley.
Then I realised about crank length.
I am about 5'8''
So, recently, I have been grabbing people and comparing my body ratios and found a bunch of consistent results.
Compared to someone who is about an inch taller than me, when I sit down I am roughly an inch or so taller than him (all just done looking at each other) arms are something like two inches shorter. Knee height was about an inch lower, Femur length approx inch and a half shorter. Arm length maybe two inches shorter.
So, found my next theory to test.
Crank length.

Having read a bunch of stuff, my 175mm is very likely to be too long.
so, the new theory revolves around much shorter crank lengths.
Now that i realised this is a thing, I looked at info. Watched a racer who is taller than me swap in for 165mm and he didn't say anything about shorter legs, so probably longer than mine overall.
Watched and read a bunch of stuff. Everything that is there points to 155mm cranks..........
But then will want to try that out and work out the long body Trex arms thing so it would be handy to try the different crank lengths on different bike set ups.
My brain argues that i will still be toppling forward. However, that guy also said that he was top heavy because he did weights, wheras my top heavy is torso length, but similar results, and he found he was toppling forward less. So well worth a try.
Apart from that, i kind of measured my hip/knee angle and i reckon it is kinda 64 degrees, and it is suggested that 69 minimum, which makes sense cos it always feels my knees come tooo high and when I look at anyone eles, their knee doesn't seem to come as high.
So, shorter crank length means that a) knee comes less high anyway b) have to raise saddle which means knee raises less as well c) perhaps the pulling forward is because my femur length is shorter than crank length....
Also, discomfort might be down to knee coming too high. I wonder if it makes my already pointy sit bones more pointy because my knee is coming too high.

Right, I think that is the lot. (i am sure I have forgotten some things)

Crikey!

Paralysis by analysis comes to mind. You seem to have taken more measurements than I've done in my whole life - and I'm a carpenter.

Crank length - I've had 180s on my singlespeed, 172.5, 175, 160, and I've never noticed a big difference.

My road bike stem is too long (and low) for me but as it's got a fancy carbon Most (Pinarello) integrated bar & stem (and lovely Pinarello bar tape) I'm reluctant to change it and put up with the neck ache if I've not been riding it for a while.

I've got short legs for my height, like you, My saddles point down at the front just a tad and I don't get numb hands. A mate did tell me that his physio (Martin Earley, TdF stage winner) advised him to tip it down a bit to alleviate his back pain. Apparently it engages the back muscles and puts less pressure on the hands. I copied him and it felt OK.

Throw your tape measure away, find somebody who knows about riding bikes who can take a look at you on the bike and make recommendations. Honest, by the sound of it you've got a weird set-up.

blocks of wood at front of pedals

WTAF?

OK, Bottom bracket and cranks.
thanks also @legometeorology
So, that is what i have missed and got confused about.
Is this right?
The crankset fit type is independent of the frame bb?
In other words, you can have press fit and screw in bb30, the same with hollowtech?
OK, no wonder I was confused. I also saw about adapters and stuff.
I suppose coming from a world that was all square taper, it was simpler 🙂

I am not too bothered about toughness, I am just wanting to work out fit.
Yes, my Marley has something similar to that. So it sounds like i can pop a sq taper on that.
I am happy to get a different bb for the mtb if that can work to try the same crank (I use my road bike to commute every day)
OK, so I can get a bb that screws in to the mtb frame that does sq taper right? That is cool. Means I can test a crankset on two bikes.

Right, so, Rx.
So, hollowlink II can be presss fit or external bb?
So, i thought i read that hollowtech II was press fit, but looking at it after your explanation, possibly not.
https://imgur.com/a/49ZDDOk
So, my RX also has an internal thread?
I got it used, but i think it was 2015.

It is an rx comp. I am not positive of the year because the pic says that the forks are C2 which mine are, but the description says C3.
Thanks again for the input.

@bigjohn
thing is, i have tried forty years of trying different things and have realised that all of them cause pain.
I have tried everything you you can possibly suggest before without taking measurements and having got the best I can manage, I cycle two miles each way every day for six years and am still bloody keen to get off that bike. But this is the best I have managed.
So, now, I have realised what everyone says only is relevant to their own ratio/weight/scenario and I do NOT fit into that 90% normal curve. So, now I need to think away from what everyone says because it doesn't work.

I am very happy to try anything that you suggest because i love cycling but have done so little because of the discomfort.

I have had a number of standard bikes oveer the decades. Like I say, I didn't realise people weren't in pain all the time.

@simondbarnes
desperate to test any theory to reduce pain.
I don't cope with spd, I think my knees need to move more than they allow.
So I use toe clips, but without straps.
So, working on the balance idea, I wanted to move my feet forward on the pedals.
The theory being, that you should be able to play the piano on your bars, right?
Well, my position is literally palms against the back of the bars to hold myself back.
So, if you stand with your feet together, anmd someone pushes you from behind, you fall over, right?
However, the further forward you put one foot, the more stable you are, yes?
So I wanted to find where my point of balance was wher I could lift hands off the bars without pulling forwards on the saddle.
A 67 degree sta didn't do it.
Add in a set back seatpost not doing it.
Add in the saddle as far back as poss not doing it.
I thought I would test movint my feet further forward.
Only way I could think was to add hzlf inch of wood between the pedal and the toe clip.

If you think it was stupid, I am very keen to hear your suggestions because I am very keen to lose the pain.

If you think it was stupid, I am very keen to hear your suggestions because I am very keen to lose the pain.

No, I just couldn't picture what you'd done!

Can you post side on pictures of you sat on the bike(S)?

find somebody who knows about riding bikes who can take a look at you on the bike and make recommendations

And do this

As we can see, I get many comments about the obvious stuff. My thinking is that they are within the 90% normal curve and something about my biology doesn't fit criteria.
As a number of people I have spoken to, they fit any bike....... Which means I fit NO bike it seems.
I am very open to suggestions. I am happy to try anything.
I am happy to admit I am stupid. Anything.
I feel like I have enough frames to try things now with the three I have. 67-75 degrees STA.
One thing I haven't tried yet is crank length and some of that makes sense, so I am now going to try that.

@simondbarnes
I have spoken to various cyclists and they all eventually shrug their shoulders.
I went for a bike fit. I said I didn't think my frame fitted, but he said he could sort it.
I wanted to find someone with a jig where everything was adjustable, but couldn't find one in my area.
I think there was one, but they had only just got it, so the yoofs would have no experience, perhaps I could look at that again.
Nobody has ever mentioned crank length.
Hence, that is my next theory.
I can post pics, but at what settings? Pick a bike, pick a set up.
Interestingly, I just set myself up to see what my hip/knee/ankle angle was so took a pic.
surprisingly difficult to acheive. So, a bit vague. but it seems like my knee is high and it agrees with a bunch of stuff that I need a 155 crank length..... worth a try.
Hence my confusion with bottom brackets having only known square taper.

I am very open to suggestions. I am happy to try anything.

It sounds like you would benefit from a bike fit. A good one will have different component sizes (cranks, stems, bars) and will be able to adjust things according to your needs and feedback. I'm sure if you post up your location someone will be able to recommend someone.

Edit: ah, missed your post above while typing. Would still be worth seeking out someone with a fully adjustable setup, even if you have to travel for it. Otherwise you are just randomly throwing stuff at the wall to see what sticks - changing one item may require adjustments to one or more other components.

I am near Truro Cornwall.
I don't have a lot of money.
Last time I spent money on a bike fit, I reckoned I needed a jig that everything adjusted.
Unfortunately, I knew my frame was wrong and he didn't have a jig, so he did the best he could with what I had.
If it is going to work, I will sell something to pay for it.

I can manage, I cycle two miles each way every day for six years and am still bloody keen to get off that bike. But this is the best I have managed.

Realise you are aware of this but with this statement something sounds seriously very wrong.  I could cycle 2 miles on a BMX without sitting down and not feel it was painful.  2 miles is only 10 minutes even going slowly.

Do you only get pain when cycling or are there other issues here?

Take a look at the bike fit videos here. I can't remember which but I'm sure I recall one discussing causes of sliding off the front of the saddle.

So I wanted to find where my point of balance was wher I could lift hands off the bars without pulling forwards on the saddle.
A 67 degree sta didn’t do it.
Add in a set back seatpost not doing it.
Add in the saddle as far back as poss not doing it.

While you are moving yourself further and further back, presumably you are not adjusting the bar position at the same time (e.g. shorter stem)? This will make you more and more stretched out and hence harder to find the balance point.

1 degree of seat-tube angle is approximately 5mm of saddle movement (the exact amount depends on the length of seatpost, for obvious reasons). its far far easier to move your saddle for and aft to mess about with angles than change frames over.

if you want to do that in isolation of effective reach, get an adjustable stem for now (like this https://www.tredz.co.uk/.System-EX-Adjustable-Stem_24665.htm) and spacer it above/below the stem to allow for a consistent bar height as you move the stem towards/away from the saddle.

toe clips are terrible, and may be leading to odd pedalling behavior. Your knees are probably fine on spds, you can get more floaty ones if you want (eggbeaters) or even all the way to speedplay pedals, or if you don't want to do that, just get a set of good flat pedals.

I don't subscribe to the "should be able to play piano on your bars", but if you want to go with that, a higher front end will probably help

what pain are you actually in?

<Realise you are aware of this but with this statement something sounds seriously very wrong. I could cycle 2 miles on a BMX without sitting down and not feel it was painful. 2 miles is only 10 minutes even going slowly.

Do you only get pain when cycling or are there other issues here?>
Nope, only when cycling. I do get a bit of a numb bum when sat in the cinema quite quickly. I sort of blame that on short legs and boney bum.
My plan is to kind of stop the sliding forward as that definitely doesn't help, then work from there.
I am not in pain if I stand up on the pedals.

</While you are moving yourself further and further back, presumably you are not adjusting the bar position at the same time (e.g. shorter stem)? This will make you more and more stretched out and hence harder to find the balance point.>
well, I am sort of ignoring bar position.
I am looking to find the balance point, in that if I lift hands away from the bars, I don't slide forward.
Having tested the theory of moving myself so far back and finding it eventually does solve the problem, but it is so far back, I started looking for a different solution.
I got a very adjustable set of bars to try and test that side of things out as well.

<

1 degree of seat-tube angle is approximately 5mm of saddle movement (the exact amount depends on the length of seatpost, for obvious reasons). its far far easier to move your saddle for and aft to mess about with angles than change frames over.

if you want to do that in isolation of effective reach, get an adjustable stem for now (like this https://www.tredz.co.uk/.System-EX-Adjustable-Stem_24665.htm) and spacer it above/below the stem to allow for a consistent bar height as you move the stem towards/away from the saddle.

toe clips are terrible, and may be leading to odd pedalling behavior. Your knees are probably fine on spd
, you can get more floaty ones if you want (eggbeaters) or even all the way to speedplay pedals, or if you don’t want to do that, just get a set of good flat pedals.

I don’t subscribe to the “should be able to play piano on your bars”, but if you want to go with that, a higher front end will probably help

what pain are you actually in?
>
Yes, I agree with what you have said.
So, I use toe clips so i can't slip off the front of the pedals ever.
I don't use toe straps, just the toe clips. As in the plastic bits at the front. It allows my feet to move about.
Why do you say they are terrible? Or do you mean if they are strapped in?
I did try spd, but my knees hated them. Also, you can't walk about when you get to the destination.
Yes, I agree about moving saddle, but it was nowherer near enough movement to be ale to test the balance theory for my body type.
As I say, it only worked with a 67 degree frame, a setback seat post and saddle all the way back with bits of wood allowing my feet to sit further forward on the pedals. It is impossible on a 73 degree frame.

</well, I am sort of ignoring bar position.
I am looking to find the balance point, in that if I lift hands away from the bars, I don’t slide forward.
Having tested the theory of moving myself so far back and finding it eventually does solve the problem, but it is so far back, I started looking for a different solution.
I got a very adjustable set of bars to try and test that side of things out as well.>

Oh, I have forgotten how to quote properly.

Yes, I agree, the reach thing is also a problem, but all bars do is give me something to hold myself back on the saddle. Whatever bike I have been on, all i do is fall forwards if I don't wedge myself against the bars I have realised. Hence the hand pain. Thanks for the link, but that would have such a tiny affect that it would be pointless. I will work on bar scenario when I can get sort of saddle position a bit better. I am pretty sure I shouldn't be sliding forwards this much.

You are right about raising the bars, I have done that as well and brought them a lot further back.
I picked up a set of these to allow me to experiment in all directions.

Oh, yes, and other things in hindsight. (I haven’t really had the time to think about it properly before.)

So, I haven’t cycled any where near as much as I would have liked in life because of the pain it cuases in short order. So I am now measuring things to try and work out if there is a solution or if I just give up on cycling at last.
The main one being sit bones, but also back pain, sore hands (just from holding myself back I eventually realised.) and knee pain. Last year my knee popped cycling up the hill out of town.
When I was more racing snake physique and ran a half marathon in decent time, under NHS guidelines, I still counted as obese, so I think I am denser than average. (yes, probably mentally as well)
Also, I realised this year some feet things that might be affecting bike fit. So, I have wider feet and wear bigger shoes to counter act the pain from that. So, work provide cap boots, but not wider size, so I wear a size too big.
Then I have realized that my toe clips have different depths which can affect things. Then I realised my boots don’t fit properly in the clips and so that pushes my feet back a bit…. Or something. Now I have realised that my clips on road bike are different depth to mtb.
Also, because cycling shoes are narrower generally it seems and I have a slightly higher instep, I need a bit more volume in the shoe, I just picked up some shoes that gave room and they are a size and a half too big. So that will affect fit as well.
So, I started this attempt to get things right with the shoes.
I have got some that (sort of) fit.
So, I don’t think I am far out in any of the parameters, but I think that perhaps they are all adding up to creating quite a lot of discomfort even after a couple of miles. I just avoid cycling because of it now. I got fed up with the pain.

I would also echo another reply questioning if moving the saddle back so far is the right thing to do.  It rotates your hips, increases weight on the hands (pain), effectively increases saddle height so that needs to be lowered.

You've mentioned numb feet and saddle pain...anything else?

I would consider crank length to be fine tuning a sorted bike setup, I think you should get to a point that one of your bikes is fitted to a point you are confident it's correct and the best you can achieve before the relatively expensive option of changing cranks (especially if you've no idea what length to start with).

You may be short of cash but I'd suggest another bike fit before throwing money at parts (cranks) with educated guesses.  Hopefully you can get recommendations seeing as the last one was 'make do' rather than a proper session on an adjustable bike.

PS How was the bike after the fit?

It might be useful to have some basics.

What dimensions are you (short torso? long legs? other-way around? long arms? etc etc)

What size are your bikes?

Whats the measurement between the centre of the crank to the saddle rail? Is it the same on all your bikes?

It would be useful to have a photo of you just sat on a bike

at 172/3cm tall, 175mm cranks are probably too long, but in isolation, might not solve much. a few years back everyone was on 175mm cranks and folks just got on with it. it sounds like there are lots of other issues going on.

I agree your riding position sounds very strange and pain after 2 miles is a very extreme situation. Something is deeply wrong.

I haven't read your responses in detail, sorry, but it sounds like trying shorter cranks is worth doing. It may even be worth setting your more extremely set back current seating position to something more conventional, then trying very short cranks, like 150mm or something. If the cranks you currently have only range from 170-175mm, it's probably not worth shifting them around between bikes (if that was your plan)

SJS do some for not too much cash
https://www.sjscycles.co.uk/cranks/150-thorn-10464-pcd-triple-crankset-mk2-black/

I also think a pic of your bike set ups, perhaps with you on them, would be good

if you want loads of saddle position adjustability, you can try one of these

https://www.sjscycles.co.uk/saddles/vk-saddle-adjuster/

which gives your saddle another ~5cm of front/rear movement

when you say "slide off" - what do you mean - is your bum sliding forwrads in your saddle? what angle is your saddle at? Flat is a good starting point, but there's nothing wrong with slightly forwards or even slightly back if it feels ok.

on the toe clips thing - in my experience they tend to encourage pushing the toes down/fowards into the pedals, rather than having a natural foot position. Feet don't move on a good set of flat pedals (although probably don't wear steel toecap boots on them - something with a flatish, grippy sole is best). Plastic flat pedals are fine, if they're the type with proper pins. DMR V6 are cheap if you're on an absolute budget https://www.tredz.co.uk/.DMR-V6-Plastic-Pedals_77540.htm

above all that I'd look at figuring out a way to raise your bars a bunch, just to try it out. for £10 you can get an adjustable stem that'd allow you to try different positions

adjustable stem

I wouldn't maybe trust that on serious offroad but for bumbling about the lanes and getting your hand position right, it should be fine

Oh, I have forgotten how to quote properly.

Thanks everyone who is chipping in.
To summarise what my current thinking is.
I was going to pick up a cheap chainset. (I have one on the way for £13)
The way I tend to try stuff out is to buy cheap (normally in the winter) and having tested it, sell again in spring so that I don't lose much money if any.
I was thinking that sq taper chainsets are likely to be picked up the cheapest.
I was thinking it would be good to try it on other frames. Especially as I am fairly sure my current one is wrong.
So, I thought I would start with the mtb. Use that as my bike to try and get the set up right. Start from scratch again.
I am thinking to pick up a cheap BB used off ebay just as a tester if I can work out which one to get.

Your money of course, but I don't think changing the crank set length is going to make that much difference. In all honestly if you're already putting blocks of wood on the pedals then something else is going on to make you end up un-comfy.

Like others have said, pictures of the bikes, (or decriptions of sizes) with you onboard would give the folks on here a chance at helping you out - lots of folks on here know exactly what to change, and you'd get some really useful advice.

I would also echo another reply questioning if moving the saddle back so far is the right thing to do. It rotates your hips, increases weight on the hands (pain), effectively increases saddle height so that needs to be lowered.

Well, I tried moving it forward and up and down and the best results were with moving back.
It reduced the weight on my hands the most.
One of the things is the terminology.
So, I don't think it is what people think of as weight on your hands.
I am just holding my whole body weight back on the saddle. I am jamming myself in.

You’ve mentioned numb feet and saddle pain…anything else?

Well, the numb feet is fixed with the flat saddle which is nice. We will progress on that one when I can get a bit further eh ? 🙂
The hands are unhappy, but better the further back I go.
The main thing is sit bone discomfort.
I also just pull forward all of the time which is why the hands feel unhappy.
I just topple forward.

I would consider crank length to be fine tuning a sorted bike setup, I think you should get to a point that one of your bikes is fitted to a point you are confident it’s correct and the best you can achieve before the relatively expensive option of changing cranks (especially if you’ve no idea what length to start with).

OK. I have tried moving everything about on various bikes and have never got it correct.
So I don't know what else to do.
What i tend to do is get used parts and sell again making little if any loss. It is like free rental.
I am thinking this is a cheap option. £13 on a set of cranks and £5-10 on a BB for the Marley.
So, the theory here, imagine if my pedals are 20mm too far forward? Is that not going to pull me forward?
Then, if my knees are coming up 40mm too high each stroke as well, isn't that going to make my bones a bit more pointy and more moving about all the time? That is surely going to create more discomfort no?

You may be short of cash but I’d suggest another bike fit before throwing money at parts (cranks) with educated guesses. Hopefully you can get recommendations seeing as the last one was ‘make do’ rather than a proper session on an adjustable bike.

PS How was the bike after the fit?

I haven't written it off, but last time, I couldn't find anyone with a jig.
Thought this would do the job.

One thing that won't cost you a penny is increasing your core strength which will take weight off your hands.

It might be useful to have some basics.
What dimensions are you (short torso? long legs? other-way around? long arms? etc etc)
What size are your bikes?
Whats the measurement between the centre of the crank to the saddle rail? Is it the same on all your bikes?
It would be useful to have a photo of you just sat on a bike
at 172/3cm tall, 175mm cranks are probably too long, but in isolation, might not solve much. a few years back everyone was on 175mm cranks and folks just got on with it. it sounds like there are lots of other issues going on.

I agree, I just got on with it and was always in pain 🙂
I did a bit of a summary above where I have compared myself to other guys and got fairly consistent results.
I will be kind of starting again. So, the other bikes are not really relevant.
My MTB is a little better (5mm shorter cranks) so I was going to work on that one primarily.
I think the other two are too far out so I think the MTB will be easiest to learn from.

I agree your riding position sounds very strange and pain after 2 miles is a very extreme situation. Something is deeply wrong.

I haven’t read your responses in detail, sorry, but it sounds like trying shorter cranks is worth doing. It may even be worth setting your more extremely set back current seating position to something more conventional, then trying very short cranks, like 150mm or something. If the cranks you currently have only range from 170-175mm, it’s probably not worth shifting them around between bikes (if that was your plan)

SJS do some for not too much cash
https://www.sjscycles.co.uk/cranks/150-thorn-10464-pcd-triple-crankset-mk2-black//blockquote >
Yes, I am expecting to start afresh with my mtb, I have some 155mm on the way. Set me back £13.
I just need to work out the BB for it on the Marley. They look like they are £5-10 used.
150-155mm is what comes up with the very few measurements, calculators there are about crank length. Watching stuff on people who have tried shorter cranks have done 165mm and they have longer limbs than me.
Once I have just given that a go, I will see where I am at and work with that.
I tried looking for a database of what is 'normal' but couldn't find anything. Hence getting blokes in the yard to measure up against lol.
I did a brief summary of my oddities further up.

 

Sure, but what sizes are we talking about. All we've got so far is that you're 5'8" and you have a long torso. You're asking folks to help diagnose your issue, and there's not a lot to go on.

can you ride no-handed? you shouldn't be pushing back on your saddle from your bars. your saddle probably wants to be flat(ish) and you just sit on it, lean forwards if you want to reach your bars.

if your sit bones are uncomfy, maybe a different saddle would help. 5mm here and there on cranks will make no difference

If you want loads of saddle position adjustability, you can try one of these
https://www.sjscycles.co.uk/saddles/vk-saddle-adjuster/
which gives your saddle another ~5cm of front/rear movement
when you say “slide off” – what do you mean – is your bum sliding forwrads in your saddle? what angle is your saddle at? Flat is a good starting point, but there’s nothing wrong with slightly forwards or even slightly back if it feels ok.

on the toe clips thing – in my experience they tend to encourage pushing the toes down/fowards into the pedals, rather than having a natural foot position. Feet don’t move on a good set of flat pedals (although probably don’t wear steel toecap boots on them – something with a flatish, grippy sole is best). Plastic flat pedals are fine, if they’re the type with proper pins. DMR V6 are cheap if you’re on an absolute budget https://www.tredz.co.uk/.DMR-V6-Plastic-Pedals_77540.htm

above all that I’d look at figuring out a way to raise your bars a bunch, just to try it out. for £10 you can get an adjustable stem that’d allow you to try different positions

adjustable stem

I wouldn’t maybe trust that on serious offroad but for bumbling about the lanes and getting your hand position right, it should be fine

🙂
Yes, thanks, I have one of those as well.
Saddle is flat and I just constantly pull forward.
Wherever I put the saddle at. So I push against my bars to keep me sliding forward all of the time.
If I put the saddle forwards, I just feel like I am toppling further forwards even more.
I can not lift my hands off the bars as i slip right forward.

I have these cranks on the way. What I will do is start afresh with my MTB as at the moment, it is all wrong, but varies a bit from bike to bike. MTB feels a little better. It has 5mm shorter cranks as well.
I have very adjustable bars just so that I am not constantly buying bits.
https://imgur.com/a/4Ua5Lw1
I was confident that would sort that out. It helped a lot.

Like I say, the cranks is the theory I have not tested yet.
I just want to give that a go and see what it feels like.
I think I would do it even if I knew it wouldn't help. Just out of curiosity.

Then I will see how I can set up my MTB from scratch and go from there.
I have got some consistency then. I have shoes that pretty much fit now. Step one.
Pick which bike to work with. Step two.
Work my way through things methodically.

Edit: I forgot about the pedals bit. So, I generally use 'normal' pedals and then have the plastic part of the toe clip at the front. I don't strap in. My feet are then free to move about which my knees seem to like and if I hit a pothole in the dark in the rain, I am unlikely to lose my footing.
Similar attitude when it comes to offroad.

Sure, but what sizes are we talking about. All we’ve got so far is that you’re 5’8″ and you have a long torso. You’re asking folks to help diagnose your issue, and there’s not a lot to go on.

Well, actually, I am asking for help to understand about bottom brackets which was confusing me.
I did a bit of a list further up from comparing with other guys just as a quick overview which was fairly consistent results when comparing body and limbs etc. I have also put in my symptoms that i have had. I am not sure how else to do it.

I wasn't expecting to get this much help on fit scenario.

What i am saying is that i will forget the other bikes and just work on the MTB.
I am pretty sure what i am using is wrong, so I don't want to start with that one. I wasn't expecting to get started on it just yet. So a lot of my answers will not be helpful as they are a bit all over the place.
As I say, I am thinking to just have a feel of the shorter cranks, then start afresh with the MTB, at which time help will be gladly sought.
Until I have tried the new cranks, I don't really know where I am. I will need to go out for some rides again to be able to report back on things.So that I can do things methodically.
I have just got some shoes that are a better fit for example.

You've not got your saddle way too high and tilted nose down have you?

Have seen exactly this before.

"I'm always uncomfortable, my balls hurt, my arse hurts, my hips hurt"

*noses saddle down, gets a bit better, noses down more, gets even better*

"My hands hurt and i'm always sliding forwards on the saddle."

*saddle is nose down 15degrees and 10cm too high.*

Sorry if I have missed any responses.

Ummm, so, having moved on a bit, it seems I can try a square taper crankset on my Ragley Marley.
Which is handy.
I am thinking I will grab a cheap one off ebay, just to try things out a bit.
I have cut and pasted and saved info from when I got the bike.
However, hunting for it now, I can't seem to find the details on line. I was hoping to double check things.

What i have is 'Bottom Bracket: 73mm, threaded GXP bottom bracket'
The 73mm part seems to match the physical dimensions on the bike. As in 73mm is the width of the frame.
Ah HAH, so the other number is axle length, right? How do I choose that length please?
Also, how do I know if it is ISO or JIS sq taper please?
Is there anything else to know?
Thanks

You’ve not got your saddle way too high and tilted nose down have you?
Have seen exactly this before.
“I’m always uncomfortable, my balls hurt, my arse hurts, my hips hurt”
*noses saddle down, gets a bit better, noses down more, gets even better*
“My hands hurt and i’m always sliding forwards on the saddle.”
*saddle is nose down 15degrees and 10cm too high.*

🙂
No, disappointingly not. Good question though.
It is flat.
I appreciate the interest, I really do.
Let me get my MTB out and have a play with fitting shoes and I will see where I am at from there. I will ignore the road bike for now as that just complicates things. The non fitting thing was only a sort of passing comment originally while i tried to understand the bottom bracket scenario.

I am quite excited to get all this help. It gives me hope that i can enjoy cycling properly.

can you ride no-handed? you shouldn’t be pushing back on your saddle from your bars. your saddle probably wants to be flat(ish) and you just sit on it, lean forwards if you want to reach your bars.

if your sit bones are uncomfy, maybe a different saddle would help. 5mm here and there on cranks will make no difference

Nope, can't ride no handed. I just slide forward off the saddle, I can't keep balanced.
I just pull forward.
My saddle is flat. I agree about what you say, I have tried that.
Let me get my MTB out and use that as a test bed properly, now I know I can get a lot of help on here.
I have just got some fitting shoes rather than too big. I will then report in with more methodology.
I tried a bunch of saddles a few years ago. I ended up with this one which is pretty flat as it stopped my feet going numb which is nice.

How do I choose that length please?

Chain line dictates the axle length on square taper BB. Your best bet is to email Ragley and ask them, I think the bike was designed with out-board BB design in mind, so it might be a bit of guesswork depending on how many front chainrings you're running and numbers of cogs out back.

Honestly, if the situation is as bad as you've described, and you really think you've tried everything, you may just need to get a recumbent bike...

You remind me of me years back when I was trying to salvage my running. I must have tried almost every style of running shoe there is -- I could always think of some other parameter to tinker with in the hope that my injuries wouldn't immediately flare up, but to no avail. My facebook marketplace profile was insane -- every month another barely used £100 pair of shoes for sale.

How much general activity do you do ? Riding two miles won't get you anywhere. You will got sore sit bones, that area takes time to build up, but the sliding forward and pushing back on the bars could also relate  to core stability and strength issues. You really shouldn't be gripping the bars - if everything is right, you just plonk them there - only grip on anything rough and descents.

One thing we're still missing is photos, just a set of side on shots, static with crank at 12/3/6/9.

There are a few on here who've done some fitting (either for money or for free) so might be able to get a sufficient pool of info to find some new stuff to try (and hopefully not buy).

Your BB as fitted will take most 24mm axled cranksets, ie Shimano, SRAM, FSA and many others meant for external bearing mountain bike setups, if you're going to pursue the crank length experiment, I'd stick with your current BB and find cheap/second hand cranksets to play with.

Having read most of the above, I think crankset is lower on the list to work on. If a bike fit by a pro isn't an option, can you find a local gym with decent spinning bikes and experiment for an hour or two. Take along an extendable tape measure and maybe string to help measure what you find.

On a spin bike you can easily set the height and front to back positions of the saddle and bars with way more range than you could on a normal bike, so with an hour's experimentation you might be closer to an answer. Oncew you find a decent position, measure height of the saddle nose, and how far back horizontally from the centre of the BB. Same with bars, height above and distance forward of the BB. Won't replicate the width of the bars of any mountain bike after 2008, but it's a start.

Obviously if you've tried all this, ignore me, especially if you've said so in the previous posts I haven't read.

What are you wearing? Thin trousers and undercrackers can easily make it uncomfortable in 2 miles

Nope, can’t ride no handed. I just slide forward off the saddle, I can’t keep balanced. I just pull forward.

I genuinely can't fathom how changing the length of the cranks is going to make a difference to this issue. But good luck, let us know how you get on.

I genuinely can’t fathom how changing the length of the cranks is going to make a difference to this issue.

It probably won't, the only (small) effect is that it can bring your power stroke closer to you. as the pedal is Xmm less far forwards.

Chain line dictates the axle length on square taper BB. Your best bet is to email Ragley and ask them, I think the bike was designed with out-board BB design in mind, so it might be a bit of guesswork depending on how many front chainrings you’re running and numbers of cogs out back.

Oh, ok, no wonder I couldn't work it out, thanks.
I will email them now.

Honestly, if the situation is as bad as you’ve described, and you really think you’ve tried everything, you may just need to get a recumbent bike…

You remind me of me years back when I was trying to salvage my running. I must have tried almost every style of running shoe there is — I could always think of some other parameter to tinker with in the hope that my injuries wouldn’t immediately flare up, but to no avail. My facebook marketplace profile was insane — every month another barely used £100 pair of shoes for sale.

*covers ears* LA LA LA
🙂
Well, my hope is that i have just been getting things wrong in the past.
I have never really really worked at it.
To start with, I didn't know other people weren't suffering.
Then I have just sort of had pops at it with many other priorities being much higher.
So, I now have the time at last to try and work it through properly.
I am hoping that it is an easy fix 🙂
I am sure that I can make it better than it is.

How much general activity do you do ? Riding two miles won’t get you anywhere. You will got sore sit bones, that area takes time to build up, but the sliding forward and pushing back on the bars could also relate to core stability and strength issues. You really shouldn’t be gripping the bars – if everything is right, you just plonk them there – only grip on anything rough and descents.

I have done quite a lot of riding in the past.
But even when I was real fit, I was always in pain.
I agree, two miles won't do anything. It IS all I cycle now as I gave up any more because it was just always uncomfortable. I have done two miles each way now every work day for 6 years. Plus I would do more as well.
My day to day work is lifting and moving crates and loading vans. Not saying i am fit, but I am active (ish).

Thanks for the input. It does give me hope. I shall get the MTB out, go for a couple of rides and probabvly start a new thread now that I know people are here that can help me. I originally was asking about BB 🙂

One thing we’re still missing is photos, just a set of side on shots, static with crank at 12/3/6/9.

There are a few on here who’ve done some fitting (either for money or for free) so might be able to get a sufficient pool of info to find some new stuff to try (and hopefully not buy).

I will do this. I am not in a position to do it at the moment, I have been sorting out stuff so I have some consistency.
I havehardly ridden the bike I think I want to use to work out my position in ages.
As I say, I only really came on here to ask about BBs.
But I am looking forward to working this out now I know I have some help.

@midlifecrashes
I had not thought of gym bikes.
That looks just the sort of thing eh?

@nickc

I genuinely can’t fathom how changing the length of the cranks is going to make a difference to this issue. But good luck, let us know how you get on.

I don't know for sure either obviously. I am open minded to the idea to try it though.
I am completely open to it not working at all for sure. I def can't get my head around how I won't lose balance and topple forward even more.
I suppose the question is: if it is correct and i am running 20mm too long cranks, now imagine you are using 195mm cranks. Or 20mm longer than you currently use. How would that feel?
I am wondering if it might want to pull your body forward on the bike as your foot is now 20mm further forward when pedal is at its furthest point forward. Might it pull you forward on your saddle? (I genuinely don't know)
Now you would have to drop your saddle by 20mm as the pedal is 20mm lower at its lowest point.
Now your knee is also another 20mm higher at the top point, so, in comparison to your hip joint, it is 40mm higher each stroke, right? How does that affect how you sit on your saddle? I feel like it might make you scrunch a bit, messing up ones stance? Plus it is a lot more movement on the seat? Plus would it make your sit bones more on the pointy bit?
And so on and so forth.
Or at least, that is what i am hoping and then ALL will be fixed like with the wave of a magic wand. 🙂

I have not seen anyone who has tried a shorter crank find any real negatives to it, but state that too long can cause issues.
Like i say, I am not trying to sell the idea, but feel it would be remiss of me to not try it for the want of twenty quid.

If you are sliding forwards off a flat saddle? Tilt the saddle slightly up. Mine are all very slight angled back. Flat I feel I'm sliding forward

After doing that you will need to reset saddle height. Starting point. Your leg straight with a heel on the pedal making sure your hips are level.

Bar height? Level with saddle is a good starting point.

Crank length. 175mm is probably too long. I've never given it much thought. At 6ft3 I just assume the larger of the common 175 and 170 will fit me. Though riding my hard tail with 170mm cranks felt fine.

I feel sure if I rode a mile  or 2 beside you and asked a few questions it would become apparent whether the issue is bike fit related, a physical problem, a combination of the 2 perhaps or possibly partially psychological . Never underestimate the latter as overthinking about bodily sensations can cause all sorts of problems . I personally have had a couple of times in my life where I began to think I had a problem with a body part or sensation and it rapidly became real ..as in real that I could feel it . It was a horrible sensation that had no cause but I became convinced I had a major physical  problem that almost disabled me until I  finally ..after a long time ...let go and relaxed ..and the issues disappeared never to bother me again . Just another thing to consider might be making you feel worse than you should .  You are in Cornwall you say ? I am in Exeter and have ridden for 55 years ..all types of bikes ..all over . I also have built numerous bikes for different folk  and spent a lot of time making them comfortable . We are all different in what feels right or wrong and as others have said ....changing your crank length is one of the last things I would focus on .  If you are ever this way I would be happy to meet up and offer advice if I can help . How far from Plymouth are you out of interest ? If it appealed I could perhaps come down that way one afternoon to meet for an hour and try and solve this seemingly very unusual problem you are experiencing .  Oh and just to clarify about the square taper length you would need for a given crankset . Although it relates to chainline etc  ..iirc different chainsets have different chainline figures , spindle length requirements etc so it can get confusing . I might even be able to help you out with that too . Just an idea ..seems a shame your being held back and possibly focusing on the wrong things , Good luck however things turn out , Bill

Or 20mm longer than you currently use. How would that feel?

Weird I'd imagine 😁 There's been some studies that show that operating longer cranks can lead to pain especially in the hip and knee, and who knows? Shorter cranks may be cycling nirvana for you , but  It seems to me that if you're cycling 2 miles and are in pain, 155mm cranks aren't going to make that much of a difference. However, I could be entirely wrong, so like I said, good luck, let us know how you get on.

It also doesn't explain how even riding no handed (presumably sitting upright) you are sliding forwards.  What would be causing a slide forwards when sat upright and putting pressure on pedals?

One of those occasions where we would really need to see what is going on to even star to understand it.

If you are sliding forwards off a flat saddle? Tilt the saddle slightly up. Mine are all very slight angled back. Flat I feel I’m sliding forward

After doing that you will need to reset saddle height. Starting point. Your leg straight with a heel on the pedal making sure your hips are level.

Bar height? Level with saddle is a good starting point.

Crank length. 175mm is probably too long. I’ve never given it much thought. At 6ft3 I just assume the larger of the common 175 and 170 will fit me. Though riding my hard tail with 170mm cranks felt fine.

I appreciate what you are saying. As said, I will start afresh with my MTB and work through it.

Your post was pretty interesting actually, as I realised that I am riding the same crank lengths as you.
I didn't intend this all to be about my fit, however, I am now really interested that so many people are thinking this will make no difference. I am surprised that this metric is considered irrelevant. So, we move our saddle 5mm and it makes a difference. I think I need to look at the mechanics of it. I am happy that it probably won't make a difference.

But now I am getting to wonder why it wouldn't matter.
So, I got a guy of similar height at work to you to compare roughly ratios of legs.
He is six inches longer to the knee from the floor. (150mm ish)
Four inches longer when sat against a wall to front of knee. (100mm ish.)

@kaiser

I feel sure if I rode a mile or 2 beside you and asked a few questions it would become apparent whether the issue is bike fit related, a physical problem, a combination of the 2 perhaps or possibly partially psychological . Never underestimate the latter as overthinking about bodily sensations can cause all sorts of problems . I personally have had a couple of times in my life where I began to think I had a problem with a body part or sensation and it rapidly became real ..as in real that I could feel it . It was a horrible sensation that had no cause but I became convinced I had a major physical problem that almost disabled me until I finally ..after a long time …let go and relaxed ..and the issues disappeared never to bother me again . Just another thing to consider might be making you feel worse than you should . You are in Cornwall you say ? I am in Exeter and have ridden for 55 years ..all types of bikes ..all over . I also have built numerous bikes for different folk and spent a lot of time making them comfortable . We are all different in what feels right or wrong and as others have said ….changing your crank length is one of the last things I would focus on . If you are ever this way I would be happy to meet up and offer advice if I can help . How far from Plymouth are you out of interest ? If it appealed I could perhaps come down that way one afternoon to meet for an hour and try and solve this seemingly very unusual problem you are experiencing . Oh and just to clarify about the square taper length you would need for a given crankset . Although it relates to chainline etc ..iirc different chainsets have different chainline figures , spindle length requirements etc so it can get confusing . I might even be able to help you out with that too . Just an idea ..seems a shame your being held back and possibly focusing on the wrong things , Good luck however things turn out , Bill

Bill, this sounds like it would be amazing.
I am first working on getting consistency. So, I found shoes that fit better.
Someone gave me an old roller a couple years ago. So, my plan is to dust off the MTB and use that to work with.
That means I don't have to keep changing back the work bike.
I have never really had the time to focus on it before, so I am hoping with peoples' help, I will, at minimum, improve things from where it is.

I wasn't expecting so many people to be interested and keen to help when I asked about BBs, but boy I am glad I asked.

Weird I’d imagine 😁 There’s been some studies that show that operating longer cranks can lead to pain especially in the hip and knee, and who knows? Shorter cranks may be cycling nirvana for you , but It seems to me that if you’re cycling 2 miles and are in pain, 155mm cranks aren’t going to make that much of a difference. However, I could be entirely wrong, so like I said, good luck, let us know how you get on.

lol, yes, weird. I hadn't thought of it like that before.
I certainly will report back. I do get knee discomfort.
Plus it did a sort of pop six months ago coming up the hill and has been not quite right since.
even if they do nothing with the bike fit, I am interested to try them as everything i read says that people found some advantages to them.
But, yes, I will be getting that MTB out and asking for hep either way for sure. Thanks.

I think the rule of thumb for working out crank length is 9.5% of your height.

I'm 178cm (5'10" in old money)  x 9.5%  = 169.1 so cranks @170mm

you're 172/3 (you said you're 5'8"?)  = 163.8, so cranks @165mm

So for a 5cm (quite a lot really)  height difference that's a 5mm (not a lot really) change in suggested crank length. But you're going from 175 to 155, so maybe it'll make more difference? 🤷‍♀️

@kerley

It also doesn’t explain how even riding no handed (presumably sitting upright) you are sliding forwards. What would be causing a slide forwards when sat upright and putting pressure on pedals?

One of those occasions where we would really need to see what is going on to even star to understand it.

My only theory i have come up that is related to cranks is that perhaps, if they are too long for my femur length, my foot is too far forward, yes?
So, might that drag my butt forward, just purely down to femur length.
Either way, I shall drag the MTB out and start the process next week hopefully.
Thanks for your interest. It is pretty interesting.

Someone gave me his old roller a while back so I am hoping that I can now take pics and discuss.

I think the rule of thumb for working out crank length is 9.5% of your height.

I’m 178cm (5’10” in old money) x 9.5% = 169.1 so cranks @170mm

you’re 172/3 (you said you’re 5’8″?) = 163.8, so cranks @165mm

So for a 5cm (quite a lot really) height difference that’s a 5mm (not a lot really) change in suggested crank length. But you’re going from 175 to 155, so maybe it’ll make more difference? 🤷‍♀️

🤷‍♀️ indeed 🙂
That is an interesting bit of information actually.
So, it is heading towards the 155mm lol.
I apparently have shorter femur, so much of my height is in my torso, which brings it a bit more down.
Hopefully things will start to work out next week. Hmmmm, forecast is a little damp next week. That's a shame.
As i said to someone else, I am also interested as I have read a number of 'normal' people who have liked some benefits from shorter cranks.

My only theory i have come up that is related to cranks is that perhaps, if they are too long for my femur length, my foot is too far forward, yes?

If you set you seat in the correct position relative to cranks (the first thing you should do) then that shouldn't happen.  In the old days the measure was Knee Over Pedal Spindle where hanging a plumb line from Knee would be in line with pedal spindle.  While that has now been discounted as an absolute rule it is still not going to be far out as a starting position.

If you are sat a lot further back than your body wants to be for the pedals then it will naturally slide you forwards.

OK, I see what you are saying.
I only seem to just be toppling forward then when I bring the saddle forward to that level.
If I remember rightly.

I am really looking forward to getting this process going.

I'm reading this thread with increasing incredulity/amusement. In my mind I'm imagining you to be either somebody with extremely odd proportions or your saddle is 6" too low (152mm).
I used to be 6 foot. After spinal surgery I'm now 5'11". (Fine thanks, only problem is it increased my BMI).
I have short femurs for my height. I can sit in a Ryanair seat comfortably. As I mentioned above I can ride 180mm to 160mm cranks without noticing much difference. I have road shoes and pedals, MTB shoes and pedals, flat shoes and pedals (on my big FS e-mtb and my fixed wheel pub bike) and nothing tips me forward or causes discomfort.

I think maybe the answer lies elsewhere.

You may well be right @BigJohn
We will find out eh?

An update. (I look forward to all the disbelief and guffaws etc etc)
So, I know I said I was going to be methodical which makes this update not a real one.
I am not necessarily going to learn from what I did.
I couldn't resist but swap the 155mm cranks onto my work bike and scoot up the road for a mile.
Things felt interesting so I left them on for the next couple of work days.
I didn't want to be trying too hard to make the new set up work. I have tried a bunch of things before and always been disappointed. I had a long day due on saturday, starting two hours earlier than normal at 0500h and an 11 hour day. So, at the end of the day, I knew that I would not be bothered about trying to make it work. I would just want to go home.

So, reasons this is not a proper comparison, (I shouldn't really be putting this out there because it is not a like for like and it is on a wrong frame I suspect. I just can't resist but tell you guys how it felt.) I couldn't quickly remove the pedals, so they are different, no plastic clips either. Also, big boots, also rucksack with at least 5kg in. Also, was kernacked.
It might help when working out the MTB some how.

Man, it is a funny thing to experience, I recommend it just for the giggle. It is like riding a childs bike.
Teeny little circles.
Definitely uses the quads in a different way to what they are used to for the last forty years.

I think, for the first time in my life, I have felt like a normal person on a push bike.
All the things everyone is saying I 'should' feel, I now do.
I instantly loved the knees not coming up so high, felt a lot more natural. They are coming 40mm less than they were and me likey loads and loads.
My sit bones feel less pointy. I sort feel heavier on the saddle but that might have been my heavy pack, but i no longer feel like I am on two knuckles. I am wondering if with my knees coming up less, I can tilt further forward to a more natural angle?
But, also, I suppose I am pushed back twenty mm maybe that allows me to balance better? Actually, a bit further because i have raised the saddle.
Now, suddenly, my hands are on top of the bars instead of pushing against them holding myself back.
I can lift my hands off the bars and my butt doesn't pull forward. It just doesn't. I now see why you can't understand what i mean. As I lift up, I rock back, no forward sliding. It is weird lol.
Now, I am not sure how to explain this bit, but I sort of feel heavier on my pedals. But in a good way.
More planted? Stronger? Dunno. Perhaps it has lifted some of the weight off my butt?

My pedalling has had to change. That would take some getting used to. But I think I sort of feel stronger pedalling.
Even though it is not using the muscle in the same way...... or something. Actually, could that be down to my knees not coming so high?

I suspect, from what everyone is saying, that the change in crank length is correcting a different issue that I have created by doing something else wrong.
But at least I think I now know how things are supposed to feel like.
I suspect people will suggest it is psychological and maybe some of it is, but the whole not sliding forward thing is not in my imagination, it is so different.
I am interested to see if we can set up MTB to feel like this with the normal sized cranks.

So, ignore all of the above lol 🙂

What to do next? Shall I start from scratch on my MTB as it is now?
I will take the advice and set it up with the current 170mm cranks and see how good it can be got?
Does that make sense?
Shall I start a fresh thread?

 the change in crank length is correcting a different issue that I have created by doing something else wrong.

Might be, but if it works for you

I suspect people will suggest it is psychological and maybe some of it is

Largely it doesn't really matter, placebo effect is still an effect. If it works, and you're not in pain then; win

I suspect, from what everyone is saying, that the change in crank length is correcting a different issue that I have created by doing something else wrong.

Did you change your saddle height after installing the shorter cranks? If not, and things feel ok, it may just have been that your saddle was too high all along. Try setting your saddle position on the MTB to the same as your work bike (relative to the pedal axle not the BB).

I mean, I would rather work out the root cause. Rather than bodging round the issue.
It would be nice not to be limited to 155mm cranks.
It is quite hard work. I guess I will get used to it. I am probably in too high a gear all of the time.
It isn't the magic bullet. It feels wrong, but it is definitely closer than I was. The fact i don't slide forward being the main one.
I wish I had 195mm cranks to send out to people and see what the affect was.

It should not in theory be any harder work but you will need to use lower gears and spin at higher RPM to get same speed.

Yes, I imagine I would get used to that.
I think I am cycling faster strangely, as I seem to have more effective strength, but that might just be my imagination. But I have a little rise on the way in that i leave in a higher gear blah blah blah
well, I could seem to do that easier even with less leverage. I thought I was a gear down.

There seems to be less strain on my knee that got damaged months back on the cycle up out of town.
It feels well silly though, like it can't be right.

I popped up the road this afternoon, only had time for a mile or two. I can lean all the way forward like, nearly chin on bars and lift hands off and hold myself on the pedals now. I can't work out the physics of it, I thought with a shorter stance, I would be less stable, but I am solid on those pedals.

I suppose I should do a test ride on the MTB before i change anything, it has been a while.