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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?
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.)
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? 🤷♀️
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.