Short(ish) version as STW logged me out halfway through my original attempt….

My road bike came with a square taper crank. I swapped it for HTII Sora not long after buying and ever since then the front shifting has been a bit rubbish at best.

Main issue seems to be that with no cable attached & L screw wound out, the mech won’t push the chain onto the inner ring. To get it to work I have to drop the mech very close to the teeth & twist it slightly so the rear end is canted inwards slightly.
It seems to me the rings on the Sora crank sit closer inboard than they perhaps did with the original sq taper crank, meaning there’s no room for inward adjustment of the mech. There is tons of adjustment at the ‘big ring’ position.

Testing this a while back, I put a BB spacer on the drive side BB cup and had the shifting working in no time at all – but this obviously reduced the crank engagement with the axle on the non-drive side so I didn’t leave it like that – it was just to prove a theory….

I sold the original crank on ebay, which looking back wasn’t the best move & I don’t think I still have the pics I used for the auction to see if I can find the BB spec (axle length) to give me a clue.

I’m tempted to try this crank from SJS cycles which looks remarkably like the crank that came off the bike, but with a BB it’s gonna be almost £50 which I don’t wanna spend unless I have some confidence it will cure the problem!

https://www.sjscycles.co.uk/chainsets/alloy-compact-double-square-taper-chainset-5034t-170mm/

Does it sound feasible that the Sora crank has buggered things up, in terms of crank ring positions??

What’s the front mech, be cheaper to change that surely? Sora chainset really shouldn’t cause any issues unless you’ve changed from a MTB or hybrid chainset?

Good question, I think it’s a Sora front mech – it’s definitely Sora shifters & rear mech, so I think the front is the same…..

No guarantees that a new front mech will sit further inboard though, is there?
It’s not that the mech is damaged, there just isn’t any more movement within the trapezium of the mech….

With no cable attached & the L screw wound right out, the mech is very close to touching the seat tube as it is. If a different mech was available that sat further inwards, I suspect it would just foul the seat tube…

No guarantees that a new front mech will sit further inboard though, is there?

Pretty much guaranteed not to.

I’d just add a spacer.

IN FACT….it’s a triple…you are using the 3mm axle spacer that’s needed?

cynic-al….its a double crankset but the shifter is a Sora triple (with the old button shifter) and I assume the mech could accommodate a triple too (don’t know as I haven’t tried).

Where are you suggesting I need a spacer? The BB?

I know it sounds silly but have you got the bb spacers on the correct sides, if you shift one from the non drive side to the drive side itll push your chainline over without affecting how much axle you’ve got in the crank.

konanige – Member
I know it sounds silly but have you got the bb spacers on the correct sides, if you shift one from the non drive side to the drive side itll push your chainline over without affecting how much axle you’ve got in the crank.

There’s currently no spacers, so no chance of swapping any from one side to the other. From the Shimano docs I read, I thought that was correct for a road bike (68mm shell); i.e. no spacers required at all.
When I tried it with one spacer added to the drive side, it worked fine, but looked to me as if there wasn’t enough spline engagement between the non-drive side crank and the axle so I removed the spacer. Although, I don’t know how much spline engagement is required for it to be ‘safe’….

For 68mm shell I think you should have the spacers installed.

Pretty sure road cranks dont come with spacers gt90000 as road bikes are all 68mm BB.

Stumpy, the correct solution is (sadly) new mech AND shifter time. A triple shifter will not reliably work with a double mech and sticking with your current mech is obviously not viable either as for some reason its not got a low enough ‘low’ position.

[edit; actually its not clear, did you have a triple on previously?]

For 68mm shell I think you should have the spacers installed.

Not on road frames / cranks

Ahh ok 🙂

Does the height of the mech need adjustment? Ie does the newer chainset have smaller sprockets?

Just a thought. It should all work together, but it’s hard to visualise without seeing it. Can you take it to a shop?

gt900uk – Member
For 68mm shell I think you should have the spacers installed.

As above, I am sure from the instructions that came with the Sora crank it mentioned no spacers and didn’t actually include any….

STATO – Member

Stumpy, the correct solution is (sadly) new mech AND shifter time. A triple shifter will not reliably work with a double mech and sticking with your current mech is obviously not viable either as for some reason its not got a low enough ‘low’ position.

[edit; actually its not clear, did you have a triple on previously?]

Yep, the one I got rid of that originally came with the bike was a 34/50 double and I replaced it with a 34/50 double…..
It all worked initially and I am sure I’ve seen other lower range bikes fitted with doubles that have a triple shifter.
I think my sister’s Fuji is like that.
It’s bloody frustrating…..

Superficial – Member
Does the height of the mech need adjustment? Ie does the newer chainset have smaller sprockets?

Just a thought. It should all work together, but it’s hard to visualise without seeing it. Can you take it to a shop?

I have fiddled with the height, but the new crankset has the same chainring sizes. It’s within the 1-2mm that I think Shimano recommend.
Yeah, I could take it to a shop but I want to be able to find a solution myself. I don’t like being beaten by these things!

Annoyingly I have never had this trouble with setting up mechs on any other bike. I am normally quite methodical at setting them up and rarely have problems but this one has got me flummoxed.

I might try a spacer again tomorrow evening and see where I end up…

Yep, the one I got rid of that originally came with the bike was a 34/50 double and I replaced it with a 34/50 double…..
It all worked initially and I am sure I’ve seen other lower range bikes fitted with doubles that have a triple shifter.
I think my sister’s Fuji is like that.
It’s bloody frustrating…..

I could be wrong about SORA but it was certainly the case at higher levels that double and triple shifters needed matching mechs, so it made using them on a double more difficult as the hieght vs spacing was off. Bear in mind that double shifters often have 2 clicks (3 positions) too, to help fine tune chain rub. You could probably only confirm by checking for a model number (*unless it says tipple on it obv)

Of course we are getting away from the point now that your front mech is not working. It may be that its an odd one designed for a wider chainline? I know shimano do do odd things like that occasionally, again they only way to confirm is find a model number on it. Id suggest you do that anyway as it might help solve the problem.

OH! Just had another thought! Different speeds matter. An older front mech will not work as well with a narrower chain. So 8 speed mech wont shift a 10 speed chain very well, the mech plates are too wide.

Does it sound feasible that the Sora crank has buggered things up, in terms of crank ring positions??

To answer this specific question, I don’t think so, as I did the exact same thing as you (switched out a square taper for a Sora HT2 -both double- having double Sora front mech and shifter) and it just worked.

This is with the 3500 series Sora (i.e. 9 speed).

STATO – Member

I could be wrong about SORA but it was certainly the case at higher levels that double and triple shifters needed matching mechs, so it made using them on a double more difficult as the hieght vs spacing was off. Bear in mind that double shifters often have 2 clicks (3 positions) too, to help fine tune chain rub.

I spent most of the evening last night looking for a solution to this.
I found probably a 50/50 mix of people saying that a Sora triple shifter works fine/doesn’t work fine with a double crankset.

There were quite a few people saying it’s possible but the shifting isn’t that great.
My shifter also have the ‘double click’ trim adjustment – but I guess that’s just at each end, rather than the middle position.

One thing I did read was saying it’s best to set the mech up from the middle position to top, rather than bottom to middle, but I’d have thought the leverage ratio would be identical in both shift positions.

I’m gonna clean everything up tonight and have another fiddle if I can face it.
I might just end up putting a spacer in on the drive side & running it like this – even if it’s only a temp fix.

STATO – Member

OH! Just had another thought! Different speeds matter. An older front mech will not work as well with a narrower chain. So 8 speed mech wont shift a 10 speed chain very well, the mech plates are too wide.

Erm……I was about to say it’s not this as it’s all 9 speed stuff. And it is…but that does seem to be an issue. To get the shift from small ring to larger ring to work, I have to set the high adjustment a bit further over (outwards) than I would like to, or the inner plate of the mech doesn’t provide enough shove to the chain to get it to move…..
Hmmmm. I wonder if this is just a mish-mash of components that is only just about working. Dunno. I suppose getting a new 9spd double front mech & double shifter would probably resolve this issue once & for all…..

genubah – Member

Does it sound feasible that the Sora crank has buggered things up, in terms of crank ring positions??
To answer this specific question, I don’t think so, as I did the exact same thing as you (switched out a square taper for a Sora HT2 -both double- having double Sora front mech and shifter) and it just worked.

Yeah, it should be possible so I don’t know why I am making such a meal out of it!!
Dunno what series shifters mine are. I think it’s all Sora from the last lot that had the button shift things, rather than double lever…perhaps 2012….?

Sorry I was thinking it was a triple.

It may be that its an odd one designed for a wider chainline? I know shimano do do odd things like that occasionally,

Guff.

Great. Well that was a complete bit of a mess waste of an evening…

Took very dirty chain off to soak in degreaser while I looked for HTII spacer that I put ‘safely away’ last time I used it, remove front mech to clean and measure width of bb shell just to make sure…

Couldn’t find spacer so gave up search after 30 mins.
BB shell definitely 68mm.

Cleaned chain and mech and decided to have another bash at setting it up.
Soon realised that maybe I hadn’t been routing the cable round the little notch near the fastening bolt so felt a renewed hope that it was actually just a mistake and I would be able to sort it out.

Took a while but seemed to get it all set up ok. Could barely contain my excitement but thought the last step should be to try it on the turbo trainer under load….

Did it work….did it ****. Wouldn’t shift to large ring from small when it was all fine on the stand. Adjusted the high screw and cable tension to get it working, but then it wouldn’t shift down again.

Given up. Gonna get it in the shop hopefully at the weekend. 2 wasted evenings now and no riding as a result.
Never had this issue with any of my other bikes, which I think is why this is sooo bloody annoying.

One thing I did read was saying it’s best to set the mech up from the middle position to top, rather than bottom to middle, but I’d have thought the leverage ratio would be identical in both shift positions.

Have a look at the 3rd last post here (by perthmtb):

http://singletrackworld.com/forum/topic/triple-front-mech-with-double-chain-rings

tillydog – Member

One thing I did read was saying it’s best to set the mech up from the middle position to top, rather than bottom to middle, but I’d have thought the leverage ratio would be identical in both shift positions.

Have a look at the 3rd last post here (by perthmtb):

Cool. Thanks for digging that out, I really appreciate it!

There’s a lot of mixed information about this out there.
My experience definitely fits more with Mick_R’s comments about the width of the cage not suiting the shifting.

This seems to be what I am finding:

mick_r – Member

Triple might work on the 40:28 chainset. It didn’t on the 38:26.

The gap between the cage plates is contoured.

If the triple mech was positioned to clear the chainrings, then the chain rubbed on one or other of the cage plates – depending on which gear you are in at the rear as the chain entry angle changes (adjusting indexing just changed which plate it rubs).

Adjusting the mech height up/down so chain didn’t rub the cage meant the mech fouled the chainrings or the chain rode off the top of the outer ring.

but perthmtb reckons it shouldn’t be a problem, so long as I use the low-middle shifter position, rather than middle-top.

The above seems to apply to mtb kit, but I presume it is the same for road stuff……

Have a look at the 3rd last post here (by perthmtb):

http://singletrackworld.com/forum/topic/triple-front-mech-with-double-chain-rings

The above seems to apply to mtb kit, but I presume it is the same for road stuff……

Sadly not. MTB front shifting is different to Road so that post does not apply.

Anyway, i did a google and confirmed with older Shimano it WAS only the higher stuff that was double OR triple. SORA 3400 is double AND triple.

So we can now focus back on the problem front mech. Did you check it for a part number when you had it off? Youd expect it to be a FD-3400.

Here are the tech docs if you had not found them.
Shifters
Triple mech
Double mech

STATO – it was hard to see in the garage last night – I could do with better lighting, but I think it did read FD-3400.

Comparing images of the triple & double mechs, the triple has a much larger back plate on the cage, which mine doesn’t have so I am pretty confident it is a double mech

Looking up the spec seems to confirm this:

http://www.nicebikes.com/carraro-915-d-ambiez-sl-al/car48pd.html

Well in that case, youve done something that has buggered up the mech 😆

Sounds like something has gone wrong with it then, we have exhausted all other options. To the Bike shop it is.

Update for those that have helped me try to sort this out…

Got it back from the lbs earlier today.
Mechanic reckoned;
– the outer was quite draggy so put a new inner and outer on.
– I’d set the mech a bit too low
– he agreed that it was reluctant to drop from outer to inner chainring even with no cable and L screw wound all the way out.
-he reckons the mech is hitting the frame before it hits the low stop, but it doesn’t seem to him that the mech is bent/damaged – wonky frame?
– he said he hadn’t managed to get the gears running silently in every position.

I mentioned getting it set up on the stand, but it then not working under load on the turbo….he looked at me as if to say ‘ah, I haven’t actually tried it outside…’

Got it home….stuck it on the turbo and shifting from inner to outer ring is very smooth.
But, shifting from outer to inner is not really any better than it was. Intermittent to say the least with a real reluctance to drop from the outer ring.

So, it’s not just me being an idiot.
Gonna try some Hope bottom bracket spacers I think. They should fit the shimano bb and are available in 1mm widths, so I’ll buy a couple and see if I can get away with just fitting one.

This is almost an excuse for a new bike…. 😆

Erm – in case anyone cares….here’s an update.

Fitted one Hope 1mm BB spacer yesterday and appear to have solved the problem.
Chain is dropping onto the inner chainring without issue now & once the high limit screw on the mech was adjusted a little to account for the chainrings sitting 1mm further outboard, it is all shifting nicely.

Tried it ‘under load’ on the turbo trainer for about 5 mins and it seems fine on there too.

I can’t imagine that Mr Shimano won’t have built in enough safety margin to the axle/NDS crank interface to cope with 1mm less spline engagement but I’ll keen an eye on that.

Happy Days…..!