Bottom Bracket/Front Mech Question

StefanP

Hey all,

I bought a new bottom bracket a few months ago. Ever since then I haven't been able to get into my 22t ring, which isnt too much of problem since I don't often use it. But it's got to the point where it's annoying, so I think I need to get a new one. BB is a Shimano ES51 68 AK 121mm width.

So my question is, would changing the BB to one with a wider shell width or a wider "overall" width solve my problem? I have a feeling its the latter, but I though I'd ask anyway.

Alternatively, I thought a new front mech would allow me to change the L-screw so that I can more the cage closer to the seat tube, as this is what is stopping me from changing into the 22t. (It does change, but only just, and with a considerable amount of crunking. Would this work? Current front mech is a Shimano Deore Topswing.

Thanks
Stefan

nicklouse

what are the cranks?

what was the old BB length?

have you reset the mech or not?

StefanP

cranks are shimano deore (old ones, with two crank bolts) I cant be too much more accurate than that, all the markings are rubbed off.

old bb length should have been 121mm like these ones, from what i remember the only difference was the AK after the 68.

I've adjusted the mech so that it shifts as best it can but, I can't get the front mech to inwards enough to stop the chain from rubbing against the cage, if you see what i mean

cooldad

If the old bb was not ak, it was 113mm which could be why the cranks are too far out.
(I think)
Did you measure the old one?

tofu21

I had the same problems with my stumpy FSR. Ended up putting a second spacer on the drive side. That sorted it

nicklouse

StefanP wrote:

cranks are shimano deore (old ones, with two crank bolts) I cant be too much more accurate than that, all the markings are rubbed off.

old bb length should have been 121mm like these ones, from what i remember the only difference was the AK after the 68.

I've adjusted the mech so that it shifts as best it can but, I can't get the front mech to inwards enough to stop the chain from rubbing against the cage, if you see what i mean

sorry Part numbers are needed.

StefanP

BB: ES51 68AK L->121->R BC 1.37 x 24
Crankset: 44/32/22 FC M510 (2007)
Cassette: SRAM PG980 on XT Hubs and Mavic 317 Disc Rims
Chain: SRAM PC971
Derailleur: Shimano SLX
Its an odd mix, for sure.
I'll go an recheck all of those

If the old bb was not ak, it was 113mm which could be why the cranks are too far out.
(I think)
Did you measure the old one?

From what i remember the old BB was the same length as the new one, the only difference was the AK after the 68

cooldad

The BB maybe but what about the axle length.
68AK is 121mm, I thought without the AK it was 113.

StefanP

Yes, certainly looks like it
http://www.huckjambikes.com/manuals/Front%20Drivetrain%20FD-M531-6.pdf
Under Specification

if the axle length was shorter on the old BB, then surely I would've experienced the same problem?

cooldad

One of us is confused.
You are struggling to get into the small ring, which suggests the axle is too short.
You seem to have replaced a 113mm axle BB with a 121mm axle which would push the rings out making it harder to get into the big ring.

Yup, I'm confused.
Mr Louse should be along shortly with a sensible answer.

nicklouse

why do you show a pdf file for a FC-M531 crank set?

you say you have a FC-M510


and you say you have a splined (octalink) bb?

in which case it should be a 118 or a 113mm axle length. (50mm or 47.5mm chain line).

but back to your problem you need to put a 1.8mm spacer between the BB and the frame on the driveside as you have got a BB for use with a chain case which would have its support mounted on the BB.

supersonic

What is the part number of the SLX front mech? The limit screw is wound all the way out?

StefanP

:oops: Well that was a bit thick, I was looking for the ES51-AK and that was the only one that came up.

That makes sense, thanks for that, appreciate the help.

Sorry its not a SLX front mech, its a Deore front mech, the L-limit screw is all the way out

supersonic

Ah... I had a problem with a certain Deore mech a few years ago - it bottomed out on itself way to early and presented the problems you are having. I would try a different derailer.