 You don't need to be an 'investor' to invest in Singletrack: 6 days left: 95% of target - Find out more
I'm changing the drivetrain on a friends' commuter bike. I've bought a Altus chainset (fc-m311) as this was cheaper than buying the rings separately. It's all square taper. Unfortunately, it won't fit onto either the original worn BB, or a new BB (BB-UN26 68/122.5).
It's like the angle of the taper is steeper than on the cranks, so the crank doesn't fit. I've tried tightening the bolt as far as I dare, but it still sticks out a lot from the BB, and if I remove the crank arm, it's clear that the tapered part of BB axle needs to move more into the crank head by about 8/9mm.
Any suggestions? Shimano spec sheet says to pair a fc-m311-8 with a 123mm bb-un26 (-K). I found the nearest match to spindle, I've no idea what the (-K) refers to.
I'm not sure what your problem is - the axle should never reach the end of the hole, it shouldn't bottom out. Can you post a pic?
There are only two taper angles - an obscure TA/Stronglight one that you'll never see, and the one everyone else uses...
"Sticks out a lot from the BB" meaning what?
122 is correct. No way will the taper be wrong.
Pics?
[url= http://farm9.staticflickr.com/8053/8142952790_2a43a7977e.jp g" target="_blank">
[url= http://www.flickr.com/photos/47298478@N03/8142952790/ ]IMAG0599[/url] by [url= http://www.flickr.com/people/47298478@N03/ ] [/url], on Flickr
[url= http://farm9.staticflickr.com/8188/8142953524_9231161cc7.jp g" target="_blank">
[url= http://www.flickr.com/photos/47298478@N03/8142953524/ ]IMAG0604[/url] by [url= http://www.flickr.com/people/47298478@N03/ ] [/url], on Flickr
Ok, 8-9mm was an exaggeration, but I'd have thought the crankarm still needed to move further onto the taper.
Looks okay to me.
You have greased the taper, haven't you?
<runs away and hides>
Actually the compact one may need a shorter BB.
Looks quite far out. If the BB has a metal ring which the crank butts up against, which it looks like from the pic, then try levering it off the bb and install the cranks without. We've had altus chainsets which would fall straight off without the bolt on the un-26 bbs.
Thanks all, I do not believe that I'm missing a metal ring? I've also tried it on a 68/113 bb, but there is still the same expanse of taper showing?