Bottom Bracket Installation Problem

PaulS77

Wonder if anyone can offer a bit of advice. Had my bike serviced last winter and the mechanic told me there was play in the bottom bracket and it'd probably only last the summer, but that it didn't need replacing immediately. Sure enough, a couple of weeks ago the cranks started to wobble a lot, a word with the mechanic confirmed I needed a new BB but he's not working at the moment so I decided to have a bash at replacing it myself.

The cranks are Sora and the BB I've bought's sold as Tiagra, 68mm English thread, fairly sure I got the right one (http://www.chainreactioncycles.com/shim ... -prod67221)

It appeared to install ok but when I put the chain back on the front derailleur won't push the chain onto the outside chain ring. I'm guessing that either I've not pushed the axle through enough so the rings are sitting further out than they should, or the BB's too narrow.

Any suggestions, other than taking it to someone who knows that they're doing

Thanks, Paul

thebadgerboy1982

As long as there is not play in the bottom bracket, you only need to adjust the limit screws and make sure the cable has enough tension in it.

Did you buy the 68 or 70mm?
Ross

keef66

Sometimes you need to be quite firm and whack the driveside crank with the flat of your hand or even a tap with a rubber mallet to persuade it to fit snugly. Then you can set about installing the non drive side crank and preloading the bearings by tightening the end cap before doing up the pinch bolts.

nicklouse

either you have fitted some spacers that you should not have done. or the crank arm is not flush with the bearing on the drive side. IE hit it. then do the ND side.

PaulS77

Thanks for the replies. Ross, it was the 68mm I ordered, marked 1.37 x 24, I'm loathe to just adjust the front dereailleur I think the fitting of the BB's the underlying problem.

When I fitted the driveside crank I did knock it in with a rubber mallet but I was nervous of hitting it too hard, so maybe I'll have another go at that.

The BB didn't come with any spacers separately, could there be any I could or should have removed from the bracket?

Many thanks, Paul

nicklouse

no spacers to fit or remove,

is the crank arm snug against the BB? i think not.

arlowood

For some reason the Shimano cranksets can be quite difficult to install, especially into a new Hollowtech BB.

You just need to give it some "wellie" with a wooden or resin mallet to make sure if has gone completely through and the drive side crank is completely flush with the bearing. Don't be too timid about it.

See me comments in this recent post:-

viewtopic.php?f=40004&t=12944992

PaulS77

It looks snug on the drive side, but clearly not as snug as it should be, I'll have another go with a mallet tonight and not be so shy this time.

Thanks all, much appreciated

andyh01

I've just had a very similar problem to this with an external BB. My issue was part of the BB innerds had somehow come detached from the cups so when I took the crank arm off, not only did the ball barings drop out on the floor but also a small metal ring had seperated from the cups and wedged itself on the inside of the crank arm that I didn't see at first and was acting like a spacer/washer on the axle between the crank arm and the external bb preventing the shaft to go all the way through.

PaulS77

That's exactly what happened to mine Andy, I was going to post a photo of it tonight in case it happened to anyone else! There was a thin plastic ring that came off the old BB left on the DS crank, I didn't notice it was on there so when I refitted the crank arm it looked like it was fitted correctly but the axle wasn't pushing through enough.

Thanks again for the help :-)

nicklouse

ahhh so you did not remove all of the BB. and the dust shield stayed on the axel. did you not think that the old cups looked odd being different and the new ones looked the same as each other?

goo to see that you sorted it.