Chris Chicago

just installed cranks on a new shimano un55 bottom bracket. bb went in last week, cranks today. thought i was done then noticed some play in the spindle. I've only done one of these before this one. could i have messed it up somehow, bumping it etc. or did i just get a lemon?

is there a way to fix the problem or just exchange it?

thanks!

HillRider

Any chance you installed a 68 mm bb on a 73 mm frame and the nds cup isn't snug against the end of the cartridge? Also, are the crank arms torqued properly so they aren't moving relative to the spindle?

Otherwise these bottom brackets are very rugged and bumping it should do nothing harmful unless done with your car.

As a first step, I'd remove the bb and see if there is any play in the cartridge when it's out of the bike.

Chris Chicago

thanks Hillrider.

It's the correct size, 68. but I took it out and there seems to be no play in the spindle now that it is removed. I had the adjustable cup pretty damn tight on there. I did have a 2mm spacer on the drive side though. that's all the facts. I'm stumped. bike is an 84 schwinn high sierra.

Airburst

Strange... I did encounter a Shimano cartridge BB that was actually a cup-and-cone unit, with the cones threaded onto the spindle and held in adjustment with a locknut (I suppose it was still a cartridge in that it was removeable as a unit). One of those could potentially work loose in a fairly short time if the locknut wasn't tight enough, but the fact that you don't have play with the cartridge out would tend to rule out the bearing.

How much play are we dealing with here? The length of the cranks does amplify the play - a millimetre of play at the spindle will be a lot more than that at the pedal, so the play may only be obvious with the cranks on. It could still be the cartridge, if that's the case.

HillRider

Shimano's Dura Ace Octalink bb was indeed an adjustable cup-and-cone design in a cartridge-like shell and required routine maintanance, unlike the Ultegra and 105 versions.

Chris Chicago

with the crank off, cartridge still installed I could visibly move it with my hand. didnt measure the actual displacement but it didnt seem right to me. maybe I f'ed up installing it.

Airburst

This was a fairly cheap square taper one, it certainly wasn't Dura-Ace....

OP, the fact that the play remains when the cartridge is in the frame with no cranks, but disappears when the cartridge is removed, would tend to suggest it's the installation of the BB that's at fault. I'm not sure quite how though...

bradtx

CC, Exchange it, a new UN54/55 will be slightly resistant to turn and have zero lateral spindal movement in my experiance.

Brad

Chris Chicago

well I reinstalled the bb, no movement. even with the crank on it's solid. kind of a mystery. hope the issue doesnt return but I'm not optimistic

onespeedbiker

Did the 2mm spacer come with the bottom bracket? If not a 2mm spacer in affect changes your BB shell width to 70mm; since the lockring has a lip around the end, it will be 2mm short of bottoming out. So even though the BB feels tight now, it may loosen up on you later. Best bet is to use a lockring without a lip https://www.universalcycles.com/shopp...3&category=347

Chris Chicago

hmm. that is a detail I had not considered. though that lipless lockring is nearly the price of the bb itself.

I think it's likely that i didnt tighten the drive side well enough the first time. bc I observed the spindle moving in relationship to the adjustable cup/lockring. ie the nds lockring wasnt shifting with the spindle. but if the problem recurs, then I may go lipless.

HillRider

If your nds cup has a lip then the 2 mm spacer probably caused the problem. BTW, there should be no need to buy a lipless nds cup new. Check around at older bike shops in their spares boxes or drawers. They should have saved the cups from replaced bottom brackets and might even give you one. The now discontinued UN-7X bottom brackets all had lipless metal nds cups.

Chris Chicago

the more I think about it, the more that makes sense. the spacer prevents the cup from fitting snug on the cartridge. but it fits snug on the frame hence the spindle moves but the cup doesnt.

onespeedbiker

Well, you could always grind the lip off yourself..

Chris Chicago

Bb went loose again after riding it. I removed the adj cup and installed a lipless one the lbs gave me. However the bb still moves. Wondering if I should remove the drive side spacer and live with it, or should I hav removed the whole bb and reinstalled it with the lipless cup, instead of just switching out the cup..

Chris Chicago

Update, looks like the adj cup lbs gave me didn't fit perfectly. Happened to have another and now the bb is tight/ snug. Hope it remains that way .