Singlespeed & Fixed Gear - bottom bracket play

i got a un72 bb used, in good condition and installed it in my new ride. it seemed fine at first, but now it has a huge amount of play going on. so much so that i can't trackstand at all anymore. it seriously feels like a full inch of play at the pedals, though i'm sure it is only a mm or so in the bb itself.

is this common? is there a way to fix it? should i just get a new one?

Can't fix it. I woudn't buy a used shimano bb. Get a new one.

do they just develop play over time?

if the pedals seem to shift independently of each other, tighten the bolts that hold the crank arms to the bottom bracket. if not, remove the crank arms, and tighten the bottom bracket.

My first assumption is that your bottom bracket is not tight enough, if you used a standard length ratchet on it, your probably didnt put enough pressure on it. You should be applying upwards of 60 lbs of pressure on the cups.

I have had this problem myself, and using a longer leverage tourqe wrench I was cappable of putting enough pressure on them and the problem dissapeared.

if the play as prior stated is independent of the bb, specifically if one crank arm moves more than the other without moving the other simultaniously, your cranks are not on tight enough and you will need to retighten your armbolts

if the two aforementioned fixes fail, you should remove your crankarms and roll the spindle, if you feel any resistance or odd"ness" or hear any noise your bb should be replaced probably.

are you sure its not just chain looseness?

do they just develop play over time?

I killed one from over tightening my chain (I think).

it's definitely not the crank arms, those are on tight. i just used huge adjustable wrench to turn the splined bb tool. may not have torqued it enough. chain isn't super tight, but there's no sag in it, so slop should be minimal. maybe i'll just try torquing it with more leverage.

My BB developed some play after a while. Turns out I had stripped the threads on the fixed cup and ended up JB welding it to the BB shell. That eventually came loose so I got my BB shell rethreaded and face and bought a new BB (Shimano something or other) and that ended up eventually stripping my BB threads and I went the JB Weld way once again. Good thing this is a conversion. can't wait to get me a new frame soon.

why do people like cartridge bb's again?

why do people like cartridge bb's again?

because they're cheap, last a long time, install and uninstall easily (esp. the plastic cup Shimanos), and need no maintenance.

The only reason most people run cup and cone is because they are attached to older Campy Pista or NJS cranks (and rightfully so). That, and people think that they're smoother, which they may be right after an overhaul, but def not after a few rainy, gritty rides.

i think i got it worked out for now. gave it some more torquing and i was surprised how much tighter i could actually go. feels pretty play free now, but we'll se after a week or so.

i think i got it worked out for now. gave it some more torquing and i was surprised how much tighter i could actually go. feels pretty play free now, but we'll se after a week or so.

I bet that was the issue, belive me, I thought it could not go any further, switched to a longer wrench and problem was solved.