Inpd

Hi,

So my BB developed a little bit of play (barely a few mm) but I can definitely feel it when the right hand crank is at the 12 o'clock position.

It's definitely play in the BB not the pedals since when I grab the crank arms I can feel some outwards movement when the cranks are at the above position.

I was planning on doing a nice 60mile ride today or tomorrow. Is it safe to do so? I know the crank won't explode but I'm thinking does this type of thing mean it will shortly seize?

For what its worth I have a "Semi Cartridge Bearing ST" BB.

Thanks.

69chevy

Check the crank arm bolt tension. It's possible the crank arm has come loose from it's square taper fit.

It's about a 10 minute job and a $20 part to replace the BB. If it is truly shot, it's a simple, cheap fix.

TrojanHorse

Does it just move laterally or does it rock? Try 69Chevy's advice first. While you're at it, you may as well remove the crank and check the BB, regrease it etc.

Inpd

It doesn't have crank arm tension bolts.

I know its an easy job but I'd have to leave it at the shop over the weekend. My question is should I go for a 60 mile ride before I get it replaced?

trailangel

No. Don't be foolish.

WalksOn2Wheels

I wouldn't. If it's already loose, it could just get more loose. Best case scenario, you start getting ghost shifts on the front because it's moving enough to push the chain off the ring. Slightly worse case: you drop the chain repeatedly. Worst case: Your arm comes completely off and you are stranded.

If it's just loose, any competent shop should be able to sort it out in less than 5 minutes. Seek out a shop today, do 60 miles tomorrow.

69chevy

Not tension bolts. The crank arms bolt onto the square tapered spindles. Check how tight these bolts are. I used the word tension to describe how tight these bolts are.

bt

go for it

WalksOn2Wheels

A picture would help best. Even if you needed a replacement BB, it's still maybe 15 minutes max if they have the part on hand. Call ahead if you know exactly what you need.

pressed001

Roger that. Better to spend your day trying to fix it than go on your ride, have your crank fall off, get caught in your rear wheel sending you head over heels whilst going 40mph downhill and then spending the next two weeks in the hospital.

69chevy

Finding a good picture was a little harder than I thought...

The ST BB essentially presses the crank arm onto a square spindle. If the pictured bolt is loose, it is possible the press fit has come loose.

If the bolt pictured is not tight, tighten it. If that fixes it, great. If not, I wouldn't ride it.

TobinH

Assuming the crank-arm fixing bolt is tight, ride it. Replace at your leisure. The axle is stepped, nothing can fall apart until the bearing races literally separate. That would take a pretty extreme event, I've never seen it on a bicycle.

Inpd

Great. Thanks TobinH. Great advice.

I'm now stuck 25 miles from home with my cranks seized pushing my bike back. Some homeless guy took my cycling shoes and old ladies are calling me a tosser ...

Only kidding. I took the advice upstream and tightened the bolts. It didn't stop the play in the cranks (its still there if I really push hard) but I can't feel anything like I did before when I ride. Maybe this is what it was always like? However, my other bikes don't have any play in the cranks no matter how hard I apply lateral pressure to the cranks.

MagicHour

Possible the bottom bracket is loose? When you apply lateral pressure do you see any movement where bottom bracket meets the bottom bracket shell of frame? If so riding with this loose can toast your frame-just putting it out there. To fix you'd need to pull cranks, tighten BB (I'd regrease too), reinstall cranks.

Inpd

Just so I understand this. The play I refer to is only present when I apply quite a bit of lateral pressure. If I can't feel it whilst riding is it an issue?

Also, is it dangerous to over tighten the cranks?


Thanks again.

MagicHour

On a square taper crank it is possible to overtighten. What could happen is that by over torquing crank arm and pushing it a little further onto the spindle than it should go, could widen over time and with subsequent reinstalls you might find that the crank arms won't stay tightened. It takes a pretty good amount of torque to do this though.

Might be good to get bike checked out by a shop just to make sure bottom bracket is properly torqued in Etc.
just wanted to point out that if BB is loose and causing the play you feel, riding on it could strip the threads potentially ruining your frame(presuming it's a threaded BB-with square taper cranks I'm pretty sure it is)

WalksOn2Wheels

Color me curious. I want to know what happened. Did you get it sorted? What was the issue?

Inpd

Happy to indulge your curiosity!

I tightened the cranked arms as suggested. This resulted in the vibrations I felt going away. There is still some lateral play in both cranks but it only happens occasionally. As other suggested I disengaged the chain and rotated the cranks and it felt quite smooth so I'm leaving it alone for the time being.

rpenmanparker 

If not sealed, cup and race BB, one of the cups may hsve unscrewed slightly. Or if a sealed cartridge BB, there may be some wear inside the cartridge. I'd get it looked at.

Inpd

A slight click developed on the drive side which I could feel through my shoe only. So I pulled the bottom bracket and it was fine. The cups were very very easy to remove so I tightended them up and click is gone!

dalava

while you are at it, just replace the old BB with the newer style cups and get a new crankset