This bike was recently bought from marketplace. All worked great till I lost both the end cap, as well as the whole arm during a ride.
After closer inspection, which should have been done before my first ride after I bought it, the left arm doesn’t fit on all the way. So I’ve basically been riding on a death machine for the past few months.
Here are the relevant details for the bb/crankset:
– SM-BB52 mountain bottom bracket
– Shimano Sora 2×9 crankset (175 FC-R3000/3030)
– 68mm bottom bracket shell
Should I order a new left arm, rebuild the current bb and remove spacers, or switch to shimano’s recommend bottom brackets (RS501/500). Thanks!
by Joch03
5 Comments
You need a road BB
Switch to the correct [bottom bracket](https://i.imgur.com/FhNwTTY.png) and get a new crank arm.
The crank has had the splines machined off, you need a new crank arm – this is obvious in image 4.
You can try fitting the crank on backward to clean out the damaged sections.
A new BB WILL NOT fix this issue.
The end cap is to preload the bearings so nothing structural and you can buy replacements for pretty cheap.
For reference… mountain bike BBs are 5mm longer, however you can clearly see you’ve got all of the spindle sticking out so I think the person that fitted this omitted the plastic spacer inside the frame/ swapped it for the original road one? Your total length should be 68mm for a road crank, if your current one is longer than remove those two black plastic spacers and refit.
See those spacers in between the frame and the BB cups? Those are not supposed to be there for a 68mm BB shell.
Remove/replace the BB, take those plastic spacers out, get a new crankset (left crank arm is trashed), install everything to spec.
You need a road BB and a new left hand crank arm.