Very much a rookie when it comes to working on bikes and especially not familiar with dealing with the crankset/BB- I’m assuming I am missing some sort of end cap bolt type thing since the inside of the BB looks threaded?
Are these pretty universal or is this the sort of situation where I need to find this specific brand’s ~special fitting~ end cap thing or whatever?
Also is anyone able to tell me what type of bottom bracket this is? I know ‘square taper’ is a thing that exists but guessing this circular looking BB is not that…
The cranks were on the bike when I bought it second hand and I never really noticed the crank loosening until I was on my commute home from work like 7 miles from home and it popped right off lol
by less_than_nick
5 Comments
Yes you need a preload cap see the thread on the inside of the spindle?
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This looks like a generic copy of a Shimano style 24mm (hollowtech II) crankset. They’re sold on Amazon, Temu, etc.
You’re missing the end caps BUT those won’t really solve your issue. Those are used to put some bearing pre-load on the bottom bracket and don’t really add to crank arm retention. It’s a similar function to the star nut and bolt in a threadless headset. Once the thing is assembled it isn’t really doing anything.
What’s retaining the crankarm is are those pinch bolts causing the splines on the crankarm to constrict on the ones on the spindle. If those were properly tightened and have not backed off, I’d wager that the splines on the arm have gotten wallowed out and aren’t really engaging the way they should anymore. You get some vibration going and the whole thing precessions it’s way loose.
If you like the bike, it might be time to find an affordable Shimano crankset.
you need to measure the thread diameters of the axle. and buy a preload cap. normally its 18mm or 20mm.
and probably the bolts on the left crank is not tighten enough.
Bike shop might have a fixing bolt for you