Hollowtech crank preload bolt - essential?

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Moodyman

Legendary Member
The one on the left crank. It fell off somewhere.

I understand it performs no role in keeping the left crank attached to the spindle. Are there any possible side effects of not replacing it?

I intend to apply gaffa tape over the hole to keep the dirt out.

I bought a replacement preload cap, but I previously replaced the genuine Shimano crank arm with an after market non-Shimano arm which is a little wider than Shimano. So, the Shimano preload cap won't reach the spindle thread now.
 

BianchiVirgin

Über Member
Location
Norn Iron
It's main function is to preload the BB bearing before you tighten up the crank. I guess, in theory, if it fell off after that, nothing should change and if you cover the hole short-term so much the better. Given that it is a crappy piece of plastic, like so much of the Shimano range, it doesn't really have a hard life.
 
U

User6179

Guest
I take it off after the crank is tightened up, got my chain jammed between small ring and frame once and had to remove the crank leg to free it but didn't have the tool to remove the pre load cap.
Mate who has the same bike had the same thing happen to him as well.
 
Treat it like your stem and bars, but horizontal. Once the cranks are preloaded, and the crank arm bolts are torqued up, you can do what you like with the plastic centre preloading bolt, I keep them in situ, because then you can’t lose it / forget to bring it on a ride.
 
Are there any possible side effects of not replacing it? Just a nagging doubt you should replace it.
Only if your cranks come loose / fall off on a ride, you’ll be able to get it home, by just sticking the crank arm back on and tightening the bolts with a multi tool, but you run the risk of the arm coming off again, if you haven’t got the plastic centre bolt, to preload the system.
 
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