(You might need the sound up) I had a pretty catastrophic chainring strike on a small stump that broke the old ring. I needed shorter cranks anyway so I replaced the whole crankset. Both the old and new crankset are Shimano XT FC-M8120, Hollowtech II.
Everything is greased, tightened, and torqued appropriately (as far as I can tell), but there's resistance when I spin the crank, particularly on one side (meaning I can feel it more during a particular point in the revolution). As you can see, it stops pretty quick when I give it a hard spin.
This was a pretty straightforward swap so I'm scratching my head on what's different. Perhaps something happened to the bottom bracket when I hit the stump? Visually, everything looked OK when I had the crankset out.
(and yes I know the bike is filthy and the chain guide is broke; this happened deep in a ride and I'm trying to get the main repair done first)
Installed this new crankset and it's oddly and unevenly tight
byu/striker7 inbikewrench
by striker7
3 Comments
How tight did you make the pre-load cap? Back it off a bit to where there’s no lateral play but not as tight as you currently have it and then tighten the pinch bolts. Report back.
I can’t say it’s the case for you but I once hit my cranks hard enough to wreck a bb bearing. It just didn’t spin freely after that and had to be replaced.
Take the crank out and spin the bearings with your fingers; see if there’s a difference.
next time give the manufacturer manuals a check, it’d help mitigate with first time issues especially if you’re unfamiliar with the installation process.
ultimately that’s why they provide service manuals, to ensure correct first time installation.
https://preview.redd.it/93jtuuqa4msg1.png?width=1080&format=png&auto=webp&s=6a395219ea3f93b709a70633062b5df69bc928fd
[https://si.shimano.com/en/](https://si.shimano.com/en/)
[https://si.shimano.com/en/dm/MAFC002/Crank](https://si.shimano.com/en/dm/MAFC002/Crank)