[DonQuix78]

Hi,

After much advice received here on mtbr I've finally gotten round to converting my 3x10 to a 2x10+bash. The chainring replacement went fine, replacing SLX 24/32/42 with Blackspire 26/38 and a Hope bash... but when I try to replace the drive side crank it noticeably grinds when rotated. The chainrings fitted perfectly with the existing bolts so there's no protruding parts anywhere, it seems to be the spindle against the BB that is making the noise.
The BB was perfectly smooth before I removed the crank and the bike is only 6 months old so it can't be knackered already. Is there a knack to re-fitting the crank that I'm missing? It's baffling me.

Many thanks in advance.

M552 crank
Shimano external BB

 

[moonraker]

I would suspect, since you moved to a bigger small chainring, that it's now rubbing the front derailleur.

 

[time229er]

just about has to be a BB ditty...can't imagine that the cranks are the problem. It really sounds like an alignment issue with the spindle and BB...I can only suggest checking to see that BB is tight. If it is, then I guess I would get a new BB. A XT can be got for less than $40. Do you have the correct tool to remove/install? I have a Park BBT-9...it also works for center lock rotor R&R...

 

[DonQuix78]

Hi, and thanks for your quick replies.

It's definitely not the FD, it's coming from the crank/BB. I have the right tools for crank and BB removal, and I've removed the crank many times before on other bikes without a problem. It's bizarre. As I say, the crank was turning silently and smoothly before I removed it to change the chainrings. I'm absolutely baffled. :\

 

[DonQuix78]

That said, my other bikes ran Truvativ/SRAM cranks and BBs.

 

[time229er]

well then, the BB is 'bout all that's left...and it does still "grind" with the chain off?

just gotta ask though, you are familiar with setting the preload on the non-drive side...just pull the crank up snug and then tighten the pinch bolts

 

[DonQuix78]

Yeah, I've preloaded the bearings with the preload cap, tightened the pinch bolts to the correct torque, everything. I removed the chain before I started as I'm going to have to shorten it anyway now I'm running 2x10. It's a mystery.

It looks like I may have to bite the bullet and replace the BB that I'm 99.9% sure is perfectly fine. Mmmmmm. The mystery deepens.

Thanks for your input though, guys. At least I'm now quite certain that I've done everything as I should and that's it's not just me missing something obvious.

 

[time229er]

good luck...let us know

 

[thomllama]

take the cranks off and check the BB with your finger.. could very easily gotten a bit of dirt or grime in around it and now it grinds against the cranks... if they spin fine without the cranks on.. slowly assemble and check the spins with each piece.. when it starts to grind/click you know the last item is the issue..

 

[DonQuix78]

take the cranks off and check the BB with your finger.. could very easily gotten a bit of dirt or grime in around it and now it grinds against the cranks... if they spin fine without the cranks on.. slowly assemble and check the spins with each piece.. when it starts to grind/click you know the last item is the issue..

The man was right. Even though I carried out all of the work indoors and in a clean environment, a TINY piece of grit had somehow made its way into the bearing cup. I had to clean the whole thing out with a q-tip to find it, but that was the culprit. Mystery solved!

Thanks for all the help, guys. Much appreciated.

 

[thomllama]

The man was right. Even though I carried out all of the work indoors and in a clean environment, a TINY piece of grit had somehow made its way into the bearing cup. I had to clean the whole thing out with a q-tip to find it, but that was the culprit. Mystery solved!

Thanks for all the help, guys. Much appreciated.

ya,.. thing is most people clean the parts after disassembly where you really need to clean everything before and during, especially things like the cranks that get a lot of crud during normal ride conditions. clean the WHOLE bike before.. crud can fall down from under the seat, cables.. bla bla bla from the jiggling of working on the bike.