Crank and BB compatibility.

qooqiiu

I currently have the shimano XT m-780 triple crankset and a press fit BB 30.

I want to try a 2x10 set up so bought an XTR m-985 double crank but it is about 6mm longer so doesnt fit my BB.

I thought these were a uniform length? The crank came with the old screw type BB but obviously that is not suitable for a push fit frame.

What do i need to do?

njee20

Should work fine, something odd going on. Have you measured it as longer, or do you have more axle sticking out of the LH bearing?

Shimano don't do PF30, so it'll have some sort of adapter in there - which one?

qooqiiu

I haven't actually installed it yet as the bike is at my dad's place. Can't see how it can be ok if it's longer. It's surely going to have lateral movement.

njee20

How are you ascertaining it's longer? Have you just measured the axle? Not got any spacers? I know my M985s had spacers on the axle, but the frame had a BB90 shell, which is only a 68mm equivalent, the same would have been needed on the M780.

Like I say, Shimano don't do different axle widths, so there's no inherent reason for it not to work.

nicklouse

qooqiiu wrote:

I currently have the shimano XT m-780 triple crankset and a press fit BB 30.

I want to try a 2x10 set up so bought an XTR m-985 double crank but it is about 6mm longer so doesnt fit my BB.

I thought these were a uniform length? The crank came with the old screw type BB but obviously that is not suitable for a push fit frame.

What do i need to do?

If the XT is being used then the XTR will work if they are the same fitting or the same design.


You might have to give some part numbers.

coulddobetter

Got confused myself recently fitting fsa bracket . Rated for 68 /73 mm shell . Then realised spacer washers ensured correct fit.

qooqiiu

Ok so I've fitted the cranks and my consern now is that the crank arms are far too close to the frame. In fact the drive side crank arm rubs slightly on the chain stay protector.

Is this dangerous?

trigger118

Are the cranks the same length as your old ones?

qooqiiu

Yes they are 175 same as the ones that they replaced.

They say on the box that they have a narrow Q factor crank arm. They are just too close for my liking.

nicklouse

Narrower Q factor means pedals closer to the BB.

njee20

Which is why they're nearly hitting the stays. That's not a problem, that's design. Narrow q-factor is designed for skinny XC frames with more heel clearance.

Bigger question is why are you running XTR Race cranks and SLR wheels with mahoosive flat pedals!?

qooqiiu

Haha. I feel like I'm being told off now. I don't like the idea of being clipped in that's all. In hindsight if i hadofbeen clipped in I may not of done so much damage the last time I rode...

I'm afraid my paranoia and OCD will struggle to relax with this setup. I've emailed CUBE to ask them if the crank is compatible/OK with this frame.

nicklouse

qooqiiu wrote:

Haha. I feel like I'm being told off now. I don't like the idea of being clipped in that's all. In hindsight if i hadofbeen clipped in I may not of done so much damage the last time I rode...

I'm afraid my paranoia and OCD will struggle to relax with this setup. I've emailed CUBE to ask them if the crank is compatible/OK with this frame.

It fits. It clears the frame. So they will say yes.

if it is suitable for YOU is upto you.

njee20

I've seen less clearance, but you may find they rub occasionally.

Particularly with flats the fact they're narrow q-factor won't make much difference - you can move your feet further out. It's quite a roadie thing to worry about, but narrower is generally reckoned to be better - more akin to a natural stance.

The Rookie

So instead of being wider, they are narrower (in a different place), loving this thread!

njee20

I must say I'm confused by the original hysterics about them not fitting because they were too wide...