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Discussion Starter · #1 ·
Hello again! Man, it's been a L O N G while since I've posted up here....

Anyway, my most recent problem began yesterday. I was installing the new shimano XTR BB and cranks on my Giant NRS carbon. The cups went in smoothly, no over-torquing issues at all, it seemed. However, as soon as the cranks went in I noticed a rather big issue.

The cranks will not 'free wheel' when pedaled in reverse, and seem to drag when pedaled forward.

You know when you have your bike up on your "ultimate bike stand" and you toss the crank arm backwards and it'll usually do 4-5 revolutions before it stops... mine stops instantly. Also the same applies when tossed forward, but when chained up to the rear wheel it does a few revolutions (I suspect the mass of the tire is carrying it around).

Basically there appears to be much more drag than there should be. The cranks and BB were NEW.

Upon close inspection of the BB I've found that the right hand side of the plastic sleeve that travels across the BB shell is not perfectly round, it's oval. It appears to have been manufactured this way because I don't see any creases that would indicate it got crushed on installation and is now out of spec. The ovaling is very slight, and I think contacts the crank arm cross member in two spots (as any oval would contact a circle in two spots..). Plus the outboard bearings never really spun like a conventional BB bearing when I 'finger tested' them before installation.

Did I just get a bad BB out of the box?
 

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You're fine. Outboard bottom brackets cause an extreme amount of resistance ewhen they're new due to the size of the bearing. With a few weeks use it will eventually smooth out to normal resistance. If you think the Shimano ones drag a lot you should try Race Face. They stop dead as soon as you release the crank when trying to spin it. The important thing is to feel if the crank spins evenly and smoothly.
 

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Discussion Starter · #4 ·
Hecubus said:
You're fine. Outboard bottom brackets cause an extreme amount of resistance ewhen they're new due to the size of the bearing.
Thanks so much for your help guys. I really appreciate it. I was going bonkers thinking I had just ruined a $300 set of cranks. Or at best, a $70 BB.

I guess it's just my unfamiliarity with the outboard bearing style BB's. Those Internal bearing BB's spin a lot easier right out of the box.

In response to the smoothness check... yes they do spin smoothly.

Whew!

I guess I just need to put a few miles on them now.

Thanks again

*back to lurker mode*
 

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Doc said:
Thanks so much for your help guys. I really appreciate it. I was going bonkers thinking I had just ruined a $300 set of cranks. Or at best, a $70 BB.

I guess it's just my unfamiliarity with the outboard bearing style BB's. Those Internal bearing BB's spin a lot easier right out of the box.

In response to the smoothness check... yes they do spin smoothly.

Whew!

I guess I just need to put a few miles on them now.

Thanks again

*back to lurker mode*
I just installed them and am having the same issue....how long does it take for them to loosen up? i was afraid i was over tightening them at first, but the resistance is the same if cups are not tightened
 

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Same thing here

I just finished installing the XTR crankset in my scalpel, and the same thing happens. I took it out and put back but still,
i was going to ask the same question, I think i just going to have to wait, and see what happens..

thanks for the replys
 
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