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BB/crank question


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Building up my hard tail. Spec says a 68/73mm BB. 

Check. 

BB says to put one spacer on the drive side, just like on my singlespeed (same frame).

but when I put the crank (SRAM) on the bike, it has a pretty big gap. Do I add extra spacers (which means the cup in the center won’t fit) or do I have to get a different crank?

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No, leave the gap. On SRAM GXP cranks, the ID of the non-drive side bearing is smaller because a ledge on the spindle hits the inside of the bearing to form a hard stop. That's why Shimano and RaceFace cranks can use the same BB but GXP is totally different.

 

The extra space on the drive side of a GXP BB allows for a bash guard, BB mounted FD, etc.

 

SRAM_SHimmySpindle.png

Edited by mack_turtle
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I had excellent GXP experience over 7 years of use and plenty of creek crossings and rainy riding (on the road).  I had to replace them when they started showing a bit of play after 8k miles.  Interestingly, I am shocked at the stark difference in the cheapest shimano BB vs going up a couple of steps.   I had a brand new cheap Shimano BB fully lock up after RHR24 this past year (definitely gruesome conditions so I didn't take it as a big deal), then replaced it with a better one for the 12 hours of warda (equally gruesome conditions).  When it came time to service my bike, I fully expected to have to replace it, but it was fine.  I was told the seals are better on the higher level BBs.  I'm not sure what SRAM does on their stuff.

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I have the spacers, if I add 2 spacers to the ND side it would probably fit. But I am thinking a GXP BB might be a more logical solution. 

Long term I will probably swap out the cranks but I am trying to get this bike up and running right now. $300 worth of parts are showing up today (dropper and then some) so digging out another $110 on cranks is not in the cards for me today. 

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9 hours ago, mack_turtle said:

GXP bottom brackets are pretty cheap, but IME the bearings shit the bed if you get them wet AT ALL. I would ditch the SRAM cranks for an Aeffect set. I bought mine for $110 online and found chainrings for as little as $15. 

I replaced so many GXP bearings on my old hardtail...  I think in 2 years I replaced the whole BB once and one side individually another 2-3 times.  

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I have a GXP BB listed in the Pay it Forward thread. You are welcome to it if you want to give it a try. I was just about to take it over to Yellow Bike because I can’t seem to give the damn thing away. It came in a box of parts, but all my cranks are Shimano.


Sent from my iPhone using Tapatalk

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Regarding the spacers... Are they suppose to fit flush with the crank spindle, or is it normal for the to be a little space?

Also, I noticed on a couple of my spacers that the internal circle has some groves cut into it... Does this mean that they are for a specific type spindle/crank that has notches that line up with these groves?

 

Edited by RidingAgain
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56 minutes ago, AustinBike said:

68mm shell and 73mm BB. Should have required 2 spacers, but with 2 installed the crank would not turn. With none it was loose and shifted from side to side. With one installed it was mama bear.

I had to test select from all my spacers to find the thinnest ones for my last BB installation (Shimano) on my hardtail.

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