I recently replaced my second Sram/Truvativ GXP bottom bracket because of play I could feel in the cranks. The first one was replaced under warranty. The bike shop couldn't figure out where the play was coming from. They could feel and see the play in the cranks with everything assembled. With the cranks disassembled, the bearings felt tight and smooth. They put it back together and the play was back again. They didn't do any further investigation and replaced the BB. Suddenly there was no more play! But why?
A couple weeks ago I was riding a different bike with the same Truvativ GXP BB and felt that telltale play in the cranks again. This bike is out of warranty so I bought a new Truvativ GXP BB figuring it was the same issue and would require the same solution. Again, there was play in the cranks when assembled. There was no play in the bearings and the bearings felt fine when the cranks were disassembled. Put it all together with new grease and torque it down and there's play again. WTF?
It turns out there's a plastic spacer on the drive side between the crank spindle and the bearing. It's there to take up the space between the two. So there's this piece of plastic with huge compressive loads on it sitting between two pieces of steel! Who's bright idea was that? Plastic, even really hard plastic, is very weak compared to steel. The plastic deforms relatively easily and eventually starts walking around causing even more wear. Eventually you feel it as play in the cranks.
Is there an alternative to the Sram/Truvativ GXP bottom bracket that doesn't use a plastic spacer between the crank spindle and the drive-side bearing?
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