Bicycle Mechanics - GXP Bottom Bracket Seal drag - what should I expect?

Bikeforums.net is a forum about nothing but bikes. Our community can help you find information about hard-to-find and localized information like bicycle tours, specialties like where in your area to have your recumbent bike serviced, or what are the best bicycle tires and seats for the activities you use your bike for.



PDA
tjspahr
07-10-10, 01:38 PM
I just installed a crankset that utilizes a GXP bottom bracket, which is new. How stiff should I expect crank rotation to be? At about 250 inch pounds of torque, a fair good spin by hand gets just over 1 revolution. Does that seem to be pretty typical, and from experience, about how long will it take the bearing seals to loosen up a bit?

Thanks,

Tom

reptilezs
07-10-10, 01:51 PM
the left cranks needs to be torque to atleast 35 ft lb or 420in lb. break in depends on riding conditions
tjspahr
07-10-10, 03:46 PM
At that torque there is substantially more drag. It is extremely noticeable by hand torqued that high. I know I'm under the torque spec, but when you say at least 420in/lbs, I thought max torque was 420...

reptilezs
07-10-10, 04:45 PM
what is the exact model crank and how are the bb spacers setup? if any. bb shell width? if you ride the bike around with the crank torqued to 250 in lb it will surely strip out and become damaged
tjspahr
07-10-10, 08:11 PM
Reptilezs,

Thanks for all the info...I ended up doing what I should have done to begin with, and pulled it apart to start over. When I pulled the crankarm/spindle assembly, the bearing seal was "attached" to the inside of the crank on the spindle. I'm assuming this was keeping enough of the spindle from going through the shell that the seal wasn't sitting against the lip on the left side of the spindle and I couldn't set the load correctly. Reinstalled the seal, put the crank on, torqued to 420 ft/lbs with no issue, and spins like it should.

Again, thanks for the help!
wheelgrabber
07-10-10, 10:41 PM
The directions recommend taking them apart and regreasing several times until they go together correctly.