Bat56

I just installed my first GXP bottom bracket and some Stylo Oct cranks. I have a 68mm bb shell so I used one spacer on each side. I greased all the parts as indicated in the directions and I used a Park BBT-19 with a torque wrench.

The problem is that this is an old bike and I am not sure the bb shell is faced well or within the required width range (as I understand things, the bb is supposed to be 68mm +/- .25mm).

I have been wrenching old school internal bottom brackets for 20+ years and I know what they feel like during installation, I know how tight to get the crank bolts, I can feel problem bumps and clicks when I pedal. With these GXP cranks I feel like I have no way to know if I did this right. The NDS fixing bolt is tight and the cranks did not bind up - is that all there is to it? I am concerned that if my bb shell is a bit wide I can crank that bolt hard and not get the spindle perfectly supporting that NDS bearing. I have read that these things need to be adjusted properly or the bearings get overloaded and fail.

Am I making a big deal out of this? Is this set-up not that complicated?

dsaul

GXP setup is not complicated. It is very tolerant of BB width variance, because it doesn't depend on the width for proper bearing pre-load like some of the other systems. GXP just captures the non drive bearing between the shoulder on the spindle and the NDS crank arm. This prevents the spindle from moving side to side and the drive side always has space between the bearing cup and the crank arm to allow for BB width differences. Just don't forget to put in the dust cover/spacer with the spline pattern in the center before mounting the NDS arm.

As far as facing the BB, tighten the cups until they just contact the shell and look for any obvious spacing around the shell. As long as it looks like there are no really high spots or large gaps between the shell and the cups, you should be fine. If you don't feel any binding and the spindle slid through without any trouble, it's probably fine.

reptilezs

do the crank arms move laterally when you apply force with your hands? i will bet the noise is not the bb

Bat56

Thanks for the info. Regarding noise - there is no noise and no play. I mentioned that in my OP to say that I can diagnose that stuff with internal bottom brackets but have no sense for potential symptoms with these outboard bearings. I'm gonna ride like its right. I'll check back in a few months. A bit longer if I end up in the hospital.

Kimmo

It occurs to me that plastic spacers might make it slightly more tolerant of poor facing...

With a GXP you should only run into trouble if your BB shell is too wide; then when you crank down on the fixing bolt you'd be applying catastrophic amounts of preload, which these don't use.

I suppose when the bearings get a bit worn and sloppy, you could apply some lateral preload with an o-ring around the spindle between the spider and DS cup.

Bat56

I have read a bunch about this design and I have looked at a lot of diagrams. I am reassured that I did the installation correctly but I am concerned that there is nothing to hold the drive side bearing seal in place. As Kimmo alludes above, it seems like an o-ring on the spindle between the crank and the drive side bearing seal would help keep the seal in place. As it is the seal can work its way out and this has been noticed and complained of elsewhere.

reptilezs

with the new style gxp bb the seal does not walk out anymore

dsaul

Like reptilezs said, they fixed that with the newer versions by adding a lip on the seal so it clips onto the bearing.