Did you look to see if there was a spacer on the GXP BB? GXP is GXP. I've never had any problems that aren't spacer related. I hope this advice does not frustrate you further and appologise in advance if it does.
Except when it isn't...
@hippy started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
Did you look to see if there was a spacer on the GXP BB?
GXP is GXP. I've never had any problems that aren't spacer related.
I hope this advice does not frustrate you further and appologise in advance if it does.