Sram XX GXP BB Spacers - 73mm shell

thejonf

Hi,
Just transferred my xx groupset onto my new trek remedy, ally frame with 73mm bb shell. Set up is 26/39 chainset, truvativ xguide iscg mounts, std gxp bb. The SRAM instructions are pretty clear that spacers are only required on 68mm shell, but without spacers on my 73mm shell the plastic cylinder in the BB gets crushed.... Unfortunately i only realised this when i tried inserting the crankspindle.
Tried it with spacer either side, was ok without the chain guide but with the guide fitted i couldn't tightenthe crank as the inner ring catches (scrapes) agains the iscg plate on the chain guide. The only way it seems to work is to put 2x spacers on the drive side bb cup (2x 2.5mm). Ayone else had an issue?
Cheers
Jono

nicklouse

73mm uses no spacers. And if you use a chain guide it has to be a slim one. So as to not let h bearings contact the drive side crank arm.

If you have crushed the dirt shield you installed incorrectly.

thejonf

Not sure what i've done wrong for the dirt shield to be crushed, but assuming that's down to me, i don't think that helps the chain guide issue. The x-guide is supposedly developed especially for SRAM 2x10 setups, yet the only way it seems to work on my bike is with the 2 spacers on the drive side, which appears to be the only way of moving the driveside outwards and stopping the inner ring grinding on the plate. This in turn doesn't help the chain line much. Looks like i'll be taking it apart again tomorrow.
Thanks

thejonf

Is there a difference between road and mtb BB widths? The BB came with both road and mtb instructions so I presume not....? Having held up the BB to frame with the dirt shield fully fitted into each cup there is still a gap between cup and shell equiavlent to 2spacers, hence the crushing issue of the shield. Are Mtb bearing cups thicker than road ones?

delcol

i had this issue when i was trying to fit my stinger device to my chromag frame.

i got a truvativ noir carbon crank, but decided to run it with a converted hope bb,, when i came to fit the chain device it was grinding on the small chainring, my chromag is a 73mm shell and the truvativ instructions say not to use a spacer, but i am running mine with a hope bb and hope instructions say to use one spacer with a 73mm shell, i did contact hope who told me to use one spacer driveside with my noir crank.. even with one spacer the small ring grinds on the stingers plate..
in the end i opted not to run the stinger as i could not get it to fit with out adding another spacer..
mine is a 2x9 set up..

thejonf

Right, just taken it all off, measured and refitted. Thought i'd post in case anyone else has the problem.
Problem with the plastic sleeve is that it did not and will not seat in the non-drive side cup.
For the correct chain line with the stepped part of the spindle into the nds cup, no spacer is required on the nds. Without spacers on the drive side however, there is a 5mm gap between the ds crank and the ds cup. This doesn't affect tightening the cranks up, but there is potential for the seal to pop out on the ds. Therefore, with my setup which is 73mm bb shell, and 2010 XX crank, requires 5mm of spacers either between the ds cup and bb shell (my solution), or between the ds cup and ds crank arm i.e. on the spindle. This still allows the step in the spindle to butt up to the nds cup as intended, with the same protusion of the splined section on the nds. This is all unrelated to the chain guide fitment, just getting the cranks to fit properly. WRT the chain guide, With no spacer on the nds, the chainset is correctly aligned and does not rub on the ISCG mounted guide. Obviously when i had a spacer on the nds, this effectively moved the chainrings inboard, causing the rub. Hope that makes senes,can post some pics if anyone would find them useful.