Defeated by a GXP bottom bracket- Resolved

[kppolich]

Hey all,

I'm admitting defeat after a 2 hour battle with a SRAM Red GXP crank and a brand new SRAM GXP bottom bracket.

If i torque it to spec the crank doesn't spin without significant effort.

If I loosen it, then it spins but there is alot of play.

2015 Raleigh RXS SSCX with an eccentric threaded bottom bracket.

Not sure if I need a wavy washer, some spacers, check BB alignment or what but I am throwing in the towel on doing this one myself. To top it off I was working on the front brake piston and one popped out, so now I need to re-bleed that too. Looks like a trip to the LBS for this guy.

[vqdriver]

Interesting. My experience with gxp has been more or less the same as hollowtech, pretty foolproof. Initial thought is that theres something missing
Cant speak to the eccentric bb tho, i suppose that could be part of it.

[Kontact]

I can't tell if you are having problems with the BB when you install it in the bike, install the crank in the BB or tighten the belt with the eccentric.

GXP does not need or want washers. The spindle floats through the right bearing and pinches the left bearing between the left crank arm and the step on the spindle.

Another thing that confuses people is when to use the washers that go between the cups and frame. If you have those in and they shouldn't be, you'll also be unable to adjust to torque the crank without bearing problems.


If you could spell out where you are having the issue, how wide your BB shell is and any other specifics you have that would help.

[macaroon]

As above, there needs to be a gap between the drive side arm and the bearing, otherwise it'll bind.

[charliedid]

What does the BB width measure?

[polyhistoric]

My experience with the RXS is that it uses a Tandem BB shell and required a 73mm width crank spindle. My attempt to fit road crank resulted in the same binding problem. I switched to a wide axle Sram s900 crank and had to fiddle a bit with BB spacers until I got it right. This is a downfall of the RXS - the stock joytech crank fit just fine, but I was just being fussy abut the "upgrade"

[chiasticon]

Originally Posted by vqdriver

Interesting. My experience with gxp has been more or less the same as hollowtech, pretty foolproof. Initial thought is that theres something missing
Cant speak to the eccentric bb tho, i suppose that could be part of it.

this. GXP works great with the standard BB, can be problematic with others. one thing I've found is that if the BB's adapter is just a little sleeve on the NDS to convert it from Shimano to GXP spindle, that's usually not ideal. Chris King GXP BB has, for example, exhibited the exact same behavior for me that you describe, on multiple bikes, and it uses this little sleeve dealie. if you remove their recommended washer, there's no play and it spins well, but you didn't technically install it correctly then, which is frustrating with a $150 BB...

not sure if that helps or not as I don't have experience with your particular BB. but perhaps you could try something similar...?

[charliedid]

Originally Posted by polyhistoric

My experience with the RXS is that it uses a Tandem BB shell and required a 73mm width crank spindle. My attempt to fit road crank resulted in the same binding problem. I switched to a wide axle Sram s900 crank and had to fiddle a bit with BB spacers until I got it right. This is a downfall of the RXS - the stock joytech crank fit just fine, but I was just being fussy abut the "upgrade"

My guess as well.

[kgreene10]

One time, I misplaced the NDS bearing cover (in more recent GXPs it’s cut to match the crank spindle threads) and had the same problem because I was obviously torquing the NDS crank arm right onto the bearing.

I also once forgot to remove the wavy water from under the DS bearing cover that typically remains on the crank when you remove from another bike.

Perhaps sometimes I’m not the most attentive mechanic.

[kppolich]

Originally Posted by Kontact

I can't tell if you are having problems with the BB when you install it in the bike, install the crank in the BB or tighten the belt with the eccentric.

GXP does not need or want washers. The spindle floats through the right bearing and pinches the left bearing between the left crank arm and the step on the spindle.

Another thing that confuses people is when to use the washers that go between the cups and frame. If you have those in and they shouldn't be, you'll also be unable to adjust to torque the crank without bearing problems.
No washers between the frame and cups


If you could spell out where you are having the issue, how wide your BB shell is and any other specifics you have that would help.

stock crank on stock BB spun just fine, it was 24mm and not gxp. Stock shell is 68, but with the Eccentric BB its wider with the cups, say 73mm. With no spacers installed there is considerable drag, most likely needing a widde spindle

[kppolich]

Originally Posted by charliedid

My guess as well.

was the wide spindle a BB30?

[cmbicycles]

Have you measured the shell width w/o cups? Once you know that measurement you are in a better place to figure out the problem. If it is 73mm, a standard road crank will not work as they are designed to fit a narrower width BB shell.

73mm is typically a mtn bike shell width, and the crank spindles are longer to fit properly whether GXP, Hollowtech 2, or megaExo, etc (all of which basically have a 24mm spindle, gxp just steps down at the end). Assuming you have a 73mm shell as was posted earlier, the stock cranks were designed for the wider BB shell, while the Red cranks were designed for a 68mm shell. The BB will screw in fine either way, but if that is the case (73mm BB shell), then the cranks aren't designed to work with a wider shell, so you'd need something designed with a longer spindle to fit that width BB shell.

[Mike Bryant]

My experience with a SRAM Force crankset on a 68mm shell with gxp bottom bracket and no spacers left a 3mm gap on the DS. Adding one spacer put the spindle in a bind. Sanded a bit of the spacer width down and installed on DS and all works (and looks) swell.


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[DRietz]

Originally Posted by Mike Bryant

My experience with a SRAM Force crankset on a 68mm shell with gxp bottom bracket and no spacers left a 3mm gap on the DS. Adding one spacer put the spindle in a bind. Sanded a bit of the spacer width down and installed on DS and all works (and looks) swell.


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That gap is supposed to be there.

[Mike Bryant]

Originally Posted by DRietz

That gap is supposed to be there.

Something changed from a previous gxp bottom bracket I wore out to a new one that had spacers for 68mm or 73mm use. Sure it would have worked fine with the gap, but I didn’t like the look. Maybe the cups were sized for the Italian standard 70mm, but the DS cup was reverse threaded for BSA. Don’t know.


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