SRAM GXP bottom bracket instructions - odd washer/spacer
I built up a bike with SRAM Force recently, and had trouble with the bottom bracket/crank instructions.
FIrstly the BB and the crankset both had similar looking instructions, but in fact they were not the same!
After some research, I concluded that it was the crankset instructions that were applicable.
These are available online here ( 4MB )
http://www.sram.com/_media/techdocs/95-6115-007-000%20Rev%20A%20-%20Road%20Cranksets.pdf
but here is the relevant bit
SRAM GXP bottom bracket instructions by geebee22, on Flickr
The bottom bracket came with two spacers/washers. The instructions appear to show one of these inserted outside the bearing on the non-drive side ( the black ring in the picture above ).
The problem with this washer is that seems to be slightly too big ( in diameter ), and as a result it makes contact with the bearing cups, rather than the external shield. Thus it is in contact with both the rotating crank arm and the non-rotating cup, and thus creates drag. It's only function seems to be to act as an additional shield to prevent crud entering the BB bearing ( there is an external shield and various other seals ).
So I have removed it, and all now seems well, but it's been bugging me a bit, so I thought I would ask for a second opinion.
Any ideas? Are the instructions wrong? Is it actually just a bad drawing of the external shield? What gives?
FIrstly the BB and the crankset both had similar looking instructions, but in fact they were not the same!
After some research, I concluded that it was the crankset instructions that were applicable.
These are available online here ( 4MB )
http://www.sram.com/_media/techdocs/95-6115-007-000%20Rev%20A%20-%20Road%20Cranksets.pdf
but here is the relevant bit
SRAM GXP bottom bracket instructions by geebee22, on Flickr
The bottom bracket came with two spacers/washers. The instructions appear to show one of these inserted outside the bearing on the non-drive side ( the black ring in the picture above ).
The problem with this washer is that seems to be slightly too big ( in diameter ), and as a result it makes contact with the bearing cups, rather than the external shield. Thus it is in contact with both the rotating crank arm and the non-rotating cup, and thus creates drag. It's only function seems to be to act as an additional shield to prevent crud entering the BB bearing ( there is an external shield and various other seals ).
So I have removed it, and all now seems well, but it's been bugging me a bit, so I thought I would ask for a second opinion.
Any ideas? Are the instructions wrong? Is it actually just a bad drawing of the external shield? What gives?
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Comments
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the spacers are for MTB only use.
the black ring shown is the bearing dust cover (will be already fitted)."Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
Parktools :?:SheldonBrown0 -
the black ring shown is the bearing dust cover (will be already fitted).
Ok, thanks very much for putting my mind at rest
I think they actually call it an "external shield".
The reason I say it's a bad drawing is that the external shield has a wavy pattern that fits the splines on the crank, thus the black ring in the drawing really looks much more like a spacer. I really wonder if whoever did the drawing actually drew a spacer not the external shield.
The "PressFit GXP" instructions have a picture of an external shield that bears a decent resemblance. SRAM should amend the GXP instructions to look the same.0 -
It sounds like you are talking about the wave washer which usually slips onto the crank spline. It helps take any play out of the cranks when you tighten everything up.
Is it a small metal 'wavy' ring?
If so, you should probably put it back on. And the reason it might be on the crank instructions and not the BB ones is because it's a SRAM crank thing, not a Travativ GXP BB thing (you need it with SRAM cranks, but you can use the GXP BB with other cranks)0 -
sorry if it is a GPX fitting then there is no wavy washer needed. the LH bearing is clamped directly by the crank arm and the axle. there is no need for anything else.
yes there is a wavy washer on the press fit but i is there more to retain the bearing. play is removed by adding grease
"Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
Parktools :?:SheldonBrown0 -
nicklouse wrote:sorry if it is a GPX fitting then there is no wavy washer needed. the LH bearing is clamped directly by the crank arm and the axle. there is no need for anything else.
yes there is a wavy washer on the press fit but i is there more to retain the bearing. play is removed by adding grease
That must be it - the wavy washer is needed on my Trek Madone - which has press fit bearings. Without the wavy washer, the cranks have too much play in them.
I have the same cranks with a regular GXP BB on my TT bike - but don't use the wavy washer on that bike :oops:0 -
The "external shield" is shown (labelled 1) in this picture from page 2 of the instructions.
Cup Assembly by geebee22, on Flickr
As you can see, the black ring in the picture at top of this thread doesn't look much like it.
Anyway, the mystery is now solved, hopefully this thread will help others struggling with this.0 -
yep but that washer is not part of the GXP set up
Pokerface
the wavy washer is because on the press fit BB the bearings are not quite as well seated in their housings.
on the GXP the drive side crank arm is clear of the bearing by a few mm. and the location is purely down to the non drive side bearing.
Also on an MTB the GXP use one less spacer than the Shimano HT2 set up. Which does catch some people out (me included) BUT they will still work with an extra spacer !
TBH the simplest are the Campy External BBs just dont forget the retaining spring clip."Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
Parktools :?:SheldonBrown0
