sram gxp bb question
Moderator: robbosmans
The VCRC GXP BB is still working fine. I put about 5000 miles a year on that bike.
I'm not sure the King BB still requires shimming.
VCRC's directions do use a wave washer, on the DS. I initially assembled it without it but put it in after I re-read the directions. The BB spins as freely with as it did without.
I'm not sure the King BB still requires shimming.
VCRC's directions do use a wave washer, on the DS. I initially assembled it without it but put it in after I re-read the directions. The BB spins as freely with as it did without.
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Thanks, you didn't regrease it or anything in 5000 miles?
Couldn't you use the wave washer on the NDS.. (building SS so chainline is important for me.. seems it would affect the chainline)
Can you explain how to original GXP spindle and BB does it's preloading without a wave washer.. how the whole crank doesn't move side to side?
Couldn't you use the wave washer on the NDS.. (building SS so chainline is important for me.. seems it would affect the chainline)
Can you explain how to original GXP spindle and BB does it's preloading without a wave washer.. how the whole crank doesn't move side to side?
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I have't regreased it.
The cool thing about GXP is there is no preload to set. The NDS bearing locates the spindle and it floats in the DS bearing. The spindle is 22mm where it goes in the NDS bearing. The shoulder where it necks down from 24mm, and the fastener on the other side, capture theNDS bearing inner race. Since the bearing is a deep groove ball bearing and there's not a lot of side force on it, it's sufficient to locate the spindle.
Old cup and cone looose ball bearings used in BBs (and wheels) are angular ball bearings, which like a decent amount of preload. But the standard bicycle cartridge bearing is a deep groove ball bearing which can only take a small amount of sideways preload before it is damaged. Most current BB designs just hope the mechanic does not preload the bearings incorrectly. But the GXP solution avoids the problem entirely. As do the few BBs that use angular ball or tapered roller bearings.
The cool thing about GXP is there is no preload to set. The NDS bearing locates the spindle and it floats in the DS bearing. The spindle is 22mm where it goes in the NDS bearing. The shoulder where it necks down from 24mm, and the fastener on the other side, capture theNDS bearing inner race. Since the bearing is a deep groove ball bearing and there's not a lot of side force on it, it's sufficient to locate the spindle.
Old cup and cone looose ball bearings used in BBs (and wheels) are angular ball bearings, which like a decent amount of preload. But the standard bicycle cartridge bearing is a deep groove ball bearing which can only take a small amount of sideways preload before it is damaged. Most current BB designs just hope the mechanic does not preload the bearings incorrectly. But the GXP solution avoids the problem entirely. As do the few BBs that use angular ball or tapered roller bearings.
I also use the VCRC GXP BB. It's smooth and easy to service. I have two of those and a few sram ceramic BBs, and I sort of rotate them on a couple bikes. I serviced one of the VCRCs and it was a breeze, the shields are durable and pop on and off quite easily. Iirc, there is also a dust cover option that keeps all crud out.
Does anyone know if SRAM has yet fixed that the spindle where it is stepped down is 22mm (metric) yet the NDS bearing ID is 22.2mm (imperial)? This used to be the case, SRAM said "it's no worry if you just crank the spindle and crank arm down tightly...
Used to be longevity of GXP bearings were counted in months due to this, but haven't heard many complaints last few years so I'm thinking the NDS ID is no longer 22.2mm?
Just curious...
Used to be longevity of GXP bearings were counted in months due to this, but haven't heard many complaints last few years so I'm thinking the NDS ID is no longer 22.2mm?
Just curious...
Re the question on NDS bearing being too large. Thanks for providing this information. It has been a headache and I had no idea why installing the GXP crank was so hard to get right ! I wrote the following reply intended for this thread a couple of days ago, but decided on postponing, since I was not sure mine was an isolated issue:
I have had a lot of trouble getting rid of crank arm play with my little over a month old SRAM Red GXP crank and a Team GXP bottom bracket.
I read all about how it needs to be torqued above what one is used to, and I did - many times, with plenty of grease, but the crank bolt would bottom out before I could get rid of all the play. I measured the ID of the NDS bearing to be 22.2mm and as you know the NDS spindle diameter is 22mm. As the crank bolt is tightened, this difference is somehow taken up, but not completely.
This weekend I tried a new GXP Team BB (manufactured same week 2013, and likely from the same batch). Maybe I did not measure accurately enough, but on this the ID of the NDS bearing is closer to 22.15mm. Finally I was able to get rid of all crank arm play. After a couple of hundred km with the new BB, there is just a tiny amount of play, which I hope will go away when re-tightening the crank arm bolt yet again.
So that's unfortunate, can it be so hard for SRAM to use bearings in their BBs that fit the spindle better?
I have had a lot of trouble getting rid of crank arm play with my little over a month old SRAM Red GXP crank and a Team GXP bottom bracket.
I read all about how it needs to be torqued above what one is used to, and I did - many times, with plenty of grease, but the crank bolt would bottom out before I could get rid of all the play. I measured the ID of the NDS bearing to be 22.2mm and as you know the NDS spindle diameter is 22mm. As the crank bolt is tightened, this difference is somehow taken up, but not completely.
This weekend I tried a new GXP Team BB (manufactured same week 2013, and likely from the same batch). Maybe I did not measure accurately enough, but on this the ID of the NDS bearing is closer to 22.15mm. Finally I was able to get rid of all crank arm play. After a couple of hundred km with the new BB, there is just a tiny amount of play, which I hope will go away when re-tightening the crank arm bolt yet again.
So that's unfortunate, can it be so hard for SRAM to use bearings in their BBs that fit the spindle better?
(2012/2014) Scott Addict R1, SRAM Red 6.6kg | 2012 Scott Scale Pro, SRAM X0, 9.4kg
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n808 wrote:Re the question on NDS bearing being too large. Thanks for providing this information. It has been a headache and I had no idea why installing the GXP crank was so hard to get right ! I wrote the following reply intended for this thread a couple of days ago, but decided on postponing, since I was not sure mine was an isolated issue:
I have had a lot of trouble getting rid of crank arm play with my little over a month old SRAM Red GXP crank and a Team GXP bottom bracket.
I read all about how it needs to be torqued above what one is used to, and I did - many times, with plenty of grease, but the crank bolt would bottom out before I could get rid of all the play. I measured the ID of the NDS bearing to be 22.2mm and as you know the NDS spindle diameter is 22mm. As the crank bolt is tightened, this difference is somehow taken up, but not completely.
This weekend I tried a new GXP Team BB (manufactured same week 2013, and likely from the same batch). Maybe I did not measure accurately enough, but on this the ID of the NDS bearing is closer to 22.15mm. Finally I was able to get rid of all crank arm play. After a couple of hundred km with the new BB, there is just a tiny amount of play, which I hope will go away when re-tightening the crank arm bolt yet again.
So that's unfortunate, can it be so hard for SRAM to use bearings in their BBs that fit the spindle better?
Was it a radial play..? I have heard problem like this and people just advised tighten it more and more, which won't fix the problem if the NDS bearing is out of tolerance like you said.
The play could (and can) only be felt by rocking the crank arm ends. I was unable to move the crank from side to side at the BB. So that could mean it was radial, but due to the arm length leverage, any play is felt easier at the ends. At the moment with the replacement BB it's just barely noticeable "on the bench". With the first BB it was an obvious problem, and I think I heard and felt it while pedaling.
I also asked VCRC about their bearing diameter, as I am considering getting one those BBs. Matt @ VCRC replied back within an hour and thinks the issue might be the width rather than the bearing diameter:
I also asked VCRC about their bearing diameter, as I am considering getting one those BBs. Matt @ VCRC replied back within an hour and thinks the issue might be the width rather than the bearing diameter:
Our SRAM BB uses two shims, an inner and outer that press into the non drive bearing/dustcap. I just measured several of each to get an estimate for you. The inner shim (which the crank arm tightens up against from the inside was about 22.10 on most. The outer shim (which is mostly a spacer to get the spacing correct for SRAM) was closer to 22.15.
Keep in mind everyone's caliper may measure slightly different so I'd say our tolerances are a little better than SRAM but within the margin of error.
One thing we do differently with our SRAM BB is supply a wave washer to be used on the drive side. My opinion of SRAM's design is that the issue is more of a width issue and not the ID of the bearing or shim. A lot of times you run out of width before you can remove the play. The wave washer "buys" you a little slack, for lack of a better term, and seems to help get rid of the play. Obviously, making sure to torque the bolt to 54 NM is needed too, but I assume you have done that already.
I hope this helps. You might try simply adding a wave washer to your current BB and see if it solves the problem?
(2012/2014) Scott Addict R1, SRAM Red 6.6kg | 2012 Scott Scale Pro, SRAM X0, 9.4kg
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Do you guys think the newer 2013 sram gxp bb is improved
I am going to check the bearing id vs spindle od to see.
Also have the frame faced before spending big money on aftermarket bb
All the kits from phil or chris king, etc all uses a 22 to 24mm sleeve and no one makes a true gxp replacement.
Because most companys converted their shimano kit which is thinner and have you add some shims here and there.
I am going to check the bearing id vs spindle od to see.
Also have the frame faced before spending big money on aftermarket bb
All the kits from phil or chris king, etc all uses a 22 to 24mm sleeve and no one makes a true gxp replacement.
Because most companys converted their shimano kit which is thinner and have you add some shims here and there.
Just because I got one rally bad SRAM BB, I'd hate to make everyone think all SRAM GXP BBs are bad.. From all I found when researching my problem, in general it works well almost always, and in theory, it should. I love not having to worry about pre-load adjustments. Just tighten the crank bolt to spec, and all play should be gone
(2012/2014) Scott Addict R1, SRAM Red 6.6kg | 2012 Scott Scale Pro, SRAM X0, 9.4kg