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  1. #26
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    Quote Originally Posted by mack_turtle View Post
    Ah, I read it more carefully and that makes sense now:

    the spacers are not there to support the bearings so much as to insure chainline?

    the spindle requires at least 73mm of length, which is why you need spacers on a 68mm shell? so if I add a spacer to the drive side of a 73mm shell, it will work because the drive side of the spindle will just slide further into the drive side bearing to compensate. this might screw up my chain line, but I don't know how accurate my chainline is anyways. I'll check it when I am done.

    does that sound right?
    umm no or yes,.. or no LOLOL

    the spacers are there to insure both chainline and bearing width of the spindle. Yes you need (well should have) at least a 73 mm support width on the spindle. but chainline is adjusted on the NON DRIVE SIDE... adding or subtracting spacers to the drive side does nothing as it just floats over the spindle. all side to side movement is controlled by the clamping of the non drive bearing's inner race. I better described in on my little blog... Trailtiretv.blogspot.com scroll down one or 2 posts.
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  2. #27
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    yes, that makes perfect sense now. thank you!

  3. #28
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    I learned something about my GXP crank and BB today, thanks all.

  4. #29
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    So with all of this talk of using spacers to adjust chainline. If you put a 2.5mm spacer on the NDS cup, that will bring the drive side crank in 2.5mm put push the NDS crank 2.5mm outboard, correct? Seems like that would be funny having a different pedal spacing on either side of the BB.

  5. #30
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    true, but if you have to put a spacer behind your NDS cup to correct your chainline, you're either measuring your chainline incorrectly, or there's something else wrong with your setup. your chainring was poorly designed, your frame BB shell was welded in off-center, or something like that.

  6. #31
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    Sram gxp 73mm bottom bracket h question...

    Quote Originally Posted by mack_turtle View Post
    true, but if you have to put a spacer behind your NDS cup to correct your chainline, you're either measuring your chainline incorrectly, or there's something else wrong with your setup. your chainring was poorly designed, your frame BB shell was welded in off-center, or something like that.
    All current mtb crank chainlines ARE poorly designed and ~5mm too far outboard from ideal. They were move outboard to gain chainring, front derailleur, and chain clearance when using short stays and big tires, not for best drivetrain performance. It decreases efficiency and increases chain drop.

    If you have the clearance moving the crank inboard is an advantage.
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  7. #32
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    Quote Originally Posted by shiggy View Post
    All current mtb crank chainlines ARE poorly designed and ~5mm too far outboard from ideal. They were move outboard to gain chainring, front derailleur, and chain clearance when using short stays and big tires, not for best drivetrain performance. It decreases efficiency and increases chain drop.

    If you have the clearance moving the crank inboard is an advantage.
    what he said... I'm using a 3x9 crank set as 2x9 with the common setup bash guard in place of the monster ring. Never moved my chain line but can easily run any gear out back and have never once dropped the chain no matter if I'm using the 22 or the 32 up front. Thou i did lower the front derailleur which helps
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  8. #33
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    Hey Guys,

    I have found this thread to be the single most useful thread in a long time on MTBR.

    So I have a 29er hardtail with a 73mm BB. I have an 2011/12 (i think) X9 GXP crank with an XO spider (42/28T).

    After my trial and error, I couldn't get the crankset set-up until I read this, and then felt much more comfortable with the fact that there is a very slight "space" between the DS sleeve and the bearing.

    BUT!! I put a 2.5 space on the NDS, because without it, the spindle would bottom out against the NDS bearing, preventing me from tightening it down to eliminate play. However, I can get the crank tight now, but there is still a very small amount of side to side play in the crank arms, but only when horizontal (to the ground). When vertical, there is no play. And when I say small amount of play, I mean MAYBE .5-.75mm at the end of the crank arm (if that makes sense).

    I figure it could just be a slightly worn out bearing. But is this play normal? How can I get rid of it? Should I be worried about it? Putting another 2.5 spacer in causes the spider to bind against DS bearing.

    What do you guys think? Thanks again for this thread!

  9. #34
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    BigMike969, something sounds wrong here. Adding spacers behind the cups should have zero change on the arm clamping down to the spindle and preventing or helping it to get tight. the only thing adding spacers to the NDS should do is pull the chain line in 2.5mm.

    the "shelf or lip" in the spindle should tighten right up against the inner bearing race and the crank arm should butt right up against the seal which traps the race on the out side. padding/spacing the cups to the frame has nothing to do with how it holds.

    Sounds to me like you have a bad BB or at least a bad bearing in one cup, but without actually looking I can't say for sure.
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  10. #35
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    Hey,

    Yeah, something doesn't seem right with it. Here's the things I did and the result:

    1) 2.5 spacers between cup and frame on both DS and NDS (thought frame was 68mm originally) --> caused spider to bind against cup

    2) 2.5mm spindle spacer (tried it on both sides) --> still caused binding, but I wasn't sure where, regardless of which side the spacer was on, DS or NDS

    3) Confused, so measured BB shell, came out to 73mm, so as per SRAM's manual, removed all spacers --> spindle bottoms out against NDS bearing, leaving -+2.5mm between DS bearing and crank arm with significant lateral play

    4) even more confused, put 2.5 spacer between NDS cup and frame, can tighten down fine, no binding, crank spins well and smooth, DS crank/sleeve is not totally flush to bearing, but out maybe .5mm (which sounds like is ok for the GXP set-up), but as I mentioned, have a very small amount of lateral play, but only when cranks are horizontal to ground, and actually slightly more on one side than the other (as in, when the DS crank arm is horizontal to ground but towards rear of bike, has slightly more play than when towards front of bike).

    As I said, I figure it's a bad bearing, but the BB is new'ish (although I did buy it used, but without it being on a bike, I couldn't tell that there was a bearing issue).

    I might try and track down a new/other BB and see if that fixes it, but I don't know that I will be able to.

    Thanks again!!

  11. #36
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    Quote Originally Posted by bigmike9699 View Post
    Hey,

    Yeah, something doesn't seem right with it. Here's the things I did and the result:

    1) 2.5 spacers between cup and frame on both DS and NDS (thought frame was 68mm originally) --> caused spider to bind against cup

    2) 2.5mm spindle spacer (tried it on both sides) --> still caused binding, but I wasn't sure where, regardless of which side the spacer was on, DS or NDS

    3) Confused, so measured BB shell, came out to 73mm, so as per SRAM's manual, removed all spacers --> spindle bottoms out against NDS bearing, leaving -+2.5mm between DS bearing and crank arm with significant lateral play

    4) even more confused, put 2.5 spacer between NDS cup and frame, can tighten down fine, no binding, crank spins well and smooth, DS crank/sleeve is not totally flush to bearing, but out maybe .5mm (which sounds like is ok for the GXP set-up), but as I mentioned, have a very small amount of lateral play, but only when cranks are horizontal to ground, and actually slightly more on one side than the other (as in, when the DS crank arm is horizontal to ground but towards rear of bike, has slightly more play than when towards front of bike).

    As I said, I figure it's a bad bearing, but the BB is new'ish (although I did buy it used, but without it being on a bike, I couldn't tell that there was a bearing issue).

    I might try and track down a new/other BB and see if that fixes it, but I don't know that I will be able to.

    Thanks again!!


    the spindle should bottom out on the bearing,.. it's how they work, the spindle traps the bearing smaller race and the crank arm pinches it on the outside (with the bb seal which has a thick metal washer/spacer build in) Soinds to me like you have something binding the crank arm from going onto the spindle all the way.

    are you using a threaded BB or a Press fit? I haven't played with the press fit yet as most of the stuff I deal with is older and before it's time. (hell my cranks are 2006 Stylo's which are still awesome and lighter than many current models )

    I do know when the went to "X-#" cranks from stylo they added a little goofy wrinkled looking washer thingy that acts as a filler and contact point on the Non drive side.

    sounds to me like you are missing it as you shouldn't need any spacers between the crank arm and the spindle...
    Attached Thumbnails Attached Thumbnails Sram gxp 73mm bottom bracket h question...-crank.jpg  

    Last edited by thomllama; 02-22-2013 at 01:26 PM.
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  12. #37
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    hey,

    Thanks for the reply.

    The frame is a standard threaded BB.

    I do still have that spacer in there, as well as everything else in the exploded diagram. I really think it's a bearing, but what confuses me is that given my BB width, and the fact that I have all the parts (according to the exploded diagram), I should be able to make it work without any cup spacers, but it bottoms out. And, I measured and re-measured the BB shell, and it is definitely 73mm.

  13. #38
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    don't know what else to tell you,.. all I can think of is that you have something stuck in the splines so the crank arm isn't going all the way on,.. or you're using a non GXP crank or something... ? if ya lived in the CT area I'd say bring it over and I'll take a look.

    last idea I got without getting my hand on it is to take the whole thng off the bike, take just the non drive bearing cup and slide it onto the spindle... examine the from the inside and make sure the spindle is bottoming out on the bearing's race, slide the crank arm on and examine how far it goes... if something gets inside the crank arm you may want to pull the 2 bolts (the main bolt and the back out bolt) and make sure nothing is in there .. stopping the arm for going on all the way...

    hey,.. thought ,.. you don't have the attachment bolt OUTSIDE the back out nut? it supposed to be trapped inside!



    take pictures will help
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  14. #39
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    I'm soooo thankful I came across this thread after reading tons of garbage for the past couple days. I was really scratching my head at a bike I purchased that has a 73mm BB cup and a spacer on each side of a GXP BB. I'm about to replace the BB and install a Blackspire Stinger, so this is just the post I needed to see. Thanks!

  15. #40
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    Quote Originally Posted by salsinator View Post
    I'm soooo thankful I came across this thread after reading tons of garbage for the past couple days. I was really scratching my head at a bike I purchased that has a 73mm BB cup and a spacer on each side of a GXP BB. I'm about to replace the BB and install a Blackspire Stinger, so this is just the post I needed to see. Thanks!
    glad it worked out for ya
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  16. #41
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    So if I understand this and the link XX crank link the max allowable width for GPX is 75.5mm, if I was running a GXP system on a 68mm BB with 2.5 or each side and decided I wanted to widen/adjust the q factor by 2mm would adding a 1mm spacer on each side do it? or would it bring the chain line in by 1mm because of the floating DS?

  17. #42
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    Quote Originally Posted by Ramjm_2000 View Post
    So if I understand this and the link XX crank link the max allowable width for GPX is 75.5mm, if I was running a GXP system on a 68mm BB with 2.5 or each side and decided I wanted to widen/adjust the q factor by 2mm would adding a 1mm spacer on each side do it? or would it bring the chain line in by 1mm because of the floating DS?
    The width of the crankset (Q factor) is fixed, can not be changed. Using/moving spacers on the non driveside changes the chainline.
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  18. #43
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    I understand in theory the q factor is fixed and should be related to the spindle length but what I'm asking is if 1mm is added on each side (not NDS only) would you not by virtue increase the total width to 75mm when completely tightened (vs. 73mm)? I'm assuming the q factor is calculated based on the pedal eye to eye width completed cinched down.

  19. #44
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    Sram gxp 73mm bottom bracket h question...

    Quote Originally Posted by Ramjm_2000 View Post
    I understand in theory the q factor is fixed and should be related to the spindle length but what I'm asking is if 1mm is added on each side (not NDS only) would you not by virtue increase the total width to 75mm when completely tightened (vs. 73mm)? I'm assuming the q factor is calculated based on the pedal eye to eye width completed cinched down.
    You really need to read this whole thread and learn how GXP cranks/BBs work.

    Spacers on the drive side have ZERO affect on chainline or Q factor.

    Additional spacers on the NDS reduce the chainline and have ZERO affect on the Q factor.

    The spacers only affect the distance between the bearing cups. The crank still just tightens against the NDS bearing. Nothing else. period.
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  20. #45
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    Some Photos

    Quote Originally Posted by thomllama View Post
    Believe me, you're not the first person who didn't understand the system,.. I've had tech's in shops that didn't get it even after I showed it to them

    Glad you figured it out
    thomllama, your explanations and analyses are spot on; we could use more threads such as this.

    I've uploaded two photos of my GXP Truvativ Rouleur crankset and (BSA spec'ed) BB cups that demonstrate what you've so capably detailed.

    Photo 01: The spindle of the Roleur crankset focusing on the shoulder that abuts the NDS BB bearing.

    Photo 02: An installation mockup. The GXP BB cups–with 2 spacers (as per 68mm BB shell width installations–fitted over the spindle. NOTE: the NDS cup is resting on the shoulder of the spindle while the DS BB cup's bearing, having a slightly greater inner diameter, slip fits, past the shoulder all the way to the crank's spider without engagement or hindrance.

    Compliments on an edjumacating thread.
    Attached Thumbnails Attached Thumbnails Sram gxp 73mm bottom bracket h question...-01.jpg  

    Sram gxp 73mm bottom bracket h question...-02.jpg  


  21. #46
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    Quote Originally Posted by thomllama View Post
    the spindle should bottom out on the bearing,.. it's how they work, the spindle traps the bearing smaller race and the crank arm pinches it on the outside (with the bb seal which has a thick metal washer/spacer build in) Soinds to me like you have something binding the crank arm from going onto the spindle all the way.

    are you using a threaded BB or a Press fit? I haven't played with the press fit yet as most of the stuff I deal with is older and before it's time. (hell my cranks are 2006 Stylo's which are still awesome and lighter than many current models )

    I do know when the went to "X-#" cranks from stylo they added a little goofy wrinkled looking washer thingy that acts as a filler and contact point on the Non drive side.

    sounds to me like you are missing it as you shouldn't need any spacers between the crank arm and the spindle...
    Thanks for this great thread. Saved me lots of headache. I panicked when I saw about a 2mm gap between the DS spindle and the bearing. My setup is a 73mm BB shell using threaded GXP on an Epic.

    I was able to torque down the NDS bolt to 48 nm and have no side to side play using no spacers. However, my crankset did not come with the "washer" that you labeled "this thing", so I'm wondering either it was shipped missing or because its a newer MY that SRAM did not update the documentation?

    Other than the missing "washer", everything seems to be functioning and again no lateral play. It was just the gap on the DS that had me worried as I'm used to either Shimano BB or SRAM PF30 BB being fully seated against the bearings.

    So question is do I still need the NDS "washer" or not?

  22. #47
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    Quote Originally Posted by nsxtc View Post
    I was able to torque down the NDS bolt to 48 nm and have no side to side play using no spacers. However, my crankset did not come with the "washer" that you labeled "this thing", so I'm wondering either it was shipped missing or because its a newer MY that SRAM did not update the documentation?
    I've two GXP cranks: the ~5 year old Rouleur pictured up thread and a year(?) old 10spd SRAM Apex Compact crank and BOTH require the NDS compression washer. Once I installed the Rouleur without the washer between the crank and the BB and it was immediately apparent by the crankset's increased drag/play that it wasn't an optional component.

    Please see the photos for clarification:

    Photo 1: the outside of the compression washer and a bearing cup. Note the outboard surface of the washer is basically flat. (I mistakenly used the DS bearing cup in the photos. Ooops.)

    Photo 2: the inboard side of the washer, the one that abuts the BB bearing. It's difficult to see from the photo but there's a shoulder encircling the splined hole of the washer that interfaces with the BB bearing's inner race, thus pinching bearing against the crank spindle's NDS shoulder.

    In this case, without that compression washer the torqued NDS crank would contact the BB bearing races. Not good.

    You're saying that your crank did not ship with the something akin to the compression washer pictured?
    Attached Thumbnails Attached Thumbnails Sram gxp 73mm bottom bracket h question...-photo-1-outboard.jpg  

    Sram gxp 73mm bottom bracket h question...-photo-2-inboard.jpg  


  23. #48
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    Thanks for taking the time and digging out old parts and taking pics for illustration and clarification.

    Yes, no compression washers. I guess I'll see if my LBS has one. Otherwise I'll have to contact the shop I ordered from and have them ship a replacement.

    Quote Originally Posted by linguinee View Post
    I've two GXP cranks: the ~5 year old Rouleur pictured up thread and a year(?) old 10spd SRAM Apex Compact crank and BOTH require the NDS compression washer. Once I installed the Rouleur without the washer between the crank and the BB and it was immediately apparent by the crankset's increased drag/play that it wasn't an optional component.

    Please see the photos for clarification:

    Photo 1: the outside of the compression washer and a bearing cup. Note the outboard surface of the washer is basically flat. (I mistakenly used the DS bearing cup in the photos. Ooops.)

    Photo 2: the inboard side of the washer, the one that abuts the BB bearing. It's difficult to see from the photo but there's a shoulder encircling the splined hole of the washer that interfaces with the BB bearing's inner race, thus pinching bearing against the crank spindle's NDS shoulder.

    In this case, without that compression washer the torqued NDS crank would contact the BB bearing races. Not good.

    You're saying that your crank did not ship with the something akin to the compression washer pictured?

  24. #49
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    @ nsxtc

    My experience with GXP configurations only extends to Rouleur and Apex cranksets. Perhaps your left crank spindle interface has a specific profile that negates the compression washer. You may have everything you need already.

    In any event please update the thread with your progress. (Valuable for future reference.)

    Keep on rolling.

  25. #50
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    Quote Originally Posted by linguinee View Post
    @ nsxtc

    My experience with GXP configurations only extends to Rouleur and Apex cranksets. Perhaps your left crank spindle interface has a specific profile that negates the compression washer. You may have everything you need already.

    In any event please update the thread with your progress. (Valuable for future reference.)

    Keep on rolling.
    most of the MTB (stylo, X9,X7..bla bla bla) have the compression washer built into the BB cup seal..but not all... it's very obvious if you need it and if you got the torque on the bearing and it's not dragging really bad you probably don't need it... it's quite obvious on the bearing seal also.. if you read the write up on TrailtireTV there is a picture of the BB cups and bearing seal diffs...
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