# GXP & BB Shell question



## dextor (Nov 10, 2008)

Does the GXP bottom bracket (English) work with 68mm AND 73mm shells or JUST 68mm? It's going to be a road set up, the crankset I'll be using is Truvativ Rouleur. I'm getting conflicting information while doing some research. One guy at an LBS told me only 68, another told me both.

I'm asking because my BB shell is 71mm. Does the GXP BB work with anything between 68 and 73mm? One of the guys at the LBS gave me a 2mm spacer to bring it up to 73 and said that should work.

And before you ask, yes it's 71mm shell and 100% English threaded.

Thanks.


----------



## DrSmile (Jul 22, 2006)

Should work, I remember mine came with spacers. It was an utter piece of crap though so after killing off 2 BBs because I couldn't get rid of the play I sent it (crank and BB) back to SRAM and told them how badly it sucked. I never heard back from them. Now I have a properly designed Dura-ace and couldn't be happier.


----------



## Cyclo-phile (Sep 22, 2005)

The bottom bracket is the same for all SRAM GXP cranksets, except Red which gets ceramic bearings. The critical factor is the length of the spindle. I believe all of their road cranksets have a spindle sized for a 68mm shell and all of the mountain cranksets are sized for a 73mm shell. If using a mtn. crank in a 68 shell you would put a 2.5mm spacer on either side behind the bearing cup.

I've never seen a 71mm shell in my experience, and it's likely to cause a lot of binding with that crankset. If there is room on your frame, ie. no welds or carbon fiber in the way, I'd suggest having a good shop face it down to 68mm. It will take some patience and a decent set of calipers to ensure 34mm on either side of the bike's centerline. Based on the bad information from the two mechanics you mentioned, I'd suggest finding someone other than them to work on your bike.


----------



## dextor (Nov 10, 2008)

Cyclo-phile said:


> The bottom bracket is the same for all SRAM GXP cranksets, except Red which gets ceramic bearings. The critical factor is the length of the spindle. I believe all of their road cranksets have a spindle sized for a 68mm shell and all of the mountain cranksets are sized for a 73mm shell. If using a mtn. crank in a 68 shell you would put a 2.5mm spacer on either side behind the bearing cup.
> 
> I've never seen a 71mm shell in my experience, and it's likely to cause a lot of binding with that crankset. If there is room on your frame, ie. no welds or carbon fiber in the way, I'd suggest having a good shop face it down to 68mm. It will take some patience and a decent set of calipers to ensure 34mm on either side of the bike's centerline. Based on the bad information from the two mechanics you mentioned, I'd suggest finding someone other than them to work on your bike.


Thanks, that was really insightful. I will try to find a LBS with a facing tool.


----------



## dextor (Nov 10, 2008)

I just came across this while doing some more research on the SRAM/Truvativ site:

http://www.sram.com/_media/techdocs/09 User Manual - GXP Bottom Brackets and Cranksets.pdf

Under 'Compatibility':
It seems like the Rouleur will work with both 70mm Italian shell and 68mm English shell, albeit a tiny chainline difference. Does that mean the spindle will also work with 70mm English shell?


----------



## Cyclo-phile (Sep 22, 2005)

An Italian BB has different threads than an English BB. I suspect that SRAM has sized the bearing cups to fit a wider standard shell while still using the same length spindle.

The SRAM GXP system works by having a stepped diameter on the spindle. On a perfect system the inner race of the non-drive-side bearing is captured between the non-drive arm and the spindle step. This mechanical lock is intended to isolate the rotational forces and prevent side forces. If the shell is too wide the bearings will be side-loaded when the non-drive arm is tightened. This leads to a lot of drag and premature wear.


----------



## cosmo333 (Oct 5, 2005)

Can you tell us what brand and model the frame is? And how the measurement is taken. Might solve part of the mystery. 

There's a lot of misunderstanding about how this system works. On the GXP road cranks (68 English or 70 Italian) it's no spacers, grease the splines and tight as you can get it. The crank bolt spec is 35 ft/lbs but the arm must be bottomed out first. Because of the taper on the splines it takes more than that to get the arm to bottom-until then the BB will be loose and the arm will fall off when you ride. It's a different install than Shimano or FSA, no bearing adjustment to make. As Cyclo said it's the step on the spindle that makes it work.

A SRAM/TV GXP road crank will not work in a 73mm English shell (some mtn bikes). Spindle is too short. No such animal as a 70mm English shell, 70 is Italian threaded.


----------



## dextor (Nov 10, 2008)

Measurements were taken with a caliper, values range from 70.7 to 71.0 around a few points taken of the shell.

Cosmo333, unfortunately it's English threaded, I'm 100% sure. Checked it myself and had a local mechanic put another English BB in, and cleaned it up by chasing it with English chasing tool.

Cyclo-phile, I was wondering myself if the Italian threaded cups are slightly modified to be narrower so the end result after install on an 70mm Italian shell would give the same length from cup-to-cup as English.

I'll shop around and see if any other LBS can do the dirty work without charging too much. I've been told by one mechanic it'll cost a lot because of the heavy elbow grease and time involved since it needs to shed 3mm.


----------



## dextor (Nov 10, 2008)

Does anyone know what's the difference between GXP BB "TEAM" vs non-TEAM?

Thanks.


----------



## CleavesF (Dec 31, 2007)

dextor said:


> Does anyone know what's the difference between GXP BB "TEAM" vs non-TEAM?
> 
> Thanks.


The difference, if you believe me or not, is the word TEAM. 

They only make the TEAM BB and the Ceramic for Red. That's it. Two options. There's no GXP for bondtrager, truvativ, or sram force/rival... it's all the same. 

The only other option is the red GXP ceramic for like 150 bucks.


----------

