sram gxp tandem bb difference?

[chiasticon]

anyone know what the difference is between sram gxp bb and the tandem version? I picked up one here a while back by mistake, don't think the seller knew it was tandem. anyway it seems to function just fine. specs seem the same. is it just built more beefy?

I'm asking because I'm after another. and it's black, versus the silver gxp one. I'd prefer the black.

[jbay]

I would expect the 22mm ID cup for the captain/pilot to be on the right hand/fixed cup/left-hand threaded side.

-- John

[chiasticon]

a fair point! totally forgot about that. zero experience with tandems, to be honest.

OK so apparently the BB I have isn't a tandem BB then. says GXP on it and it's black. so either Sram made an oddball black one or it's made by someone else... weird.

[Tandem Rider]

I've replaced ours several times over the years, bb cup/bearings are the same as on a single. The spindle is not being replaced, you're overthinking it.;)

[jtbadge]

The Rival level GXP BBs are black. I have one. Not sure whether they're still making them.

https://www.sram.com/sram/road/products/sram-rival-bb

[chiasticon]

The Rival level GXP BBs are black. I have one. Not sure whether they're still making them.

https://www.sram.com/sram/road/products/sram-rival-bbAHA! you may be onto something!

I'm guessing that the one I have is from a Rival group then. I've only ever seen the Team/Truvativ one and the Tandem one available separately. and I've never purchased a Rival crankset or group as a whole, so I've never seen this BB. the price and features listed are the same as the Force one, but that one's silver (and looks like the Team/Truvativ one). if they are indeed the same, it's a shame the Rival one isn't available outside of buying a crankset/group. black is mo' betta' than silver.

[jbay]

I've replaced ours several times over the years, bb cup/bearings are the same as on a single. The spindle is not being replaced, you're overthinking it.;)They can't be the same, though. One pair of cups - for the captain/pilot - have to be reversed relative to those used on a single bike.

Note how the two timing cranks in the photo below are different. The upper one belongs to the pilot. The spindle is [permanently] attached to that crank, whereas the spindle is attached to the triple/drive crank in the stoker's position. Ergo, the 24mm ID bearing has to be on the left hand side in the pilot's bottom bracket and, as a corollary, the 22mm ID bearing must be on the right hand side.

http://www.cannondale-parts.de/WebRoot/Store20/Shops/61764971/5227/1B7C/EBE5/20CD/C1A7/C0A8/29BA/84AE/DSCN6941.JPG

-- John

[Tandem Rider]

They can't be the same, though. One pair of cups - for the captain/pilot - have to be reversed relative to those used on a single bike.

Note how the two timing cranks in the photo below are different. The upper one belongs to the pilot. The spindle is [permanently] attached to that crank, whereas the spindle is attached to the triple/drive crank in the stoker's position. Ergo, the 24mm ID bearing has to be on the left hand side in the pilot's bottom bracket and, as a corollary, the 22mm ID bearing must be on the right hand side.

http://www.cannondale-parts.de/WebRoot/Store20/Shops/61764971/5227/1B7C/EBE5/20CD/C1A7/C0A8/29BA/84AE/DSCN6941.JPG

-- John

You are correct, the front cups are flipped. The cups are still the same though, the eccentric insert is reversed in the frame, this allows the cups to go in the other way. He still needs to just buy regular cups. AFAIK, there are no special bearings for tandems.

[jbay]

AFAIK, there are no special bearings for tandems.I wish there were! Chris King are the closest thing I've found.

-- John

[Tandem Rider]

Haha, I've had to resign myself to the fact that tandems eat parts, fast. Chains, brake pads, and tires especially.

[chiasticon]

You are correct, the front cups are flipped. The cups are still the same though, the eccentric insert is reversed in the frame, this allows the cups to go in the other way. He still needs to just buy regular cups. AFAIK, there are no special bearings for tandems.so... what is the gxp tandem BB then...?

[Tandem Rider]

I believe that the cups/bearings are simply standard English threaded units, same ones are used on tandems as are used on single bikes. I seem to recall the same ones being used on both road and mtn cranks as well, but I could be mis-remembering that one.

Have you pulled it apart yet to check dimensions and look it over? That will probably clear up your befuddlement. I just go down to the LBS and pick them up whenever I need a set, no special order, and they don't stock tandem specific parts. We have them on our gravel/touring tandem so they only last a year or two with all the river crossings and grit.:)

[GregL]

We have Truvativ GXP bottom brackets/cranks on our tandem. To the best of my knowledge, the rear (stoker) bottom bracket is a conventional GXP bottom bracket with 24mm ID on the right (drive) side and 22mm ID on the left (sync chain) side. The right cup is left-hand threaded.

The front (captain) bottom bracket has the 24mm ID on the left (sync chain) side and the 22mm ID on the right (drive) side. Just like the rear BB, the right front cup is left-hand threaded. All the cups are marked to make sure they are installed in the correct location.

Summary: the tandem GXP bottom brackets are in fact different between front and rear positions.

Greg

[Tandem Rider]

We have Truvativ GXP bottom brackets/cranks on our tandem. To the best of my knowledge, the rear (stoker) bottom bracket is a conventional GXP bottom bracket with 24mm ID on the right (drive) side and 22mm ID on the left (sync chain) side. The right cup is left-hand threaded.

The front (captain) bottom bracket has the 24mm ID on the left (sync chain) side and the 22mm ID on the right (drive) side. Just like the rear BB, the right front cup is left-hand threaded. All the cups are marked to make sure they are installed in the correct location.

Summary: the tandem GXP bottom brackets are in fact different between front and rear positions.

Greg
Ahhh, I see, I don't think ours ever had cups like that, unless my old brain has forgotten about flipping the insert. On ours, the front right cup is right hand threaded, simply an act of flipping the eccentric around would make either one work. (And no they don't unscrew themselves any more than an Italian bb does). I learned something new today :beer:

[GregL]

Ahhh, I see, I don't think ours ever had cups like that, unless my old brain has forgotten about flipping the insert. On ours, the front right cup is right hand threaded, simply an act of flipping the eccentric around would make either one work. (And no they don't unscrew themselves any more than an Italian bb does). I learned something new today :beer:
You are 100% correct. If you flip the eccentric, then you can use a standard GXP BB in the front position. Just like an Italian BB, you have to ensure that it is torqued to appropriate values and checked on a regular basis. I may have to resort to this option as the front-specific GXP bottom brackets are hard to find. Or pick up an Enduro bearing press and replace the bearings pressed into the cups.

Greg