subguy658

OK, so I have researched this to death to no avail. Many have asked the question, but no one ever answers it....

I have a 2011 Spec. Roubaix Elite Apex, which utilizes a Truvativ Power Spline bottom bracket. In the near future, I would like to upgrade the gruppo to SRAM Rival, which will require a new (different) bottom bracket. The bottom bracket shell on the frame has a faced surface on only one side (the chain side). The other side is threaded, but no face. For the power spline BB, no face is needed on that side.

My question is, what bottom bracket can I get to accept the SRAM Rival Crankset? There is a thread on RoadBikeReview called "Apex to Red crankset upgrade questions" where a guy put on a SRAM GXP with external bearings (on the same frame as I have, it turns out), however this doesn't seem right because the non-chain side of the bracket shell has no face. What is he gronking that bearing against? On my bike, the bearing would be grinding right up against the carbon.

I am hoping that this thread doesn't turn into a power spline hate session, we already know it is heavy and that it isn't the best design. What I ask is that someone tell me what the correct BB is to use when upgrading this particular set-up to SRAM Rival, maybe address my concern about the lack of a faced surface on the left-hand side.

Thanks Loads!!

Pepper Grinder

Pics of BB shell please.

Your only choice is a GXP BB for those cranksets.

subguy658

Thanks Pepper Grinder. Here are some pictures of my BB shell with the power spline BB installed. Note that the drive side of the shell has a machined face that the non-drive side lacks. The power spline does not need a face on the non-drive side, as the threaded end on that side has no external flare and it seats by compressing the metal cylindrical shell between the two bearings. (See power spline image). The SRAM GXP BB (see image) has flares on both sides, which to me would indicate that both sides of the shell need faces to get a proper seat. Unlike the power spline, the non-drive side cup does not compress the cylinder, as it is made of plastic.

While I have no doubt that a GXP BB will thread into my frame's shell, my concern is the lack of a seat face on the non-drive side of the shell... People have done it (see reference thread in original post) - my question is whether or not it is the right thing to do (won't come loose, no damage to frame, etc.). I am looking for input from someone who has experience with this situation. Thanks to all for looking!

fietsbob

Remove the installed 'power spline' BB, put it with the other crank, (to sell as a set) ; because
the Sram uses an entirely different one, external.

that is what the new top line stuff is these days, external BB. comes withset whemn you specify.



you need a separate set of tools too, to remove the old one , and install the new one .

The new installation tool should be capable of usiing a 1/2" drive torque wrench to know it's in tight enough.

Might turn the job over to the bike shop, so you dont have to buy all the tools , some only used once.

subguy658

Feitsbob, thanks for the input. I have all the tools needed and understand how BBs are installed. My question is concerning the shell faces as described above, and if the SRAM GXP (the only BB you can use with the Rival set I want to install) is appropriate for the type of shell I have.

reddog3

There's an aluminum BB shell "insert in that carbon frame. They didn't face the non-drive side as it wasn't necessary. There should be enough material protruding beyond the BB area to accept some facing. Hard to tell from the pics, but it appears there is. Hard to say though since it's a carbon frame, and each one could be slightly different in that area. You'll see when you pull the non-drive side ring. If there's enough material (aluminum) have it faced.

The "facing" doesn't need to be nearly as wide/fat as on the drive side. Make sure though that the sheel width after facing is close to 68mm. GXPs are somewhat sensitive to shell width, but there are shims supplied to make up for any discrepancies and to adjust chainline. Follow the installation instructions on SRAMs site for GXP.

subguy658

reddog3, Thanks so much for the recommendations. I have been looking high and low for information about doing this upgrade and most seem to dodge making recommendations. I think you are right, there just might be enough metal there to face it off.

TeamCNY

Subguy, what became of your quest?



OK, he hasn't logged in a year.... Anyone else deal with this?

subguy658

So the aluminum insert, although having no face on the non-drive side, is exactly the correct width specified for the GXP bottom bracket. And even though there isn't any "height" to the face, the face was perfectly flat. When you snug the GXP up against it, the bracket does not damage or touch the carbon. It fit perfectly and I have had zero problems with 2500 miles since that upgrade to SRAM Rival. My apologies for not following up!