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Crankset compatibility: Specialized Stout XC vs. SRAM GX 1000 GXP

Bicycles Asked by erkil1452 on March 16, 2021

I need to replace the crankset on my Specialized Rockhopper 29 Expert (year 2017) due to damage. I would prefer not to replace the BB to minimize the cost/effort.

The original crankset is described by Specialized as:

Specialized Stout XC, 2-piece 2×10, 24mm spindle, anti-corrosion
hardware“

and the BB as

BSA threaded, external bearing, 73mm width

I have concluded that since most of the drivetrain is SRAM (except of the rear derailleur weirdly), the crankset SRAM GX 1000 GXP would be a suitable replacement since it features 24 mm spindle, has the same 36/22T, the same BCD, setup and looks generally similar on pictures (yeah, I know).

Unfortunately, it fits pretty well, except of one minor detail – the shaft seems a bit too long and there is couple mm wiggle space left when I install the left crank. I have since learned that the BSA threaded is something else than BB30 that the SRAM GX 1000 GXP apparently features, even though they have the same radius. I am very confused by all the different parameters to watch for.

What I want to ask – is there an adapter for this? Or simpler – what should I buy that will fit the BB? Or is this is a lost case and I need a new BB? I do not really feel a need to upgrade the 2×10 setup and just want to fix the bike.

Thanks for help!

Edit: I have found here that the Shimano and Sram Threaded BBs differ. Since my spindle is 24 mm all the way, it is probably compatible with the Shimano system. Would e.g. COMET MODULAR CRANKSET work on my bike better then?

One Answer

The parameters involved are as follows:

  1. Your frame’s bottom bracket shell, which is BSA threaded.
  2. The spindle type, which is where you ran into trouble. Shimano specifies a 24mm diameter spindle. SRAM’s GXP is a 24mm spindle that tapers to 22mm on the left crank. I don’t know if there’s a substantive reason for this, or if it’s just to avoid any patents that Shimano had on its Hollowtech II system.

The FSA crank you linked appears to have a 24mm spindle, so this should fit as is. Some companies may make spacers to adapt a Shimano BB to a GXP axle, but I can’t remember who does off the top of my head.

BB30 is a different bottom bracket shell standard entirely. It is one of the press fit BB standards. Many press fit BBs are made to take 30mm axles, but 30mm axles are less common in threaded BBs (but it is possible, and BBs are made for that purpose).

Correct answer by Weiwen Ng on March 16, 2021

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