I have 12 speed MTB and Zwift is sold out of the Zwift Hub 12 speed. If I buy an 11 speed hub, will a 12 speed cassette fit onto it?

Thank you,

Whose gears do you have on your MTB? Is it SRAM?

Yes, it’s SRAM.

SRAM mtb’s use XD freehubs (and no, a SRAM 12sp cassette it wont mount to a Shimano 11-sp freehub) but one exception applies …SRAM sell a low-end NX PG-1230 that uses Shimano freehub.

If you don’t know what you have, the bike specs should tell you (post them up here if you are not sure) but you can also tell by counting the # of teeth on smallest cog - NX has 11 whereas all other SRAM Eagle 12-sp cassettes have 10t.

There was a recent discussion of using a mountain bike with a 1x drivetrain with a 32t chainring with the Hub, and the conclusion was that the high gear is too low. Using a PG-1230 will make the high gear lower since 11t is the smallest cog that can fit on a Hyperglide freehub body. If your bike can support a larger chainring, you could use the PG-1230 with a larger chainring and a longer chain. Exactly how big the chainring needs to be depends on your power, whether you expect to sprint in Zwift, etc.

Better options would be to get a road bike, or a trainer that has an available XD/XDR freehub body such as a Kickr Core.

I found my MTB unusable with the 32 crank/12 cog combo. Even in 32/10 it would spin out on the hub like i would with 32/50 on a real road. I ended up swapping to a gravel bike with a 48 up front. Its much much better but I think having a 50 or 52 would be even better up front.

My bike has a SRAM NX Eagle, 12 speed 11-50T cassette. My concern is if the axle on the 11 speed Zwift Hub is long enough to accommodate a 12 speed cassette.

Yes the SRAM PG-1230 cassette is designed to fit on a Hyperglide 11 speed freehub body.