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Looking to swap out the 7spd tourney drivetrain on my son's bike for a 10spd setup.
It has a 7 speed tz31 cassette at the moment - from pictures it looks like a 10spd HG cassette should fit, but I can't tell from the specs.
Anyone know if it is a straight swap, or if it needs a new hub?
I think that might be a freewheel and not a proper cassette hub.
The freehub is probably too narrow. 8/9/10 (and MTB 11) all use the same hub width, but 7 was narrower.
If you've got a spacer behind the 7 speed cassette, you might be lucky. Otherwise, you could lose a cog, and run 9 of 10, or, if the smallest sprocket is 12T (or more) you may be able to get a 10 speed cassette on using an 11T lockring as it will sit in the recess of the 12T sprocket.
Yeah that TZ31 is not a cassette, it's a freewheel, meaning that the whole lot screws onto the hub. This is a different system to what we're used to on MTBs.
SJS cycles have a 10 speed screw-on https://www.sjscycles.co.uk/freewheels/sunrace-10-speed-freewheel-1136t/ but it comes with warnings about axle length so I don't know if there's a standard axle length. Measure your kids' bike's dropout spacing.