Mixing and matching drive trains and cassettes

Cardinal-Red

Hi all,

I currently have a direct drive trainer, with a 9 speed cassette attached to it. I only have 1 bike, which I move between being fixed to the trainer and attaching the rear wheel for outdoor rides.

It's no big deal but the swapping over can be a bit of a faff.

I mentioned this to a friend who offered me his old bike for free for winter. It's a 7 speed Shimano drive train though.

So my question I guess is what's the worst that could happen if I mount the 7 speed frame and drive train onto the 9 speed cassette?

paul_the_pedaller

I seem to remember that the old Sedis chains were 7/8/9 compatible, the difference being the external width. I would say it was worth a go, my old training bike was 6 speed running 8 speed Athena ergos and it was fine once the stops were adjusted. For the sake of a chain there's not a lot to lose.

whyamihere

You might get a couple of gears which run ok, but you won't be able to change gear - The size of the gaps between cogs is too different. The 7 speed shifter will overshoot the next cog significantly.

Cardinal-Red

Ah ok, so all cassettes are basically the same width, and the number of gears determines the spacing; rather than them getting thicker as gears increase.

That makes sense.

I'll scour e-bay for a cheap 9-speed bike then!

markhewitt1978

Cardinal-Red wrote:

Ah ok, so all cassettes are basically the same width, and the number of gears determines the spacing; rather than them getting thicker as gears increase.

That makes sense.

I'll scour e-bay for a cheap 9-speed bike then!

That's only true up to a point. 8/9 speed are the same size. 10 speed is actually smaller! 11 speed is bigger again.