i have a 7spd hyperglide on a 105 hub. Can I simply buy a 8spd hyperglide cassette and slide it on? I believe the 8spd cassette is 1.5mm wider than the 7spd cassette.

You may need to purchase a longer axle. It may also be the case that the race is deeper or not as deep requiring different spacers to be added or subtracted. You may also need to redish your wheel.

I don't think so, but if you can borrow someone's, it's worth a try.


I believe you can swap out the freehub, and then go 8/9/10, with a longer axle and slight re-dish. LBS did it for me for $35 and parts. Worth it if they are nice, repackable hubs.

Do you always need to redish after adding more gears?

No.

hmm, so needing the cassette, a free hub, and the work to do it - any way to tell if it will fit as is

if there is a spacer behind the 7s cassette than you already have an 8 speed freehub.. if not you have a 7 speed freehub and it will not fit.

Disclaimer: someone might pipe up and say you can do it by building some sort of custom 8 speed cassette out of 9 speed sprockets and spacers or something but I don't recommend going through the trouble of something like that. Better to do it properly and change the freehub or buy a new wheel.

thanks for the replys, i was reading on sheldon's page about this and read about just that thing - unfortunately i have a 7spd hub - not going to do the 8 of 9 setup - cause i don't have a set of 9spd STIs and chain to go with it - using 8spd Sora STIS with the alternate routing and it works, but if i could just swap the cassette I would. 7spd i have now is a J 12-21 with a 42/52 double and it takes some serious mashing for me to climb the steep grades on two of my "local" rides.