Using 7 speed shifters with 8 speed cassette?

Should work, but chain might not be aligned perfectly in all gears. I've often swapped 7 speed and 8 speed wheels on bikes with 7 speed or 8 speed shifters, and each combination works to a degree. For the last couple of years or so on my commuter, I've been using 8 speed shifters on a 7 speed freewheel and it sounds like some gears are not quite perfectly aligned. I'm soon to upgrade that bike to an 8 speed wheel.

Anyway, it's easy to try it out and see.

Forgot to say that the 8 speed cassette won't fit on the 7 speed freehub. If you remove one cog, you might need a spacer instead. Not sure of the exact numbers, but check Sheldon Brown's site, he has all the details.

Thanks for that info, I will go to his site and have a look. I may have to buy a better 7 speed cassette or dismantle one of the old 8s.

Well, I'm glad I waited. The lady brought the bike over today and surprise, surprise, a 7 speed spin-on 14-34 Mega Range Freewheel!! :eek:

I ordered a Shimano MF HG50 11-28 7speed freewheel from the LBS. 😎

I decided to offer her a speed option:
a pair of 650c "training wheels",
the Front, a Deep-V with a Conti Gator Skin, 650x23,
the Rear, a road rim on a Deore hub with a Conti GP, 650x23
use the 11-32, 8 speed MTB cassette, the 32 tooth not selectable,
this will make one horny ladies MTB/Tri-training bike! 😄