6spd to 8spd cassette?
 

Recently for my not-vintage GT 7spd I replaced wheels and, because the wheels are for 8, 9, 10, I added 4.5mm of spacers to make it fit. Could I have used an 8spd cassette?

If so, could I put an 8spd cassette on a new set of 700c wheels for Mr. Raleigh, who has a 6spd cassette on 27 1 1/4 currently?

Mr. GT could use an 8 or 9 speed cassette, but that's when the chains get narrower and you might need to replace your front chainrings (not positive).

Mr. Raleigh probably has a 126mm dropout spacing, and the 700c wheels with a 8spd cassette are probably for a 130mm spacing, so it'll probably squeeze in ok. Again, 8spd = narrow chain so there could be more upgrades than just a cassette to worry about. Plus you need to make sure your brakes have at least 4mm of downward adjustment to make sure they'll work with the smaller diameter 700c wheels.

Thanks!
 

I was planning on replacing chains when I replaced cassettes--but didn't think of the front chainrings.

Thank you.

8-speed chain = 7-speed chain = 6-speed chain = 5-speed chain

A 9-speed chain is narrower, and a 10-speed chain is narrower still.

If the bikes are friction shift - you just have the problem of frame spacing and OLD. If you've got indexing, the tooth spacing on 7 and 8 are so similar you can get one to shift the other.

For the GT since you could already fit the 8s hubs, yeah, you could've gone 8.

Mr R will need his dropouts spread to take the hub and have to have the brakes worked out.