Originally Posted by
gthomson
This is an 80's bike with Shimano Index shifters originally on an older wheel and 6 speed freewheel. The wheel had seen better days, spoke nipples were all threaded and didn't tighten well so I could never get them true. No real reason to change to a 6 speed, other than to not have the extra cog that doesn't get used. Bike rides and shifts decently, going up the 6 cogs. More for esthetics i guess than anything.
The first step is to determine if you current 7 speed wheel (freehub) uses a Shimano hyperglide (HG) cassette. I don’t recall Shimano making a 6 speed HG cassette, but they made Uniglide (UG) 6 speed cassettes.
There 2 compatibility issues between HG and UG. The first is UG uses an external threaded first cog and HG uses an internal threaded lockring. Also HG cassettes have one wider spline to align all the cog ramps in the correct orientation. UG has uniform splines.
The linked 6 speed cassette appears to be HG compatible as it uses a lockring and has a wider spline. You may need to add a spacer behind the cassette since the 7 speed width is 31.9mm and the 6 speed is 29.5mm. I’m guessing a 2mm would work.
John