Not sure if this has always been around, but when I converted one of my steel bikes over to 700c wheels a few years ago, I was told there was no option for a 6-speed cassette so I had to use a 7 speed. This popped up on Amazon and I assume it fits that need for people converting old 12 speeds to newer wheels? Does anyone have any experience using one of these on a newer wheel set with Shimano hubs? It would be nice to get my bike working with the original 6 speed that I had with the original wheel set and 6 speed freewheel.

High Performance 6 Speed Bike Cassette with Stainless Steel Aluminum Alloy Replacement Cycling Accessories for Mountain and Road Bikes : Amazon.ca: Sports & Outdoors

I would only ask why? If you have 7sp working why go back to 6? 6sp was friction shifting and friction shifters don't care how many speeds you have as long as it swings from the smallest cog to the largest. I put a 10sp wheel on a formerly 6sp bike and it worked fine in all 10 speeds.

I can't see why you'd want to go back to a 6-speed. Back when 5, 6 and 7 were popular the cassettes were screw-on, and they could be a nightmare to get off the hub. The hub you have now makes a cassette change much easier. Building on what zacster says above, if I was you and had friction shifters on the bicycle I'd think about going up to an 8-speed cassette if it will fit on the wheel and in the rear drop-outs. Just my 2 cents.

Most old 12 speeds which today we'd call 6 speeds or a 2 x 6, were freewheel and wouldn't be able to use this cassette. But any that have a 11 cog on them might could use this cassette. Most freewheels I ever have seen only had a 14 tooth on them for the smallest tooth count.

I've never seen a bike with a six speed cassette. I know they exist, but they were rare and not anywhere for me to see.

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.

If your wheel uses a freewheel, then that cassette won't work with it. Shimano's first indexed shifting ("SIS") was for six-sprocket clusters, both freewheel and cassette versions were made.

If this is an SIS downtube shifter, 7-speed indexing modules (part #3 in the illustration below) came out later and could be swapped into the lever to make it work with 7-sprocket clusters. But they haven't been made for decades, and finding one might be a problem.

The 6-speed cassette you link to is likely designed for a 120mm freehub. Such hubs are made mostly for the purpose of converting singlespeed/fixed gear bikes to a derailleur drivetrain. My guess is that the 6sp cassette would fit on an 8/9/10sp freehub body, but you would need to add a bunch of spacers behind the cassette to take up the extra space. If aesthetics are your primary concern, I'd think an 8-speed cassette would look better than a 6-speed cassette that has an oddly large gap between it and the spokes.

The original indexed shifting was horrible. I have a bike with Suntour indexed shifting and it also had a lever to turn it to friction. Not sure if shimano did the same.

But looking at that cassette it had ramps on it and those would improve the shifts.

Shimano's SIS system also had an option to revert to friction shifting. But the SIS indexing was quite reliable, if you used a full-SIS drivetrain (shifter/derailleur/cluster). The friction option was to appease racers using neutral-support replacement wheels that were not compatible with SIS indexing.

The original SIS system did not have those ramps. Those came in with Hyperglide, and Hyperglide sprockets won't install on a SIS/Uniglide cassette without some modification.

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