Single speed conversion on free hub
 

I found a dumpster Schwinn that I am restoring. This is my first time doing such a project. The bicycle originally had a 7 speed rear cassette. I want to convert the bicycle to single speed. I've removed the rear cassette to expose the free hub. What next? Do I buy a single cog, install spacers and tighten the lock ring? I don't want to talk about gear ratios. I need some education on how a single speed conversion works. My free hub has 9 splines (one that is very thin unlike the others). Do I need to take measurements to make sure the cog will fit? What determines the size of the spacers?

Best,
blaubner

you got the basics.. < ideally >
a single speed conversion cog should not have the shorter teeth
of a cog optimized for shifting..


(some freehubs of 7 speed era used the high gear cog
to hold the stack on)






....

...you can probably scrounge up some free spacers from old cog clusters at a bike co-op or from discarded cog clusters. You appear to be describing a Shimano Hyperglide freehub, and there's a lot of stuff bouncing around that will fit. You need enough of them so you can get your single cog to run more or less in the center of the freehub. or wherever the chain line is straightest to your crank chain wheel.

You also need enough spacers so that when you tighten the lock ring, there is pressure on the stack, so stuff does not move around back there.

So up to now you've got no money invested.

What do your dropouts look like? If they are vertical, you are going to need some kind of slack take up device but that kind of negates the single speed panache. . The simplest way to do that is to just keep the existing derailleur in place.

If you have horizontal dropouts, you could try to disassemble your existing cassette and find or fabricate some spacers to make the cog that you like line up with your chainring. I'd look to see if I could find some PVC plumbing that had about the right ID. It doesn't have to be perfect because the free hub body will hold your cog concentric. You'll need to keep the smallest rear cog because it has ridges to match up with your cassette lock ring.

Good luck.