im building a singlespeed commuter for my brother that he can treat like crap, lock up outside and eventually have stolen. super on the cheap dumpster find style. its a rampar hi-ten pile.

i want to use the 52t outer ring with a 20t or 21t freewheel [approx. 70 gear inches] but when i measure from the centre of the frame to the chainring its 52mm.

52mm chainline? the rear spacing on the bike is 126mm. is this doable or am i gonna have to figure something else out?

thanks in advance

i should mention aesthetics are not a concern so if the answer is to use a bunch of spacers on a old road cassette hub thats cool too. just wondering about options.

Running the ring on the inside might make things easier on you.

Get a $25 thrift shop 10 speed, chuck the derailleurs/shifters, shorten chain, leave entire freewheel/cassette on the hub, pick appropriate chainline (inner ring ideal) and gear ratio. Done.

This is how you make a really cheap singlespeed...

Just run the chain from the inner ring (which is probably a 42) to the 15-16 tooth cog on the old freewheel... your chain line will be pretty straight, you won't have to buy a freewheel, and the bike should not be at any great risk of being stolen.

the bike had mashed up 27" wheels. also, i can not flip the 52 because it is a one piece with the crank arm. the 42t ring was bolted to it.

find another trash bike?

If you are set on using that 52 in it's current position chain line will be an issue if you use a freewheel but with a cassette you can position the cog with a good chain line.

If it's a really old bike the rear dropout spacing may be tight as newer hubs are 130 mm and the old Rampar is certainly a 125 mm.

i've decided to grind off the teeth on the 52t and bolt back on the 40t[i thought it was 42t]. the 52 will act as a 'chainguard' or something... also i'll have a more reasonable chainline.

thanks for the input folks.

I did the supercheap method of using the inner 42T ring with the 17 cog on the rear freewheel. I found the bike at the dump (err, recyling center). I put maybe 25 dollars into it by buying a powerlink, some new handlebar tape, and some new cables/housings. Now it's a completely functioning bike.