I just built a weird single speed with parts I had on hand that were left over from other projects.
The frame is a mid-1980s MTB with semi-vertical dropouts and it has a Suntour roller-cam brake under the chainstays and a Deore cantilever brake up front. The stem has this really weird size of 21.?mm diameter. I wanted to swap out that stem so I could use a drop bar but wasn't able to find a stem that'd fit. It'd be easier and cheaper to swap the 1" threaded fork for one with a larger inner diameter steerer tube fork that'd take a common drop bar quill stem.
In the meanrime and to use the Tecktro inline drop bar brake levers I have, I to cut a drop bar really narrow ass the cuts had to be made just where the curve from the top of the bar starts from the straight portion so thast I could get the bar through the stem.
I've used an old Exage crank with a 39 ring on it. That's coupled to the 16 teeth cog of a three cog freewheel. I removed the other two larger cogs and the spacers.
A small problem is that with this chainring and cog combination the chain is a bit slacker than I'd like. The gear does run well and doesn't bounce off even on rough terrain because the chainline is pretty good. I have three options to snug up the chain which is 3/32 by 1/2 inch.
#1 . is use a 40 teeth chainring. That will only work if ONE tooth = 1/2 a chain link. Does it?
#2 . is replace the solid nutted axle with a hollow one with a quick-release and grind/file the axle so that it fits tightly between the dropouts but does NOT rest in the dropout itself.
#3 . is to order a 3/32 link online.
The easiest and cheapest is option #1 . Does one tooth bigger on a chainring equal a 1/2 link increase in the chain length? If not is there another way to take up that 1/2 link of slack?
Thanks and cheers from Miele Man