sunburst

My son and I were converting his Peugot into a fixie on Sat and I had thought I could use the Peugot's old chain. It had a 6-speed freewheel (with SIS derailluers), so I figured it had a wider chain than modern ones with 8, 9 or 10-speed cassettes. The fixie wheelset I bought had a 3/32" 15T cog (can't remember the brand). Also, I measured the width of the cog's teeth with calipers, and they seemed to match the width of the chainring's teeth.

At any rate, we were almost finished when I tried to install the chain. The teeth of the cogs seemed to fit between the sides of the chain, but the distance between teeth seemed to be a problem. I thought maybe the chain was stretched and measured it with my handy hashbar tool - no problem. It actually seemed that the teeth were too far apart (not too close, as in the case of a stretched chain).

I pulled a fairly new SRAM singlespeed chain off my singlespeed conversion and it worked fine. And the old Peugot chain seems to fit the singlespeed BMX freewheel (although I haven't installed it).

So why didn't the old 6-spd chain fit the fixie cog? Any ideas?

sch

Fixie cogs and CW are nominally 1/8", not 3/32" so you may find an occasional
5-6spd that will fit, they are not 'supposed' to. The chain pitch is the same
(1/2"). Sheldon Brown says either 3/32 or 1/8" chains will work on fixies and
since your cog is nominal 3/32 should be no reason why it wouldn't work. Chain
pitch (bicycle) is one of the few inch world standards in a metric era.

planyourfate

I would personally replace the chain when making and changes in the drivetrain. If the chain is stretched it will damage the cog faster.