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verktyg

What brand in the hub?

If it's a Normandy or Maillard hub it's likely to have French threads.

I don't have the specs for the lock ring threads but here's the thread standards for the cog mounting threads:

French threads 34.7mm x 1mm (1.366" x 25.4 TPI)

English threads 34.8mm x 1.058 (1.370" x 24 TPI)

Italian threads 35mm x 24 TPI (1.378" x 1.058mm)

ISO threads 34.92mm x 1.058 (1.375" x 24 TPI)

As you can see, French threads are slightly smaller than the standards. Any of the others can be forced on but will damage the hub threads.

If this bike has been used a lot and you don't have any spare metric cogs, there's a good chance that some "watch repairman" has already forced an English or ISO cog onto the hub.

The aluminum hub threads will probably survive this once or twice but I wouldn't recommend switching cogs a lot and never go back to a French cog if this is the case. Someday you may try to stop with a fixed gear cog and get an unwelcome surprise. Embarassed

Chas.

verktyg

ppppp

Thanks for the information, the lockring is french thread, 33x1. Mavic uses them on their track hubs. For luck! The exact cog mounting thread i will messure. Now i 'm using a BSA cog from dura ace.