31mm steer tube bore

anyone know what years CCM used a 31mm steer tube bore? I went to change out the headset in what appears to be a 46 twin bar and the bore is 31 mm. My 64 and 67 CCMs have the common 30mm bore but I havent ever checked my older bikes. 


My  three 1960s parts catalogues show two different part numbers for CCM headset cups. While they do not detail the specifics, a couple catalogues mention that the change took place in 1959 and one mentions that the later version is stamped "59", though presumibly this practice would have been discontinued after a transition period. I assume the change was the mounting diameter. 

Earlier catalogues show the headset to be unchanged (other than finish) from 1923-1958.  There was an extensive change in 1923, with a new headset designed around larger 3/16" ball bearings, as opposed to 5/32" ball bearings.

It is also worth noting that the fork crown race has two different part numbers, starting in 1969. Again, the specifics are not detailed but I assume it is a change in the mounting diameter, as there are two common standards.

Awesome, thanks very much for the information. Looks like i am going to be using shim stock to make the newer style headset fit the older frame. Two layers of 0.010 stock should be about right

Thanks for that post, Tmar. I was not aware there was a change to the headset in 1923. I have two 1918s, a 1922, and two 1925s that are all works in progress so I'm happy to know this!