1965 CCM Mark IV ; Tire size options.

Hello,

You will need to use the rim bead diameter as your guide to which tires will fit. If I remember correctly, the 26 X 1 3/8 tires fit on a rim with a bead diameter of 590mm.. The 26 X 1 1/2 tires will have a bead diameter of 571mm if they are Canadian size, or 559mm if they are American. Other 26 tires are 650B (584mm bead diameter) and 26 X 1 1/4 (597mm bead diameter). From this you can see that any tires that you use on your bike will need to have a 590mm bead diameter, or will have to be designated as 26 X 1 3/8. These tires should be available, even if you have to buy them on Ebay or Ebay U.K.. When so many tires claim to be 26, it is deceptive because they may all have different diameters and fit on different rims.

John Williamson

Here is a picture of a tire chart poster I have .I had copies  printed from the OG one 

This is informative but doesnt include the 26x1-1/2 or 28x1-1/2 Canadian sizes (571 and 622)

https://www.sheldonbrown.com/tire-sizing.html

Forgot to paste the link

Thank you....!! definitely clears up the sizing equivalents.

I wonder how much leeway therer is?  as a temp solution  what would be the result if I used a 559mm bead size on a rim meant for 590mm bead size? The tire would not hold onto the rim when inflated?

I expect you wouldn't get a 559 tire onto a 590 rim without destroying the tire.

I once tried a 622 onto a 635 and there was no way. And thats way less of a difference

We are talking tire diameter here. Would you try to put a 13" tire on your car that needed 15" tires?

John Williamson

I believe this was specifically why the automotive industry did away with 16.5" rims and tires. They were close enough that people would try to mismatch them w the standard 16" size

Duro makes a nice 26 x 1 3/8 whitewall that would look great on your bike.

The tire on the left is an original 1963 Dunlop 26" and the one on the right is a modern 28" Duro.

Thanks  all for the feedback!