Early model brake caliper on late model forks?

[lukeS]

Im wanting to swap out my early model 34mm front end on my '76 for a late model one. My question is, will my front wheel, rotor and caliper work with a newer 35mm front end?

 

[5twins]

The front wheel will work but not the rotor and caliper. The rotor is offset differently and the caliper mounting holes won't match the newer fork lowers. You'll need to get a later rotor and caliper, probably a MC too as the piston size is different.

 

[lukeS]

Thanks 5twins, that answers my question.

 

[arcticXS]

Now I never had an early XS with 34 mm forks, but I do have a -77 standard with the later twin disc front brake, and a couple of RD 350s with the same single disc brake and opposed piston caliper as the earlier XS models.
The stock, later XS dual disc setup can best be described as piss poor and pig heavy.......
At least on the much lighter RD 350, the opposed piston and single disc setup is a very good brake for that period. It may be that the 35 mm fork offers some advantages over the 34 mm, but the later brake caliper and disc design is definitely no upgrade, in my opinion. If possible to do, a dual disc setup with the earlier calipers and discs would provide the best braking using oem components. If you decide to upgrade to a modern disc/caliper combination, the 35 mm fork would be a worthwhile upgrade

 

[MtnBoy]

Along these lines, are the brake tabs on the rear of the slider spaced differently on 34's vs 35's?