72 rotor 79 wheel question

[Johnnny13]

I helping a buddy rebuild a 1972. Currently he has the 72 forks and early model single disk caliper. He has 79 wheels that already have a rotor on them. My understanding is that the offset of the late model rotor is deferent then offset of the early model rotor. I assume that if I get a hold of the early model rotor I can bolt it to the late model wheel and everything will be good to go? I'm fairly certain the 72 front rotor is 306-25831-00-00? Is there a option where I could use the 72 forks, 79 wheel, 79 rotor, and 79 brake caliper? not sure if the late model caliper would mount to the 72 forks?

 

[arcticXS]

No, the later caliper won't bolt to 76 and older forks. But that is not a problem, I think the earlier caliper is a better caliper, being two piston, vs. one on the later version. 72 disc (rotor) is an odd one, I believe. A disc from a 73 to 76 should work with the 79 wheels, AFAIK.

 

[gggGary]

But that RH 72 fork leg is a one year wonder comparable with nothing but the 72 rotor axle etc.

 

[arcticXS]

I

But that RH 72 fork leg is a one year wonder comparable with nothing but the 72 rotor axle etc.

I do realize that the disc and hub on a 72 wheel is totally different from 73 up, and that the axle hole in the rh leg is larger, in fact similar to the sprocket setup on an RD350.
But isn't the caliper the same as 73-76? And the hub on 73-76 cannot be very different from a 77 onwards. If my assumptions are correct, then a 73-76 disc and a bushing for the axle is what it takes, not much more.

 

[Johnnny13]

I appreciate all of your help. I think getting 75 to 76 forks, a early model caliper and late model wheels should work.

 

[650Skull]

Using a 77 wheel and a set of 73 forks and the 73-76 rotor and caliper will work.........early, 73 to 76, and later 77-83 (although 82 and 83 hubs are 48 spoke), rotors swap on all spoke hubs from 73-83................ calipers have to be fork specific, early 73-76 and later 77-83..............wheels, 73-83, will fit any year fork

 

[arcticXS]

An old thread for sure, but my personal opinion is that 76 fork sliders may be preferrable. Because the caliper is behind the fork slider, and the old 2 x48 mm piston calipers were still used. (On a side note, the most sought after Brembo 2 piston calipers, like used on Ducati 900 SS and Guzzi LeMans had 2 x48 mm pistons...No further explanation should be necessary)