Front Brake Rotors 79 GS1000s

[Simmons1]

I searched a bunch but didn't really find an answer.

Does any one know if I can use a pair of slotted disks from a 1980 GS1000s on a on 1979 GS1000s

Thanks!

[sealpup]

I had the same issue, but I made the mistake of buying new aftermarket 1980 rotors before asking the question. No, they don't fit, unless you also swap the brake calipers. Also I can't recall if the mounting hole centres on the 79 forks are suitable for the 80 calipers. I did find a place in the US that refurbished 79 1000S rotors by drilling out the rivets and replacing the braking surface (outer ring) with a brand new section. From memory the cost was around $500 + shipping to/from Oz. I decided to put up with some unsightly scoring instead...

[salty_monk]

Yep if you bring along a set of the newer calipers too (any year). They all fit. Or upgrade to twinpots...

[Simmons1]

That is exactly what I was planning to do. I have set of trudisk resurfaced slotted rotors and a newly overhauled set of front calipers also from a 1980. I assumed the calipers would bolt right on.

When I went to mount them on 79 forks the bolt spacing was off a little bit to mount the calipers. The bolt spacing on the 80 calipers is touch smaller than the 79.

I was thinking I would make the bottom hole in the fork a little oblong to make them fit. I almost started messing the holes in the forks but stopped to ask about being able to use the 79 calipers first. Wasn't sure if I needed to oblong the top or bottom hole, or both.

Thoughts?

thanks!

[Grimly]

Oddly, just to muddy the waters a bit.
I've got GS1000 legs on my 850. I'm using the 850 calipers I've acquired over the years. The calipers have come from 850s, 1000s, and other bikes, but they all interchange (with the obvious exception of the mounting bracket and mount positions on the L forks).
The 80 850 is the recipient of the above. When I rebuilt the front brakes of the 79 850, I used later calipers no problem at all.
Mixing earlier and later wheels with solid or slotted discs works fine, too.