Hello Everyone, 

I need to pick someone’s brain about a conversion issue. I recently bought a 1979 Brat and am attempting a rear disc conversion. I pulled the backing plates and calipers from a 1986 GL-10 Turbo. The backing plate bolted onto the rear trailing arm after removing a quarter inch off of the back of the arm. Then I ordered some new rotors (made for an 86 GL-10), then I pulled the hubs off of a set of gen 1 brat front brakes I had lying around and my intent was to bolt the hub directly to the new rotor. However, as I was getting ready to bolt the hub and rotor I found the bolt pattern did not exactly line up. I took some measurements and found the gen 1 brat hub has an approximate pattern of 4 x 90 and the new GL-10 rotors have an approximate bolt pattern of 4 x 100. So my question is are the hubs from the mid 80s slightly larger than this of the gen1? Thanks for any help you  might give.

Front and rear hubs don't interchange - let alone from a gen 1 to a gen 3. Generally you need all the parts from a rear disc vehicle including the rear hubs. 

GD

^^ Weird... I have 3 vehicles with gen 3 hubs, and only 1 is gen 3.

The idk what to call it.. spindle assembly?, is different, but the inner hub section itself should be the same, if it is one with the splines the same. Some Turbos and whatnot use different ones. the gen 3 rotors are vented and have completely different calipers and mounts. That results in different steering arm legnth, etc, Which is where the main differences are. Front to rear does require finding a donor vehicle with rear discs. Or doing some rather annoying fabrication of either the arm or custom spindle assemblies...again, not sure that is the correct name. 

Bottom line, it has all been done, spend some time doing a few in depth searches on the forum. Take a look at what others Have done, not just what they were told wouldn't work, and then decide how much work you want to do, go from there. 

Best of luck, keep us updated.