Graydon, just went thru this on my 86... The pre 87(July 87> use the double
piston girling) turbos and tquattros use the single piston app, girling/ate
with a larger but thinner rotor. The 7-87 on use a thicker rotor with
different vents, a different caliper carrier and a different brake line, with
dual piston ate calipers... To upgrade (just did it) takes some research and
is not worth it unless the rotors are shot anyway.... figgrd the whole
switch ran about 350.00 without the pads....