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Re; Coupe brake Upgrade
What you essentally have done is upgrade your front brakes to
that of a 1985-87 Coupe's. Except for the problem of the master
cylinder, which on th 81-84 coupe's is 20.64mm bore. On the 85-87
coupe its 22.20mm, and on the late model(feb87)Coupe with rear disk's,
its a whopping 23.81mm. 87Q uses a 25.4mm mstr cyl.!!
All these size's equate to braking effictiveness, and pedal feel.
Along with the four different sized master cylinders, you got four
different sized proportioning valves(Rear brake pressure regulators)
The 81-84 coupes use a 811-614-151 as does the feb-87 coupe. The 85-87
coupe uses a 443-614-151H, and the quattro's use two versions of its
The most important item in a brake "upgrade" is the correct rear
proportioning valve. You DO NOT want the rear's to lock up before the
fronts, especially in the wet!! It will cause you too lose control
of the vehicle!!
I installed the rear disk's from an late 87 Coupe onto my 86(drums)
along with the correct prop valve. It works as factory intended it too!
Plus once inslalled the rear prop valve MUST BE ADJUSTED CORRECTLY.
Especially if you change the springs and it lowers the car, also if
you've installed larger(15 or 16inch) wheels!
Stickey tires make brakes more effective.
Remember its not the brake's that stop the car. All the brake's do is
stop the wheel's spinning, the only thing in contact with the
ground is the tire's: hence the tire's stop the car! When you
"lock" your wheel under hard braking, the law of physic's takes over.
Stopping a car cannot be effective unless the wheels are turning! ABS!!