Bob,

I have a 90 740T wagon and I am not sure if there is a difference. In any case, to check if you need to replace your rotors you generally check (with a micrometer) the amount of rotor width you have left and compare that with the minimum allowable for rotors of your year car.

The specs according to the Haynes book are the following for a 82-88:

Front Brake Discs:

Ventilated:

New: 22.00 mm (.87 in)

Wear Limit: 20.00 mm (.79 in)

Solid:

New: 14.00 mm (.55 in)

Wear Limit: 11.00 mm (.43 in)

Rear Brake Discs:

Standard:

New: 9.6 mm (.38 in)

Wear Limit: 8.4 mm (.33 in)

Multi Link:

New: 10.0 mm (.394 in)

Wear Limit: 8.0 mm (.252 in)

You can determine whether you have ventilated or solid rotors by looking at them in the following way: Look at the rotors as you face the rear of the car (standing in front of the rotor if you have it on a lift). Therefore you will be looking at the rotor/disk head on. If the rotor has slots that look like they let air through, then it is the ventilitaed type.

I only know this because I was in an auto hobby shop measuring them the other day and I had one of the other mechanics explain it to me. Straight forward as I know. Just remove the tire and just check.

William Polania