Mix and match brakes

Chuck Moreland · 04-09-2002, 10:56 PM

I have a set of used Carrera rotors laying around. New they are 24 mm 282.5 mm, but now they measure 23.3 mm.

I have M brakes and rotors on my '77, new the rotors are 20 mm 282.5 mm.

The pads are the same shape and thickness for both setups.

So, the idear is to use the Carrera rotors in the earlier M calipers to get the better rotors. The rotors can be turned down to 22.5 mm and used to 22 mm. That means I have a 2.5 mm challenge.

Seems there are two potential pitfalls:

1 - the pads when new might not fit. Even mildly worn pads should fit fine.

2 - the rotors do not fit between the calipers halves. But it is only a mm or so and can easily be machined off the calipers.

I wonder if anyone has tried this?

masraum · 04-09-2002, 11:01 PM

The calipers in Carrera's have a spacer inbetween the two halves to enable the use of the thicker Carrera rotors. I guess you could grind off some of the braking material, but I don't know how well any other method work other than getting a pair of Carrera calipers.

Early_S_Man · 04-09-2002, 11:33 PM

Chuck,

If you are going to have machining done ... why not have a thicker set of spacers (your 'M' calipers already have a set to widen them from the solid-disk size to the 20 mm vented size) made from 3/8" bar stock? All you need to complete the job are some longer Allen bolts and 8 of the seals that happen to be identical to VW part 311.615.277.

KTL · 07:07 AM

Wish you'd posted this earlier (like last week) Chuck. I just sold my calipers from my 87 for $75!!! I woulda given you the first shot, had I known. New seals and ready to go. Oh well, sorry.

Edit: ooops. Forgot M and A have different bolt spacing. Never mind

Chuck Moreland · 04-10-2002, 07:41 AM

Kevin, that's what I get for "retiring"

For $75 I would certainly have just changed out the calipers. Those '87 do fit my car. If any one else is looking to dispose of a similar set...

As for the spacer in the caliper, I keep hearing that if you split the caliper halves you are destined to have leaks.

Bill Verburg · Bill Verburg's Garage

If you're vewy, vewy carefull they can be reassembled without leaks, but I wouldn't want to do it. The other issue is piston size. The front M has 2x48mm pistons as do the narrow A, the wide A, and the S. The narrow rear M, as used thru 83 has 2x38mm pistons and the wide rear M as used on the 84-89 carrera has 2x42mm pistons. The smaller pistons on the front will move the brake bias to the rear. You will then need an adjustable bias valve on the rear circuit to compensate.

If you want a relatively cheap upgrade for the an M equipped front look for the struts and brakes off of an 84-89 Carrera.

Bill Verburg · Bill Verburg's Garage

FYI there is a pic of a kit to widen the early M rear as used on non vented rotors for use on the 20mm wide vented rotors at;

M widening kit

also lots of neat 914 stuff!