Brake Pad chatter from 930 brakes on '85 Carrera (Zuffenhaus)

[Carrera 3.0]

I recently purchased an '85 Carrera that has an awesome 930 suspension/brake set-up done by Zuffenhaus. The front brakes use a 930 caliper with Zuffenhaus's custom back plate, and it mounts onto a Carrera rotor. The retaining clip is there, as seen in the photos, but I can hear the pads bouncing around incessantly when driving. Under braking, of course, the sound goes away.

The previous owner explained the sound by stating that Zuffenhaus used a "floating disk," and that the noise is unavoidable. I'm not familiar with exactly what the first part of that sentence means, and I'm hoping that the latter part isn't true. I'm getting ready to do pads and rotors in front anyway, so I'm hoping that there is a way to ditch the chatter while I'm at it. Any ideas?

[9elf]

Floating rotors mate - The rotors are not firmly fixed to the hub but rather they are allowed to move sideways on little dogs (shake the rotor side to side to see the movement).

Also, have a look from the back to see the dogs.

Porsche ditched the floating rotors after 2 years ('78-'79) on the Turbo due to the chatter.

They are great brakes for your car and not cheap.

The pads are not jumping around - the rotors are moving on the dogs creating a tapping/knocking noise.

ps. doesn't look like a Carrera rotor to me, looks like a 930.

[Carrera 3.0]

Thanks for the helpful info - they are great brakes, car stops like a champ.

I assume this means there's nothing I can do about the noise other than maybe louder exhaust and stereo to drown it out?

[Ronnie's.930]

If the pins/buttons that attach the rotor to the hub have sufficient length/space, you can shim them with thin spring washers - this takes up a bit of slack and doesn't let the rotor float/clatter so much. This is common practice with motorcycle floating brake rotors when used on street bikes, but I don't know for certain if that is possible with your rotors (you would have to look into that).

*** EDIT - OK, I just looked into this for you on the 930 Forum (tons of threads on floating rotors over there), and what I wrote above is totally inapplicable to the 930 floating rotor setup (entirely different design to the motorcycle rotors I referenced). But here is a thread with some good, noise reduction info for you -

'79 930 - Brake refresh in progress

[Craig_D]

Originally Posted by 9elf

ps. doesn't look like a Carrera rotor to me, looks like a 930.

Yeah, those are definitely not Carrera rotors, those are floating 930 rotors (and expensive).

[James Brown]

it LOOKS like the pads are done so before you trash the floaters, re-surface the rotors and new pads, then see how much they "click"

[Steve@Rennsport]

Originally Posted by James Brown

it LOOKS like the pads are done so before you trash the floaters, re-surface the rotors and new pads, then see how much they "click"

Pads look OK to me, but the rotor drive dogs likely need to be cleaned to ensure they "float" properly. Floating rotors do make noise when cold and at low speeds; its the nature of what they are! If someone doesn't like the noise, there are alternative rotor/hat assemblies that are just as durable.

Don't resurface them; that removes rotor mass which is something you don't want to do. If they are worn to spec (30mm), its time for replacements (dealer only).

[James Brown]

Steve, you see pad meat in the 2nd picture? i see the backing plate almost touching the rotor. And you can't surface them to correct runout?

[FPB111]

Looking at your "hat" it appears that you have VCI floating rotors. I ran different permutations of the 930 brakes, both floating and non-floating, on my 1972 for 17 years. You can also mount their non-floating rotors to those "hats". Which is what I finally ended up using. Take a look at the VCI website. Scroll down to the replacement parts. You can get non-floaters for ~$299 each.
VCI - Porsche 911- 930 69-89, 914/6 brake upgrade page

[Steve@Rennsport]

Originally Posted by James Brown

Steve, you see pad meat in the 2nd picture? i see the backing plate almost touching the rotor. And you can't surface them to correct runout?

Everyone sees one-dimensional pictures differently so all I can do is offer an opinion. Certainly, I'd like to see FAR FAR better pictures here so thats the caveat for any observations here.

Correcting runout or taper removes mass (material) from the rotor and that's completely counter-intuitive to me. The whole idea is to conserve mass for maximum heat dissipation which is very important for any car used at the track.

When a rotor is worn out, I replace it. Same goes for any other consumable on these cars.

[eimkeith]

Hi there!

The calipers in question are the fronts as shown, correct? If so, there are no Zuf parts there (our inner caliper half is used on the rear so that the rear caliper will mount directly to a Carrera trailing arm.)

I'd try a different set of pads first - some cheaper pad manufacturers don't keep the same backing plate tolerances (width-wise) which can allow the pads to shuffle back and forth in the caliper. See if you can get the pad to shift back and forth with no pressure applied to the hydraulic system.

Similarly, if the rotor hat mounting blocks have looser tolerances (the OEM Porsche hats are looser than ours, for instance) then the rotor can click also.

The rotor hats in the photo are not Zuffenhaus pieces, for what its worth.

Also, check the torque on the caliper mounting bolts and the caliper assembly bolts!


Hope that helps.

[Iciclehead]

I have Turbo brakes fitted to my '75 and would make a few comments.

First. They rattle, particularly at slow speed. When you disassemble the floating rotors you see why, there is just that little bit of "float" that allows the rotor to move and make noise. Once you apply pressure, the force of the pads on the rotors takes up that slack and the rattle goes away.

Second issue. I have tried two kinds of pads, now have Mintex on the thing. Issue is that the discs seem to collect a small amount of pad material at slow speed driving that gives you a noticeable vibration when applying the brakes. I struggled with that (since the whole set up was brand new, what could be happening) until a more senior Porsche tech said that I had pad material unevenly stuck to the rotor and recommended an Italian tuneup. Basically it was 5 runs at full throttle to about 140kmh and then hammer on the brakes as hard as possible, re-accelerate and do it again. Idea is to get the brakes hot enough to burn off the excess pad material. Worked perfectly, but it needs to be done about twice per summer...the vibration comes back.

I love these brakes, they give me great confidence in stopping, but they are not "normal", they make more noise and need more care than the run of the mill M's or A's.

Dennis

[Carrera 3.0]

Thanks to everyone for the helpful input!

What photos would be helpful? In the short term, I'm concerned about the varying opinion on whether or not the pads have life left, especially since they have only a few thousand miles on them.

[Carrera 3.0]

Got another look today at the brake set up and took a better photo. The pads look practically new, and the rotors were resurfaced at the time the pads were replaced. I don't have #'s from resurfacing! but I'm inclined to believe they should be ok. Doing some reading on the 930 forum, it looks like giving the brakes a good workout and trying to shed resin buildup could be the cure for the minor pulsing I am feeling.

[James Wallace]

Have you called Aaron at Zufenhaus? He'd probably have some input for you as well. Aside from the fact he has a very cool shop, I found him to be a very straight shooter when we did business a few months ago.

Good luck with that sweet looking brake set up.

James

[James Brown]

oh yes, better, good pads

[Steve@Rennsport]

Originally Posted by james brown

oh yes, better, good pads