Turbo Floating rotor brake noise or ??

[Dennis Kalma]

Frustration reigns supreme at the moment. I have '78 Turbo brakes on my '75, with the '78 floating front rotor set up. The hub/dog assemblies are custom CNC machined copies of a "real" Porsche set up, rotors are brand new Porsche cross drilled/ventilated to match.

At low speeds there is a persistent metallic, rotational rattle coming from the front of the car. Sound is proportional to speed and goes away as long as the brakes are applied (even slightly). I have checked the rotor runout (in spec) and there is only minimal play between the hub and rotor (when you shake the rotor, you can hear a very small metallic "click"....seemingly too small to cause the noise.

Latest diagnosis was bad wheel bearing. Just finished replacing the driver side (where the noise appears to be coming from)....zero difference in sound.

I don't actually think that the rattle goes away at higher speeds, just there is more noise going on which masks the sound once I get over 70 kmh or so.....

I can't for the life of me figure out what else it can be....transmission is fairly freshly rebuilt (no difference in sound in different gears), CV's are brand new (less than 5000 km) and the sound really "sounds like" it comes from the front, it is not engine speed dependent at all. There is no wheel runout on either front wheels....bearings are adjusted correctly I believe.....

Can anyone who has a floating rotor set up comment on any noises it makes? Allegedly Porsche got rid of that set up in part due to noise concerns....but when you look at the number of parts, I suspect it was really cost that did the floating set up in.

Also, if I upgrade to Turbo hubs and matching rotors can I get rid of the floating set up and still use my 4 piston calipers or are those different too?

Thoughts?

Dennis

[Steve@Rennsport]

Hi Dennis:

Indeed, noise & cost did the 930 floating rotors in,....

They still make that clicking at speed, you simply cannot hear it as other noise masks that sound. The degree of wear on the dogs & rotors determines how noisy they will be.

Now,......you cannot install the later-model Turbo rotors/hubs on a narrow bodied car as there is no room and the tires will protrude FAR outside the fenders.

There are other rotor options; http://www.rennsportsystems.com/1-f.html

[Dennis Kalma]

Thanks for the comforting reply Steve, you were one of the people who I was hoping to weigh in on this little irritation of mine.

I guess I was thinking about the '80 Turbo, where the suspension was the same but the floating rotors were gone. I had heard that it required a different hub and then used a conventional rotor just bolted to that hub.

Now these other options...any one that would allow me to keep everything but the front rotors and floaters? PM me if you can give me a rough idea of price....

I guess the other thing is that what you are suggesting is that the noise is normal and won't hurt anything....I can go blasting forth without worrying about my brakes imploding....

Dennis

[don911]

Yep, it's those floating rotors. I have factory rotors with VCI T-locks. The noise wasn't bad when everything was new. Now that they have a few miles on them, there's a lot of clacking going on. Just tell yourself it's the sound of performance.

[Steve@Rennsport]

Hi Dennis:

The noise is normal and will not hurt anything. I would add that ALL floating rotors require some periodic maintenance to clean the ID of the rotors, OD of the hats, and the drive dogs so everything continues to "float". Failure to do that will accelerate some potential warpage problems since the two pieces cannot move freely,....


I'll PM you about the custom 930 rotors on the Brake page of our website.

[dean]

Originally posted by Dennis Kalma

Can anyone who has a floating rotor set up comment on any noises it makes?

Dennis

Mine make the clickey-clack sound at slow speeds. It don't hardly hear it at all anymore. The first 20 miles I thought something was wrong but now I am used to it.

My thoughts- Drive faster

[ChrisBennet]

My floating rotors made more of a "clock clock clock" sound at low speeds.
-Chris