revolution993

i guess am not the only one with the squealing problem

ARM993

Brake squeal, what brake squeal? I thought that was Porsche's built in deer deterent system.

Tim@BHP

Re: 993 noise (Yes we have a noise problem too!)

My Company BHP sells ultra performance dual use brake pads for street / track operation. I’m chirping up on this discussion to share what I’ve learned about noise and this application.

Of all the Porsche applications we sell, only the 993 gives us noise problems. These are cars with new discs/pads and everything done by the book. Yet there is noise. The interesting point here is that the front pad shape for the standard 993 is identical to the Stop Tech ST45 caliper. Stop Tech sells our XPS friction part number S0953 for their kits and it is the same S0953 we sell for the front of the standard 993. Yet the Stop Tech application makes NO NOISE! I mean it’s silent on every platform they have installed. (including Porsche) It was this (non) connection that got me scratchin….

Noise is a function of high frequency harmonics that are amplified by numerous components in the un-sprung mass of the suspension corner. More often than not, brake noise is caused by harmonics from the pad to disc and /or pad to caliper interface. What I’ve found in both 993 applications (Turbo and N/A) are the Brembo calipers for these cars utilize racing derived brake pad abutment plates. The brake pad abutment plates, are secured to the caliper by two screws approx mid span. Once the abutments plates are secured to the caliper the lower portion of the plates (abutment tangs) hang down and have a 90 degree bend on which the brake pads rest. These abutment tangs are the chief source for noise for this application. They are functioning as tuning forks and are significantly amplifying the noise.

I am working on a redesigned pad abutment plate design and testing continues until then here are a couple of tips to minimize the noise.

High brake line pressure stops will always be quieter than low pressure stops because the high frequency harmonics are dampened by the friction material under load in compression (high brake line pressure) and shear.(torque output) Audible noise for the 993 will almost always occur under light braking applications. (Low line pressure and low torque output)

Wash your calipers and pads especially if using German based friction formulas. I.e. Pagid, Textar and our own BHP The Brake dust from these composites are highly abrasive and will add significantly to noise. (Note: Wash at ambient temperature and never hot.)

As German based friction material wears it will slowly consume the disc. As this wear progresses, a high groove will form on the outer radius of the disc. This high spot is a major noise generator. Machine/replace the discs or on the cheap, machine the outer radius of the brake pads. (The noise will come back at some point in the future when the pads wear some more.)

As for the gooey junk that is sold to be applied to back plates I offer this. It will wear out in time and this goo may not have a high temperature tolerance. (Burn) So if you’re tracking the car leave the goo off the pads.

Im going to keep working on this noise problem and at some point we will have a cost effective solution. If anyone has questions feel free to drop me an e-mail.

JasonAndreas

Replacing the spring plates with new gets rid of the noise and then your good for another 7 years. I noticed that corrosion, brake dust, etc. build up behind the plates and bends/pushes them outwards causing them to grab onto the pads unevenly. With new plates the pads are loose in the caliper and they don't squeak. A solution from PAG was to add a coating to the backside of the spring plates but I don't know how well that will work long term. They also come slightly pre-bent in the opposite direction. The horizontal portion (the part acting as a tuning fork) of the spring plates doesn't seem to change/bend/etc. with mileage.