cbweaver1

I had the exact same problem with my 997.2 GT3. It occured twice on the front right caliper. Once on the inside pad and once again on the outside pad in two seperate instances. I was also running the backing plate. I think your assumptions are correct about expansion but I don't have the measuring tools at those levels to confirm it. My solution was to remove the backing plate and in an abundance of caution shave down the surface of the pad ever so slightly (starting with the second brand new set right out of the box) on that side of the car to prevent it from happening again. This was done because when the new set was put in there was too much surface contact and the problem seemed like it would start all over again once that set was bedded in. Whalah! No more problem.

I may try to put the backing plates back on after some of the pad has worn down to make them last longer but haven't done that yet, I might not even mess with them any more at this point as they feel good. FYI, I was working with Pagid Yellow 19's. I believe they are the same thickness as your 29's but I can't confirm that either. I've asked the speed shop I go to ask some of their customers and no one else had this problem. While I am disappointed to learn you had the same problem I am a bit relieved that some one else finally had this problem. I wonder if it is just associated the GT3 and not the RS? If I learn of anything new I'll keep you posted and please do the same.

Regards,

Chris

911rox

Hey Peer, i think I may be able to answer a couple of your questions...

The plates are there to reduce heat transfer to the pistons and thus the brake fluid. If you've upgraded your fluid this would be less of a problem....

The RS29s are 1mm thicker (per pad) than the OEM pads and usually removing the plates helps offset most of this additional thickness... Unfortunately not in your case...

Maybe you could give the pads a rub on some sand paper or similar to see if you can lose a splash of thickness... Just thinking out aloud... Once, my mechanic deglazed the pads on my Nissan with a short rub on concrete to lose the sheen... They performed fine for the rest of their life....

TrackDays247.com

Indeed it is ok the abrade the pads - use a VERY flat surface. The noise suppression plates (not the insulator pucks) can be removed from earlier cars and indeed most on Rennlist REMOVE them altogether.

Post a few pics of your anti-noise devices so we can get a better look...Porsche ahs changed the design *4* times over 14 years...

Carrera GT

I think the race shop you've found is giving you good advice. I'd advise against discarding the backing plates, but it's fine to run a new pad without the backing plate until they wear in. If anything, I'd recommend getting Titanium backing plates to improve the heat reflection/shielding performance -- allowing higher pad temperatures without "heat soak" into the fluid in each piston in the caliper (the real cause of brake fade and failure.)

As noted, if the rears fitted without dragging, then leave them alone and focus on getting the fronts cleaned up -- the less often the rear calipers are removed, the better. Sooner or later, all these cars will end up with studs or TIME SERTs.

It's not the first time Pagid has produced a pad that's needlessly thicker than the pad it's meant to replace. Why, I dunno. Crazy. I seem to recall it was a problem for the rear pads in a 996 GT3.

Don't use sandpaper -- it has aluminum oxide which will deposit in the pad material then transfer and weld onto the surface of the rotor, causing irregular surface wear resulting in the "warped rotor" pedal feel -- not easy to remedy once the damage is done.

If you want to DIY, it should be a reasonably successful process to reduce the pad thickness with belt sander or power drill and grinding disk -- working the pads and rotors by hand would be very hard work to bring the pads down -- from your description, you only need to take 1 mm off the face of the pads on one rotor, but somehow, it doesn't always work out as easily as it sounds. The "primitive" advice from 911rox to rub the pads on concrete could be good advice -- I'm not sure what's in concrete, but I'm pretty sure there's no metal oxides in there. Once you took a millimeter or so off the face of the pad, some vigorous planing across some especially clean (no oily or greasy driveway) flat concrete would potentially remove any abrasives from the pad surface by depositing into the more porous surface of the concrete. Primitive, but could well do the trick in a pinch. And you're presumably only working with one set of pads and one rotor, so you might get lucky. Pad material can be somewhat fragile, but it's pretty hardy when it's new, so don't be too rough with it (the edge chipping can get worse and deteriorate across the pad.)

The trick to doing this the "right" way, is to find Garnet paper instead of conventional sandpaper. I have some 3M "roloc" discs loaded with Garnet paper, which I found on the shelf in a local tool store, but it appears that 3M no longer offer this product (at least, I can't find it on the Web or at the 3M store site.) I had some rotors with the classic pad "image" transferred when the car was stopped (because the pads were on fire ...) and the Garnet paper did a great job of resurfacing the rotor and deglazing the pads. Expect to apply some elbow grease and wear eye and breathing protection -- these are nasty chemicals and the finer materials are invisible in the air, but they'll happily glue to your lungs.

Keep in mind that once you have the pads resurfaced (and I'd take time to clean the rotor that was binding) you'll need to repeat the bedding process to transfer pad material to the rotor surface and ensure consistent performance.

TrackDays247.com

Good advice, yet the Ti backing plates are completely unneeded for a GT3.

Carrera GT

The Ti plates are useful depending upon who's driving -- fast lap times or bad braking technique ... either way ... and pay for themselves by allowing more pad wear before replacement.

TrackDays247.com

On a GT3 they concentrate heat into the pads and won't allow it to dissipate properly. Not used by pro teams, they'd use them if it were of benefit.

Carrera GT

I dislike generalizations. In general. Pro teams are not necessarily working to the same goals as mere mortals and even when constrained to homologation rules, their use of factory parts common to the street car equivalent is a world apart from amateurs. If a pro team removes the backing plate for the same pad, rotor and caliper, their motivations could range from hot swappable pads in pit stops (perhaps it's better to forego the benefit of a backing plate than foul a pad swap) to finding that in extreme, sustained heat saturation of the rotor and pad, the insulation performance of the backing plate does not advance the cause.

If you have documentation from a caliper vendor or from teams, I'm curious to learn what they do when constrained to using factory road car parts. Personally, I loathe these kinds of rules -- they don't save money or raise competition or promote closer racing, they're just dangerous and invite disaster.

TrackDays247.com

Eh? I'm out.

TRD0524

Pro-Teams also like to keep their cars in 1 piece, spend less on parts without performance deviation, and sometimes the ends of pro-Teams and DE cars do overlap.

The ACO homologates stuff for Europe, however in ALMS GT and GT-C classes, equipment is a bit different. Keeping it as short as possible, here were the IMSA regulations for 2010 and 2011 ALMS GT-C:

ALMS GT-C Class in 2010:

You had to use factory calipers, rotors/pads/fluid was open. As I know it, almost all teams ran factory Porsche shape pads without any modifications or shims. Cars did not have ABS. Depending on brake pad choices, teams sometimes ran different master cylinders (AP racing twin master type). Teams also overhauled and re-sealed their calipers after every 3-4 races (some more cautious than others).

Top teams used either Endless RF650 or Castrol SRF brake fluid.

ALMS GT-C Class in 2011:

You have to use the factory calipers, but PMNA did a special machining process to increase the pad thickness. They also used titanium piston caps on the stock pistons for 2011 as well. PMNA does this for teams who send in their calipers for a cost of $2,200.00

Cars did not use ABS as well and brake fluid choices stayed pretty much the same. Brake pads/disks are open as well.

Keep in mind, the 12 hours of Sebring are as hard of a race as it gets for the Cup cars using OEM calipers. Cup cars are lighter than street cars, and don't have ABS but the average temperatures of both are around the same. The upgrades all end up being the same (2 piece rotor upgrade, pad upgrade, fluid upgrade).

997 RS-Rs and Grand-Am cars use a completely different spec and therefore do not relate to factory base cars.

Just to clarify, I do think titanium shims are a good idea for street cars and do work well to protect calipers from heat. There are Inconel shims as well that are used sometimes. Is it 100% necessary, probably not.

TRAKCAR

Great post

What's that do besides repacing the (Burned off) rubbers?

peer

Thanks to all of you for the responses, it is good to know that I am not alone with this problem. I am interested in grinding the pad and cleaning the rotor and if anyone has a link to a product that I could use on a sander or other power tool it would be greatly appreciated. If not I think a nice slab of concrete will have to do (may make for an interesting scene on the sidewalk).
What other front pads are you guys using? I do not think I would get the pagids again based on this experience.

TRD0524

Compared to 2010, 2011 test results showed some temperature reduction in the caliper body. This was read by caliper temperature stickers on the caliper body. Track was Sebring.

All racing calipers: Racing Brembo/Brembo GT-R, AP Touring Car/AP Racing Motorsports, Endless Mono-6, ALCON Racing calipers all use titanium piston caps with or without cooling holes. Main reason is to keep the disk/pad temperatures from going into the caliper and fluid.

Peer: You would have to use a belt sander, or take it to a good machine shop to have the excess material machined off. If you use a sander, have to mark 6 points on the pad, and make sure you sand it off evenly (using a digital caliper).

18.5 mm thick (including backing plate) should work. I have heard the Pagid pads are 19 mm thick but that should not really be a huge problem as I have seen 19 mm pads work.

Carrera GT

I like the idea of marking six level points on the pad, then using a belt sander to bring it down 0.5mm and test fit. Should suffice. You'll want a straight edge to check your progress.

The magic number from 3M for Garnet paper is 110N.
ref:http://services.shop3m.com/search/in...start=0&end=25

I don't know if you'll find a belt for a belt sander (a Porter Cable will last you a lifetime) but it would make quick work of the pad. I used 3 inch roloc discs with no apparent trouble.