FineProperty

My 01 996tt has about 28,000 miles on the original rotors, and I'm sure the car was never tracked before me. As my car (and the driver) have gotten quicker at the weekend Driver Ed events at the track, the brakes are showing signs of wear. I went with MPSC's and the suspension and brakes are now the weak link.

The front brakes after the last weekend have concentric grooves (rings) all the way around and across both sides of both rotors. Stock pads. High temp brake fluid. I am certainly braking hard, I race karts every other weekend and you can almost slam the pedal to the floor in those (F1 style).

I almost just PM'd TomK, but I thought as others get faster at the track this might be worthwhile.

Am I in need of new rotors because of the scoring? There's still a lot of pad left (70%), but I'll toss them for a whole new setup. Frozen rotors and Pagid Orange? I don't want squeal.

tkerrmd

short answer IMHO is to get new rotors (frozen if possible [50% longer life]) AND new pads.
I would not turn the current rotors and I'm pretty sure porsche motorsports wouldnt either. I never use old pads on new rotors. Soooooo.............new rotors and pads.
Dont forget anytime replacing anything I always consider the "upgrade" options. In this case hey you are getting new rotors, you could consider the 14" rotors and keep your stock calipers (just a thought!)
If you have only been running stock pads the pagid oranges are a huge improvement much better "bite". Just make sure you follow their website on proper bedding in. That avoids all the trouble and also squealing. Mine are so good I stopping changing back to stock when not at the track.
Oh yeah about upgrades, the GT3 cup front ducts and rear GT2 brake ducts are cheap, OEM motorsport parts that really help prevent boiling!
You really are correct about the suspension weak link. Man wait till ya change that!!
Bottom line is glad you are tracking the car and enjoying yourself!!!!
here's a pic of the front duct
tom

ca993twin

I'll stick my neck out and say that grooves in the rotors are not unusual, and once the brake pads have conformed to the surface, offer no significant long term disadvantage over a fresh, flat surface. I would only replace the rotors when they are worn past the minimum thickness specification. With R compounds, you can probably enjoy some benefit with a better brake pad material... and you certainly can benefit from some substantial suspension upgrades.

tkerrmd

I do agree with Steve in that in general all my pads and rotors have "grooves" to some extent and that's not my barometer for rotor replacement either. Steve is right about that the thickness is the reason or when the cracks between the holes start to go from hole to hole. I made my recs on the fact that the rotors also had 28k on them and now starting to track may be a safer way to go. Certainly dont "have" to at this moment though!

ebaker

I think grooved rotors on a car with 28000 miles are normal. Since you haven't even worn out a set of pads it's unlikely the rotors are bad.

FineProperty

Thanks for the feedback. Nice to know I can relax about driving it now, it brakes fine and has not gotten any worse since the track. And, the upgrade route is where my brain always takes my wallet. The MP Sport Cups have shown the weakest link is the suspension, and all of the talk here and elsewhere are leading me to the Moton/JIC/pss9 choice.

I'd love to be able to change the height for street/track use, but I don't think I can get the balance right for both. My town has some severe snow in the winter, and hence some severe driveway curbs at daycare/starbucks/parking garages, etc. I'm thinking I could dial the suspension in for the 30mm ride height drop, then crank the coilovers up a specific number of turns on each corner for street use. Thoughts?

38D

I wouldn't worry one bit about grooves in the rotors. As far as cracks go, I replace my rotors when they look like this:

Joe Weinstein

Oh, and forget about 'frozen rotors' unless you can show me a controlled
double-blind experiment that proves it. I studied metalurgy, and the 'frozen'
claims are bogus. As far as iron is concerned, it is already 'frozen' at room
temperature, and lowering the temperature further removes energy, not
adding it, and any readjustment of the existing iron crystals would need
energy. Lastly, even if cryo treatment actually did anything, any effect would
be completely undone as soon as the rotor got red hot again under heavy use.
Do some googling about cryo treatment and you'll find people claiming your
Tuba will sound better after they freeze it for you... The scientific activity that
spawned the bogus commercial behavior has to do with trying to 'freeze' metals
*from a high-heat non-crystaline state* to a room-temperature solid state
quickly enough to prevent any crystalization. This unordered atomic structure
is like glass, and is called metalic glass. It has some very good strength
characteristics, because engineers know that metal failure occurs and propagates
along the thin unordered borders between adjacent crystals. (The other desirable
option is monocrystals, which would be 100 times as strong as typical real metal).
Metalic glass has been created only in thin strips of metal that can be extruded hot
and cooled quickly by conduction because of their big surface area to volume ratio.
Joe

tkerrmd

Joe thanks for the scientific update! I think I got the first few sets at the advice of a racer who "swore" by them. No randomized double blinded controls to point to however. At$150 a pair I have just been doing the fronts but after your advise I think I will abandon that habit, thanks.

Joe Weinstein

Well, let us know if the next non-frozen set lasts any differently than your last frozen set...
Joe

tkerrmd

quite honestly havent kept accurate data but "gut" feel was that the cracking was much reduced and increased the rotor life.....guess that's what prospective randomized double blinded studies are for!!

ca993twin

Tom,

Just a brief note from an odd duck from the 993TT side: it so refreshing to see posts from you... you are never argumentative and defensive... you just "calls 'em as you sees 'em", and don't mind backing up when you think its the right thing to do. Keep up the nice tone! As it happens, this thread is very constructive and quite interesting (thanks Joe).

tkerrmd

Steve, that was awful nice of you to say!!!! There are many people on this forum (yourself included) with much more experience and knowledge than I have. I only say things that I am pretty sure of, have done myself, or was told by someone who I respect and trust. the last one probably gets me in the most trouble. As a researcher myself I go with the whole multicentered randomized double blind blah blah blah stuff but the car stuff gets more to my impulsive or emtional side... When I realize that or someone gives a better explaination, I'm always ready to learn more or stand corrected, no ego problems!

thanks again Steve

Gary (Fl)

Now all you have to do is learn how to drive....

tkerrmd

Gary, see ya at Sebring!!