slotted GTS rotors?
05-29-2009, 01:06 PM
#31
Rennlist Member
This cracking shown here is normal for holed rotors. remember, ive been abusing the S4 size rotors for YEARS now (7 full racing seasons) they crack-out at about mid season. these started show cracking at an earlier time, as my thoughts were maybe that the porsche rotors were not the quality as the zimmermans. anyway, the extra force with the diameter, with the more aggresive pad has caused this issue. a wider pad wouldnt do much as most racing systems have this size of pad. Stoptech uses the S4 pad on their 13" brake system. (so does ferrari use near the same size pad on their 14" system) I did feel a vibration at sears that went away at laguna, but that could have been a warping that started a hot spot and then the cracking area at one specific area. dont know. Ill try the GTS rotors and see if steve can put some slots on them.
mk
mk
Yes I agree there are a number of racing brake options that use that sized pad. Everything I have seen shows the factory rotors are far superior to the zimmermans. I was told that the added pad to surface area will dissipate the heat faster than if you use a smaller pad on a larger rotor. I would call Paul like I mentioned when you get a chance he has done some unique brake conversions including Cayenne Turbo S Rotors and calipers on a race car that supposedly would stop a tank.
05-29-2009, 04:45 PM
#32
Nordschleife Master
This cracking shown here is normal for holed rotors. remember, ive been abusing the S4 size rotors for YEARS now (7 full racing seasons) they crack-out at about mid season. these started show cracking at an earlier time, as my thoughts were maybe that the porsche rotors were not the quality as the zimmermans. anyway, the extra force with the diameter, with the more aggresive pad has caused this issue. a wider pad wouldnt do much as most racing systems have this size of pad. Stoptech uses the S4 pad on their 13" brake system. (so does ferrari use near the same size pad on their 14" system) I did feel a vibration at sears that went away at laguna, but that could have been a warping that started a hot spot and then the cracking area at one specific area. dont know. Ill try the GTS rotors and see if steve can put some slots on them.
Here is the pic of my old S4 rotors after almost an entire racing season.
mk
Here is the pic of my old S4 rotors after almost an entire racing season.
mk
I cant believe you would have raced on something like that? I get if you just noticed it but you appear to monitor your rotors regularly, that should have been replaced many many moons ago, thats honestly shocking MK
05-29-2009, 05:17 PM
#33
Rennlist Member
Thread Starter
actually, they always get to this point about about 3/4 of the season. If it is really slight, i race one more weekend on it. this started to appear just after the Laguna race. (hard on brakes) after the 1st race at thunderhill, it was getting worse, and after the 2nd race it looked like this. I can fit my finger nail into it. pretty bad, I agree. Ok already, its going in the trash. Im going to use some flat GTS rotors and have Steve cut some slats into them. 
Keep in mind, this is a new rotor, just bought it when I did the brake upgrade to the larger rotors, and spacers for the calipers, so "ages ago" is March '09?
mk
Keep in mind, this is a new rotor, just bought it when I did the brake upgrade to the larger rotors, and spacers for the calipers, so "ages ago" is March '09?
mk
THAT ROTOR IS TOAST! COMPLETELY USELESS THROW IT AWAY, DONT PUT ANOTHER MILE ON THEAT! If the rotor explodes which its very likely to do you are going to have a huge huge mess! Thats a serious safety issue!
I cant believe you would have raced on something like that? I get if you just noticed it but you appear to monitor your rotors regularly, that should have been replaced many many moons ago, thats honestly shocking MK
I cant believe you would have raced on something like that? I get if you just noticed it but you appear to monitor your rotors regularly, that should have been replaced many many moons ago, thats honestly shocking MK
05-29-2009, 08:35 PM
#34
Nordschleife Master
yeah you said it was your S4 rotor
regardless i have to suggest to you that you never let them get that bad, thats honestly very scary and i have to imagine that if there were any tech inspection many races prior that they would have had you replace those. Its scary you raced on those, it really is.
regardless i have to suggest to you that you never let them get that bad, thats honestly very scary and i have to imagine that if there were any tech inspection many races prior that they would have had you replace those. Its scary you raced on those, it really is.
06-12-2009, 04:48 PM
#35
Rennlist Member
Thread Starter
Thanks David! They came in yesterday and today i had them at the shop.
They were pretty decent, but had a 1mm lip on them. The normal thickness is supposed to be 32mm and the absolute limit is 30.00mm. The shop wasnt going to do it as they thought it would fall below limits. it came out to 30.04mm.
$40 later plus shipping, I have almost new GTS rotors that maybe have 3 races to go before they are below wear limits.
anyway, Ill give them a shot and they should work out fine. nice and straight now though!
Im a little worried if the material removed will make them be more proned to warping? They have to be more structurally strong than the cheeze grater holely rotors, but we will see. Ill bring a set of my old S4 rotors, just in case.
thanks again,
mk
They were pretty decent, but had a 1mm lip on them. The normal thickness is supposed to be 32mm and the absolute limit is 30.00mm. The shop wasnt going to do it as they thought it would fall below limits. it came out to 30.04mm.
$40 later plus shipping, I have almost new GTS rotors that maybe have 3 races to go before they are below wear limits.
anyway, Ill give them a shot and they should work out fine. nice and straight now though!
Im a little worried if the material removed will make them be more proned to warping? They have to be more structurally strong than the cheeze grater holely rotors, but we will see. Ill bring a set of my old S4 rotors, just in case.
thanks again,
mk
06-12-2009, 04:52 PM
#36
Rennlist Member
Thread Starter
So Ryan, you saw no rust rings. AND, take a lot at a 2008 Porsche 997 C4S! Look at the front rotors. same thing. they use GTS style calipers and pads but leave about the same .4" of space down near the hub. Proof that the S4 to GTS brake conversion without the "red" GTS calipers is an accepted idea within porsche. (as far as unused brake rotor area is on the inside.)
anyway, as you can see there was no rust ring anyway.
Im surprised no one wanted to do the modification.
mk
anyway, as you can see there was no rust ring anyway.
Im surprised no one wanted to do the modification.
mk
06-14-2009, 01:28 AM
#37
Rennlist Member
Thread Starter
on the car and did a little brake bedding today! they looked a little rough after the machining and right at tollerance. 30.07mm. . now, they look pretty smooth as the pads get friendly with the rotor.
just hope the rotors didnt NEED holes to work right. Ill find out in a few days!
Thanks again David.
mk
. now, they look pretty smooth as the pads get friendly with the rotor.just hope the rotors didnt NEED holes to work right. Ill find out in a few days!
Thanks again David.
mk
06-14-2009, 01:40 PM
#39
Mark,
Curious why you guys are running drilled rotors in the first place? Do the pads you use require them? You race a hell of a lot more than I do, I figured it was common practice to NOT use drilled rotors for a track car.
I'm hoping to not open a big (drilled vs. non-drilled) can of worms. I'm just curious. I would try the slotted ones like you were asking for originally, you shouldn't have a problem at all then I would imagine, or plain solid rotors. Do the stock Zimmerman GTS rotors not hold up well?
Curious why you guys are running drilled rotors in the first place? Do the pads you use require them? You race a hell of a lot more than I do, I figured it was common practice to NOT use drilled rotors for a track car.
I'm hoping to not open a big (drilled vs. non-drilled) can of worms. I'm just curious. I would try the slotted ones like you were asking for originally, you shouldn't have a problem at all then I would imagine, or plain solid rotors. Do the stock Zimmerman GTS rotors not hold up well?
06-14-2009, 01:43 PM
#40
Rennlist Member
Thread Starter
Well, here we go .
GTS rotors , 30mm thickness on a fresh turn. Doesnt look very racey, but they should work. Those pagid blacks sure took the rough turn to almost shiney finish after only a 10 mile jaunt. (but a hard jaunt at that )
mk
GTS rotors , 30mm thickness on a fresh turn. Doesnt look very racey, but they should work. Those pagid blacks sure took the rough turn to almost shiney finish after only a 10 mile jaunt. (but a hard jaunt at that
)mk
11-16-2013, 09:54 AM
#41
Rennlist Member
I'm having the same cracking issue Mark experienced with my cross drilled GTS rotors. Does anyone make a slotted one these days? Or Mark, did you keep them solid?
11-16-2013, 11:10 AM
#42
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From experience with my customers - they use solid rotors on the track. Downside is cost in that solids are more expensive than the cast hole rotors. GTS rotors are cast hole and are not prone to cracking as easy as X drilled. I have not seen slotted rotors for the GTS - not saying they are not available somewhere.
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
11-16-2013, 11:53 AM
#43
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Isn't there anyone who offers slotting/drilling service as well as cryogenic treatment? I thought I had read that either somewhere here or in the racing/DE forum. The slotting was effective in removing pad gasses and the cryogenic treatment made them stronger or at least less prone to cracking after either dilling or slotting.
11-16-2013, 12:19 PM
#44
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Isn't there anyone who offers slotting/drilling service as well as cryogenic treatment? I thought I had read that either somewhere here or in the racing/DE forum. The slotting was effective in removing pad gasses and the cryogenic treatment made them stronger or at least less prone to cracking after either dilling or slotting.
