As a follow up to a previous post regarding the fitment of front 350 mm GT3 / Cayenne rotors on the 996TT I’ll offer up the following info. In my particular case, the car is a’03 996TT with stock 4 piston front calipers.

Chuck May from IMGT3 was gracious enough to send me the measurements for the ATE rotors I was hoping would fit. In this case, they were ATE 350 mm GT3 / Cayenne front rotors, ATE part number CW34123 / CW34124. After comparing the measurements with a new Porsche 330 mm front rotor, there were some small differences but I was hopeful that they would still work. Some apparently have had success with fitting them on their cars with no modification other than the spacer kit. In my case (your results may vary) they were not going to fit without some slight modification to the front calipers.

The critical measurement of course is the offset from the inside face of the rotor hat to the rotor face. The measurements I obtained for the offset were 62.8 mm for the stock rotor and 61.1 mm for the ATE (inside of hat outside of rotor face), a difference of 1.7 mm. The rotors had identical thickness at 34.0 mm. The hat thickness of the stock rotor is 6.35 mm vs. 7.5 mm for the ATE, but is really inconsequential in terms of fitment. The 330 mm Porsche rotor weighed 23.0 # vs. 26.5 # for the ATE. The opening diameter of the hat is different as well, with the ATE rotor being a little smaller, but in terms of fitment I found it didn’t matter. The last thing that may be of issue for some, is that the ATE rotors do not have the small countersunk holes in them so you can use the small phillips-head screws to screw them to your hubs. Others have posted that it’s relatively easy to drill the holes and countersink them in the ATE rotors if you really want them.

Prior to pulling my stock rotors, I measured the clearance of the large centering pins inside the calipers to the rotor face, and in my case came up with 1.5 mm. Actually, there was a little more clearance than that, but I wanted to allow a little margin for heat expansion under use. Because the difference in offset from my static measurements was 1.7 mm, I knew things were going to be tight. However, I was hopeful that I’d have just enough slop when tightening things up to make things work. Unfortunately, I was disappointed. When bolting down the ATE rotors (using Vivid’s spacer kit) the caliper pins unfortunately contact the outside face of the rotor. The contact is minimal, and I could actually rotate the rotor with some force, but of course this was while cold. I suspect that when things heat up, the clearance issue would become a major problem.

It would be relatively easy to grind down approximately 2 mm from the outside caliper pins to make these rotors work. The calipers would in fact be offset from the center of the rotor by the 1.7 mm difference in offset, but I don’t believe that would cause any issues in terms of brake performance or wear. I know that some have said they have done this, but in my case I didn’t want to go this route.

The price on the ATE rotors was pretty much unbeatable, so I still think they are a viable alternative for those that looking for more economical solutions. However, unless you’re willing to do a little slight modification to your calipers, I don’t think these are going to work. Again, your results may vary, and much of this is just a rehash for what others have said all along in terms of fitment. Sometimes however, you just have prove things to yourself!

 

Did this mod with my 6 pots. It's fantastic. For 200 bucks shipped for both rotors. Directionaly vented. More pad to rotor surface area touching. You can't beat this mod. Brake feel better, it also pushes out the wheels 1.5mm out more so a bit of a spacer. Apparently GT3 guys get about 18 track days plus street driving.

 

Was any modification to the 6 pot calipers necessary?

 

what's the use of those pins anyway, i have never seen those on anything else?

 

So these will work fine w/o modification if you run 996 gt2/gt3 rotors?

 

Keeping an eye...or Two on this one...

 

I have run the stock (or OEM equivalent) 997TT rotors on the front. The 997TT rotors have the SAME offset as the 996TT rotors. Thus, no modification to the calipers is required. Of course caliper spacers & longer caliper bolts are required due to the larger rotor diameter.

The 997TT rotors are larger in diameter and have (from my ****tail napkin math) about 7% more swept surface area. However, they are still cross drilled and still suffer from cracks after hard track use just like the 996TT rotors due. The ATE rotors are slotted, not drilled, and those that have run them have indicated that while they will eventually suffer from some heat cracking as well, they still last noticeably longer. Also, the ATE rotors are cheaper than the 997TT OEM rotors and significantly cheaper than any other available slotted rotor. Of course, unless you're willing to do some slight modification to your calipers you're out of luck with the ATEs (or any GT3 rotor for that matter I would guess).

Not trying to push any particular solution to the caliper spacer issued, but Vivid does sell the stand alone caliper spacer kit by itself. Pricing is available on Vivid's web site. Dan may even give you a break on the price if you call him directly.

 

Ate doesn't make those for the 997 turbo?

 

I want to change my front brakes to have longer longevity on the track and possibly better heat dispersion. I want to stay with my 4-pod fronts for now, but really want to stop burning up OEM 996TT drilled rotors on the track. I have searched and read as much as I could find, here and elsewhere and I am down to three options:

1.) Get Coleman to make proper offset slotted rotors in 330 or 350/vivid spacer kit

2.) Girodisc 996TT two piece 350s with proper offset w/vivid spacer kit

3.) ATE Cayenne 350s/vivid spacer, and modify the caliper to deal with the 1.7mm offset

Option three is by far the least expensive and the GT3 guys swear by the ATEs, so that's very appealing. I have no issue grinding the guidepin on the caliper to make these fit, but wonder about the offset. Has anyone done this? If so, any issues? How do new Pagid Pads fit in with the offset?

 

I'm looking to go 350mm initially, retaining my stock calipers for now.

Girodisc's are really nice, but they are obviously very pricey. Been having a hard time pulling the trigger due to price.

I've used ATE rotors in other applications, and have been very happy and would consider this route for sure. Hopefully more info will become available, possibly a good installation write-up (with pics)

Surprising ATE just doesn't make a 997TT rotor, that would make it much easier.

 

I want to change my front brakes to have longer longevity on the track and possibly better heat dispersion. I want to stay with my 4-pod fronts for now, but really want to stop burning up OEM 996TT drilled rotors on the track. I have searched and read as much as I could find, here and elsewhere and I am down to three options:

1.) Get Coleman to make proper offset slotted rotors in 330 or 350/vivid spacer kit

2.) Girodisc 996TT two piece 350s with proper offset w/vivid spacer kit

3.) ATE Cayenne 350s/vivid spacer, and modify the caliper to deal with the 1.7mm offset

Option three is by far the least expensive and the GT3 guys swear by the ATEs, so that's very appealing. I have no issue grinding the guidepin on the caliper to make these fit, but wonder about the offset. Has anyone done this? If so, any issues? How do new Pagid Pads fit in with the offset?

 

Based on comments in this thread, the ATE rotors are cheaper and more durable (no cross drilling) than the 997TT counterparts.

I certainly will consider the 997TT rotors, but would like to review all options available before making my final decision.

A bit confused as to what you are hyperlinking above, maybe I'm blind but I'm not seeing rotors for the prices you are quoting ? What else can you tell us about the rotors your are recommending ?

 

thanks RB4. Looking to make a decision within a week or so.

 

RB4, can you get the 350mm 2 piece rotors at a discounted price? How about pads too? If so I would be very interested as I will need these and the prices you quoted blow away the prices in your link.

 

I have Coleman 330 mm rotors. They have lasted me a whole season (probably 10 events, 20 track days).

The best part is, they aren't even close to done yet, I think there is another 10-20 days on them, only heat marks, no cracks at all. Pads are a mix of Pagid Black and Pagid RS29 Yellows.

Initial investment in the hats, and then only $134 per replacement rotor. The 330 mm disk with hat weighs 18 lbs. ATE sounds great, but I'll pay a little bit more for lighter weight. How much time are you guys getting out of the ATE rotors before replacing?