Joe731

Someone was asking about this, so I figured I'd start a new thread.

Here are my experiences to date with the 991 GT3RS

Tires

MPSC2s on Fronts: Replaced first set after 69 heat cycles -- they still had tread on inside and center, outsides were treadless, and they were way heat cycled out. I should have replaced them sooner. Maybe 45-50 heat cycles

MPSC2s on Rears: Replaced first set after 39 heat cycles as the left rear corded on the far outside. Replaced the second set after 37 heat cycles for the same reason. In both cases there was plenty of tread across the entire tire except for the cording, which I now believe was due to rubbing, given the tech bulletin in the "setup" thread. I am addressing the fender rolling issue now. Though there was lots of tread left, both sets were on their way out from a heat cycle perspective. I am running -2.7 degrees of camber all the way around.

Pads

Fronts: I have been using RE10s. On my third set now. First set lasted 39 sessions (my first 39 so not driving as hard as subsequent sessions). Second set lasted 29 sessions and I got every mm of use out of them by the time I changed them

Rears: I have been using RE10s. First set lasted 58 sessions. On second set now.

Rotors:

Fronts: I have been using AP Racing J hooks. First set lasted 68 sessions and the J-hook slots were gone in the center and faint on the inner and outer edges. No fatal cracks, but I followed the advice of changing the rings once the slots were gone

Rears: Still on factory stock at 81 sessions and counting. Ordered some J-hooks to replace them once worn.

Brake Fluid

Using Motul RBF600 and have had no issues. Started fresh at the beginning of the season. did a light bleed at pad changes, and did a full flush at 81 sessions as the fluid was 4 months old. Never felt any boil or softness in the pedal. Good venting on RS

Oil

I've been using Mobile 1 and sending to Blackstone each time. Started season with fresh oil after break in. Changed after 38 sessions, changed again after another 28, changed again after another 16. From the Blackstone reports I think I will aim for 16-25 sessions as the viscosity seems to drop with more sessions. For me, there are advanced days and 5 day track get aways that rack up sessions quickly, so I need a range of sessions. Latest Blackstone report attached.

Macca

Hi Joe

Thanks so much for the data points. I'm sure other RS and GT3 owners will chime in.

Wow, you have done a lot of track work with this car in a short time. Assuming 4 X 30 minute sessions a day then I am estimating around 20 track days so 40 track hours on the car.

A few things. Your tyre longevity seems very generous. I've found the tyres start going off after 30 heat cycles and rarely push them beyond 36 before changing them, even though they have some tread left (rears are usually better than fronts). There is no way I could get 60 cycles from them however.

The other data point that it now rested me was brake longevity. I have just bought a set of RT RE10 to try and was hoping based on others feedback far better longevity. Currently I get 6 days (24 of your sessions) out of the factory OEM fronts and have managed 14 days out if the rears (56 of your sessions). I had expected the RE10 to last me twice that. I'm using factory rotors.

The oil changes are interesting. This is fundamental the keeping the valve train intact on these cars. Historically with my first two engines I did not change the oil till service. I think this was a mistake. If viscosity is changing with heat then I think the oil needs to be changed far more frequently on track with these cars. With the G engine I've a 4 track day routine. Four full days then change.

For the fluid I've been using Castrol SRF and doing exactly as you have. If the pads last as long as I hope they all for me then I will change the fluid every 6 months or 6 track days. I haven't found the fluid to be an issue through use but time seems to be more it's enemy...

Very useful data points Joe. Hopefully Trakcar and others will chime in. It would be interesting to know your camber settings, and other mods and the style of tracks you run. Looking at your tyre and pad usage it's very hard for me to guess...

zedcat

2015 GT3: MPSC2 fronts 20 to 24 sessions (20-30 min sessions). If I could get 40+ would probably take to the track more. Alignment is not very aggressive due to a lot of street use.

Got about 34 sessions on oem front pads, 50+ on rears.

usctrojanGT3

40+ heat cycles? Wow, I've never had tires last me more than 30 cycles (RE-71Rs on the GT4 were good for 26 with a little more life to them).

MaxLTV

My last set of MPSC2s lasted 13 sessions (20-30 minutes) on fronts and 17 on rears till wearbars in the middle and no rubber on shoulders. That's on a GT3.

Front PFC01 pads lasted about 40-45 sessions, and rotors are less than half done after 40-45 sessions. Seems like brakes last me longer and tires lasting much less compared to others who posted so far. To be fair, brakes are very much pad-dependent. With a different type of pads, I was getting only 35 sessions out of both pads and rotors.

SmokinGTS

In our cars the oil is the most important thing we can do. I change mine after 3-4 track days and am using Liquid Moly Energy 0-40. This is a very high grade oil and cost about 3.00 more per quart than Mobil 1. I find the Cup 2 tires are gone due to heat cycling out after 18-24 sessions if I am lucky. They still have tread left.

orthojoe

Am I reading this right?

Your front tires lasted as long as your rotors? That doesn't sound possible

On my plain gt3 the front cup2 will last 15 heat cycles and the front AP rotors will last 175-200 heat cycles!

soulsea

I don't even know what to make of this data, especially in regards to tires ... it seems way off unless you're puttering around the track.

I haven't tracked my RS yet but my SC2s last on average 2/3 hpde days, 15 x 25min sessions max before they start completely going away to the tune of 1sec per lap, by the 4th day they are throwaways. This was both on my C7 Z06 (which I appreciate is a different car) but also on my 15 TTS. Seriously, on the TTS they were dangerously gone after 3 DEs. I can't imagine the compound of the SC2s or the Dunlops is much different on the 991 GT cars that it performs three or four times the heat cycles that it does on other vehicles.

Someone correct me where I'm wrong, but if f by 'lasted' you mean they didn't fall off the wheels then I guess you're right, but if by lasted you mean they retain up to 80% of their original grip, which is really the only thing that matters, then I just don't buy it.

MayorAdamWest

Agreed with others. These numbers indicate something very odd. Your tires last 3x as long as mine, yet your rotors last less than half.

For me
20 session on tires (~20 minutes per session), but really past their prime after about 12
About 100 on the AP rings. (20+ track days)
Around 30 on Ferodo front pads (rears last twice that)

Mika911

With a ratio of approximately 1:3 track/road:

Cup2 rears after 3000mls due to cording
Cup2 fronts after 3600mls - plenty of treat, but lost grip
Front pads OEM after 4200mls - still ok for road but generating too much heat
Front discs OEM 4200mls beginning to show small cracks (due to running pads too thin)
Rear discs and pads still going strong after 4200mls

Overall incredibly good consumption. Much better for example than GT4, which munches its front tyres.

levd

Wow. I only kill rotors with 3rd set of pads in average.

zedcat

For me rotor life ends up a judgement call due to cracking rather than wear/thickness. Pad thickness and tire wear are more simple direct measurements. Here are my front rotors with about 50 sessions. The cracks in the center make me nervous. Wouldn't hesitate to run a session on them but not sure I want to start a 2 or 3 day event at a track like COTA. And don't really want to bring spares and all the gear to change during an event. So I'll probably replace them.

levd

The rotors on your picture are good for at least one more set of pads.

I'd say these rotors are almost new with some break-in done

zedcat

LOL. Thanks. Like I say it's a judgement. The rotors are on second set of pads (at about 80% ). The rotor thickness is easy to mic, but the crack length criteria is fuzzy to me. The common guidance around here is they should not connect holes and not extend to the edge but also I've heard/seen Porsche criteria of 5mm and 7mm max. The photo crack measures out at about 10mm and most of the center holes are similar. Had the car at the dealer for tires awhile ago and they were advising to change them (not a surprise.) Not going back on track until it cools off a little here and decide then.

levd

I'd bet some money these rotors will survive at least the current set of "80% left" pads, if driver won't go crazy with significantly overheating the brakes far beyond any reasonable limit.