285/35-20 Square Setup for Track

[bsclywilly]

Making the dad-mobile more track worthy. Went with a square setup so tires can be rotated easily with much more width up front to better match the weight distribution of the Taycan. 20x10 +55 offset is about as wide as you can go in the front with a reasonable clearance to the upright and tires flush to fender. Running 20mm Rennline spacers with 68mm extended lug bolts in the rear. Wheels are Rotiform TSF.

Tires are Bridgestone RE71RS in 285/35R20. Likely one of the best 200TW tires available today. Came heat cycled from Tirerack so I don’t have to waste a track session. What a difference in grip compared to the OE Pirelli P7 Blues. Can’t wait to hit the track with them. Note the load rating on these are only 100W but I’m confident they’ll be fine compared to the minimum OE spec of 101Y since they’re not going to see max payload. Slightly smaller diameter compared to OE but that takes a backseat to tire choice. OE sizes are just super limited or non existent in anything higher performance than a PS4S.

Also swapped a set of XP20 track compound brake pads from Carbotech. Front pad profile is shared with Panamera, Cayenne, and Macan. Lookup “FMSI D1349” for compatible pads. Mike Jr. at Carbotech was great to work with and getting the pads prebedded also helps a lot since it’s a task to bed in track pads on the street with brake regen and this saves a precious track session. The rears were harder to find the right profile. FMSI D1655 and D1390 will work but the friction puck profile isn’t exactly the same. And they’re too thick. Carbotech is able to make a custom profile based on the OE pad and at the right thickness.

 

[f1eng]

Presumably you have to switch off all the possible stability control settings when running tyres so different in width and diameter to the ones the electronics are programmed for at all times not just track running.
If not any intervention the PSM made near any programmed limits would be "wrong" and maybe dangerous for these tyres.
Or are these tyres just fitted once you get to the track?

 

[bsclywilly]

Presumably you have to switch off all the possible stability control settings when running tyres so different in width and diameter to the ones the electronics are programmed for at all times not just track running.
If not any intervention the PSM made near any programmed limits would be "wrong" and maybe dangerous for these tyres.
Or are these tyres just fitted once you get to the track?

PSM/ABS is based on wheel speed deltas so as long as your front and rear axles are not running significantly different diameters, the computers are not going to know the difference. Even the OE tire options vary front and rear diameters by a percent, and a couple percent difference comparing 20” and 21” tire options. So, no issues.

I was actually surprised how little difference they felt compared to the stock tires just driving in town and backroads. I was expecting to feel more weight and feedback from varying road surfaces with the wider fronts but I suspect some of it is muted through the electric steering assist. Also, the fact that regen doesn’t use the mech brakes much, you wouldn’t even know you’re driving with a high temp track pad. I could see myself driving on this setup as a daily if I wasn’t concerned about preserving the tires for track days.

One benefit I’m also hoping to see is that with the better mechanical grip balance, PTV+ should also be less intrusive and should see less rear brake wear as it doesn’t need to artificially correct for understeer.

 

[bsclywilly]

Wow, this car is a hoot when the chassis is well balanced! Visited Laguna Seca again this week with the new setup. Dropped 3.8s off the lap time (1:43.4 lap), but the best part is that the balance was consistent lap after lap for the 15-20 minute sessions. No brake fade, and the fronts did not need to be 'managed' at all, read - taking it easy on brakes and turn in. It is still a heavy car so response to steering feedback is going to be slower. Reviews for the RE71-RS also note lower turn-in response but the car was still easy to balance with steering and throttle mid corner.

I am still amazed at how much camber Porsche runs on their cars stock. The fronts can't be adjusted and I have as much rear camber taken out possible, and my tire temps are pretty much ideal. I'd take out another 0.25 degrees of camber at each corner, if I could. Great for the track, too much camber for the street (particularly if you drive in anything less than normal chassis height as you gain negative camber the lower you go). Getting up to 200F (93C) and very evenly distributed averages across 4 tires means they're sharing the work well. Ran 35psi all around. Temps taken at 37psi.

Hitting over 1.8g too. Don't mind the low forward acceleration, it's only a CT4

Brake pad compound was amazing. They are Carbotechs second highest friction compound and highest temp range. For the tires, it was maybe a bit too aggressive bite but based on my brake temps, I needed them for the upper temp range. Brake temp paint indicated I was getting over 1670F (910C) on the front rotors and 1470F (800C) in the rears. My IR gun was maxed out when I went to take front rotor temps so good thing I ran paint as a backup check. Most amazing is how little wear I saw. Only about 0.5mm-1mm on the pads and 0.1mm on the rotors from a 4 session day. My previous track day with stock brake pads ate through 2mm in the front and 4mm in the rears as they were working well outside their intended temperature range. Ran Motul RBF600 brake fluid, but I feel a higher temp and lower compressible fluid would further improve the experience. I did have some inconsistent pedal travel when the brakes got hot. I read Endless RF-650 is the nice stuff. The Motul I just had laying around.

So much more fun on the track with proper tires and brakes!

The downside, for a few days driving on the street, looks like about a 7% decrease in range. But who cares, this is a setup for the track.

Also, met up with our OG forum member @daveo4EV in his GT3!

 

[Genyosai]

Also swapped a set of XP20 track compound brake pads from Carbotech. Front pad profile is shared with Panamera, Cayenne, and Macan. Lookup “FMSI D1349” for compatible pads. FMSI D1655 and D1390 will work but the friction puck profile isn’t exactly the same.

This is great info. I like Carbotech, too. I usually run XP20 fronts and XP12 rears on my Giulia Quadrifoglio at Road Atlanta.

Now I want to track my e-tron GT as a comparison to my Tesla P3D (which overheats after 4 laps), but I have to come here to find this sort of info because the e-tron forums seem to have no one tracking their cars.

I'd found the front pad shape number, but like you, had difficulty finding the rears. What I'll probably do is buy a set of new OEM rears and take them to Carbotech for modification into a set of XP12s (I'm not far from them in NC).

Anyway, thanks again for the info. Even though I have an e-tron GT, I'll post back here after I've done a track day in it.

 

[bsclywilly]

I'd found the front pad shape number, but like you, had difficulty finding the rears. What I'll probably do is buy a set of new OEM rears and take them to Carbotech for modification into a set of XP12s (I'm not far from them in NC).

That's what Mike Jr. at CT suggested too. They can make a custom profile based on the pad you send them. I was going to do the same next time but you may save me the trouble. Thanks!

 

[Genyosai]

That's what Mike Jr. at CT suggested too. They can make a custom profile based on the pad you send them. I was going to do the same next time but you may save me the trouble. Thanks!

Yep. I've actually had this done on my track-dedicated Tesla Model 3 Performance.

The rear, outer pad on that car has a retainer spring built into one of the ears of the pad. Without that spring, the pad chatters terribly when no pedal is applied.

So, I sent my stock pads to Carbotech so they could replace the stock compound with theirs.

 

[Maimai]

Great write up! Couple of questions:

1. What is the reason for running spacers in the rear?
2. Are you aware of any aftermarket brake pad option for the 410mm rotor (10 piston caliper, PSCB)?

 

[bsclywilly]

Great write up! Couple of questions:

1. What is the reason for running spacers in the rear?
2. Are you aware of any aftermarket brake pad option for the 410mm rotor (10 piston caliper, PSCB)?

1. I run the same offset wheels on all 4 corners so they can be rotated for even wear.
2. No, I'm not sure if the PSCB rotor needs a special compound, you may be out of luck there, or risk wearing out the surface coating on those rotors. If you got a set of replacement pads, you could call up a pad manufacturer such as Carbotech and they can custom make a pad for you in any of their available compounds. If you're just doing a couple track days, I wouldn't stress about it and run the stock brakes. Upgrade the fluid if you're experienced and run the brakes hard.

 

[Maimai]

Thanks a lot. After reading about PSCB, I realize this is probably one of the worst setup for track. Wear down the rotors by 0.1mm and they are finished... Will make sure to avoid this brake from now on

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