I just put R888s on my 997.1 C2S, and I plan to use the tires on both road and track. I'd appreciate suggestions on what pressures to use. Some info:

- The Toyo website suggests hot pressures of 32 to 38.

- Porsche recommended cold pressures at the door are 37 F and 44 R.

- Porsche recommended cold pressures in the owner's manual are 33 F and 39 R for partially loaded.

- Porsche recommended cold pressures in the owner's manual are 36 F and 44 R for fully loaded.

Based on this info, I'm thinking cold pressures of 31 F and 36 R for the road, to keep a difference of 5 between F and R, and to keep the hot pressures around 34 to 39 on the road. For track use, I'm thinking hot pressures of 33 F and 38 R, lowering the cold pressures as needed to get there.

 

i think the track pressure is fine, however I think for the road the cold pressure should be as P recommends.

 

i run 8's on track in my .1 C2S. firstly, the goal is to have the same pressure all the way around when hot (i.e. i dont think i've ever known someone who purposely ran a differential between front to rear on the track). remember, tires have an optimum sweet spot and that's where you want all 4 to be during your session. you dont want them scattered all over the performance range of the tire. i start at around 25 or so with the goal of 35 hot all the way around. anything above that and 8's get greasy on me.

for street, quoted manufac pressures are primarily for mpg not performance. that said, you can run them at whatever safe level is good for you - to max mpg? to min tire wear? to max street performance? up to you. the only time i drive 8's on the street is to the track and sometimes i will drive them at track settings, sometimes street settings. depends on how lazy i am before leaving the house/track.

 

+1

 

I've never run the same pressures on all 4 corners in a 911. This will be my 23rd year of tracking Porsches.

 

Years of track experience with R888...however I've stopped using them due to tread seem splitting they are having issues with. Keep an eye out for this issue.

I've found for the track running hot 32 front 34 rear worked good. Anymore than that and the 888's get greasy and the rear will wear out the center fast.

Also to run these tires with proper heat range across the tread you will need to start out camber at -2.5 front and -2 rear. This is just a starting point but will get you way into the ball park. I have run -2 front and -1.7 rear at the least.

As far as a street tire.... Keep in mind that every time you drive them and they cool off that is a heat cycle. That is the way a r compound tire works. You have about 16 to 20 heat cycles at most the then the compound get hard and its really unusable at the track.

 

I drove R888's on the track for a while until I discovered NT01s. Here's what worked for me on the R888:

Front: 27/26 (inside/outside)
Rear: 26/25 (inside/outside)
The goal was to get 35 all around.

On my home track, the outside tire gained more, so a 1lb difference side-to-side cold led to even when hot.

As for street pressures on the R888:
Don't. Those things are deafening and not the right tool for street driving in varied conditions. Save your R-comps for track work and get something inexpensive but grippy for the street like Sumitomos or Yokohamas.
But if you must, I'd go with 35/40 (f/r). The door sill lists MAX pressures, and I find that -2 is a little more comfortable because I'm never carry the max load.

 

To clarify the tire pressures shown inside the door, there's a yellow sticker next to it that says "for more comfort, the tire pressures in the manual may be used as long as the total occupant weight is less than 350 lbs and speeds do not exceed 100 mph". I'm paraphrasing but you get the message. Dave

 

I wanted my hot track psi to be about 32 front, 34 rear, no higher, so I'd start cold at about 7psi under those (25 front, 27 rear). With those lower pressures, I never had the "greasy" problems that lots of people talk about, all the way to the rear cords. Due to initial heavy wear on the outside of the fronts, due to understeer (ploughing around turns), I installed adjustable lower control arms, and set camber at -2.1 front and -1.8 rear. I'd like more camber for the track, but this is my DD, and I find that this mild track camber does not wear my street tires badly, hardly at all, actually.

 

I'm new to the track but 32 / 34 hot seems on the low side which IMO could explain the wear on the outside of the fronts. Dave

 

They stopped wearing on the outside edges after I increased the negative camber. Also, when they did finally cord, they corded right down the center, as if my pressures were still too high!

 

Lack of camber will explain wear on the outside of a tire. R-Comp tires require different pressures than street tires. Plus the R888's we are speaking about have an extremely stiff sidewall compared to a street tire that has comfort designed into it.
Hope this helps....and welcome to tracking your Porsche...It will be the greatest thing you learn to do. Enjoy!

 

Thanks all for the input. I'll likely be tracking the car for the first time this weekend (VIR), and will try 33F and 35R hot, and will tweak from there. I'll use a pyrometer, though the tires will probably cool a lot by the time I can do it.

I've heard that running R-comps on the street doesn't get them hot enough to heat cycle them, and I know of others using them year-round (other than winter), so I'm inclined to be lazy and give that a try. But I'll try adjusting the street pressures so that they're around 35F and 38R warm, which should be around 32F and 35R cold. But yeah, these R888s are loud on the street.

I may try the stock alignment settings for this first event with the car and see how that goes before tweaking the alignment.

 

I'll be there in mid-March with Zone 2. You also? If so, we can talk tires then too.