spiller

Have done a couple of track days with 315/30 and 245/40 and setting personal best times with these tires...I previously ran R888. However, I can't shake this feeling as if the tyre is moving/rolling around on the rim during higher speed/high load corners. Despite the lap times being OK, im not entirely comfortable with the car, particularly the rear end because of this feeling.

My car has an aggressive track alignment, solid bushes, and race dampers and heavier springs so it's quite a bit stiffer than a standard GT3. There are no signs of wear on the outer edge of the tire. I'm running hot pressures of around 30psi front and rear. Before people suggest running 32/36 or something like that, I have tried that with the R888 and the car is simply undrivable like this. With all of this in mind, I am not exactly sure what I am feeling and if it is normal or not?

My theories are
a) perhaps the car is too stiff for the tyre and I either need to run a softer compound or soften the car a bit

b) the feeling is normal and is due to tyre pressures, as opposed to running higher pressures which may give a skatier, more progressive feeling

c) I don't know

As I said above, it's really only evident in higher speed corners. I have a pyrometer which I have not used yet but I feel I am in the ballpark with the pressures at this point.

Thoughts?

PorscheG96

I think you partially answered your own question and the rear pressures are too low. I may have felt the same sensation as you and slightly higher rear tire pressures, about 35 psi hot, fixed the problem. If this solution doesn't work for you then I'd check for bad links in your rear suspension. What's your static toe setting? It sounds like your rear wheels aren't maintaining alignment with heavy load / travel and making you feel uneasy. It doesn't sound normal.

kk2

I run them at 32f/33r. Rock solid.

Spyerx

I do 32/34 on my 997. 30 hot is way too low.

4porsh

I agree with what other above have said. Tire load deflection or deforming?
i also like when the tires wear down, they seem to move around less. Could be the tread blocks are less once worn but the car does feel more stable and set quicker. It's all fun.

spiller

I couldnt tell you what the toe settings are but I had locking plates fitted and the car re-aligned recently. The car has cup toe links fitted and everything was checked before the track day.
deflection/deforming is a good way to put it. A feeling like the car is moving around on the tyres is how I can describe it.

I will try higher pressures next time around, i'm just very apprehensive to do so because last time running pressures in that region resulting in a big spin. Although that was with the R888s (same compound I hear) but I'm mentally scarred haha. Have any of you used a pyrometer at the above pressures? I should probably use mine and eliminate the guess work!

AudiOn19s

I used only nitto's the first 3 years I had my car. I used a probe style pyrometer often to insure setup was completely dialed in for them. I found that 36 front and 37 rear got the middle temp reading where it needed to be once I got camber specs to my liking.

I still leave the car setup for nitto's since I rarely run different rubber.

AudiOn19s

...the rest of my thoughts here

Nitto's move around a lot in general. They require more slip angle to go fast than even most street tires I've driven. I personally feel learning how to drive quickly on nitto's will give you a comfort level with the car that is second to none.

spiller

I assume the middle temp needs to be within 5-10 degrees of the inside temp? Are you still feeling a lot of movement even at 36 and 37? I have to say I find these higher pressures very interesting as almost everyone down here in Aus is running low 30 psi on R-compound tyres, yet it seems higher pressures are favored by US guys. People look at you like you are crazy if you suggest pressures in the mid 30s down here. Perhaps it comes down to differences in the environmental conditions?

Appreciate everyone's input!

powdrhound

32/33 hot. Run the 305/35 instead of the 315/30. Much better on all fronts..

Spyerx

also when the tread blocks are new they do move around more. sweet spot is when you have just the middle grooves left.

spiller

well i'm glad to hear I have the pressures wrong as its an easy fix! Will give them a go next month and update this thread.

Rceron

Side walls on in Nittos are not stiff and could be giving you that feeling as well. Went to Hoosiers and the problem was solved. I too run high spring rates.

spiller

I was thinking about this also. I'll still try the slightly higher pressures but in the long run once I can find some dedicated track wheels I'm going to Advan A050 and use the Nittos on the street (I don't drive in the rain). You guys unfortunately don't get the A050 over there but by all accounts they're a fantastic tyre and around 2 seconds per lap quicker than NT01

powdrhound

I've been running NT01s for about 5 years. I found that the 315/30s felt soft with a tendency to roll over and you had to run higher pressures to compensate, around 36 hot. The 305/35s feel much stiffer overall and I can run lower pressures with them, 33 hot. The 305/35s carry a higher load rating and consequently feel more "solid". Compared to the 315, they provide more grip.