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I normally dont measure the tires cold. Hot is what matters and I run 27F 29R...
 

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Need more detail on that question:

What size wheels? What size tires?

I started at 23/26 (cold) and then lower from there (using a probe type pyrometer) when using R888s on the stock wheels with the stock tire sizes. Over the course of the day I think I let about 1.5 pounds out of the fronts and one pound out of the rears.
 

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Need more detail on that question:

What size wheels? What size tires?

I started at 23/26 (cold) and then lower from there (using a probe type pyrometer) when using R888s on the stock wheels with the stock tire sizes. Over the course of the day I think I let about 1.5 pounds out of the fronts and one pound out of the rears.
using a probe type pyrometer is the only way you will get them set up correctly, along with your quality air gauge.
use his 23/26 as a starting point, and then go from there.
 

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Ok...how do you properly use a pyrometer? I know you want to know the outside, middle inside temps and you want them even. But what does that really mean.

Yes, I will probably start by just using this info on GTR 2 but its all a learning game.

BTW, I run my R888s 26 PSI front and 28 PSI rear hot. Alwats seem to start with them over inflated and then have to seriously back off pressure after my first run. First run Im not pushing anything and just learning the track.
 

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as of now, im on TD 1.2 wheels, 16x7 front, 17x8 rear factory size R888 and im running the PSI reading on the door jamb of the car, its like 26/29 f/r if i remember correctly

any PSI recommendations?
 

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Ok...how do you properly use a pyrometer? I know you want to know the outside, middle inside temps and you want them even. But what does that really mean.
If a tire has temps like this (one tire, left/middle/right):

140 160 140

then you have too much pressure and you should let some air out.

If a tire has temps like this:

140 120 140

then you don't have enough pressure and you should put some air back in.

If a tire has temps like this:

140 140 140

then you should play the lottery. :)

That's the basics. Of course things like camber can effect temps and you will often see uneven temps across a tire, but basically you want temps that make sense.

If your rear drivers side tire has temps like this:

140 145 148

and you are running -3 degrees of camber in the back then it sort of makes sense. The inside of the tire should be a bit hotter than the outside because of the camber, and everything is sort of linear.

I do think that 26/29 cold would be too much pressure for a R888 on stock wheels, however a lot of this also depends on how hard you run the car. I know that with the AO48s there were folks who were running their rears a few pounds LOWER than their fronts because they were running their cars HARD. While the first few laps were squishy, once the rears got up to temp their cars were some of the fastest on the track. Of course they were running at 10/10th (or often more like 10.5/10th). If you are running the car 5/10th or 6/10ths then 26/29 might be fine.
 

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as of now, im on TD 1.2 wheels, 16x7 front, 17x8 rear factory size R888 and im running the PSI reading on the door jamb of the car, its like 26/29 f/r if i remember correctly

any PSI recommendations?
Track or street? For track, I would go down. Minimum of 3 lbs per tire.

For street... sounds about rightish, but who the heck knows? You would have to use a pyrometer, or just look for uneven tire wear.
 

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^ Heard the advice from one of the dealers to run rears lower than fronts. Dont think Im at the level where thats right for me. However, I think Lap This has some nice footage of my rear stepping out on me in some twisties. Since I cought it...it should make for some cool footage.
 

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Since I very rarely have the rear of my car step out Im not sure lowering the rear pressures would do much good. In fact It makes the car harder to rotate mid corner.
 

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You have a little more force pressing down on your rear! Might make a little bit of difference.

Edit: Assuming your racing with a wing.
 

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Yes I'm running 15/16, but I would assume the tire PSI should be similar. It would at least be a good starting point. Those temps are for hot BTW.
 

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Discussion Starter #16
I just did 23 front 25 rear cold for stock sizes.

These tires feel FANTASTIC and just grip and grip. Imagine they'd be even better after a little break-in.
 

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I just did 23 front 25 rear cold for stock sizes.

These tires feel FANTASTIC and just grip and grip. Imagine they'd be even better after a little break-in.
:up: Yes, they do, and they will!

I've got 24f/26r cold (80 degF)... stock sizes. I've checked the temps with an infrared thermometer after a canyon run and they look nice and linear across the tire face.

Coi, which auto-x are you going to in Sept?
 
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