Analyzing Tire Temps

[aston@ultrasw.c]

I spent some time at the track recording tire temps and pressures.

I started at high pressures and worked my way down.

I did 5 hot laps to make sure everything was up to temp.

Car is an 86 911 weighing 2,350 running Nitto NT01s 255/225

The tires were past their best. Pressures are hot. No cool down.

....Temperature...................Pressure
....Lo ..Lc.. Li....Ri...Rc.. Ro.... L....R

F 160 165 169 167 158 142 _ 33 33
R 165 174 189 183 172 158 _ 35 36

F 162 167 171 171 167 156 _ 32.5 32.5
R 169 178 190 189 176 167 _ 34 33

F 160 162 165 167 149 144 _ 29.5 30
R 163 171 185 180 165 158 _ 32 32

F 162 165 169 160 149 149 _ 29 29
R 169 174 180 180 169 162 _ 31 31

F 160 162 158 160 151 145 _ 27.5 27.5
R 167 174 181 181 174 160 _ 29.5 30

F 151 154 156 160 145 144 _ 25 25
R 154 163 171 169 162 156 _ 27 27

This is my first attempt at analyzing such data so here goes:

Higher pressures result in a greater temp range across the tire: up to 14 deg.
Lower pressures reduce the temp range to 8 approx.
Run lower pressures.

Inside edge is significantly higher than center or outside. Particularly at the rear.
Camber is -3 in the front and -2 in the rear.
Reduce camber to -2.5 and -1

Make adjustments and repeat.

How does that sound?

[winders]

Never try to analyze what new tires might like using old tires.

The inside should be hotter than the middle or outside if you are reading temps in the hot pit. I am not seeing "significantly higher" temps on the inside versus middle or outside. Well, except for the right side tires so I am assuming this test was done on a track that runs clockwise.

Instead of reinventing the wheel here, why not check to see what are others with a similar car and the same tires are running for camber and pressures?

What is the ideal temp for these tires? What are the hot pressures you should be shooting for? This is information the tire manufacturer should be able to give you.

[aston@ultrasw.c]

Apparently for the NT01 Nitto recommend:

Camber: -2.5 to -5.0
Hot inflation pressures: high 30's to low 40's
Operating temperatures: 140F - 220F
Optimum tire temperature: 200F
Caster: as much positive as possible

[winders]

Based on those specs, it would appear you are not getting enough heat into the tires and that you are running too low a pressure. But, you need to test with near new tires to figure out what you really need to do.

I would leave camber alone until you have a chance to run newer tires. Find someone fast that is using the same tires in a similar car and ask what camber and pressures they are running.

[aston@ultrasw.c]

Here's maybe a stupid question.

I would expect work, wear and temperature to be highly correlated.

The inside edges seem to be doing the most work as indicated by the temperature. However, the outside edge of the tire wears at a much greater rate.

How can this be?

[winders]

Originally Posted by aston@ultrasw.c

Here's maybe a stupid question.

I would expect work, wear and temperature to be highly correlated.

The inside edges seem to be doing the most work as indicated by the temperature. However, the outside edge of the tire wears at a much greater rate.

How can this be?

Well, that would indicate you don't have enough negative camber.

By the time you get in from the hot lap, the outside of the tire has been sitting up in the air getting cooled. The middle of the tire is getting some cooling, and the inside is still on the road getting the least amount of cooling. Personally, I would be looking at tire wear as an the indicator for proper camber. If the outside is wearing the most, it means the tire is up on the outside edge when cornering hard. You want the tire flatter on the track at high lateral loads.

[KaiB]

I agree with everything Scott says (huh?)....

Anyway, I always ask the question which begs to be asked:

Is the car doing anything you don't want it to do, or are you not able to do something with the car you would like to do?

[aston@ultrasw.c]

Originally Posted by winders

I would be looking at tire wear as an the indicator for proper camber. If the outside is wearing the most, it means the tire is up on the outside edge when cornering hard. You want the tire flatter on the track at high lateral loads.

I started a prior thread with tire wear data.

My observation was the outside 1/3 was almost gone and the inside 1/3 still had useful rubber remaining - particularly at the front.

I was asking about increasing neg camber given that I already have camber plates and offset ball joints.

Some suggested that tire wear was not a good indicator of tire performance and I needed to obtain temperature data!

I expected to find the outside edges way hotter but that's not what I measured.

[aston@ultrasw.c]

Originally Posted by KaiB

I agree with everything Scott says (huh?)....

Anyway, I always ask the question which begs to be asked:

Is the car doing anything you don't want it to do, or are you not able to do something with the car you would like to do?

OK good question.

Generally the car is quick, changes direction very well and is fairly neutral.

However, tire wear is uneven, see prior thread.

I would like to get a little more use out of a set of tires.

A race weekend is about 12 heat cycles over three days.

I would like to get 2 weekends/set.

By Sunday of the second weekend, things are getting kinda hairy.

When the tires begin to wear out the car starts oversteering, especially under power out of slower corners.

[winders]

It depends on what kind of tire wear.

If you are getting more wear on the inside of the tire versus the outside, you camber might still be okay. Why? Because braking load is being handled by the inside part of the tire and causes additional wear. But, when you have more wear on the outside edge of the tire, you can be pretty sure you need more negative camber to even out the wear.

Is there no one in your area that has setup a similar competitive car with the same tires that you can query?

[winders]

Originally Posted by aston@ultrasw.c

By Sunday of the second weekend, things are getting kinda hairy.

When the tires begin to wear out the car starts oversteering, especially under power out of slower corners.

That means the fronts are working better longer than the rears.....

[aston@ultrasw.c]

Originally Posted by winders

Well, that would indicate you don't have enough negative camber.

By the time you get in from the hot lap, the outside of the tire has been sitting up in the air getting cooled. The middle of the tire is getting some cooling, and the inside is still on the road getting the least amount of cooling. Personally, I would be looking at tire wear as an the indicator for proper camber. If the outside is wearing the most, it means the tire is up on the outside edge when cornering hard. You want the tire flatter on the track at high lateral loads.

I did try to come off the track as quickly as possible (without causing distress) and stop in the hot pit.

I did not have a pit crew, so I had to leap out of the car and do the measurements myself

[winders]

Originally Posted by aston@ultrasw.c

I did try to come off the track as quickly as possible (without causing distress) and stop in the hot pit.

I did not have a pit crew, so I had to leap out of the car and do the measurements myself

Do you watch F1? Have you seen the infrared camera shots of the front tires from above? Tires cool off very quickly and the more negative camber you have the worse it is. Tire temps are important but I look at wear and try to stay in the right window for hot pressures. Of course, really pay attention to the stop watch. That is the ultimate indicator!

[aston@ultrasw.c]

Originally Posted by winders

Do you watch F1? Have you seen the infrared camera shots of the front tires from above? Tires cool off very quickly and the more negative camber you have the worse it is. Tire temps are important but I look at wear and try to stay in the right window for hot pressures. Of course, really pay attention to the stop watch. That is the ultimate indicator!

I have seen the F1 IR cam. It's interesting but not very informative.

Is the difference between yellow (hot) and blue (not so hot) 5deg, 10deg or 100deg?

[winders]

The point really isn't the difference. The point is that tires cool rapidly when not stressed so you will always see the inner edge hotter than the outer edge unless you are lucky enough to have infrared sensors aim at your tires and collect the temperature data in real time.

Again, is there no one in your area that has setup a similar competitive car with the same tires that you can query?

[aston@ultrasw.c]

Unfortunately no one seems to run the older 911s any more.

I am surrounded by 997s, E46s, and Z06s.

[KaiB]

A bit of oversteer is a good thing.

Again, I agree with Scott. The watch is the ultimate story.

The rest does not matter.

[Cajundaddy]

I agree with winders. Tire temps can become like chasing rainbows. I have run NT01 for 6 yrs in a much heavier car (2950 lbs with driver). My ideal pressures are 35 hot (after cool down lap) and the tire is rolling over just to the very tip of the sidewall pointer when chalked. This is when the car feels the best and lap times are the lowest. I am a bit camber challenged at -2/-2.5 but tire wear is pretty good. Different cars and different driving styles will get different results.

On my car NT01s tend to grip well right down to the cord with little or no cycle out. If I run 4-5 qualifying laps they will get greasy but one tidy 9/10ths lap will bring them back in.

[Sboxin]

Originally Posted by aston@ultrasw.c

This is my first attempt at analyzing such data so here goes:
Higher pressures result in a greater temp range across the tire: up to 14 deg.
Lower pressures reduce the temp range to 8 approx.
Run lower pressures.
Inside edge is significantly higher than center or outside. Particularly at the rear.
Camber is -3 in the front and -2 in the rear.
Reduce camber to -2.5 and -1
Make adjustments and repeat.
How does that sound?

First, let me say you have built an Excellent 911 track car -- I have seen your posts before.

We race a similar car and have used Nittos in the past - currently use Hoosiers.
I would not recommend that you lower the tire pressures or reduce the suspension camber.
You did not mention using the old sidewall chalk marking test - - this is important to see what difference the pressures make in the tires ability to use all the tread surface.
Also, because you (like us) have more tire wear on the outside the camber may still not be large enough.
We used 35 and 38 PSI hot for Nittos on our car 2550# with driver and fuel. This was determined from role over and driver feedback, which is the most important information IMHO of course. When the driver says tires are slipping then we assess and make a change. After 15 laps and the front or rear slips then its time to do something. After a year of racing we arrived at numbers that were good for the driver and helped get the most out of the tires - - and Nittos are good all the way to the cord -- just not as fast as Hoosier for us - - and we ran several years on free comp Hohos.

You might think about coming up to Phoenix and driving with Brian and Erik at some NASA events - photo attached.

Edit: and you have one of the best Porsche track technical specialist there in Tucson - Dave Radmacher
Regards,

[aston@ultrasw.c]

Originally Posted by Sboxin

First, let me say you have built an Excellent 911 track car -- I have seen your posts before.

We race a similar car and have used Nittos in the past - currently use Hoosiers.
I would not recommend that you lower the tire pressures or reduce the suspension camber.
You did not mention using the old sidewall chalk marking test - - this is important to see what difference the pressures make in the tires ability to use all the tread surface.
Also, because you (like us) have more tire wear on the outside the camber may still not be large enough.
We used 35 and 38 PSI hot for Nittos on our car 2550# with driver and fuel. This was determined from role over and driver feedback, which is the most important information IMHO of course. When the driver says tires are slipping then we assess and make a change. After 15 laps and the front or rear slips then its time to do something. After a year of racing we arrived at numbers that were good for the driver and helped get the most out of the tires - - and Nittos are good all the way to the cord -- just not as fast as Hoosier for us - - and we ran several years on free comp Hohos.

You might think about coming up to Phoenix and driving with Brian and Erik at some NASA events - photo attached.

Edit: and you have one of the best Porsche track technical specialist there in Tucson - Dave Radmacher
Regards,

Thanks, sincerely.

One day I might graduate to Hoosiers but I can’t afford it. This is supposed to be a hobby not an obsession.

I won’t be reducing the camber: that did not sound right.

So should I add more front negative?
If so, how?
I already have camber plates (maxed out) and offset balljoints.
I have the idea to stretch the lower A arms but not sure how to go about it.

Do you do NASA at Inde Motorsports?
Perhaps I have enough experience to run with you guys!
Is that the UPS 911?