Heat is wearing your tires faster, but how much faster?

[DigitalRelay]

I was practicing for a league race recently, Gr3 911 at Willow Springs BOP with tire wear at 4x, and I noticed my tires were wearing out far more quickly compared to other drivers. I have a dedicated display unit on my sim rig which shows tire temperatures and after more practice, it seemed like if I kept the tire temps under 195°F or so, the tires lasted longer. It made me wonder if there was a threshold limit or exponential slope and if I could find what those thresholds were. After searching for the information and finding a few clues - a Kierth video showing increased wear at higher temps, a Tidgney video that referred to "around 90°C" being the limit, and a Wombleleader video that narrowed it closer to 88°C on racing softs - so I decided to do my own testing.

I setup a custom race in GT7 update 1.55 at Northern Isle Raceway for 10 laps in the same car with tire wear at 4x and capture the in game footage, while separately capturing the tire temp overlay on my laptop and syncing the footage after the fact. I ran five full races on racing soft tires. While monitoring temps on my DDU, I tried to keep temps at 180°F the first race, 185°F the second, 190°F the third, 195° the fourth, and 200° the fifth. I then repeated this test on racing medium tires, but I added a sixth race where I pushed as hard as a I could ignoring temps, which went over 220°F. I did one more test on racing hards, but cut it to three races - 185°F, 195°F and pushing hard with temps over 220°F again. I went back to the footage and paused crossing the line on the last lap and took a screenshot of tire wear, then overlaid the tire temp aim from that session. After compositing the screenshots for easier comparison, here are the results.

It appears to me that each compound has a different threshold. It also appears the relationship of heat to tire wear is sloped or curved, and that each compound has a threshold where the curve gets exponentially worse. For racing soft tires, I think it's around 190°F/88°C. For racing medium 194°F/90°C. For racing hard 199°F/93°C.

A couple other notes...

I was surprised just how hard it was to maintain tire temps like this. I had many restarts if I either slide and the temps spiked, or if I went over the target temp by a few degrees because it would take several laps of slowing down to try to get them to come back down. It seemed like once that heat is in the tire, it takes time for them to come back down. I found pushing a little hard the first 3 laps brought the temps up, then I'd adjust my driving to lift going into the turns, coast and then slowly apply throttle as the turn straightened up. This was pretty much the approach Tidgney mentioned in his video as a tip to avoid overheating tires.

Going into this, I knew tire temps were a thing, and that sliding and spiking temps made grip worse, but I now have a much better understanding that the relationship of tire temps to wear is more complicated than that.

One last thing, if you're racing in races where tire wear is a factor, I think you'd want to consider having a way to monitor tire temps in real time. That could be an app on your phone or tablet, a laptop, or a dedicated display unit. I have used Eziodash on my iPhone and it looks and works great, but trying to go back and forth using it as my phone and a dash was a total pain. A spare smartphone or tablet would be better. Since I'm already running Simhub for bass shakers, wind simulation, and rumble pedals, it was very easy to add a $44 Vocore screen, 3D print a housing and mount it on my rig permanently.

I posted a video on my YT channel going into more detail on testing and what I learned.

If you have insight that I might have missed, I'd love to hear it.

 

[Pau1_13th]

Nice effort, appreciate it since im driving in vr I cannot use a temperature display, but it still helps to estimate how to drive careful enough if one sees that the degradation grows exponentially.

 

[bduddy]

I'm not sure this shows exactly what you say it does, because to keep the temperatures down you also have to drive slower in the corners, meaning less sliding and less opportunity for wear. But I don't disagree that tire temperature definitely plays a big part.

 

[Meythia]

I think a better way of testing for temperature as the culprit would be doing the same driving style on 2 different track temperatures.
Eliminate as many variables as possible - maybe use different ingame daytimes, maybe just restart the race until you have a high and a low temperature race.

 

[DigitalRelay]

I think a better way of testing for temperature as the culprit would be doing the same driving style on 2 different track temperatures.
Eliminate as many variables as possible - maybe use different ingame daytimes, maybe just restart the race until you have a high and a low temperature race.

While I did my testing, I closely monitored tire temps on my DDU the whole time. Anytime I slid, I could see tire temps spike. If they spiked from a slide, or if they crept up over the target temperature by more than 2 degrees, I restarted the race. I must have restarted a dozen times.

In my opinion, focusing on maintaining tire temps is more useful than a consistent driving style. Although driving style affects tire temps, the temperatures themselves determine the rate of tire wear. You can easily measure and track tire temps. It would be far more difficult to measure and track driving style. Consistent driving does make it easier to maintain temps though.

It'd be great if there was a circle test track where I could get the tires up to temp and hold them there. Start at 175°F and log tire wear for 10 laps. Then repeat the test but increase temp by one degree. Then I could calculate a numerical value for tear wear by temperature, per tire compound. I'm mostly thinking out loud here in case it sparks a better test idea.

Edit: I just had one more thought on this. I use Coach Dave Delta software, and I see that it captures tire temps along with all available telemetry. Maybe that could be useful.

 

[shadow0460]

I find that if I run soft tires, I need to feel for the controller to vibrate when they're sliding. Hard tires react better to sliding, though.
Just for example, on Pouhon at Spa (the double apex left hander about halfway through), with soft tires I'll maintain the same speed longer through the second apex but I don't push the car to understeer at all. If I'm running hard tires I can hit the gas sooner, turn the wheel a bit more, and let the front tires plow a bit through the second apex.
I think maybe we're expected to slide more on harder tires.

 

[Medronio]

So is there kind of tire temp windows?
Let's say soft tires for example:
Below 70°C tires are too cold and do not provide best grip.
Between 70 and 85° tires are in optimum range.
Above 85°C tires are too hot and will degrade much faster and provide not enough grip?
And if so, can we make a table for each compound so I can add the data to my dashboards tire colours please?

 

[Tired Tyres]

They should go back to the coloured tyres. Blue, green, yellow, orange and red. The last one means get in the pits you idiot. If its a colour blind issue, they could make the tyres bigger and put B, G, Y, O and R letters in the tyre colour.

 

[Medronio]

Well, as long as they don't do this, we have to use the dashboard workaround.
But what are the temperature limits?

 

[DigitalRelay]

So is there kind of tire temp windows?
Let's say soft tires for example:
Below 70°C tires are too cold and do not provide best grip.
Between 70 and 85° tires are in optimum range.
Above 85°C tires are too hot and will degrade much faster and provide not enough grip?
And if so, can we make a table for each compound so I can add the data to my dashboards tire colours please?

Yes, it does seem that way, although I didn't test for the lower range where tires need a certain temp for grip. The images I posted indicate wear rate at different temps. You can use the images as a starting point to build a table, but I had a hard time getting precise conclusions. It's very difficult to maintain an exact tire temperature, and you need to figure the amount of tire wear from a very small image. Also, there have been a couple of physics updates since I did this, and it is unknown if or how much that could affect the data. The conclusion I drew from this test is that in general tires wear faster the hotter they get, and that there seems to be a point where the tire wear increases disproportionately. I pointed out those rough temps per compound in the original post. If anyone wants to do further testing to try to extrapolate this data, I'd love to see your results!