Guide To Interpreting Tyre Temperatures In Motorsports

Detailed Guide To Interpreting Tyre Temperatures On Racing Cars

Like finger prints at a crime scene, your tyre temperatures can reveal hidden clues about what is really happening out on track.

With a few simple temperature measurements, you can uncover your racing cars’ most hidden handling secrets, get crystal clear setup direction AND have objective data to know if your changes are working.

Staggering

… and yet so simple – when you know how.

To that end, I have put together a detailed guide to try to help you to interpret your own tyre temperature data.

It starts off with why (bother). Then what (you can learn). Then how (to interpret the numbers).

Race tyres are not just black and round! Make sure you are getting the most out of yours.


Contents:


First a quick suggestion:

Whilst notionally simple once you get the concepts, this does get involved and does include some maths.

Consequently, I have baked all the interpretation logic into a free spreadsheet for our newsletter subscribers. If you want it just pop your name and email in the form below for instant access.

If you’re not ready to join us yet πŸ˜‰ then (as always) there is everything here in the article for you to build your own.

Either way, I do suggest you get your hands on an automated analyser tool to help you if you can.


Why Are Tyre Temperatures Important?

If you are in any doubt about the importance of getting your racing car tyre temperatures right, then have a quick scan of my article on What Your Tyre Temperatures Should Be.

In summary, the tyres are the only part of the racing car that touches the road. All the forces resolve through the tyres and their condition completely defines your grip levels.

This means that no matter how good your engine, your aerodynamics or your racing driver, if you have not got the tyres working then you’ll be loosing time.


3 Things You Can Learn From Tyre Temps

There are lots of things you can learn from the condition of your tyres however you might consider these 3 as the fundamentals:

  1. Correct Temperatures. You will (of course πŸ™‚ ) be targeting a specific hot tyre temperature to maximise your grip whilst minimising your tyre degradation for your given session. Measuring your tyre temperatures across the tyre tread tells you if you are hitting these targets and if your camber settings are optimum.
  2. Correct Inflation. Whilst you are (hopefully!) also targeting a specific hot pressure, your tyre temperatures can tell you how effective that hot pressure target is. Tyres do this by telling you if your tyre is under or over inflated.
  3. Handling Balance. If the tyre temperatures of one axle are significantly different to the other axle, this can indicate a handling imbalance. This will result in the driver complaining about understeer or oversteer and they will be slow.

Of course all three are somewhat related.

The over-aching goal is simply to maximise the grip each tyre is capable of producing individually, whilst also maintaining a good handling balance.


Racing Tyre Temperature Spreads

Starting with the individual tyre, and regardless of how you measure your tyre temperatures, you are probably familiar with the concept of thinking of the tyre in three sections, the:

  1. Outside Edge
  2. Middle
  3. Inside Edge

Outside and inside are relative to the car with inside being closest to the car and the outside closest to the kerb. See my epic racing car sketch below: πŸ™‚

Where to take tyre temperatures on a racing car.
Where to take tyre temperatures on a racing car.

The reason why you want to consider the tyre in these three sections is that a tyres’ temperature will vary across its tread width.

The differences in temperature in these three zones are what enables you to interpret how well the tyre is working. These differences can be referred to as your “tyre temperature spreads.”

You can get more sophisticated about this but I personally find that that quickly gets overwhelming. So, hat-tip to sophistication but I’ll keep it on easy-mode here πŸ˜€


Interpreting Tyre Temperatures – Individual Spreads

With individual tyre temperature spreads you can start to answer the first two questions:

  1. Are your tyres the right temperature for maximum grip?
  2. Are your tyres properly inflated?

1. Correct Temperatures

Regarding the temperatures two things you can learn are:

  • Is the tyre temperature in your target temperature range?
  • Is the wheel camber setup correctly?

To understand if your tyre temperatures are in range, the easiest thing to do is simply average your three readings and check.

Remember you are (probably) targeting a temperature range (or “window”) and not just a single temperature number.

Therefore to check, take the average together with your temperature window, and then you can quickly work out if the tyres are too hot or too cold.

Regarding the camber there is quite a lot to this that I’m not going to go into here.

Simply though, camber is a setting on the suspension. Negative camber is where the top of the tyre leans in towards the car and can often give you some advantages. These advantages are to do with trying to generate more cornering force by having the tyre presented to the road at a more optimum angle. Camber can be a very powerful tuning aid and is adjustable on most racing cars.

You can determine if you have too much (or not enough) negative camber by comparing the outer and inner tyre temperature readings.

What constitutes too much (or not enough) camber will be individual to each tyre and your setup preferences.

Saying that, you will likely come to a decision that says either you want to set your camber so you have no spread difference, or, you will have a preference for the inner temperature to be hotter.

2. Correct Inflation

For maximum grip and least degradation you want to have as much of the tyre tread in contact with the road as possible. Have a look at this cutaway image of a typical tyres’ construction:

Tyre construction cutaway image
Image credit: Wikipedia

I appreciate that is not a normal racing tyre but I thought the annotations good and racing tyres are similar enough.

I remember the first time I saw one of these images and being quite astonished as I really had no idea how much went into the construction of a tyre!

Inflation pressure is critical.

A tyre edges are stiffer than the middle. If you look at the sidewall, perhaps you can imagine that poking the tyre vertically where the label says “Innerliner” would result in more flex than pressing at the “Shoulder Insert”?

This is because there is nothing really supporting the middle of the tyre, except, of course, the tyre pressure.

Tyre pressure is therefore very important.

Too much pressure and the middle of the tyre will bulge / flex up. The load across the tread will be focused too much in the middle and not enough at the edges. You will have less grip.

Equally, if there is not enough tyre pressure then the opposite happens. The tread does not have enough support and flexes inwards. The result is the cars load is focused more on the edges of the tyre and not enough in the middle. Again less grip.

What you want is to have a tyre pressure that results in the load being evenly distributed across the tread.

You can tell if the load is being evenly distribute by looking at your tyre temperature spreads.

Mathematically, the way you do this is minus the middle reading from both the inner and the outer readings.

As a result you get two numbers.

If those two numbers are the same then the tyre inflation is OK. However, if the numbers are different then the tyre is either under or over inflated.

Incidentally, I have written another article on how to set your tyre pressures perfectly every time. If you find that your pressures are out, maybe that will help you get yours corrected quickly.


Still with me?? πŸ™‚

Great!

I have covered a fair few concepts so far but personally, I learn better with real examples.

Therefore, before leaving the optimisation of an individual tyre, let’s have a quick look at a worked example using the spreadsheet.

Pick it up below if you want or just follow through with the images.


Your Data Driven’s Tyre Temperature Analyser πŸ™‚

Interpreting racing car tyre temperatures -  free spreadsheet
[YDD] Tyre Temperature Optimisation Tool

Above you can see a screen image of the spreadsheet tool I’ve pulled together to support this article.

It is a Google Sheet and I’ve designed the layout so that it fits nicely on a smart phone screen. My thinking is that you’ll be using this in the pits to record your tyre temperature – possibly even one handed.

The inputs are on in the grey boxes on the left and the automated tyre analysis is on the right.

I’ve laid these out quite specifically so you simply have to work down the screen.

First you set your targets, then you record the tyre temperature measurements.

This is laid out starting at the Front Left, then moving to the Rear Left, Rear Right and finally Front Right.

This is the order I expect you to be moving around the car and I believe is a convention (?) – certainly for clockwise tracks.

If you have a look at the analysis section you can see the interpretations I have discussed put into a digital form.

The analyses update automajcially so all you need to do is simply add your temperature readings.

I will quickly take you through the analyses so that you can start to see how the theory translates into practise:


Temp Profile

Temp profile section of free spreadsheet

This shows a “sparkline” chart of the three tyre temperatures. I find visuals like this easier than reading tables of numbers in terms of trying to spot trends and features in data.

Looking at the Front Left, you can see that the Outside temperature is below the Inner temperature. If you remember, this implies there is some negative camber applied to the wheel.

Also the sparkline is not straight (like it is for the Right Rear.) It looks like the middle temperature is a bit lower than it should be. Which leads too …

Inflation OK?

Inflation check section of free spreadsheet

… the conclusion that the tyre is under inflated. Under this section you can see the word “Under” to help you quickly assess whether it is under or over inflated. The inflation box is also red to draw your eye to the issue.

You can make a judgement call on how important the under or over inflation is by looking again at the sparkline.

If it is like the one for the Front Left, I’d perhaps be ok with it. If it looks like the sparklines for either the Left Rear (Under) or Front Right (Over) I would be more concerned.

Camber OK?

 Camber section of free spreadsheet

You can see that all the tyres in this example have a certain amount of negative camber. Remember to assess the camber you compare the inside temperature to the outer temperature.

What I have done here is to put in a suggested target for this temperature spread. If you look at the targets, you will see “Camber” under “Temp Spreads” with the value 4. This means I am targeting a 4 ℃ spread between the Inside and Outside tyre temperatures (since updated with separate front and rear spread targets 😎 )

The analysis then works out the temperature spread in ℃ (this is the 8 in the box) and then compares that to the target.

You are either “OK“, “Too Much” or “Too Little.” Again, you can use the actual spread and target to judge if this worth worrying about or not.

As discussed earlier, your individual tyre and setup preferences will determine what value you should aim for. This gives you the option to monitor it.

In Window?

Window section of free spreadsheet

The “In Window” box by rights could / should be the first one. I’ve put it here so it is next to the balance assessment (more on that below) but hopefully you’ll still see it easy enough.

Like the camber box, this takes a figure and compares it to the tyre temperature target that you’d have inputted. The tyre temperature that is used is the figure in the box and this is the average of your three measurements.

In the targets section you have the target temperature you want for max grip, plus I have added a “Window” value.

For the example, the target temperature is 80 ℃ and the window is +/- 5 ℃ from the target.

This means that if your average tyre temperature is less than 85 ℃ and more than 75 ℃ the analysis will say you tyres are “OK.”

Below 75 ℃ and it will say the tyres are “Cold.”

Above 85 ℃ it will say they are “Hot“.

Like I said at the beginning, there is nothing too hard about this. It just takes some thought and a bit of maths which is where I think a spreadsheet can be really useful.

Hopefully you now understand how you can tell how well you are optimising the grip for each tyre.

But what about the overall car balance?


Interpreting Front To Rear Car Balance With Tyre Temperatures

You might have heard professional racing drivers and teams struggling to get both the front and rear tyres to “come in” (or get up to temperature) at the same time.

The issue is that once there is a handling imbalance caused by an imbalance of tyre temperatures it tends to get worse. For example: overheating front tyres can lead to understeer that can lead to even higher front tyre temperatures, and then even more understeer.

Of course, the driver has a large influence over how to warm up the tyres but it is also a factor of your underlying setup, weather conditions and the track.

How To Use Tyre Temperature For Handling Balance Interpretations

To use tyre temperatures to help you understand handling balance, again you take an average.

This time you take an average of all the front temperatures and then all the rear temperatures.

The interpretation of this data is a little more subtle however.

This is because both hot and cold temperatures can cause the same handling effects but for different reasons.

Take a look at the summary table below. It has example data with a suggested interpretation of the racing cars’ behaviour.

Note: The target tyre temp for max grip was 80 ℃ with a window of +/- 5 ℃ :

Front Ave Temps ℃ (℉)Rear Ave Temps ℃ (℉)Interpretation
95 (203)95 (203)Frt & Rear too hot – loss overall grip
65 (149)65 (149)Frt & Rear too cold – loss overall grip
65 (149)80 (176)Front too cold – Understeer
80 (176)65 (149)Rear too cold – Oversteer
95 (203)80 (176)Front too hot – Understeer
80 (176)95 (203)Rear too hot – Oversteer / Traction issues

As you can hopefully see there is a little more going on here.

What I mean is that you cannot simply say that if the front is less than the rear you have understeer. This is because it depends on both by how much and at what temperature each axle is at.

For example, if the front axle is at optimum grip (i.e. 80 ℃) and the rear is a lot hotter (common πŸ˜‰ ), then it is likely that you will have oversteer.

However, if the front axle is colder and the rear is at optimum temperature you are likely to have understeer.

The temperature differences might be the same amount and the same ratio (i.e. front colder) but the handling balance can be complete opposite.

Clearly it is no wonder pro-teams moan about tyres the whole time 😎

How To Handle Automatically Analysing Handling Balance

In my spreadsheet I’ve ended up using this fairly fiddly nested “IF” statement. This is to ensure you always automatically get the right interpretation:

=if(and(W8=2,W14=2),”Balanced”,if(and(W8<>2,W14=2),”Understeer”, if(and(W14<>2,W8=2),”Oversteer”, if(and(W8=1,W14=1),”Frt & Rear Too Cold”, if(and(W8=3,W14=3),”Frt & Rr Too Hot”, if(and(W8=3,W14=1),”Likely Understeer”, if(and(W8=1,W14=3),”Likely Oversteer”)))))))

It works fine and produces the little graphic below:

Interpreting racing car tyre temperatures - Balance section of free spreadsheet

There are however some edge cases. In practise, this means you will have to look at the other metrics to properly interpret what is going on – i.e. if a rear tyre is very hot and a front tyre is very cold.

Left To Right Balance Too

For completeness, I’ve also included a left to right “balance.”

Ideally you are looking for the same average temperatures on the left and the right.

With a large difference left to right it might be causing you issues with braking stability, rotation or traction issues.

As a side note to asymmetrical temperatures, it is worth considering what else might be contributing to heating up a tyre on one side.

For example, it is quite common to have a racing car that has an exhaust exiting right in front of a rear tyre. The interpretations you make in that situation would be different (i.e. add heat shielding) if your tyre is not in a good working window.


Summary

As you can see interpreting your racing car’s tyre temperatures can give you huge help in optimising your setup and car balance.

I find it really does feel like being a detective at the crime scene – collecting the evidence (tyre temperatures) & then trying to piece together the story of what has happened (and how it can be improved 😎 )

Hopefully next time you have the opportunity you will try measuring your tyre temperatures and run the calculations in this way.

Using Analysis Tools To Help

You’re very welcome to use my spreadsheet but of course it is not that difficult to build you own (maybe apart from the balance assessment bit?)

If you do go your own route I do recommend making sure that it is see easy to see on your phone. Clearly a Google Sheet works on both phones and laptops. However, a phone is easier than a laptop to carry round, especially when you’re taking measurements.

Even if you are using a temperature gauge that can store the numbers, it might still be easier to have the option of doing the analysis on your phone.

Here is what my spreadsheet looks like on an iPhone 6 screen:

Interpreting racing car tyre temperatures - Input section of free spreadsheet

And here is the analysis section, also on an iPhone 6 screen (landscape):

Interpreting racing car tyre temperatures - Analysis section of free spreadsheet

Everything is within one view, with minimum scrolling about. Hopefully the design makes the analysis pretty clear too?

I hope you have enjoyed reading this guide and found it useful.

I also hope that next time you are interpreting your racing car tyre temperatures you will have much a clearer idea of where to improve.

Hopefully that will also make your racing car much faster!

By the way, clearly if that demo analysis screenshot was real data from your actual racing car, you’d have some serious work on your hands! … But anyhow …

Best of luck πŸ™‚


Enjoyed Reading This?

If the temperature of your racing car tyres are out, you’ll be left wresting a bear. Avoid that & gain control of your cars grip levels in this detailed guide: https://www.yourdatadriven.com/what-should-the-temperature-of-your-racing-car-tyres-be/

Want to take the guess work out of setting your tyre pressures? Try this article including a free calculatorhttps://www.yourdatadriven.com/how-to-set-your-racing-car-tyre-pressures-perfectly-every-time/