Upping the grip: tyre pressures and temperatures

As I mentioned in my last post, I came across a great little device at my last supersprint which left me very impressed. A pyrometer (see pic) is a basically a temperature sensor, but it doesn't require contact with the object to take a reading. It measures thermal radiation, so you just point it at the object you wish to measure the temperature of and wait for the readout.

For the amateur track day goer, I think this is a great way to add a little "science" to my car setup - the idea being to take a little bit of the guesswork out, and make calculated changes to the car. So how would I use a pyrometer to help with my setup? By measuring tyre temperatures and drawing some basic conclusions from the data.

To maximise cornering grip, we want as much of the tyre touching the road as possible - how much of the tyre is touching the road is known as the contact patch. Wheel alignment plays an important role in maximising this patch, but so too does tyre pressure. If a tyre is over-inflated, it will "stand up" and not use the edges, and if too soft, it will flex - both detrimental to cornering grip.

Using a pyrometer, I can gather some useful information on how hard each section of the tyre is working and thus check if I have a good contact patch. After a session on the track, you can take three readings on each tyre - the outside section of the tyre, the middle of the tyre, and the inside section of the tyre. In this case, we are not particularly interested in the actual temeperature value, becuase it will vary a lot with the conditions. What is more important is uniformity - if the temperature across the three sections of tyre are similar, then the full tyre is touching the road the majority of the time, and thus being used to it's full potential. If, however, the edges of the tyre are cooler than the centre, it may suggest that the tyre is over-inflated. Conversely, hotter edges than the centre may suggest that the tyres are under-inflated. If the tyre is hotter on one edge than the other, it may indicate a handling bias which requires you to make a suspension change. This is pretty basic stuff, but as I said, it gives you an opportunity to inspect your car and take a more educated guess about making changes.

Given that it can read the temperature of anything you point it at, the pyrometer can also be used to monitor the temperature of brake rotors, your gearbox or diff, anything really! All these items have a safe operating temperature range, so I could check these periodically to make sure everything is in check.

So in summary, a great little device. I think that if I made the effort to do this at every track day, along with logging some basic weather information, and track temperature, it would help greatly in determining a suitable starting point for the conditions, and get me into that sweet spot sooner!