Motorsport Wheel Alignment: How to Optimise Your Tyre Pressures
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How to Optimise Your Tyre Pressures
05.24
| 00:00 | - At this point, you might be thinking, this is all well and good but how do I know what my ideal tyre pressure should be? And fair enough. |
| 00:08 | Working this out can be done in three separate ways depending on your budget. |
| 00:12 | At the bottom of this scale, you'll be relying on the stopwatch, data if you have it and how the car feels on the track. |
| 00:19 | If you want to get a little more serious and scientific then you can use a tyre pyrometer which is just a flash name for a tyre temperature sensor to check the tyre temperature when you get back into the pits. |
| 00:30 | And if budget is no problem then onboard infrared tyre pyrometers that monitor the real time tread temperature on the track are the ultimate. |
| 00:39 | Let's look at our budget approach though since most track day enthusiasts will at least start here before progressing to the other options. |
| 00:47 | What we're going to do here is drive the car and get our tyres up to a normal operating temperature. |
| 00:53 | To get you in the ballpark, I'd suggest aiming for a hot pressure close to the recommended pressure on your factory tyre placard. |
| 01:00 | You'll find this placard usually fitted to the driver's door pillar or alternatively in the car's information manual. |
| 01:07 | Every tyre is different however and the correct pressure could be higher or lower than this. |
| 01:12 | We then want to drive one to two laps at normal race pace, taking particular note of how the car feels when you turn into a corner, how the balance is mid corner and then how easily you can apply power on the corner exit. |
| 01:25 | If you have even a modest datalogger in the car which by the way I highly recommend, you can also correlate your feedback to data such as lateral g force in the corners and of course your lap time. |
| 01:36 | Next you're going to make a change to tyre pressure. |
| 01:39 | While professional race drivers may be able to notice a change of half a psi or less, chances are that you won't so what we want to do is make a big enough change that the effect is noticeable and I'd initially suggest a two psi increment. |
| 01:53 | At this stage, we don't know if we need to go up or down in pressure so pick a direction and go with it. |
| 01:59 | What we want to do is re run our initial test and look for any differences in turn in, mid corner grip and balance as well as corner exit. |
| 02:07 | Again, when we correlate this with our data, we should be able to note a difference which may be better or it may be worse at this point. |
| 02:15 | Of course if you go in a certain direction with your tyre pressure and the car handling deteriorates, then stop and try going in the opposite direction with your pressure change. |
| 02:24 | Once you've found the sweet spot for your tyre pressures, you can then start making more subtle changes of perhaps one psi and also altering the pressures front to rear which will affect the balance of the car between understeer and oversteer. |
| 02:37 | If you want to get a little more technical then a tyre pyrometer will help you see how you tyre pressure affects the temperature of the tyre tread. |
| 02:45 | In essence, when the tyre tread is working more evenly on the track, the temperature of the tread will also be more even. |
| 02:52 | The tricky part is that the tread temperature will be affected by camber and toe as well as tyre pressure, so if the camber or toe are incorrect then we won't ever be able to get consistent tyre temperature readings by adjusting pressure alone. |
| 03:06 | When you're using a tyre pyrometer, we're actually measuring below the surface or the tyre since the outer tread will very quickly lose temperature when the car comes to a stop. |
| 03:16 | What we want to do is measure the tyre temperature at three points across the tread, the inside edge, the centre and then the outside edge. |
| 03:23 | What we're aiming for is a nice even temperature reading across all three points. |
| 03:28 | If on the other hand, the centre is hotter than the edges, we have too much pressure. |
| 03:32 | And if the outside edges are hotter than the centre, we're under inflated. |
| 03:37 | Just like our tyre pressure, this data needs to be collected as soon as the car returns to the pits as the tyre temperature will stabilise and drop very quickly. |
| 03:46 | This is also best done by coming into the pits on a flying lap instead of after a full cool down lap that you'd typically do at the end of a race. |
| 03:54 | Practice sessions with an open pit lane are the best place to gather this data, since you can gather the data you need, then return to the track rather than sitting there with the brakes and engine cooking, due to high temps and a lack of airflow. |
| 04:07 | The last and best option is to fit infrared tyre temp sensors to the chassis that can report on the temperature across the tyre tread while the car is on track. |
| 04:16 | The reason this is superior to the tyre pyro in the pits is that we're getting a true indication of the tread temperature mid corner which is where it counts. |
| 04:26 | Since the tyre temperature changes quite quickly, using your tyre pyro back in the pits can give us data that's a little inaccurate compared to what actually happened mid corner. |
| 04:37 | For example, if we're running three to four degrees of negative camber, and a reasonable amount of toe, then this will show a higher temperature on the inside edge of the tyre and in turn it can distort our tyre pyrometer readings back in the pits, particularly if there's a long straight between the exit of the last corner and the pit entrance. |
| 04:55 | Of course the downside with onboard infrared tyre temp sensors is the significant investment in the sensors themselves as well as mounting these sensors and of course a datalogging package that's compatible with them. |
| 05:07 | While this might be the choice of top race teams where budget is no problem, you'll find plenty of club sport through to professional race teams making do with nothing more than a traditional tyre temperature pyrometer back in the pit lane. |
