Tyre Pressures

[LifeW12]

What is the actual effect on the car by having soft and hard tyre pressures? Is it a suspension or tyre wear thing?

[McLaren]

Grip: lower pressure = more grip,higher pressure = more speed.

Probly other things aswell though.

[Jabberwocky]

it is more to do with handling as well

lower tyre pressures means that the tyre deflects when under cornering load, so it can dial out under/over steer.

tyre pressure can also change and is changed by tyre temperature. hot air expands etc.

[scotty]

What is the actual effect on the car by having soft and hard tyre pressures? Is it a suspension or tyre wear thing?

What do you specifically want to know? ie, effects on handling, wear, etc...

[LifeW12]

I'd like to know what 1lb in or out actually does. Drivers are doing it all the time and I don't understand how the car is effected.

[Jabberwocky]

I think the tyres are used as suspension as well because the car is that rigid.

so it have something to do with that.

[Selcouth_Feline]

I can't really comment on F1 but on road cars:

Tyre pressures affect the handling of cars quite substantially. If you are on track, you will tend to run with lower (cold) tyre pressures than on the road because you will be making the tyres work a lot more aggressively, causing the air in them to heat up more and therefore inflate more. If your tyres have too high a pressure, you may find your car gets very oversteery (as I found out once ).

Tyres tend to have optimum points where the rubber is at it's most 'sticky' therefore you want to make sure that at true race pace, your tyre temperatures are at the optimum point - and obviously you can partially control this via pressures.

Also, the contact patch between the road and the tyre will be affected by tyre pressure - this isn't as simple as it sounds as you might have a different optimum for different corners so you might trial different tyre pressures to see which gives you the quicker lap time. Tyre pressure can be adjusted to change the handling characteristics of your car. By increasing tyre pressure, the tyre profile becomes more round, which decreases the size of the contact patch. If you increase front tyre pressure, the car tends to become tighter (added understeer), and if you increase rear tyre pressure, the car tends to be looser (added oversteer).

I'm not an expert - the above is my understanding from talking to random people So anyone who's more enlightened, please feel free to correct me on the above! I just know that when I used to have my Lotus, the tyre pressures were key and changing them slightly would change the overall handling characteristics of the car substantially.

[scotty]

^^ That, also far as i know that explaination applies generally to most motorsports including F1, although too high a pressure in the tyres at either end would cause under/oversteer due to a loss of grip, and potentially excessive wear on top of that due to the tyres themselves overheating (due to the high tyre pressures). During races you might see teams putting tyres on in the pitstops with slightly different tyre pressures to try and help cure any handling problems (which are usually, again, under/oversteer issues), maybe in association with changing the front wing angle.

In F1 you'd rarely see problems where a car has tyres with completely wayward and inappropriate pressures due to the Bridgestone techs assigned to each team, hence the tyres would always be in the right ballpark, just maybe needing a tweak to solve handling ailments as above.

In the wet though, this is quite a crucial setup component. You want the tyres to be at a pretty high pressure to open up the grooves and clear water more effectively, however, go too far and, as in the dry, the tyres will overheat and wear quickly - and the last thing you want in the wet is for you tyres to be shot! A recent example of this going wrong for a team was in qualifying in Brazil - i forget if it was Button or Vettel (or even both), but they basically explained that their underperformance in that session was due to getting the tyre pressures wrong on the final run.

Hope this helps a bit, and that i wasn't just stating the obvious.

[Selcouth_Feline]

and potentially excessive wear

That's a really good point. Running excessively low or high tyre pressures for a long period of time will make your tyres wear in a way they probably weren't meant to. If you have a geo setup place near you, they normally keep tyres to demonstrate what long periods of running on tracking that's out and/or the wrong tyre pressures - and it also demonstrates what we said above about tyre-road contact patches.

[LifeW12]

Thanks for the info! I think I'm understanding it

[welshie]

To soft and the tyres over-heat and dont work effectively (less grip) also risk of graining and delamination, to hard and they struggle to reach working temperature as well as having a smaller contact area with the road and having negative effect on suspension (less grip). Is a relatively small window for perfect operating pressure and temperature.

[LifeW12]

Does the camber and toe of the wheels also have an effect of wear as well?

[Selcouth_Feline]

Does the camber and toe of the wheels also have an effect of wear as well?

Absolutely. There are generally three things you can change when looking at tyre/suspension setup (although you can't always adjust all three - on all of my cars, I've only ever been able to adjust two of the three elements because of my suspension)

If you look at a car tyre from the front, camber is the amount the tyre leans in towards the car at the top (negative camber) or leans outwards (positive camber). This will affect the wear as it will shift the contact patch more to either the inside or outside of the tyre.

When you turn the steering wheel, the front wheels respond by turning on a pivot attached to the suspension system. Caster is the angle of this steering pivot, measured in degrees, when viewed from the side of the car. Positive caster is when the top of the pivot is leaning toward the rear of the car; if it is leaning toward the front, it is negative caster. To be honest, I don't think this has much affect on tyre wear however it will affect the handling of your car.

If you are looking at the car from above, toe is whether the tyres are pointing in or out at the front. Toe-in means that the fronts of the tires are closer to each other than the rears; Toe-out is the opposite. An incorrect toe-in will cause rapid tyre wear to both tyres equally.