Can downforce affect tires temperature

[CHT]

Using the same theory of a pressure cooker, does anyone know if car with higher down force will increase the tire pressure within the tires and hence affecting the temperature of the tyres?

[raymondu999]

I'm not sure about how the gas theories of PV & T are affected by downforce, but downforce in and of itself (seen as a force) will mean more deformation of the tyre surface as it rolls along on the straights, which would produce heat. The added normal force between the track and the car also increases the friction/grip between the tyre and the tarmac - resulting in quicker cornering as you carry more speed through corners, which in turn also build more heat.

[Holm86]

The downforce alone will not affect the pressure in the tires. It will give you a slightly larger contact patch which will generate more heat though.

But just as if you measure the pressure of the tires on a car that sits on jack stands so no tire is touching the ground and then measure the pressure again after the car is on the ground there will be no difference. Because the tire doesnt deform that much so the volume does not change.

[CHT]

The downforce alone will not affect the pressure in the tires. It will give you a slightly larger contact patch which will generate more heat though.

But just as if you measure the pressure of the tires on a car that sits on jack stands so no tire is touching the ground and then measure the pressure again after the car is on the ground there will be no difference. Because the tire doesnt deform that much so the volume does not change.

At highspeed it is know that the down force could hit more than 3 times the weight of the car, under such circumstance will it affect its pressure?

[strad]

Downforce is load...the more load the more heat build up I would think.

[tim|away]

Using the same theory of a pressure cooker, does anyone know if car with higher down force will increase the tire pressure within the tires and hence affecting the temperature of the tyres?

The tyre doesn't heat up because the air pressure goes up, it's actually the other way around. The friction between the surface of the road and the tyre heats up the tread, which in turn heats up the air inside therefore increases the pressure.

Simply speaking, more downforce results in higher speeds through corners and thus higher loads on the tyres.

[Holm86]

Using the same theory of a pressure cooker, does anyone know if car with higher down force will increase the tire pressure within the tires and hence affecting the temperature of the tyres?

The tyre doesn't heat up because the air pressure goes up, it's actually the other way around. The friction between the surface of the road and the tyre heats up the tread, which in turn heats up the air inside therefore increases the pressure.

Simply speaking, more downforce results in higher speeds through corners and thus higher loads on the tyres.

Precisely. The downforce alone does not increase tire pressure.

[Stradivarius]

The downforce alone will not affect the pressure in the tires. It will give you a slightly larger contact patch which will generate more heat though.

But just as if you measure the pressure of the tires on a car that sits on jack stands so no tire is touching the ground and then measure the pressure again after the car is on the ground there will be no difference. Because the tire doesnt deform that much so the volume does not change.

This is incorrect, although I would agree that the change is very small. If you step on a balloon, it will pop as a result of increased pressure.

There is a number of ways to explain this. The simplest one is perhaps this: If you apply a force on an inflated tire, f.eks. by putting the car on the ground after having it sit on jack stands, the tire will deform. The tire will no longer be round all the way, it will have a plane surface where it touches the ground. You may argue that the deformation is only slight, but there will be some deformation. This means that physical work has taken place, just as if you had been compressing a spring, only here you are compressing the gas inside the tire. Since energy doesn't simply disappear, this energy will be found somewhere else. If you jack up the car, the tires will deform back, i.e. the flat contact surface will become round again. The energy source of this deformation is the tire pressure. So this is actually examples of adiabatic compression and expansion (as long as there is no significant heat exchange during the compression or expansion), which involves changes to the pressure and temperature. But this effect is very small compared to those that govern tire pressure and temperature on an f1 car, which is mainly friction (heating) and convection (cooling).

[Holm86]

The downforce alone will not affect the pressure in the tires. It will give you a slightly larger contact patch which will generate more heat though.

But just as if you measure the pressure of the tires on a car that sits on jack stands so no tire is touching the ground and then measure the pressure again after the car is on the ground there will be no difference. Because the tire doesnt deform that much so the volume does not change.

This is incorrect, although I would agree that the change is very small. If you step on a balloon, it will pop as a result of increased pressure.

There is a number of ways to explain this. The simplest one is perhaps this: If you apply a force on an inflated tire, f.eks. by putting the car on the ground after having it sit on jack stands, the tire will deform. The tire will no longer be round all the way, it will have a plane surface where it touches the ground. You may argue that the deformation is only slight, but there will be some deformation. This means that physical work has taken place, just as if you had been compressing a spring, only here you are compressing the gas inside the tire. Since energy doesn't simply disappear, this energy will be found somewhere else. If you jack up the car, the tires will deform back, i.e. the flat contact surface will become round again. The energy source of this deformation is the tire pressure. So this is actually examples of adiabatic compression and expansion (as long as there is no significant heat exchange during the compression or expansion), which involves changes to the pressure and temperature. But this effect is very small compared to those that govern tire pressure and temperature on an f1 car, which is mainly friction (heating) and convection (cooling).

No this is incorrect. When you step on a balloon it expands invards at that point. But et expands outwards in another place. Because the surface is elastic. A balloon pop pops when it cant expand anymore. Because then the pressure rises.

Same as a tire. It deforms on the contact patch but that will be compensatet for other places on the tire.

[Steven]

Another point to make is that less downforce makes drivers more prone to spin the rear tyres.

Spinning will temporarily heat the tyre and wear off the thread. It's often heard that teams are putting on a bit more downforce to protect the tyres. For sure it's not a constant influence to the tyre temperature, but less downforce can briefly cause spikes in tyre temperature, something which the Pirellis have somewhat of a problem with.

[CBeck113]

Both of you are correct - to answer CHT's question you would need to know if the tire is expanding with or without an air pressure rise. There will be pressure peaks since the volume of the tire changes at the road surface due to the downforce and then over the rest of the tire due to the increase in internal pressure resulting from the reduced volume, but the pressure only permanently increases when the tire can no longer increase its volume.

[Holm86]

Another point to make is that less downforce makes drivers more prone to spin the rear tyres.

Spinning will temporarily heat the tyre and wear off the thread. It's often heard that teams are putting on a bit more downforce to protect the tyres. For sure it's not a constant influence to the tyre temperature, but less downforce can briefly cause spikes in tyre temperature, something which the Pirellis have somewhat of a problem with.

Well there is to questions in this thread. "Can downforce affect tire temperature". Yes it can. Low downforce means the tire skids over the surface more. This creates friction between the tire and the road surface. This friction heats up the surface of the tire only and very quickly. And this uneven heating is what causes blistering of the tires and causes fast degredation.

High downforce means higher loads to the tire and the heat comes from friction within the tire itself. That spreads the heat over the whole tire and that is what you want.

But the second question was if downforce directly affected the pressure of the tire. I say it does'nt. And if it does its very minimalistic and not relevant.

[Holm86]

Both of you are correct - to answer CHT's question you would need to know if the tire is expanding with or without an air pressure rise. There will be pressure peaks since the volume of the tire changes at the road surface due to the downforce and then over the rest of the tire due to the increase in internal pressure resulting from the reduced volume, but the pressure only permanently increases when the tire can no longer increase its volume.

Precisely.

[Stradivarius]

The downforce alone will not affect the pressure in the tires. It will give you a slightly larger contact patch which will generate more heat though.

But just as if you measure the pressure of the tires on a car that sits on jack stands so no tire is touching the ground and then measure the pressure again after the car is on the ground there will be no difference. Because the tire doesnt deform that much so the volume does not change.

This is incorrect, although I would agree that the change is very small. If you step on a balloon, it will pop as a result of increased pressure.

There is a number of ways to explain this. The simplest one is perhaps this: If you apply a force on an inflated tire, f.eks. by putting the car on the ground after having it sit on jack stands, the tire will deform. The tire will no longer be round all the way, it will have a plane surface where it touches the ground. You may argue that the deformation is only slight, but there will be some deformation. This means that physical work has taken place, just as if you had been compressing a spring, only here you are compressing the gas inside the tire. Since energy doesn't simply disappear, this energy will be found somewhere else. If you jack up the car, the tires will deform back, i.e. the flat contact surface will become round again. The energy source of this deformation is the tire pressure. So this is actually examples of adiabatic compression and expansion (as long as there is no significant heat exchange during the compression or expansion), which involves changes to the pressure and temperature. But this effect is very small compared to those that govern tire pressure and temperature on an f1 car, which is mainly friction (heating) and convection (cooling).

No this is incorrect. When you step on a balloon it expands invards at that point. But et expands outwards in another place. Because the surface is elastic. A balloon pop pops when it cant expand anymore. Because then the pressure rises.

Same as a tire. It deforms on the contact patch but that will be compensatet for other places on the tire.

The balloon example wasn't a good one, as CBeck113 points out, it depends on whether it expands with increasing pressure, which most balloons don't. But a tire definitely does expand with increasing pressure. At least all tires that I know. If you want to increase the tire pressure, you put more gas into it.

Besides, it doesn't really matter if you compress the gas or expand the rubber. Heat will still be generated, either by adiabatic compression, or by friction when the rubber deforms.

[amc]

Since the only thing holding the car off the ground, and in equilibrium, is the tyres, we know that the weight of the car is equal to tyre pressure * contact patch area.

Let's say the car weighs 7000N, and the tyre pressure is the minimum allowed 19PSI (131000 Pa). Assume all four tyres carry the same load and are of identical dimensions, the contact patch is rectangular and extends the width of the tyre, the tyre does not bulge anywhere, and also that the elastic effects of the rubber can be ignored. This is a hideous oversimplification, but it's close enough for practical purposes.

The contact patch area is equal to (7000/4)/131000 = 0.013m^2, per tyre. Given a tyre width of 0.35m, there will be a section of the tyre that is 0.038m (38mm) long in contact with the ground. Based on that, the tyre's volume will decrease by... drum roll... 0.004%. At a higher level of downforce, let's say 20,000N all in, the tyre volume decreases by 0.012%. Both are negligible, so the temperature is not affected by downforce with respect PV = nRT, adiabatic expansion, and all of that stuff.
In fact, due to the 'centrifugal force' (urgh!) the tyre will actually expand slightly at high speeds. This could even cool it down!

However, the maximum deflection (vertically) of the tyre in each case is 0.55mm and 4.5mm respectively. This is significant. An 8-fold increase in the deformation will result in a 64-fold increase in the heat energy generated by the tyre. (Correct me if I'm wrong on this, I'm basing it on hysterisis and E = (1/2)*k*(ΔL)^2.)
It is this that is significant in terms of creating the heat in the tyres, as well as the large shear forces in the rubber surface.

But no, I'd say that purely in terms of the gas laws, downforce cannot affect tyre temperature.