Managing Tire Temperatures

[gcdugas]

I know this is SEEMS over-simplified but for teams that are struggling to keep the temps up, or in the right range, might the answer be found in adjusting the toe-in (both F&R). Just a quarter degree can increase the scrub enough to raise temperatures measurably. Yes, that heat comes from increased mechanical drag on straights but, like wing adjustments, the pay-off could very well be worth it if your corner exit speed is higher. Every team has ways to control how much brake heat goes into the rims. Every car essentially has their tires being cooled by the air to essentially the same degree. So why are some cars able to keep the temps up and others struggle to get heat into the tires. It seems that there are only three factors in tire temp, brake heat contribution, atmospheric cooling, and mechanical contribution via alignment geometry, mostly toe-in.

Am I over simplifying things? What say ye?

[Tim.Wright]

It's true that toe angle will affect the tyre temperatures - I showed something similar a few years ago here
viewtopic.php?f=6&t=19377

While it can be used as a temperature tool, it has a massive influence on the vehicle handling so you are quite restricted in what you can change. There's no point in having the correct temperatures if cornering balance is wrong.

[izzy]

I know this is SEEMS over-simplified but for teams that are struggling to keep the temps up, or in the right range, might the answer be found in adjusting the toe-in (both F&R). Just a quarter degree can increase the scrub enough to raise temperatures measurably. Yes, that heat comes from increased mechanical drag on straights but, like wing adjustments, the pay-off could very well be worth it if your corner exit speed is higher. Every team has ways to control how much brake heat goes into the rims. Every car essentially has their tires being cooled by the air to essentially the same degree. So why are some cars able to keep the temps up and others struggle to get heat into the tires. It seems that there are only three factors in tire temp, brake heat contribution, atmospheric cooling, and mechanical contribution via alignment geometry, mostly toe-in.

Am I over simplifying things? What say ye?

a lot of the issue is about the carcass temperature, more than the surface. They have get the carcass to flex, to get the tyre to really mould to the tarmac, and it does that better when it's warm, and in typical F1 circle fashion they have to flex it to warm it up!

That's why the load / downforce on it is such a factor and how a tyre can go 'dead' in a race when it literally can't be warmed up again whatever they do. The tricky bit is to warm up the carcass without melting or graining the surface, which running it toed in or out would do

[Dex35]

As I have a tendency to over-complicate things, I have wondered how much effect on tyre temperature there would be if there were a cool/warm/hot stream of air coming out of the floor bulge that houses the rear tyre temperature sensor.
I am not intimating a “moveable aerodynamic device”, just whatever incidental air flow there might be, but that air passing through a throttleable heat exchanger.

In the same vein as the floor mounted heat exchanger that Ferrari was running about Monaco time last year.

BTW, IIRC an endurance team (Peugeot?) was found during practice to the (early 1990’s?) Le Mans race to have the working guts of a microwave oven (Klystron) mounted in the front fenders, “shining” on the front tyres of one of their cars, to keep them warm during any rainy periods. They were told to remove the device, and as I know, nothing more was ever said about it.

[DiogoBrand]

It's true that toe angle will affect the tyre temperatures - I showed something similar a few years ago here
viewtopic.php?f=6&t=19377

While it can be used as a temperature tool, it has a massive influence on the vehicle handling so you are quite restricted in what you can change. There's no point in having the correct temperatures if cornering balance is wrong.

Doesn't it give a negative effect on top speeds as well?

[Dr. Acula]

I know this is SEEMS over-simplified but for teams that are struggling to keep the temps up, or in the right range, might the answer be found in adjusting the toe-in (both F&R). Just a quarter degree can increase the scrub enough to raise temperatures measurably. Yes, that heat comes from increased mechanical drag on straights but, like wing adjustments, the pay-off could very well be worth it if your corner exit speed is higher. Every team has ways to control how much brake heat goes into the rims. Every car essentially has their tires being cooled by the air to essentially the same degree. So why are some cars able to keep the temps up and others struggle to get heat into the tires. It seems that there are only three factors in tire temp, brake heat contribution, atmospheric cooling, and mechanical contribution via alignment geometry, mostly toe-in.

Am I over simplifying things? What say ye?

a lot of the issue is about the carcass temperature, more than the surface. They have get the carcass to flex, to get the tyre to really mould to the tarmac, and it does that better when it's warm, and in typical F1 circle fashion they have to flex it to warm it up!

That's why the load / downforce on it is such a factor and how a tyre can go 'dead' in a race when it literally can't be warmed up again whatever they do. The tricky bit is to warm up the carcass without melting or graining the surface, which running it toed in or out would do

That's exactly how it is.
Rubber has a pretty poor thermal conductivity. It's about the same as wood.
What we saw in the last 2 seasons with the rim designs is basically an attempt to get heat into the carcass from the brakes/inside. Although gases in general are extremly poor thermal conductors, way worse than even rubber, because of the very limited amount of air inside the wheel and because it moves around much, it should be possible the heat up the air inside the wheel fairly quickly through the rim and so to heat up the carcass much faster. If you can do this from inside, you don't have to deal with the thick rubber insulation.

[ispano6]

I know this is SEEMS over-simplified but for teams that are struggling to keep the temps up, or in the right range, might the answer be found in adjusting the toe-in (both F&R). Just a quarter degree can increase the scrub enough to raise temperatures measurably. Yes, that heat comes from increased mechanical drag on straights but, like wing adjustments, the pay-off could very well be worth it if your corner exit speed is higher. Every team has ways to control how much brake heat goes into the rims. Every car essentially has their tires being cooled by the air to essentially the same degree. So why are some cars able to keep the temps up and others struggle to get heat into the tires. It seems that there are only three factors in tire temp, brake heat contribution, atmospheric cooling, and mechanical contribution via alignment geometry, mostly toe-in.

Am I over simplifying things? What say ye?

a lot of the issue is about the carcass temperature, more than the surface. They have get the carcass to flex, to get the tyre to really mould to the tarmac, and it does that better when it's warm, and in typical F1 circle fashion they have to flex it to warm it up!

That's why the load / downforce on it is such a factor and how a tyre can go 'dead' in a race when it literally can't be warmed up again whatever they do. The tricky bit is to warm up the carcass without melting or graining the surface, which running it toed in or out would do

That's exactly how it is.
Rubber has a pretty poor thermal conductivity. It's about the same as wood.
What we saw in the last 2 seasons with the rim designs is basically an attempt to get heat into the carcass from the brakes/inside. Although gases in general are extremly poor thermal conductors, way worse than even rubber, because of the very limited amount of air inside the wheel and because it moves around much, it should be possible the heat up the air inside the wheel fairly quickly through the rim and so to heat up the carcass much faster. If you can do this from inside, you don't have to deal with the thick rubber insulation.

Suspension geometry will also dictate how much the tires straighten out under dynamic load. While under load or at high speeds, the geometry can be such that as the suspension squats the toe diminishes or induces more toe in.

The complaint from drivers appears to be that the tires overheat when you get too close and follow another car. If the tires are overheating when following too closely, how could you possibly cool them down? What is causing the overheating if these new tires have poor thermal conductivity? Exhaust temperatures and lack of free flowing air?

[DiogoBrand]

a lot of the issue is about the carcass temperature, more than the surface. They have get the carcass to flex, to get the tyre to really mould to the tarmac, and it does that better when it's warm, and in typical F1 circle fashion they have to flex it to warm it up!

That's why the load / downforce on it is such a factor and how a tyre can go 'dead' in a race when it literally can't be warmed up again whatever they do. The tricky bit is to warm up the carcass without melting or graining the surface, which running it toed in or out would do

That's exactly how it is.
Rubber has a pretty poor thermal conductivity. It's about the same as wood.
What we saw in the last 2 seasons with the rim designs is basically an attempt to get heat into the carcass from the brakes/inside. Although gases in general are extremly poor thermal conductors, way worse than even rubber, because of the very limited amount of air inside the wheel and because it moves around much, it should be possible the heat up the air inside the wheel fairly quickly through the rim and so to heat up the carcass much faster. If you can do this from inside, you don't have to deal with the thick rubber insulation.

Suspension geometry will also dictate how much the tires straighten out under dynamic load. While under load or at high speeds, the geometry can be such that as the suspension squats the toe diminishes or induces more toe in.

The complaint from drivers appears to be that the tires overheat when you get too close and follow another car. If the tires are overheating when following too closely, how could you possibly cool them down? What is causing the overheating if these new tires have poor thermal conductivity? Exhaust temperatures and lack of free flowing air?

As far as I know the overheating is caused by the understeer, which in turn is caused by the dirty air. It may also have something to do with the dirty air not being able to cool the tyres as much, which is what happens with other heat exchangers.

[gcdugas]

[/quote]
That's exactly how it is.
Rubber has a pretty poor thermal conductivity. It's about the same as wood.
What we saw in the last 2 seasons with the rim designs is basically an attempt to get heat into the carcass from the brakes/inside. Although gases in general are extremly poor thermal conductors, way worse than even rubber, because of the very limited amount of air inside the wheel and because it moves around much, it should be possible the heat up the air inside the wheel fairly quickly through the rim and so to heat up the carcass much faster. If you can do this from inside, you don't have to deal with the thick rubber insulation. -- Dr. Acula
[/quote]

I'm not so sure about your claims about the teams trying all they can to get the brake heat into the rim. Most of the brakes now have carbon shrouds directing the brake air swiftly trough the wheel and out in a controlled manner that almost prevents the rim from contacting the hot air.

[Maritimer]

I'm not so sure about your claims about the teams trying all they can to get the brake heat into the rim. Most of the brakes now have carbon shrouds directing the brake air swiftly trough the wheel and out in a controlled manner that almost prevents the rim from contacting the hot air.

Except teams have been designing their rims to heat the tires since last year, if not before then. The rears on all the cars have increased surface area on the inside and around the shroud to pull in heat.

[SiLo]

I think it's not necessarily to heat the tyre, it's to evenly heat the tyre through the carcass. They don't want to heat it too much, just evenly.

[izzy]

A lot of what's been said about the wheel rims has been basically disinformation. One big thing is this:



the inside is SMOOOOTH

well anyone with a phone can tell you that if you want to transfer heat you want it roughed up or textured, which doubles the transfer just with a bit of sandpapering!

[gcdugas]

A lot of what's been said about the wheel rims has been basically disinformation. One big thing is this:

https://d2d0b2rxqzh1q5.cloudfront.net/s ... 918406.jpg

the inside is SMOOOOTH

well anyone with a phone can tell you that if you want to transfer heat you want it roughed up or textured, which doubles the transfer just with a bit of sandpapering!

I tend to agree. The brakes are shrouded completely. If they wanted more heat from the brakes it is nothing for them to channel the hot air differently. There is more heat available than they could ever use. Those brakes operate at 1000 degrees F. With little effort they could channel the air directly to the rim so that it got hot enough to melt the tyre.

[Dr. Acula]

A lot of what's been said about the wheel rims has been basically disinformation. One big thing is this:

https://d2d0b2rxqzh1q5.cloudfront.net/s ... 918406.jpg

the inside is SMOOOOTH

well anyone with a phone can tell you that if you want to transfer heat you want it roughed up or textured, which doubles the transfer just with a bit of sandpapering!

You don't want necessarily the maximum amount of heat you technically could achieve, to actually go through the rim. You only have to bring the tyre in the right temperature window and keep it there.
Also you have to consider that over the width of the rim there's quite a big temperature gradient going on. At the very inside and outside of the rim you actually lose some heat because there's relative cool air flowing by.
If i remember correctly the first iteration of the Merc rims with the "improved heat managment" just had a "diamond cut pattern" around in the area where the brake disc were located

Not sure if the picture shows a Merc rim, but that's basically what it looked like.

[izzy]

I tend to agree. The brakes are shrouded completely. If they wanted more heat from the brakes it is nothing for them to channel the hot air differently. There is more heat available than they could ever use. Those brakes operate at 1000 degrees F. With little effort they could channel the air directly to the rim so that it got hot enough to melt the tyre.

yes exactly, you can just imagine the Mercedes engineers sniggering over their lattes while the supposed technical journos are posting articles about the spacer and how the fins keep the tyres cool

it's all about vortices, i'll find the right thread to post something about that