Ducting radiators/exhaust air to keep tires warm and grippy?

[g-force_addict]

Will ducting warm air to tires be the next best thing for PUBLIC ROAD DRIVEN sports cars?
As it keeps tires warm and grippy, thus ready for spirited maneuvers.

The only downsides I can think of would be
- Worse aerodynamics.
Or maybe not as aerodynamic studies show a drag reduction as shown in option B


- Possible tire overheating from prolonged aggressive driving.
Unlikely on public roads.
Possible on racetracks. Can be solved by temperature controlled flaps ducting the hot air elsewhere when tires get too hot.

- Added complexity.
Packaging issues may arise, specially for ducts to rear wheels.

- Brake overheating.
Solved by either brake cooling ducts and/or high temperature resistant brakes.

[g-force_addict]

The only downsides I can think of would be
- Worse aerodynamics.
Or maybe not as aerodynamic studies show a drag reduction as shown in option B
http://s18.postimg.org/v9abjsw9l/radiat ... _tires.gif

Aerodynamicists usually advice to place the radiator air outlet BEHIND the front wheels as it is a low pressure area.

Would ducting hot air to the full wheel well be that bad?
How would tire rotation affect?
Would some giant air outlet vents behind the front wheels be needed?
Something like

[g-force_addict]

Not only in roadcars.
Hot air tire heating is also useful in racecars. Even F1 cars.

An interesting idea that Renault now came up with is to actually use part of the hot air exhaust gases to heat up the rear tires. The R28 now features a modified rear wheel shield with an aerodynamic tunnel in it. This catches air from the inside of the shield and churns it out again just above the rear tire. Such device prevents the tire from being cooled by airflow, but allows a more constant temperate, hence improving its grip.
In the image, the device is seen from different angles, with the yellow lines marking the airflow through it.
http://www.f1technical.net/development/206




Exhaust gases are now blown out of the side of the sidepods, close to the car's floor. With drivers having had problems earlier on in the season to get their tyres up to temperature, the side effect of this layout could well benefit the car's behavior, as well as adding downforce.
http://www.f1technical.net/development/344


It has been proposed and maybe even actually tried in Formula SAE
If you have to use two radiators, and if they are mounted on each side pods, I would mount them in a way so that the hot air that is getting pulled by the fan is targeting the rear tires. This will help you to heat up the tires before acceleration, skid pad, and autocross.
http://www.fsae.com/forums/showthread.p ... 63783e8e89

Another item I've wondered about are "tire warmers." Do they consider the radiator and exhaust tire warmers? Can these be used to heat the tires?...
that is why we have decided to put our radiators in front of out front wheels...
http://www.fsae.com/forums/showthread.p ... ffler-Baby

Racecars must rely on speed dependent airflow.
Roadcars don't have this restriction as they can add as many cooling fans as they want.

[Cold Fussion]

I would say you primarily want to limit the blockage in the radiator duct so you can have proper flow through the duct. For a road car heating the tyres is not important and if you can't heat the tyres properly in your race car, you should probably revisit the suspension design. The warm air is probably better ducted for aerodynamic/cooling gains rather than heating the tyres. For SAE I would have to check the rules, but I don't think heated tyre blankets are banned so that would be a better way of heating the tyres before acceleration, but more crucially the autocross run. At FSAE-A atleast, the track was so dirty during acceleration that you would get bigger gains by sweeping the starting box compared to heating the tyres.

[Shrek]

I always wondered if you could use radiator exhaust to cool the brakes while also keeping some temperature in the brakes while helping the drive

[WaikeCU]

Didn't the Coanda exhausts direct some heat towards the rear tires?

[Tim.Wright]

Pretty sure you will have durability problems if you are constantly pumping hot air over the tyre carcass

[Kiril Varbanov]

It would be somewhat hard to manage the optimal working temperature of the tire from a constantly blown hot air source. Unless, of course, you have a way to control to airflow (on|off) and to monitor the tire temp via sensor.

[WaikeCU]

It would be somewhat hard to manage the optimal working temperature of the tire from a constantly blown hot air source. Unless, of course, you have a way to control to airflow (on|off) and to monitor the tire temp via sensor.

What if you car has problems warming up rear tyres? We've heard these issues in the past when drivers had problems putting in a quick lap in quali, simply because they had trouble putting heat into the tires and make them work.

[Kiril Varbanov]

It would be somewhat hard to manage the optimal working temperature of the tire from a constantly blown hot air source. Unless, of course, you have a way to control to airflow (on|off) and to monitor the tire temp via sensor.

What if you car has problems warming up rear tyres? We've heard these issues in the past when drivers had problems putting in a quick lap in quali, simply because they had trouble putting heat into the tires and make them work.

To some extent the Coanda-style exhaust blew hot air towards tires inner shoulders, but I think we are talking about public road cars? In that department, the tire warm-up is not such an issue. Or at least not to the extent of F1. It's a problem in karts, though. I had my rear bruising the wall last Sunday on lap 2....
Again, I think we should be looking more at predictability and durability.

[g-force_addict]

For a road car heating the tyres is not important

Yes it is important.
Even a bit driving at low speeds some 30mph can make a huge difference. Also when driving a car early in the morning, a car kept in a garage (even if unheated) vs in the driveway can make a huge difference.

For example dragster tire manufacturers recommend to heat the tires some 15 F above track temperature.
http://www.mickeythompsontires.com/tech.php?bulletin=s1
By the way all the tire burnout drama to heat tires just 15 degrees?

The problem is that nobody's supposed to be drag racing between traffic lights at all, so it would be politically incorrect to advertise this increased performance by heated tires.

So this only leaves shorter distance braking and improved emergency maneuvers like the moose test
http://en.wikipedia.org/wiki/Moose_test

The good thing is that once engines have warmed up the radiator coolant is kept at the same temperature a bit above 100 Celsus REGARDLESS OF AMBIENT TEMPERATURE. So this can help keeping a much more constant tire temperature.
Air that passed thru a radiator can have a temperature around 60 Celsius so I honestly think that tires can consistently be radiator-heated to 40 Celsius.

For some extreme performance "street"/autocross tires serious grip begins at just 120 Fahrenheit (49 Celsius). Just above the 40 Celsius I mentioned.
"That said, they produced close to their maximum cornering power at temperatures as low as 120 F, so unlike some of the other tires in this category, the Rivals are actually quite flexible and usable in a wide range of temperatures"

The grip difference is enormous
"Having spent the summer beating on a set of 245/40ZR17s on our friend Vinh Pham’s lightly modded Scion FR-S, we’ve learned quite a lot about these sticky BFGs. For starters, on stock FR-S rubber we were seeing max cornering g-forces of about 1.0 to 1.05 g, while the Rivals bumped that up significantly to right around 1.3 g at our local test track. To put that into perspective, we generally see about 1.4 g with a DOT competition/track tire, so the Rival compound is clearly closer to that of a race tire than a street tire.
Lap times confirmed just how fast the Rivals are, knocking a full 3 seconds off our best lap time. That’s a massive improvement"
http://www.superstreetonline.com/how-to ... rce-rival/
So in my opinion even if they add more tread grooves to handle some wet weather, performance should remain this high as long as tire heating is provided.

I don't think any street tires can ever match these 1.3g when cold.
Specially true since the US Department of Transportation requires a minimum treadwear rating, if I'm not mistaken of 140. So tires can't be too soft.

[98mystique2]

For a road car heating the tyres is not important

The good thing is that once engines have warmed up the radiator coolant is kept at the same temperature a bit above 100 Celsus REGARDLESS OF AMBIENT TEMPERATURE. So this can help keeping a much more constant tire temperature.
Air that passed thru a radiator can have a temperature around 60 Celsius so I honestly think that tires can consistently be radiator-heated to 40 Celsius.

I have to clear this up as it came up in a search of keeping tires warm. The coolant temperature in the engine is generally regulated by use of a thermostat which opens to let coolant flow through the radiator. The radiator temperature is not a constant 100C and the radiator its self will have warmer coolant at the inlet then the outlet. On a cold day it might take 10 minutes to even get coolant to be passed into the radiator.

[gambler]

Exaust on the rear works pretty good if you have inboard barkes and a hard spec tire, short race. Personally I think exaust has the ability to "clean the marble dust" or sweep it into the "groove" for the competition to have to deal with. I also think exaust has more potential as aero tooling ... hot air may flow different than ambient air.