11 replies to this topic

[Kimi on nopein]

A road car's owners manual tells you to increase tyre pressures if you're carrying a lot of people and/or other weight. It gave me the following idea: What if you had a tyre valve (in a F1 car) that could decrease pressure as the car becomes lighter?

1. Advantage?
2. Legal?

[Slumberer]

Well the problem, as I see it, would be that although as the fuel load comes off and the car becomes lighter, the tyres still have to deal with the aero loadings which are far greater.
The actual change in force pressing down on the tyres would be a fairly small percentage.
The tyres are designed to cope witha large range of loads as the aero loading changes with speed so it wouldn't make much of a difference.
(I still like the idea of a wheel hub that acts like a CVT pulley though!)

[McGuire]

It would be a great thing if we could alter tire pressure to compensate for tire temperature. F1 cars use tire warmers but many series don't. When these cars go out on cold tires, their pressures must be set very low -- too low for decent handling, and the driver must be very careful until they come up to proper working temperature and pressure. He can over-abuse the tires or even crash the car. When you see a car handling badly just after a pit stop, it is liable to be as much due to cold, underinflated tires than a heavy fuel load.

There have been a number of pressure-relief devices which attempted to correct this problem. So far none have been accurate or reliable enough for high-speed racing use. The obstacle is centrifugal loading on the tire/wheel assembly. Anything involving a spring is probably not going to work.

[scarbs]

yes it would be an advantage and yes it is illegal...

[Monstrobolaxa]

But would that advantage be big enough to compensate the extra weight that this system would bring? Don't forget you'd need a small compressor, all the air hoses to connect to the wheel/tire, would probably need a bigger battery (and teams are already running on the limit of the small batteries....if the revs fall to much they loose battery power and stall), besides that if it was like a Paris-Dakar jeep the upright and wheel bearing have to be redesigned!

[panzani]

The original question is just about decreasing tyre pessure, no pumps, just a sensor and a valve - as I understand it.
It would not be of any value as long as the aero load is probably the same - if not greater due to the higher speeds - while the fuel loads decrease. And I could not find on the Sporting Regulations why it should be deemed illegal.
It is just like a controlled puncture, isn't it?

[Monstrobolaxa]

But in any case reducing the tire pressure without increasing it....specially with the proposed new regs....the reduction of pressure might bring an advantage in a determined part of the race but with the new regs tire changes are illegal so they can increase the pressure cause it is legal to fill the car with fuel and compressed air....but filling a tire to the correct pressure takes a long time...not 4 or 5 seconds....

So reducing pressure and not being able to "repressurize" it again....and filling the fuel tank, will it really bring an advantage?

[Pioneer]

Its illegal but in a roundabout way.

I'll post the exact regulations if someone asks (I'm feeling lazier than my usual pdf copy/pasting self).

Basically, it is illegal to make modifications to any aspect of the suspension while the car is in motion.

Thats all well and good, but there is also a section at the head of the rules with definitions of various terms, and there the complete wheel and tire assembly is defined to be part of the suspension.

[panzani]

Originally posted by Pioneer
Its illegal but in a roundabout way.
I'll post the exact regulations if someone asks (I'm feeling lazier than my usual pdf copy/pasting self).
Basically, it is illegal to make modifications to any aspect of the suspension while the car is in motion.
Thats all well and good, but there is also a section at the head of the rules with definitions of various terms, and there the complete wheel and tire assembly is defined to be part of the suspension.

I see what you mean Pioneer, good point, but Article 10.2.2 of the Technical Regulations says powered device, which is not the case - even though Article 10.2.3 says no adjustment, which could be the case depending on FIA's interpretation:

10.2.2 Any powered device which is capable of altering the configuration or affecting the performance of any part of the suspension system is forbidden.
10.2.3 No adjustment may be made to the suspension system while the car is in motion.

Anyway, they already change front/rear brake bias and 10.2.3 was not invoked AFAIK.

[McGuire]

Originally posted by Monstrobolaxa
So reducing pressure and not being able to "repressurize" it again....and filling the fuel tank, will it really bring an advantage?

Not in F1 as they use tire warmers. But in Champ Car and other series where cars must go out after each pit stop on cold and therefore seriously underinflated tires (as little as 17 PSI) there would be a considerable advantage. The tires could be inflated to a suitable cold pressure and then bled off to ideal warm pressure as they came up to temp. As it stands now these cars handle fairly poorly on the first one or two out-laps. They will often even exhibit severe bottoming due to the soft sidewalls and full fuel load.

But as we all know, racing tires are extremely sensitive to pressure for optimum performance: as little as one half PSI hot. It is my understanding there are no relief valves that operate to that degree of precision. Dirt sprint cars have been known to use tire relief valves with some success, but that is a very different application from several angles.

[Pioneer]

Brakes are not defined as part of the suspension system, tire/wheels are. 10.2.3 covers it regardless of the powered device rule.


I could swear that CART was in fact using these a couple years ago.

[Monstrobolaxa]

CART did have a strange thing on the "filling" valve but those where pressure sensors.