35 replies to this topic

[murpia]

In this video, Nico Rosberg quotes the Pirelli tyre pressures at 0.8Bar:



Sounds a bit low, I would have expected about 1.1->1.2Bar (hot).

Maybe he's refering to cold pressures, but does anyone have any more data on what pressures the Pirelli's run at when hot?

Thanks, Ian

[desmo]

Wasn't there a lowest allowable pressure limit at one point a couple or three years back in F1? i'd expect them to run them as low as could be got away with.

[bigleagueslider]

Ian,

The 2011 F1 regs require all measurements to be taken with tires inflated to 1.4bar, and the internal gas volume must remain constant. Otherwise, there are no other rules regarding tire inflation pressures. However, there are very specific rules regarding the size of the inflated tire's contact area.

Rules aside (and not having any expert knowledge of F1 tires), I could imagine a scenario where having a tire with low inflation pressure might be of benefit on an F1 chassis. A tire with low inflation pressure would have reduced radial stiffness in the sidewall. At low speeds (ie. cornering), the reduced dynamic CF in the tire body would result in a slightly reduced tire OD, which reduces chassis ride height, which in turn should help create more aero downforce. At high speeds (ie. straights), increased dynamic CF in the tire body would result in a slightly increased tire OD, which would increase chassis ride height, which in turn should help reduce drag. It would function as a crude form of active ride height.

That's my amateur theory anyway........for what it's worth.

slider

[munks]

First off slider, couldn't you have spelled out Centrifugal Force and Outside Diameter (or did I get those wrong ... centripetal centrifugal mumbling to myself)? My opinion on your theory is that there is probably some effect there but it wouldn't be a significant factor in the design or usage of the tires. While this doesn't directly translate to your situation, the previous Bridgestone tires only grew maybe 1mm in radius at top speed (unladen). That's primarily limited by the belts, and doesn't tell us the change in tire spring rate, but I think it suggests that the centrifugal force probably isn't much of a match for the stiffness of these tires. The video itself mentions the carcass stiffness is quite high.

Back to murpia's original question, though: yes, 0.8 bar is surprisingly low, even if they were talking about cold pressures. Bridgestone was definitely running more in the range you were suggesting.

[munks]

Wasn't there a lowest allowable pressure limit at one point a couple or three years back in F1? i'd expect them to run them as low as could be got away with.

I'm not gonna dust off the rulebook because I'm lazy, but I don't think there was ever any rule about this (aside from what slider mentions). But you might perhaps be remembering when one or more of the previous tire companies had strong suggestions for the minimum pressure on safety grounds. For example, before the Michelin-shod teams pulled out of the USGP, they first suggested running a minimum pressure (which I believe Toyota had been below when they had their blowout). Even in other years, I think Bridgestone had a suggested minimum pressure due to standing waves being spotted on the tires in the oval section of Indy.

[cheapracer]

Hmm I wonder if they are leaking air throughout the race as the fuel weight goes down?

[murpia]

Back in the grooved Bridgestone days there were 3 pressures of interest (actually 12 as FL, FR, RL & RR would all be set slightly different):

Cold pressures are what's set when the tyres are mounted (20degC)
Blanket pressures are what's measured when the tyres come out the blankets ready to go on track (80degC)
Hot pressures (normally just referred to as 'pressures') are what's measured in the box at the end of the run (100degC +)

You would also I assume have TPMS pressures on telemetry in real time, which would continually change.

I know Bridgestone (& Michelin) had lower limits on blanket pressures they would allow the car out of the box with. This was to protect the tyre from carcass damage as it warmed up. These would vary track to track but were around 1.0Bar (14psi).

Cold pressures would be around 0.7Bar at 20degC I (roughly) calculated to achieve 1.0Bar at 80degC.


Since the Pirellis are not grooved and totally different in construction it's possible they run at 0.8Bar hot pressures. But the more I think about it the more I assume Rosberg is referring to cold pressures.

Regards, Ian

[murpia]

Hmm I wonder if they are leaking air throughout the race as the fuel weight goes down?

Doubful, but I expect the sets they put on at the pitstops have less and less pressure set as the race goes on and the fuel burns off.

Active 'leaking' is banned.

Regards, Ian

[cheapracer]

Active 'leaking' is banned.

I know pressure blow offs (tyre's get hot, pressures go up) are banned (V8 Supercars were the first many years back when they were Touring cars still) but wonder if they aren't getting rid of air some other way as in actually dropping pressures.

As it's a known time parameter it is as simple as a small hole.

[OfficeLinebacker]

I know pressure blow offs (tyre's get hot, pressures go up) are banned (V8 Supercars were the first many years back when they were Touring cars still) but wonder if they aren't getting rid of air some other way as in actually dropping pressures.

As it's a known time parameter it is as simple as a small hole.

A NASCAR team got caught with bleeder valves in their valve stems. It was a controlled release of pressure by time I think. They got caught when there was a rain delay and when they ended the red flag the car's tyres were all flat.

[desmo]

I'm not gonna dust off the rulebook because I'm lazy, but I don't think there was ever any rule about this (aside from what slider mentions). But you might perhaps be remembering when one or more of the previous tire companies had strong suggestions for the minimum pressure on safety grounds. For example, before the Michelin-shod teams pulled out of the USGP, they first suggested running a minimum pressure (which I believe Toyota had been below when they had their blowout). Even in other years, I think Bridgestone had a suggested minimum pressure due to standing waves being spotted on the tires in the oval section of Indy.

Yes, thank you. This is probably what I was remembering.

[DrProzac]

Yes, at least Bridgestone specified minimum and maximum safe pressures. Though I don't know if the regulations force them to be within the safe range.

[Lee Nicolle]

In this video, Nico Rosberg quotes the Pirelli tyre pressures at 0.8Bar:



Sounds a bit low, I would have expected about 1.1->1.2Bar (hot).

Maybe he's refering to cold pressures, but does anyone have any more data on what pressures the Pirelli's run at when hot?

Thanks, Ian

PSI please, most of the world understands that.

[murpia]

PSI please, most of the world understands that.

http://en.wikipedia....e_United_States

We can but hope...

Regards, Ian

[munks]

Hey, I'm from the States and I would prefer kPa over both psi and bar. Yes I realize I'm in the minority.

[gruntguru]

Yeah well I'm from Aus and I prefer PSI over kPa. That is only because of habit and my era (pre-metric childhood). When it comes to engineering/scientific calculations, I am 100% metric - infinitely easier than imperial or American units.

[bigleagueslider]

Inches and pounds put 12 American astronauts on the surface of the moon. Can't say the same for millimeters and Newtons.

[Catalina Park]

Inches and pounds put 12 American astronauts on the surface of the moon. Can't say the same for millimeters and Newtons.

Didn't Wernher von Braun use metrics?

[cheapracer]

Inches and pounds put 12 American astronauts on the surface of the moon.

350 cubic inches and 4000 pounds of Chevy van that took them to the backlot movie studio?

I saw Capricorn One.

Edited by cheapracer, 20 August 2011 - 05:11.

[Tony Matthews]

Inches and pounds put 12 American astronauts on the surface of the moon. Can't say the same for millimeters and Newtons.

Didn't Wernher von Braun use metrics?

And didn't this conflict put a Mars Lander into the red dust at high speed as one team were using Imperial and another using Metric for the retro-rocket fuel needs? You have to laugh...

[mariner]

Canuck will probably know more about this incident than me but a few years back there was a potentially catastrophic in-flight problem on a Canadian plane because the aircrew requested the fuel load in gallons and the fuelling guys had switched over to litres ( being Canada and not the USA).

IIRC corectly the plane just ran out of fuel in mid flight to the initial disbelief of the crew. The pilot requested an diversion runway ASAP and was given a very nearby "disused" airfield. Again IIRC he was a a glider pilot in his spare time so to get down fast in a very short distance he side-slipped the big jet to the panic of the passengers but all was well and he landed OK.

I said "disused" because there was a motorsport connection in that a car club was holding a sprint meeting on the "disused" runway but luckily nobody got hit.

I seem to remember an interview with one of the car club members who said something like " I went into the motohome to get a coffeee and when I stepped out I saw a huge jetplane coming down the runway straight at me"!

[murpia]

Inches and pounds put 12 American astronauts on the surface of the moon. Can't say the same for millimeters and Newtons.

http://science.nasa....jan_metricmoon/

Looks like the tyre pressures on the next Lunar Rover will be in Bar, though...

Regards, Ian

[munks]

Looks like the tyre pressures on the next Lunar Rover will be in Bar, though...

I didn't read the article, but is this a joke? Bar is mostly only relevant for being on Earth near sea level, no? Of course if the Lunar Rover isn't *really* going to the moon, as cheapracer would have you believe, this might make sense ...

[DrProzac]

PSI please, most of the world understands that.

I'm afraid it's the opposite

While most know what ft, inch, pund etc are, the same can't be said about PSI and similar units.

Inches and pounds put 12 American astronauts on the surface of the moon. Can't say the same for millimeters and Newtons.

Money, competition (thanks to the cold war) and determination put them there, not units.

Didn't Wernher von Braun use metrics?

Eh, units are units, just stick to one system when doing your calculation. And keep in mind that the USA is not "most of the world"

@up: 1 bar = 100 kPa. As simple as that, doesn't matter if its on the moon or not (of course atmosphere pressure -or lack of it - makes a difference as far as pumping the tires is concerned )

Edited by DrProzac, 21 August 2011 - 09:48.

[munks]

Oops, you'll have to excuse my idiocy, I was confusing bar with atmospheres.

[RDV]

20-22psi front and 18-20psi rear.

[Fat Boy]

20-22psi front and 18-20psi rear.

That makes sense. At less than 1 bar / 15 psi (hot), I think you'd have some pretty serious issues with carcass failure. Having never ran those tires in particular, I don't really know, but that seemed quite low.

[Lee Nicolle]

I'm afraid it's the opposite

While most know what ft, inch, pund etc are, the same can't be said about PSI and similar units.


Money, competition (thanks to the cold war) and determination put them there, not units.




Eh, units are units, just stick to one system when doing your calculation. And keep in mind that the USA is not "most of the world"

@up: 1 bar = 100 kPa. As simple as that, doesn't matter if its on the moon or not (of course atmosphere pressure -or lack of it - makes a difference as far as pumping the tires is concerned )

F1 is largely British based and they generally work in PSI, as do Aussies and Americans. To me the last bastion of imperial measure. And I have had both germans and irish work for me who also used 30lb in the tyres.
And actually not many people ever talk bar in most countrys, the unit is KPA. Which can get messy also as 200kpa is about 28lb. The old pound is generlly a nice measure in pressure, at least in tyres and even aircompressors.


And getting back to low pressures that seems to be a trend to make the tyres comeup quicker, particularly when cold. While I have no idea what F1 wants them to come up too I suspect it is a round the 32lb mark like most race tyres on tintops at least.
Though most peopple I know start at mid to high 20s in tintop racing on a remotely normal 15-35 deg day

[gruntguru]

Lower . . . .

[RDV]

gruntguru-Lower . . . .

20-22psi front and 18-20psi rear, just check with the teams or Pirelli....
edit- That's hot, to be precise....

Edited by RDV, 06 September 2011 - 13:43.

[Lukin]

GG might have been talking about Lee's post, starting cold pressures "at mid to high 20s" comment?

[gruntguru]

Yes it was this.

I suspect it is a round the 32lb mark . . . . . . mid to high 20s in tintop racing

[cheapracer]

Lower . . . .

$21,348?

[gruntguru]

Lower . . . .

[Tony Matthews]

Up a bit... left - left, oooh, yes!

[cheapracer]

Up a bit... left - left, oooh, yes!

"The Price Is Right" you goose