Soft vs Hard Tyre

[Roy]

Anybody knows what the friction-coefficient between tyre & track surface is? I'm sure it is more than 2.0 because I have read it somwhere in one magazine, but I forgot the exact number.

And how different is it between soft-compund and hard one? What is the range?

Thanks

[Jason]

Anybody knows what the friction-coefficient between tyre & track surface is? I'm sure it is more than 2.0 because I have read it somwhere in one magazine, but I forgot the exact number.

And how different is it between soft-compund and hard one? What is the range?

Thanks

Soft tyre produces more grip and less durability, suitable for warm track tempreature, low grip tracks. Harder compounds produces less grip but more durability, suitable for track that has high grip and the tracks that are hotter. e.g Sepang

[Roy]

Soft tyre produces more grip and less durability, suitable for warm track tempreature, low grip tracks. Harder compounds produces less grip but more durability, suitable for track that has high grip and the tracks that are hotter. e.g Sepang

Thanks Jason,
Of course I know that soft produces more grip and less durability than hard.
What I asked was "the friction-coeff" between those tyre-surfaces and the track surface in average (it must be in range from hard-compound to soft-one).

Friction-coeff is a ratio between normal force (weight + downforce) and maximum lateral-force that tyre can stand.

Roy

[Jason]

Soft tyre produces more grip and less durability, suitable for warm track tempreature, low grip tracks. Harder compounds produces less grip but more durability, suitable for track that has high grip and the tracks that are hotter. e.g Sepang

Thanks Jason,
Of course I know that soft produces more grip and less durability than hard.
What I asked was "the friction-coeff" between those tyre-surfaces and the track surface in average (it must be in range from hard-compound to soft-one).

Friction-coeff is a ratio between normal force (weight + downforce) and maximum lateral-force that tyre can stand.

Roy

3.0 for soft and 1.5 for hard I guess

[DaveKillens]

I don't think the friction-coefficient is that great between "hard" and "soft" compounds. To me, it appears the greatest difference is tire wear, and longevity.
Yes, soft tires do grip more, and you can obtain quicker times from them. Better lateral acceleration, better braking, and less likelyhood of wheelspin under acceleration.
The classic scenario was a few years ago when they used qualifying tires, which were good for two laps under full load. Then, of course for the race, they fitted much harder (durable) tires. But the difference between lap times was just a few seconds, not a huge difference like 30 seconds.

[ginsu]

Except when Senna was driving in qualifying. He put down some stunning laps on qualifying tires.

[DaveKillens]

In Monaco, in 1988 Aytron Senna put in what many consider the greatest single qualifying lap in recorded motor racing history. He qualified his McLaren 1.4 seconds quicker than his teammate in an identical car, Alain Prost.

[gforce]

I had read that the maximum traction equals c.o.f times 'g'.Corners with forces above 4 g are not uncommon ,I think.

[DaveKillens]

There are two aspects of tire grip which result in lateral acceleration. There is "mechanical grip", provided purely by the tires gripping the road surface, and there is the total grip, which is augmented by the downforce. In low speed corners, where the wings and aero really aren't working, this is where you see just the suspension settings, driver input, and tire grip coming together. Mechanical grip.
But as speeds increase, and the wings and other bits start to work their magic with the air, it pushes down on the chassis, which in turn pushes down on the suspension, and tires. Since there is relatively no mass to the air, you have a tire being forced down with 3 or 4 G's, but the mass is the chassis isn't really there, it's just the air pushing down. This is important to remember when the car begins turning, because the tires are being fooled into believing they are being forced down by a chassis much heavier that it really is.
So I'm just going to pull numbers out of the air, but if you can have a tire with a coefficient of friction of 1.0, in a low speed corner the best you can get is 1 G of lateral acceleration. But at high speeds, in a very fast corner such as 130R, you can get 4 G's download. Added to the mass of the car, you wind up with a theoretical cornering force of 5 G's.

[Roy]

... [deleted]
So I'm just going to pull numbers out of the air, but if you can have a tire with a coefficient of friction of 1.0, in a low speed corner the best you can get is 1 G of lateral acceleration. But at high speeds, in a very fast corner such as 130R, you can get 4 G's download. Added to the mass of the car, you wind up with a theoretical cornering force of 5 G's.

Dear Dave,

Theoretically you’re right, if I have tyre’s coeff. of friction = 1, then I’ll have max-lateral-force = 1 x (weight + downforce). Weight and lateral-force are commonly measured in G. But it is not common to mention downforce in G since downforce is NOT a function of mass. So I prefer to say downforce in kgf.

Then back to our topic, when cornering (say it is fast corner) the speed is around 200kph, I believe the downforce is not as big as 4G. It is “only” about 650 kgf or about the same weight as the car itself. Then we have normal-force about 1300 kgf. The maximum G-force that tyre can stand is about 4.5G or about 3000 kgf. Then we have the tyre CoF is 3000/1300 = 2.3.

That’s why I believe that tyre’s CoF is about 2 point something. What I’m not sure is how big the different between soft tyre and hard is. Anyway, I don’t believe that the different would be 1.5 to 3.0 as said by Jason.

Roy

[pyry]

but they have said that an f1 can ride upsidedown at 160kph, which means it generates the 650kg at that speed, and maybe nearly a 1000kg at 200, that qould probably push the CoF to about 3

[DaveKillens]

I was just trying to illustrate how downforce affects grip, versus sheer mass.
But if I was to guess at coefficient of friction, I would guess that a soft tire has around 1.3, and a hard 1.2. And the downforce would be around 2 to 2.5 G's at max speed. Maybe I'm way off the mark, but that's my guess.

[Reca]

At http://www.avonracing.com you can download the data about avon F3 and F3000 tyres used few years ago.
I downloaded them long ago so I don’t remember the data exactly, should look in the other computer, but IIRC for F3000 the peak of (lateral force / vertical force) was at about 1.7-1.8.
BTW, the peak, and the slip angle at which the peak is located do change with vertical force, and other parameters.
Just take a look these are very interesting data.

As for soft vs hard, certainly I don’t think there’s a huge difference, in F1, between the two different tyre compounds available in term of maximum grip, I wouldn’t even call the two specifications soft and hard, most of times are two different tyres, not only in term of compound but also of construction, designed to work in different conditions.
Qualifying tyres used for example in motogp are a totally different matter, these guarantee an enhanced grip good for at least 1 sec per lap, roughly 1% improvement on laptime, but I don’t know how much it corresponds in term of maximum grip.

[Roy]

but they have said that an f1 can ride upsidedown at 160kph, which means it generates the 650kg at that speed, and maybe nearly a 1000kg at 200, that qould probably push the CoF to about 3

Well, there's no exact number of downforce at a given speed. It depends on wing-setting and aero-efficiency. However, if one tyre needs more downforce to resist the same lateral-force, it means that it has less CoF, in this case it must be less than 2.3, NOT 3.

[DaveKillens]

Back many years ago the same theorists who said it was impossible for a bumblee to fly also said that the maximum theoretical coefficient of friction between a tire and surface was 1.0. But with the invention of sticky tires that can grip every microscopic pore and ridge on a road surface, it has gone over 1.0. So a jump to 3 is too much to assume, the number has to be much lower, somewhere more than 1.0, but most likely less than 1.4.