14 replies to this topic

[Christiaan]

When grooved tyres first came they were very different from those we have now, even this year. I remember that the tyres lasted very long and when they were in the pits they left a track of rubber like a snail's slime. The tyres seem o behave very differently now , what changed?

The first thing I thought (and apparently a lot of other teams) was that if you drive a grooved tyre long enough, it will eventually be a slick, and give you better control. This has turned out to be wrong, does anybody know why?

[SlowDrivr]

In the "tire question" thread, PDA stated that at the end of the race the tires must have tread left in them.

[SalutGilles]

Not only must it have tread still on it, but I think I have an idea as to why that doesn't work.

I think that the tread must be of a very different construction than the tyre's innards, which would have to be harder, and not meant for grip, anyway. the tread, wether on a grooved tyre, or a slick, is what provides the grip, and is what is used up.

Theoretically, slicks would never need chanding, as they have no tread to wear off, but they do loose the grippy stuff, rendering them a "bald slick" by the time a grooved tyre becomes slick, it is not a slick, but rather simply bald

[PDA]

Christiaan - in the first year of grooved tyres, there were two suppliers, and they made the tyres of the softest compaounds possible. Now there is only one, and they have been asked by FIA to make harder tyres to stop the escalation of cornering speeds. I did read one comment when a driver (unamed) was asked the difference between the medium compaund and the soft compund, and the answer was along the lines: "the medium compund is as hard as rock, the soft compound is only as hard as wood"

[Chris]

I am surprised, I thought that the grooved tyres are improving, on certain tracks, when the grooves tends to disappear. That one of the reason the lap times are well better before the pit stop than after. The other reason being the fuel weight.

I think in Hockenheim some pilots preferred to run on tyres withe 2-3 laps.

Am I wrong ?

[Pascal]

I think the problem has to do with temperature.

On grooved tyres, their temperature probably rises slower than on slick tyres where a larger surface is directly in contact with the track. On some circuits, it has been noted that slightly worn grooved tyres seemed to work better, and that's probably due to the fact that their harder compound reaches better its optimum temperature. Now the risk is that whenever the grooves disappear, the "footprint" gets suddenly larger, causing the tyre to overheat in a matter of a few laps. But this is just a theory on the subject, and I'd welcome any confirmation about it...

And as for the regulations about having some treads left, it sure doesn't seem to be strictly enforced since the penalty of using "bald" tyres is to quickly experience a puncture. Not a risk worth taking if you ask me!

[Martin]

Pascal - With regards to temperature. Not only is the footprint smaller with grooved tyres but also the grooves must act like cooling ducts making the tyres even harder to warm up.

[ozoner]

Chrisitaan,

I'm not so sure about the tyres not leaving marks like snail trails.

I know for a fact that there are still lines left in the pitlane fo the Melbourne circiut from this year's first GP! I was looking at them with my own little eyes the other night...

Cool.

-oz

[DangerMouse]

Quite the opposite folks, a grooved tyre will cause more squirm in the tyres carcass inducing increased heat generation, this is main reason grooved tyres have to be made much harder than slicks - to control the squirm and thus tyre temperature.

[Christiaan]

Er squirm? what is that and how does it come about?

[DangerMouse]

80+% of the heat generated by a tyre is the friction between the plies that make up the tyres carcass, if a tyre has tread of any sort it causes the carcass of the tyre to deform more as the individual thread blocks (or grooves in the case of F1) move about distorting the tyres carcass to a greater degree, this movement of tread (or grooves) is known as squirm.
Grooved F1 tyres are harder than their slick couterparts simply to control tyre squirm and so tyre temperature, this is why they grip less than slicks not just because of the reduction in the “footprint”

[tak]

Danger Mouse is absolutely correct. Heat in a tire is generated by the rubber 'squirming'. Just like a larger pencil eraser, the rubber itself deflects.

This is the reason that rain tires are destroyed so quickly when the track dries out--the tread blocks are small, the rubber is soft, and the tires overheat very quickly.

One of the reasons for going to grooved tires was that it fundamentally forces a harder rubber compound...Of course, if your in a tire war...

[Christiaan]

I do believe the scientific word for squirm is HYSTERISIS

am I right?

[Telemetry Man]

I've just read the GPDA has sent a formal petition to Mosley for the return to slicks.
I think it's falling on blind eyes and a huge ego.

[Yelnats]

Yes, and Hysterisis is the reason for the change in performance as a slick wears down. Less rubber means less squirm which means less heat and a loss of grip. It's much harder to get heat into worn tires as we see on CART re-starts where drivers sometimes lose control after leading a race for many laps.