F1technical.net

Paul Hembery of Pirelli say that the current tire has a special tread layer below the normal thread. This layer has very low grip, so when you wear the tire down there is a very noticeable performance reduction. It prevents the drivers from trying to get a little more distance on the tires and developing a tire failure.... and bad PR for Pirelli!

This is a very impressive feature.

1) Is this done in any other motor racing series?

2) Does two compounds mean that two belts of rubber must be laid up during construction?

Brian

No comment on race tires, but you can cut open a mini van tire and see 2 or 3 different types of rubber above, below, or alongside each other. Generally obvious enough that you can see it with the naked eye.

I've certainly seen it on ordinary road car tyres. Sports motorbike tyres have different compounds on the shoulders and centreline to balance grip and longevity.

I'm not surprised that the F1 tyres are built this way - would perhaps explain the chunking of the early Pirelli tyres.

Jersey Tom wrote:No comment on race tires, but you can cut open a mini van tire and see 2 or 3 different types of rubber above, below, or alongside each other. Generally obvious enough that you can see it with the naked eye.

I do not see the value of this in a street tire. please expand.

Brian

Just_a_fan wrote: would perhaps explain the chunking of the early Pirelli tyres.

Why, poor bonding between the layers?

Brian

Its not down to the compound that the rubber contacts the ground with that is different to Bridgestone & Michelin, its down to the tyre sidewalls. I was listening to Alex Rossi in the second GP2 race weekend at Bahrain and he said it was the tyre wall. The Bridgestones could be driven at 110% to 115% for around 95% of the time and be fine. The Pirellis have to be driven at 85% of quick lap pace for 110% of the time. He said you have to be around a second off ultimate pace at the start of the stint to be around 3 seconds off ultimate pace at the end of your stint and with that you will have possibly been able to make your tyres last 3 laps longer.

Pirelli have advised that they will possibly have to go softer for 2013 but bring the compounds closer together as well. In order to keep racing close and exciting, however they have also been advised that in 2014 or 2015 there is a possibility for a new tyre war and a new tyre formula as well

If you gave the teams time they will be able to make the Pirellis last the entire race, Thats why Pirelli have to be one step ahead and with that Pirelli will always make racing more exciting than using DRS or KERS. Both of which id have the rules changed as well in order to make F1 more about strategy and tyre management than anything else.

ESPImperium wrote:Its not down to the compound that the rubber contacts the ground with that is different to Bridgestone & Michelin, its down to the tyre sidewalls.

No, Hembery said specifically that when you wear down to this second compound that the tire falls off a performance cliff, but that the tire will operate at the bottom of the cliff without failure. Talking about 2-3 sec from the last lap on the main/top compound to the next lap on the secondary compound. There should be no motivation for the driver to stay out now losing 2-3 sec per lap.

Brian

hardingfv32 wrote:

Jersey Tom wrote:No comment on race tires, but you can cut open a mini van tire and see 2 or 3 different types of rubber above, below, or alongside each other. Generally obvious enough that you can see it with the naked eye.

I do not see the value of this in a street tire. please expand.

Brian

Roll video...

[youtube]http://www.youtube.com/watch?v=9M9ZAbVg0Xo[/youtube]

[youtube]http://www.youtube.com/watch?v=Iwlob3L_YZw[/youtube]

F1 used to have a rule that the tire (EDIT: I should probably say 'tread' here) be made of a 'homogenous compound'. This would seem to violate that rule, but maybe they tossed that one when they went to a single supplier.

Anyway, yes, this helps explain the sudden massive drop-off in laptime. Not knowing much about compounding, I was guessing in another thread that they boiled off all the resin or some other additive.

Common on motorcycles to have 3, 5 or even a full on gradient between compounds.

Interesting. So basically they have a superslow compound that shows up after they run out of the primary compound. That really does explain the cliff. Maybe said compound is superhard (and hence superslow) and that's how Vettel got 60 laps on a set of soft Pirellis last year? In Monaco too. Traction events aren't generally that kind.

There's quite a bit of give-up even before hitting the brick compound in there so I wouldn't make it a 100% contributor. It's interesting. And while it does put a premium on new tires... one could make the argument that it gets washed out in some cases if everyone has to hit that cliff at the same amount of tread wear.

Of coarse this is 2-3 sec of extra give-up on top of what you have already developed during the run.

Brian

As Philip mentioned, very common on bike tyres;
http://www.bridgestonebikersclub.co.uk/tyre/BT-16.php
I have them on mine...

Mikey_s wrote:As Philip mentioned, very common on bike tyres;
http://www.bridgestonebikersclub.co.uk/tyre/BT-16.php
I have them on mine...

This is COMPLETELY different....... I am talking about the rubber underneath the top tread, NOT next to the top thread.

Brian