WRC Most liked posts in thread: WRC: Tires (or Tyres)

RallyMini370 · Oct 29, 2012

For top teams tyres can be a difficult choice....for us further down the ladder we do with what we can get at a good price and drive the best we can.

Crashton · Feb 3, 2013

^^^ I so want a set of those for my MINI. :drool

ScottinBend · Feb 3, 2013

mmmmm......spikey

Steve · Feb 4, 2013

Michelin's version:

Crashton · Feb 4, 2013

Those are great. Many years ago I helped a friend stud a set of Cooper Weather-Master tires 560-13 for his Datsun 510 rally car. A long hard job, but boy did they ever stick.

Steve · Feb 6, 2013

Tyre firms roll out new rubber for Sweden (WRC.com)

06 Feb 13

Both Michelin and DMACK will introduce new winter tyres for this week's Rally Sweden, the only pure snow and ice round of the FIA World Rally Championship.

In contrast to last monthâ€™s Rallye Monte-Carlo where drivers had four options, regulations limit each supplier to one type of studded tyre for this once-a-year snowfest in the Scandinavian forests.

Both suppliersâ€™ offerings have 384 metal spikes, each 20mm long, inserted into the tread block on each tyre. The studs can protrude from the rubber to a maximum of 7mm and provide astonishing grip as they cut into the frozen ground beneath the snow and ice.

Michelin, which supplies the majority of the WRC drivers, will provide an evolution of the X-Ice North tyre used in 2011 and 2012. After two WRC tests in December 2012 and January 2013 the firm says the new rubber, the X-Ice North 2, is a big improvement in performance terms.

Changes are focused chiefly on a revised tread pattern and the amount that the studs protrude from the rubber blocks.

Michelin Competition's technical director Nicolas Goubert explained the factors that his engineers had to consider when designing the new tread pattern: "A particularly open pattern will allow snow to be cleared quickly but, on the other hand, a compound that is too flexible can have a negative effect on the carâ€™s stability. An excessively open tread can also result in the rubber blocks being too fragile for exposed dirt and stones.

"The development team spent several months optimising the overall package and the result is a new tread pattern which features some innovative technical solutions with regard to its so-called â€˜sea-to-landâ€™ ratio and the rigidity of its blocks."

The amount of stud sticking out from the tyre is another tricky compromise. "The longer the exposed part of the stud, the more grip it provides on ice. However, excessively protruding studs run the risk of being pulled off because each time they strike the ground, the weight of the car causes them to buckle flat," explained Goubert.

"When exposed to long portions of dirt, very long studs, or studs which are made from too soft a metal, are prone to being pulled away from the tyre or becoming damaged. When designing the X-Ice North 2, we worked on the proportion of the stud that is exposed, as well as on our choice of metal with a view to improve the resistance of the spikes without compromising grip," he added.

DMACKâ€™s new DMG-ICE tyre features a new construction and compound aimed at improving performance on frozen gravel and ice. And a revised â€˜T-Barâ€™ studding method, which was developed in partnership with driver Jari Ketomaa and its motorsport partners in Finland, is designed to aid stud retention.

Dick Cormack, DMACK motorsport director, said: â€œLast year our weakness was on frozen gravel and weâ€™re confident that all the hard work and technical development with our new tyre will really pay off. Weâ€™ve developed a unique studding method in-house and that gives us more control over the quality and studding process.

â€œHowever, the compound and construction has also been improved and weâ€™ve seen real steps forward in terms of performance during winter testing,â€ he added.

Ketomaa won Rally LiepÃ¢ja-Ventspils in Latvia last weekend, the second round of the FIA European Rally Championship, on snow and ice. He will pilot an Autotek-run Ford Fiesta RS in Sweden.

DMACKâ€™s other top runners include Czech driver Martin Prokop in a Fiesta RS and MINI WRC driver Michal Kosciuszko from the Lotos WRC Team.
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Steve · Feb 10, 2013

Studs: can 0.5mm make a difference? (best-of-rallylive.com)

10/02/2013 10:05 am

This weekend, Michelinâ€™s WRC partners are competing on studs which protrude half a millimetre less from the tyresâ€™ tread blocks than they did in 2012. But does such a small change really make a difference?

The narrow tyres used for Rally Sweden are unique through the fact that each one is equipped with 384 studs. The regulations state that the latter may not exceed 20mm in length, and that includes the visible part which protrudes from the tread blocks.

It is these tungsten-tipped spikes which provide the vast majority of the grip on the Scandinavian eventâ€™s icy stages, allowing the drivers to reach staggering speeds of up to 200kph.

The exact amount of metal which protrudes from the tyreâ€™s surface can be decisive in determining the carsâ€™ performance. The longer this distance, the more grip the studs deliver, but the more the â€˜leverâ€™ effect exposes them to damage in difficult conditions, such as frozen or loose gravel. It is consequently important to seek the most effective compromiseâ€¦

In the case of Michelin, at the time of its withdrawal from the WRC at the end of 2005, its partners could choose between several options (ranging from 8mm to 6.5mm of exposed stud) as a function of the prevailing conditions. Today, however, each tyre manufacturer may only offer its partners a single possibility.

The studs on DMackâ€™s tyres, for example, protrude 7mm from the tread blocks, which was the solution preferred last year by Michelin who returned to the WRC in 2011. Meanwhile, for obvious planning reasons, a decision needs to be taken before production of each yearâ€™s tyres begins, which was late-December in the case of the French firm for 2013, after an initial round of tests in Sweden. For this cut-off date, a stud length of 6.5mm was chosen, especially since a new tyre has been developed for this yearâ€™s rally (the Michelin X-Ice North 2), featuring a more open tread pattern which helps clear fresh surface snow, allowing the studs to bite into the firmer ground underneath.

But does half a millimetre really change much? We asked the rallyâ€™s 2011 winner Mikko Hirvonen who is one of the current stars with the most experience of Rally Sweden. â€œHalf a millimetre certainly makes a difference,â€ the CitroÃ«n driver confirmed on Saturday evening. â€œIt has definitely helped stud durability, for example, while the more open pattern gives more progressive handling on the snow. The combinaion is a real improvement.â€
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Steve · Mar 1, 2013

DMACK has new gravel offering in Mexico (iRallylive.com)

01.03.2013 19:37

DMACK WRC competitors Martin Prokop and Michal Kosciuszko will have new gravel tyres for Rally Mexico next week: the DMG+2 gravel tyre will be used for the first time in 2013.

Prokop will have his Jipocar Ford Fiesta RS WRC, and Kosciuszko his Lotos WRC Team MINI WRC, run by Motorsport Italia.

Nicolas Fuchs, who did so well in the PWRC last season, will also use DMACKs on his Mitsubishi Lancer 9.

WRC crews have an allocation of 28 tyres for the event - four at each of the six tyre-change opportunities and 4 for Qualifying.

DMACK has decided to go with a new H3 hard compound with the DMG+2 tyre. In case the weather turns damp, Prokop and Kosciuszko can opt for up to 16 S3 soft compounds.

The event is 394.88 km - tyre management will be critical - as usual - but DMACK says the Mexican gravel is not very demanding and the altitude, though high, remains reasonably constant as far as pressure is concerned.

Qualifying begins at 1123 local time on Thursday on a 6.27km long stage, with Start Order selection at 1300.

The opening 1.05km Monster Street Stage Guanajuato is at 2009.
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Steve · Aug 1, 2013

Pirelli to make WRC return in 2014 (WRC.com)

01 Aug 13

WRC competitors will be able to select tyres from four manufacturers in 2014 after Pirelli registered as an official supplier to the Championship.

The FIA confirmed this evening that the Italian manufacturer will join existing suppliers DMACK, Hankook and Michelin next season.

FIA Rally Director, Jarmo Mahonen said: â€œWe are obviously very pleased to have competition between four manufacturers next year, three of whom are already supporting our Championships.

â€œHaving Pirelli return to the series is also very positive, and together these four brands will provide a great platform for open competition as well as choice and variety for our competitors.â€

Pirelli was the control tyre supplier to the WRC from 2008 until the end of the 2010 season and supplied the tyres for the WRC Academy cars in 2011 and 2012.
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Steve · Feb 28, 2014

Scorpions abound in Mexico... (iRallylive.com)

28.02.2014 12:24

Pirelli is only a couple of rounds into its return to the World Rally Championship, but the brand will be equipping more than a fifth of the entries in next weekâ€™s WRC Rally Mexico.

None of the big WRC teams have yet budged from the Michelin hegemony, but Italyâ€™s Max Rendina, with a Mitsubishi Lancer Evo X, Paraguayâ€™s Augusto Bestard, also in an Evo X, Italyâ€™s Lorenzo Bertelli in his distinctive green Fiesta R5, Gianluca Linari also of Italy, in a Subaru Impreza WRX, Peruâ€™s Jorge Martinez in a Subaru Impreza STI, and Mexicoâ€™s Ricardo Cordero in yet another Evo X will all use the new Pirelli Scorpion XR gravel tyres in hard and soft compound form.

The XR is designed for harsh conditions, and is symmetrical, meaning tyres can be swapped from left to right on the car. Drivers have an allocation of 40 tyres to choose from, but can only use 20 at the 5 tyre-changing opportunites.

Pirelliâ€™s PR people have issued this quote from senior tyre engineer Matteo Braga: â€œMexico, with its high temperatures and high altitudes, presents a very tough challenge for any tyre, but we are confident of the abilities of the Scorpion XR to cope with the rocks and heat. With the cars losing up to 20 per cent of their engine power due to the altitude, this actually has an effect on the tyres, because although there is less power the cars can slide more if they do not have enough traction. The current XR is a very different concept to the tyre that was last seen in 2010, with new dimensions and a new non-directional pattern, making use of all our latest technology. It has been specifically created to respond to the needs of the most recent FIA regulations, so we are all looking forward to seeing it perform in competition.â
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Steve · Jun 4, 2014

I've not noticed these before. Covers to stop mud clogging the wheel nuts.

Crashton · Jun 4, 2014

Old sprint car trick. Although they use big foam plugs not carbon fiber.

Steve · Aug 20, 2014

Michelin's new "full wet" tire ready to go in Germany.

Crashton · Aug 27, 2014

Yes it does lots of sipes going on there.

Steve · Feb 10, 2015

[ame="https://www.youtube.com/watch?v=DN9zo8z7g80"]WRC Rally Sweden 2015: Tech Special - YouTube[/ame]

Crashton · Feb 11, 2015

Boy I'd love a set of those for my MINI. :arf:

Steve · Feb 12, 2016

Here's a bizarre stat from Michelin.

"Collectively, the 460,800 studs available for Rally Sweden weigh almost 2 tonnes and measure 1km laid end to end!"

Steve · Oct 10, 2017

This is about more than just tires but it fits here.

[ame="https://www.youtube.com/watch?v=uXnAUqHHq2k"]WRC - RallyRACC 2017: Tech Special (gravel vs. tarmac) - YouTube[/ame]

minirab · Oct 10, 2017

Very good info, those guys sure don't work at Jiffy Lube.

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