Halfway through the 2018 World Rally Championship was a good occasion to examine the new things going on in the WRC’s world of tyres, notably on account of the arrival of the MRF tyre.
The MRF tyres are being developed with a view to being homologated for championship use in 2019.
Currently three tyre suppliers are approved for WRC championship use – Michelin, Pirelli and DMack – although Michelin are contracted to supply all four WRC registered World Rally Car teams.
Basically, each tyre supplier must provide two different tread compounds, each in limited quantities for each event, but each must use the same basic construction.
Michelin’s current WRC rally tyre is the LTX Force, which was introduced for Rally Mexico in 2017. For sake of definition, the alternative compound tyres are referred to either as hards or softs, even if these labels are not fully accurate.
Helping us explore rallying’s special art is George Black, tyre consultant for M-Sport.
Will Michelin's domination of the WRC come under threat in the coming years?
George Black: The “soft” tyre in reality it is not really a soft tyre. If you list their available compounds from super hard to super soft, the current “soft” Michelin tyre is in fact a medium compound!
Going back historically to where this compound came from, in the days before alternative compound control tyres, this family of compound was what we used as standard compound.
It was brought into the range of available tyres again last year because it was felt that we needed this level of compound as a soft, as we had to go harder for certain events.
The hard tyre we have now is like the special hard level of compound we used to use in Greece, Safari, Jordan, Cyprus, that extreme type of event.
Michelin does not now have a pure soft tyre in the range, which is one of the reasons why DMack were so successful, for example, in Wales last year, not just because Elfyn Evans was a local driver, but their soft tyre last year was considerably softer and more suitable for cold, wet conditions in Wales.
Martin Holmes: And the tyre construction always stays the same?GB: The construction has been the same now for Michelin for quite some time. Because of the regulations you cannot change the construction between the hard and the soft tyres.
If they wanted to change the construction for the soft tyre they would also have to make a completely new hard tyre as well.
As long as Michelin keep their current H4 compound as their hard tyre they are stuck with the existing construction they have, because both compounds must share the same construction, both for rough rallies like Sardinia and relatively smooth gravel rallies like Finland.
As regards puncture risk, there is no greater risk in using soft. The degree of puncture resistance is the same for both.
George Black discussing tyre tactics with Ford driver, Mikko Hirvonen, at Rally Mexico in 2007. Photo: Holmes
MH: We hear a lot these days about puncture alarm systems. How do they work?GB: It's the same as you have in higher spec road cars which have got a tyre pressure monitoring system. Basically, until the start of last year it was a device that was not allowed within the WRC because it transmits a signal.
Regulations said sensors which transmits signals back into the data-logger were not allowed.
From January 2017 it was allowed to have this type of transmitting device within the car and M-Sport started using it straightaway. If a pressure starts to fall then you'll get a alarm coming up on your dashboard saying, for example, that your rear left tyre has maybe only got 1.2 bar in it.
M-Sport were the only ones to use it at the beginning. Then as our drivers started saying in public that they knew when they had a slow puncture because the alarm came on, other teams started using it.
I think Citroen were the first ones to come after us, but they only used them last year on tarmac though, but they're doing it on all the rallies this year.
We set the alarm on the dash so for your tyres which normally run at 2 bar, if the tyre pressure drops below (I think) 1.2 you get an alarm that you're losing air pressure. Then it’s up to the driver/co-driver to monitor that alarm and decide what to do.
MH: Is this a modification to the wheel or the tyre?GB: It's nothing to do with the tyre, it is purely on the wheel. There are different systems, perhaps you've noticed on our wheel we've got two valve holes. We use one valve hole purely for the sensor and the other one conventionally for pressuring the tyre.
Other teams use a sensor within the actual valve of the wheel. We have them available on all wheels, snow, tarmac and gravel.
Round and Black ..... M-Sport's George Black with Michelin tyres during a round of the WRC. Photo: Holmes
MH: This year we have the prospect of another tyre manufacturer preparing to come to the WRC. Do you think we're entering a phase of a tyre war in the World Rally Championship?GB: Not for the next couple of years, but obviously it's possible. Michelin have the contract to supply tyres for the registered World Rally Car teams for another two years, but for anyone who is serious about coming in, like MRF, then it's going to take them some time if they don't already have worldwide rally experience.
I think it would take them a year or maybe two years to get up to speed with the different events and choose suitable compounds and constructions.
These must be capable of withstanding impact damage in Portugal and Sardinia, yet have the performance that you need for Finland and Wales. You can't make an ideal tyre, you've got to have a compromise.
I think it will take a new supplier some time to find the required compromise between performance and reliability. First of all they need to do more work on their constructions than they do on their compounds.
I believe they (MRF) didn't have punctures in Sardinia, but they had some fairly big bulges and other damage on the sidewalls, indicating the sidewall is not particularly strong.
MH: We haven't seen much of Pirelli recently, although they're a recognised tyre supplier.GB: They have been completely out of WRC for a couple of years. They came back this year with tyres for WRC2 teams, just a small step to assess the situation.
Mind you, if there is a change in the WRC tyre supplier contract, maybe they will be back in WRC.
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