Dunlop tyre testing with a GT3

The new Sport Maxx Race 2 is bespoke for the 991.2 GT3; PH sees how it's made (and how it skids)

Margins are low in the volume tyre market. People buy rubber on price, usually resentfully, and intense competition means tyre companies will never make their name or fortune there: for the commonplace 195/65 R15 tyre size, there are no fewer than 232 individual brands competing for business. That's why Dunlop these days focuses on the premium end, particularly the self-defined 'ultra ultra high performance' (UUHP) category - tyres that don't have to be generalist all-rounders, but can be focused more on the areas that matter to PHers - that's performance, and bringing a bit of motorsport feel (and cred) to roads and track days.

Which is how I found myself at the sprawling Mireval test track in the south of France, on a baking hot week day that even the air-con in the shuttle minibuses struggled to cope with. I was there to test the latest Dunlop premium tyre, the Sport Maxx Race 2, as approved by Porsche for the 991.2 GT3. In, would you believe, a GT3.

Yep, it's that car again!

There was no time to waste. Barely had I been briefed which way the first corner went (turn right) than was I bustled into a GT3 (PDK first, thank goodness; manual could come later) and introduced to my French instructor whose grasp of English, I'd find, was partly reliant on hand gestures. Bang went the safety zone at least a few times during my first few laps, although savouring the car, the glorious howl of the engine, its wonderful response, linearity and build-up of power towards the redline may also have distracted me.

Car and tyres warm (the new tyre is said to heat up faster than before, not that it was an issue at Mireval), it was time to concentrate on the reason I was there. Tyre tests like this are always tricky, as without running lap after consistent lap with racks of different brands to swap between, it's hard to make an absolute call on what the nuanced differences are. Here, I'd assess more of the general feel of the tyre, and leave the spider charts to the Porsche engineers who were clearly sufficiently impressed to give Dunlop OE status.

And? Well, there was no trace of driving on jelly, despite the searing track temperatures. I didn't once sense, say, any loss of steering precision or tightness; the front end remained solid and not an ounce of rubber was introduced at speed into a steering setup that was so robust as I was finding my way - even after both the instructor and I lost count of our laps and stayed out to ramp tyre temps up yet more.

Dunlop or Michelin are your OE GT3 tyre choices

Back to the pits to digest the track layout and grab some water, before going back out again in the manual GT3. This instructor was gruff and didn't say a word, nor did he appear to have any sense of mortality as I somewhat scrappily, ahem, explored the limits; nothing scared him, which I don't know whether was reassuring or not. Either way, the confidence the Porsche's rear end gave me on power was something to behold: the transition between grip and drift was magnificently clear and measured, helping me edge it out around the melting circuit with almost F1-line precision. It was all so very robust, I never once felt the confidence-sap of any underfoot wooliness or squiggle. The GT3, a brilliant car, stayed that way in the heat no matter how brave or ham-fisted I became. (Oh, and the manual gearbox is brilliant.)

Sufficiently hot and sweaty, I headed indoors to find out how it was all achieved. Porsche GT lead Jan Frank was there, to explain how the company's target was more dry grip with no loss of wet grip: "We start out with a sheet of paper - the spider graph for the first generation (of tyre). The first bit is easy: we simply modify every peak in the way we want, then give it to Dunlop to come up with the tyre to achieve it...".

It's not all fun and frolics you know!

Lead engineer for the Sport Maxx Race 2 was Helmut Fehl. "One of the biggest gains with the new tyre is increased extreme grip thanks to a new compound," he starts by saying. Before then admitting that all this is secret sauce and he can't tell us how it does this. Ah. Good job there are bits we can see then: on the outside, for example, bridges feature between the grooves, aiding lateral stiffness, block stability and thus reducing tyre bend in corners. Stiffening up the tyre tread pattern reduces the response time and increases lateral G-forces. It sounds rather strange, but the ridges also mean the new tyre can use less rubber - and this makes it stiffer and lighter.

"The new tyre has better steering precision and better high-speed stability - here, our focus is not on static stability, but more on driving dynamics. The tyre has to be stable for all the laps, not just the first lap." Moaning F1 drivers on Saturday afternoons would dream of such a tyre. Fehl says the shape has been optimised, for more even heat distribution and to keep as much rubber on the road surface as possible, and heat-resistant Aramid fibres are used in a hybrid overlay on top of the inner construction, again to aid stability across a broader range of conditions and speeds.

Groove ridges make tyre stiffer and lighter

How did Porsche assess all this? By meeting regularly with Dunlop while developing the GT3, said Frank. And it's a pretty thorough process - remarkably, one where Porsche is willing to modify the car if the tyre gains are worth it. "If a tyre delivers better grip in corners but spoils the front-rear balance, we can work with the tyre partner to get the balance back by changing the car. You don't get this when working on a Golf! Such a very focused and tight partnership means even marginal things can be fixed and perfected." He likens it to an approach rather more motorsport-like: "There, you have one tyre, and modify the car like hell..."

The inference is clear. A new GT3 is at its absolute best only on Dunlop Sport Maxx 2 (or the alternative Michelin rubber - "we build 50 a day so we need to be able to guarantee supply" says Frank when justifying why Porsche has two tyre partners, both of which deliver spider graphs almost identical to one another: "I can't say which is best," he tactfully grins). Fit non-OE tyres and who knows what small, tiny niggles you're reintroducing to the car that chassis and tyre engineers spent so long tuning out?

It's a fascinating science, one laden in things we can't see and they can't tell us, but which the confidence-boosting joy of being able to do silly things in a Porsche at silly speeds in predictable safety makes so interesting. That one of the biggest improvements is the long-run stability of the tyre, meaning people like yours truly who need a bit of a run-up can still experience the tyre's best on the fourth or fifth lap, is enough of a gain for me. Because the glory of doing what I did in that GT3 during my snapshot test still makes me tingle with excited satisfaction as I type.