Why Supercars doesn't use a full wet tyre

Grooved rubber was a hot topic in the Supercars paddock on Sunday after the second of two 250-kilometre races was called off due to rain.

The field did complete a number of laps behind the safety car before being called back to pitlane where they sat for 35 minutes before a decision was taken to abandon the race.

Opinion between drivers was split over whether that was the right call or not, while TV interviews during the initial stoppage drew a number of references about the Dunlop control wet weather tyre not being a "full" wet capable of dealing with the standing water.

The long-standing wet, relatively unchanged over Dunlop's two-decade stint as the control supplier, is designed to be more of an all-rounder suited to the relatively mild Australian weather, and therefore more tolerant to drying conditions.

However that does leave it vulnerable to rare instances of monsoon rain, such as what was seen at SMP over the weekend.

According to Kevin Fitzsimons, head of Dunlop's Supercars programme, introducing a full wet is entirely possible, but would drive up costs and increase wastage given how rarely it would be required.

"[The current tyre is] classed as a wet weather tyre but it's really an aggressive intermediate," Fitzsimons told Motorsport.com.

"It's got a lot more grooves than a standard intermediate has if you had a full wet, an inter and then a slick. But it's harder in its compound than what a full-blown wet would be. And a full wet would have a much more aggressive pattern for channelling out water.

"It would also fall to bit on a drying track 80 per cent faster than this current wet tyre does.

"The tyre is fine when the conditions are right, but when there's heavier rain like we had on the weekend it's not ideal.

"We could make a more effective wet tyre but it won't last like the current one does. So the teams will need to have slicks, intermediates and wets. That means they'll need more wheels to mount them on.

"And how long can you store them for? Four months? Six months? Twelve months?

"It's just a money thing. We don't have that many wet race meetings, it's not like we're in Europe and we're constantly fitting wet weather tyres.

"For 20 years [the current wet tyre has] been fine. These comments come up every now ands then, particularly when guys haven't had a good weekend. It's an easy thing to point the finger at, that the wet tyre isn't ideal.

"We know it's not ideal in every condition – but it does the job its designed to do perfectly well. And that's to not throw blocks at spectators after eight laps on a drying track."

Fitzsimons added that the teams often don't help the tyre with set-up, particularly if they think the track may dry out during the race.

"It comes down to car set-up as well, where there's a compromise when [teams] are hoping it may dry out," he said. "So they leave the dry set-up with the camber on.

"That means two-thirds of the tyre isn't in contact with the road surface and it's not pumping the water out. You're basically driving on a 150mm wide tyre as opposed to a 300mm wide tyre.

"We get the tyres back and the outside blocks haven't even touched the track. They've still got all the vent dimples on them. It's really, really obvious."

As for Sunday's wash-out, Fitzsimons conceded that there was probably a bit too much standing water for safe racing even if cars were running a full wet set-up.

"here was a lot of standing water," he said. "[The tyre] can only pump out what it can pump out. If you're going really, really quick and it can't squeeze the water out, that's when you get aqua-planing.

"When the red flag happened I walked down to pit exit and looked through Turn 1 and there was a significant amount of standing water. The surface at SMP is particularly worn, that's why we saw guys in the Shootout driving way off the apex trying to find some sharp stones to dig into the tyre. It makes it difficult."