With the Finke Desert Race imminent Toyo Tires technical and competition manager Steve Burke provides an update on the black art of off-road race tyre technology.
Team Toyo has never been better represented in the Australian Off Road racing scene – Billy Geddes, Brad Gallard, the perennial favourite Bruce Garland (we call them the BGs), and now the sensational entry of the high powered Peter Kittle Racing Team. We figure they’ve come to us because our tyres have something to offer. But what? What makes an off-road competition tyre successful?
Fit for purpose
The first consideration is it must be suited to the terrain. The AORC is held for the large part in outback conditions where suitability to uneven (‘loose’) surfaces and rugged rocks is paramount. You’ve got to be competent on hard- packed surfaces as well, but its best to lean towards rugged. You’ll get more consistent results.
Evolution of race tyres
Unlike tarmac circuit racing or even rallying, there’s not a huge difference between our race tyres and our off-the-shelf customer off-road tyres. The conditions dictate that. Compound and case technology has to be robust to meet the demands of off-road driving. It’s not a quantum step-up to racing.
Toyo brought its first race tyres – designated M/T-R – to Australia only three years ago. Before that we’d all been racing on shelf-tyres. Not a lot of people know it – the race tyre used by Toyo globally is based on our Australian-spec customer tyre. Why? Because Australia is designated a harsh environment.
Size matters
There’s been a major push for off-road racing tyres to get bigger. 39s have become the latest buzz size (and there are even 42s available, but not from Toyo). Why? It’s pretty much about ground clearance and being able to push through. But for every upsize, there’s a downside. Extra size means extra weight, kilos and kilos of it, and unsprung weight puts additional stress on every component – from suspension through brakes and steering. Circuit racing technology calls for minimal unsprung weight. That doesn’t compute in off-road racing because you need your wheel/tyre combination to be as rugged as your truck. But you also don’t need to over-engineer the solution.
Some people think 39s are the answer, others stick with 37s. The battle continues.
Compounds and construction
You’d not be smart to use a race tyre on the road. If you’re looking for an essential difference between the two technologies it is that the race tyre has removed all the features that make a road tyre comfortable and safe. Let’s talk about them:
- The race tyre takes the siping out of the tread blocks. Sipes are the very small grooves in the tread blocks which provide a biting edge for improved traction, especially on wet sealed roads. Sipes are deleted from the competition tyre to minimise cutting and tearing of the shoulder blocks.
- The ply cord is thicker in the off-road race tyre. That helps sidewall stiffness which works well with your suspension set-up and helps again with turn-in and torque control. It’s not comfortable though, and it’s heavier too.
- Belt angle across the crown of the tyre is also different. The steel belts are laid in a different manner to create stiffness.
In both the case of cord and belt the parallel goal is to make the tyres more resistant to cutting or puncture. If you were looking for one word to describe our race tyres, it’s aggressive. Great for the track, not so great in general use.
Heat is not a problem
Race tyre technologists spend a lot of time concerning themselves with heat build-up in their purpose-built tyres. You keep hearing the expression “the tyres have gone off” as compound or construction limitations kick in. Not so with Toyo’s off-road race tyres. The tread block construction which dispels rocks to provide grip also dispels heat.
Don't cut 'em or groove 'em
A lot of people look to rallying for a guide as to how they can get an advantage out of their tyres. The rally fraternity uses special tools on site to cut grooves into their tyres depending on the conditions on the next stage. For a start that pretty much guarantees they’ll destroy the tyre by stage end, and secondly a rally car does not weigh anything like a Trophy Truck. I’m sure the day will come when people start to look for minute advantages – but right now there’s much more to be gained by trusting manufacturers like Toyo, and making adjustments further up the handling chain with damper adjustment.
