If you operate a fleet of heavy vehicles there was a clear message from Nigel Price, from the Serious Crash Unit at NZ Police, at the EROAD Fleet Day in Christchurch in February. He made it clear that trucks take longer stop when travelling at the same speed as a car, and it’s not because of the weight, brakes or driver; it’s the tyres!
According to Price, trucks are designed with brakes and suspension systems that are more than capable of stopping the vehicle when fully loaded. And while distraction and concentration is an issue for all fleet drivers, a delayed reaction on the brake pedal isn’t what increases the stopping distance.
Tyres have three main functions; 1) carry the load; 2) allow the vehicle to turn corners; 3) help it stop when the brakes are applied. Fleet Managers want them to do one more thing – last a long time to reduce operating costs.
Truck tyres have two key attributes – load carrying capacity and durability according to Price.
“Trucks have tyres to do the job,” explained Price. “And the tyres they need to do the job are of a much harder compound (than car tyres).”
“Now I can give you truck tyres that will stop in the same distance as a car tyre. That’d be great. Apart from the fact that if you drove from here to Nelson (300+ kilometres from Christchurch), you’d have to replace your tyres. But it would stick to every corner. Though you’d have to replace your tyres. So that’s not a viable.”
“I can give you tyres that would never wear out. That will guarantee that the truck will fall off every corner on the way.”
“So we’ve got to have some compromise. We’ve got to have truck tyres that can take over 100 psi to hold the weight that’s sitting on the back of the truck. So, they’re made of a harder compound compared to car tyres. They are longer wearing with a reasonable wear life and the capability of holding the weight on the back of truck. But it has its drawbacks.”
Price also made the argument for driving trucks at lower speed limits than cars because of the tyre compound.
“Truck tyres are harder compound. They only have 80% of the braking. Now, the calculations vary between 75 and 85. So a truck on dry seal is like driving a car on wet seal. A truck on wet seal is like driving a car on gravel in terms of its braking ability. And a truck on gravel is like driving a car on ice. There’s a pretty rough sort of estimate, but I’ve kept it very simple just to get a point across.”
“My point is that your drivers, and you fleet managers need to look seriously at the fact that the driver hasn’t got braking as good as a car, and they’ve got a rough idea, or some sort of rough concept, of how much braking less braking he’s got. And then we may actually start winning the battle.”
