Too Many Spares???

4WD Tips      July 2, 2013      David Wilson

Just last week I was in Port Augusta delivering some training to SA Government. Leaving my accommodation on Friday morning I noted a 150 Prado parked alongside me and I had a quick look at its fitout. It struck me that it was unnecessarily burdened with too many spares (wheels).

Now being prepared is a good thing when you’re going bush. The last thing you’d want is to have some omission rear its ugly head and cause a hiccup in your schedule, for when you’re out there earning your keep, productivity is King. But the flipside of this is going out there with too much, and too much of the wrong stuff. If you have a look at the pic below you’ll see what I’m referring to, a vehicle that has three spares.

Now the agency running this vehicle has had no doubt a run of trouble with tyres running out of air in the most inconvenient of places, so they’re now working on the law of averages that if you take enough replacements with you, you’ll have all bases covered. But at what cost?

I did a quick calculation in my head on the dollar value of the questionable components seen on the vehicle. The twin-spare wheel carrier retails for around $3,800, the roof-rack around a $1,000, two additional spare alloy wheels and tyres add another $2,000. That totals $6,800. That’s a LOT of money but what has it achieved? Well its probably satisfied some safety audit, but an audit based on ill-informed presumptions. From our experience having all that mass sited behind the rear axle is likely to INCREASE the risk of a loss of control via an oversteer moment which can lead to a similarly INCREASED rollover potential enhanced courtesy of the roof rack. The other bogey is the same rubbish Dunlop Grandtreks (Passenger car construction tyres designed for bitumen rather than dirt) are seen on each wheel, so the puncture risk (the reason all this effort has occured) is exactly as bad as it was before.

It is possible to be puncture-proof. With the selection of appropriate Light-Truck tyres with a significant increase in Load Index (the true barometer of tyre strength) and a vigilant attention to detail on pressures, punctures can be a thing of the past. I’d much rather spend $1,500 when the vehicle was new and fit it out with five replacement Light-Truck A/T (all-terrain) tyres like Bridgestone’s D697 and armed with a decent compressor for another $350 and a decent gauge for $30, have a kit that was working on the premise that prevention is better than the cure, rather than what I witnessed, which was more like throwing cure after cure at the situation and never really fixing the problem.

With the right tyres all that matters is monitoring pressures. Starting with the placarded pressures on the vehicle (which on a Prado are as little as 210kPa = 30psi) and employing a 20% reduction in speed once you hit the dirt (170kPa = 24psi) and SLOWING down by the same margin (i.e. no faster than 80kph) the tyre will now have the flexibility to absorb the impact much better, provide a much more comfortable ride and pull up in shorter distances should you need to stop in a hurry. So there’s plenty of positives for running up and down any of the major SA outback tracks. When the conditions change and the requirement is for more serious off-highway travel the rules change some, with sand and/or mud likely requiring an up to 50% reduction to maintain mobility (accompanied by a now maximum speed of 40kph).

The intent with the fit-out of this vehicle was good, the safety of its operators is hugely important, but the result was overkill and problematic. It’s better to seek out simpler solutions that are less weighty and expensive! If you’re running a vehicle fleet and would like independent advice on vehicle fit-out give us a call, we’ve likely encountered your requirement and/or need in the past and can quickly offer a solution (plus we don’t sell accessories so we won’t be making recommendations based on what we think we can load your vehicle up with).

PS If the tyres were swapped out when the car was brand new there was likely a credit on offer for the original Japalops of around $500, making the move to the stronger A/Ts even more attractive.




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