Workshop: Tyre Test


Words by Chris De Wet

Rubber Remedy

I am the proud owner of a Land Cruiser 70 Series 2014 model Station Wagon fitted with the V8 turbodiesel. It is well built, will last for many years, and it’s a Toyota, which is another positive. My problem is that the engine is revving at a high 2400rpm in 5th gear at 100km/h. I believe that dropping that down to 2150rpm would result in much better fuel consumption, without the engine taking any strain. My investigations showed that there is a manual-to-auto conversion available in Australia, but this is aftermarket and so would void the warranty. Alternatively, one could change to a longer 5th gear or longer differential ratio than the standard 3.9:1.

Toyota has decided on this average gear ratio, which is suitable for customers across the spread of users. They have been testing other options, including a 3.7:1 ratio, which they have stated has an effect on towing performance. This alternative ratio is not available until their tests have been concluded.

Which left me to investigate the third option: that of longer tyres. I therefore designed a test to verify any changes in fuel consumption. The standard tyre size is 265×70 on 16-inch rims, and the standard tyre is the Dunlop Grand Trek AT1. Using these tyres, in the first months of ownership, I recorded my fuel usage under various conditions. I used a GPS to determine a correction factor of km travelled on the vehicle odometer and refer to true distance in the following statistics.

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