Thread: 101 Fuel Consumption and Wider Wheels and Tyres

A few years back I travelled out through the Corner Country in the 101 with 9.00x16 tyres. In that wide open country and in company with others speeds tend to be slower and more relaxed and I found overdrive comes into its own. Cruising along in 4th O/d with revs about 1200 the truck was giving 11mpg on gas and 15mpg on petrol.

I recently completed a trip up through NSW black soil country with similar roads as the corner country but a little flatter with no sand dunes but a a bit more mud. This was the first long trip I have done on my 8" wide rims and 315/75 muddies. I am going to put on wider flares as mud was splattered all down the sides of the vehicle. The tread is well covered but the side biters just clear the flares and through up a lot of mud.

In this trip I only got 9.9mpg on gas and 13.4 on petrol. While other factors may come into it, it is clear the wider tyres are harder to push through the air and certainly through the mud. I have a vacuum gauge fitted and when you transitioned from a smooth surface to mud the extra load on the engine can be felt and was obvious on the vacuum gauge.

I suppose my experience with increased fuel consumption with muddies is consistent with other vehicles switching to muddies. A 10% increase.

Interestingly at 100kph cruising speed there didn't seem to be much of a difference - bad all round.

Garry

Fair enough. In theory then you're consumption should be better.... unless you're having to really rev the engine to achieve the same speeds.. If the wheels are slightly smaller, would 4.7:1 diffs and no overdrive help?