mpg vs tyre size

[TimberCutterDartmoor]

In theory yes, bigger tyres act as higher gearing, cover more ground for same effort. I'm not sure how much by though, does it also reduce torque to though?

 

just checking this out, will i get reduced mpg if my 4x4 has bigger tyrse fitted . old dmax was on 17" the new 1, is on 18", ???

 

Bigger wheel or tyre?

 

Only if the aspect ratio isn't reduced to preserve the original tyre diameter i.e. lower profile tyre on bigger rim.

[inthewoods]

Something like this...

 

 

Since going from a/t to BFg muds I've dropped about 6mpg but on the plus side I don't get stuck anymore

[Stubby]

The rolling radius is what affects gearing . Small wheel dia high profile tyre could have the same rolling radius as large wheel dia low profile tyre .

[Sburdy]

I found when running my original 205/55/r16's at 50mph my truck was revving quite high. Swapping them for 235/85/r16's and driving at 50mph made a big difference on both engine RPM and fuel consumption. Also i think it pulled better more suited to the gearing i think..

[marne]

Don't forget about the fact, that because of the higher gearing you drive more miles, but your counter still counts the same (low) amount. When switching from 195/70 R15 to 225/70r15, I actually drove 5-6% farer compared to the 195, while my counter showed the same distance. So my increased consumption in reality was 7.5% more instead of the shown/calculated 12.5%.