Big Mags and fuel consumption.

[vzuterus]

I have a VZ Ute that I just put a set of 18' mags on (I had stock wheels previously). All of a sudden, according to my computer the fuel consumption has from from 7.9 litres/100km to 10!! Can anybody shed some light?

The other strange thing is that my speedo has stayed dead accurate.

[Shounak]

Mags would weigh less then stock steels I'd imagine.. If anything it would improve fuel economy.. But most likely have a negligible effect..

[Ralph1]

I was always told bigger wheels need more power to turn them, hense more fuel.

[deathsminion]

My 18's are a hell of a lot heavier than my 15" VR calais, and my stockies.

[Z()LTAN]

dudes its simple lol. the more rubber u have on the road the more friction so therefore more fuel usage anything ??X8 will make more traction but more friction..

[portercg]

dumb question, if the 18" tyre and wheel package is higher overall than the stockers, it will put your speedo out to read a slower road speed than actuial road speed and cause a false reading you your fuel computer?

checked that?

[Z()LTAN]

that dosnent happen... much as they have low profile tyres with the bigger rims

[vt1538]

Speedo should stay accurate as the circumference of the tyre is similar. Also the footprint of the tyre if any different should be slightly smaller on the 18s as the profile is smaller so the sidewall should not distort as much. It might just be the tyre composition or tread that is causing the change.

[ucwepn]

Yeah its somthing about larger wheels taking more energy to spin than smaller wheels, Thats why its harder to spin the wheels with bigger rims. But going 100+km/h you should get better economy because the bigger wheels carry more momentum. Its got something to do with gravity (like that old school science experiment with the swivel chair and holding a spinning bicycle rim) if you did that same experiment with a smaller rim it wouldn't have the force of the bigger rim.

[drewins]

it depends if the tyres are simliar in circumfrance and the profile is alot lower. if thats the case you shoiuldnt see much difference in your speedo.

[VYSSion]

Originally Posted by ucwepn

Yeah its somthing about larger wheels taking more energy to spin than smaller wheels, Thats why its harder to spin the wheels with bigger rims. But going 100+km/h you should get better economy because the bigger wheels carry more momentum. Its got something to do with gravity (like that old school science experiment with the swivel chair and holding a spinning bicycle rim) if you did that same experiment with a smaller rim it wouldn't have the force of the bigger rim.

Not quite. It's more like cogs on your racer bicylce, with a larger circumference tyre it's harder to push because your drivetrain has to turn more to make the wheel do one full revolution than if you had a smaller circumference tyre.

[Ralgon]

how much wider are your new tyres? i know in 4wd tems narrower mean waaayy better fuel economy. on my 4runner going form 10.5 to 9.5 gave me nearly the same difference,is a lot harder on it's little 4 pot though