18s to 19s (Fuel Economy)

[laney]

Hey guys. I was watching Test Drive on channel 9 today and they said that tyres can make up 1/5 of your fuel economy. I thought about this as i have recently updated my VY SS from factory 18s to VX GTS 19s. Excuse me for sounding stupid, but i am pretty sure that they are wider than the 18s????

Can anybody verify this?????

From my impression the fuel economy with the 19s is worse. I did travell with golf bag, 2 suitcases for 4 hours and i swear that the fuel ecomomy was better when i drove home with the 18s.

Has anybody else noted a significant difference when changing tyres?

The suitcases and golf bag always accompany me on my trip home. However the clubs had to be in the boot. The gf took the front seat.......

I didn't think that a change like this would have altered my fuel economy. Do tyres ever advertise that they are good "fuel economists" ? ? ?

[Mungrel]

I havent noticed any difference going from 17s to 19s (the 19s are wider in my case)
Going from 15s to 19s perhaps, but it would be minimal IMO (im talking .01s of a L)

About the only thing you may notice would be increased inertia. For example feels like it takes longer to accelerate and decelerate due to the larger, heavier rolling mass. Once again, that would be minimal IMO.

[hadafew2many]

If you change your diameter you should take to a tuner who will alter the computer to compensate including speedo etc...then fuel will be f all difference....:)

[NewV8]

When you go to a larger wheel you should also go to a lower profile tyre to keep your rolling diamiter the same.

[2 cylinders shy]

I think it would work the other way around?
Larger profile sidewall = softer = more rolling resistance = worse fuel economy :confused:

[BLACKWAGON]

Some silica tyres advertise better fuel economy on the radio everyday.

[iamhappy46]

Big heavy wheels with lots of weight on the outside will increase your rolling inertia and therefore require LESS throttle input to keep at a constant speed which means you can use less fuel when maintaing that constant speed. Same as a standard flywheel, which absorbs the inertia as its speed increases and takes forever to slow down. The inertia in the heavy wheel keeps the car rolling... of course, stop start traffic will mean you need to put more energy into the wheel to get it moving and stopping requires more effort as well.

A lightweight 17" or 18" rim(Speedy Lite7 @ 7Kg per rim comes to mind) will be good around town for stop start driving but on the highway, would require more throttle input to keep the wheel at that constant speed. It does however have the added advanatge that it is easier to accelerate with as you have less mass to get moving :)
It is not much of a difference between light and heavy rims but it is something to be aware of...

[SS Enforcer]

Hey guys. I was watching Test Drive on channel 9 today and they said that tyres can make up 1/5 of your fuel economy. I thought about this as i have recently updated my VY SS from factory 18s to VX GTS 19s. Excuse me for sounding stupid, but i am pretty sure that they are wider than the 18s????

?

Just read the tyre size on the sidewall. You should have had 235x40x18. Now they should be 245x35x19. The difference is about 1.3 kph at 100 K's. The difference in width is 10 mm.

cheers