as i use my superb as a taxi ive noticed something quite shocking.

well to start with, with a full tank of diesel with the car sitting on the std 16" steel wheels i was getting an average of 530 miles to a full tank.

since fitting the 19" merc amgs wheels im getting a shocking average of 420 miles on a full tank.

to me that doesnt sound right.! surely fitting larger wheels cannot make the car consume an extra 100 miles worth of fuel.?

ive now refitted the std 16" steels and the mileage has increased back to an average of 530 miles.

it maybe normal but it had me surprised to say the least

as i use my superb as a taxi ive noticed something quite shocking.

well to start with, with a full tank of diesel with the car sitting on the std 16" steel wheels i was getting an average of 530 miles to a full tank.

since fitting the 19" merc amgs wheels im getting a shocking average of 420 miles on a full tank.

to me that doesnt sound right.! surely fitting larger wheels cannot make the car consume an extra 100 miles worth of fuel.?

ive now refitted the std 16" steels and the mileage has increased back to an average of 530 miles.

it maybe normal but it had me surprised to say the least

Is the overall diameter of the wheel+tire bigger on the 19's?

I thought cars usually measure the distance travelled based on a knowledge of the wheel diameter (ie if you turn the wheel once it travels so far).

If you run bigger wheels + tires then the car might think you've only travelled 1 mile, but actually you've travelled 1 and a bit miles.

This also has the effect of making your speedo read low, and would make your MPG read lower.

It is also down to rotating mass of different wheels weight. There are various fact that influence your mpg incase like yours.

1. Total mass of wheel & tyre.

2. How many rev you do per mile (each difference will corespond to rpm of engine and will result in dec/inc of mpg).

3. How wide is tyre. You will find huge difference between 205 & 225 in profile.

4. Quality of a tyre and how much grip you get. New tyres always save you few miles compering to used tyre.

Is the overall diameter of the wheel+tire bigger on the 19's?

I thought cars usually measure the distance travelled based on a knowledge of the wheel diameter (ie if you turn the wheel once it travels so far).

If you run bigger wheels + tires then the car might think you've only travelled 1 mile, but actually you've travelled 1 and a bit miles.

This also has the effect of making your speedo read low, and would make your MPG read lower.

i thought of that, but 100 miles less? seriously?

when the 16" and 19" wheels were stood side by side,the 19s were ever so slightly taller.

i suppose the 16s would allow for a more squished area as opposed to the 19s.

i think ill do abit more testing on this.

A bigger wider tyre has greater rolling resistance than a narrow tyre. Just think of the difference in the size of it's "footprint". You've gone from what? A 185 or 195 tyre to 235 or so, an increase of nearly 25%, plus these ultra low aspect ratio tyres are generally made of a stickier tyre compound. Result you will get poorer fuel consumption.

This is like the kids with a 1000cc Corsa, who fit over wide tyres and then complain their car is gutless.

its most probably the width of the tyre. I use more petrol since putting 245's on the front than I did having 205's when I put my winters on which are 195 it uses even less petrol. also the added weight of the 19's won't help.

Also have you got your tracking checked since fitting the wheels? Worth checking as that can increase fuel consumption

Use a sat nav to record miles, that way you will know exactly how far you actually travelled.

Use a sat nav to record miles, that way you will know exactly how far you actually travelled.

good plan i over looked that idea.