Hi all, 

I had 16” wheels with 205 wide Goodyear and Dunlop tyres with a fuel economy rating of A/B, with these tyres I was confortably getting 54mpg on my 1.6 diesel DSG. 

 

I swapped the wheels to 18” with 225 wide tyres, overall they are the same size as the 16” just lower profile tyres. 

 

I wanted goodyear tyres with a B fuel economy rating but was convinced by the sales chap to get Falken FK510, these were rated E for fuel economy but I was advised would be minimal addition fuel expense compared with the difference in price from the Goodyear’s. 

 

Over the past 1200 miles I have averaged 45.2mpg. 9mpg less than my old tyres and wheels. A 16% drop. 

Tyre comparisons between A and G suggest a difference of 7.5%. 

 

I have put out the old wheels and tyres back on and I’m back to averaging 54mpg. 

 

I appreciate that the 18” tyre is wider and therefore more contact with the road but I am surprised and the significant difference between the two. 

 

Averaging 18k miles per year the difference between these 2 tyres is £401 a year in fuel. 

 

Has as anyone else experienced this drop, I’m in two minds whether to sell the 18” wheels and tyres (although the do look better) and go back to the 16” or change the tyres for the B rated that I should have bought in the first place!

Is the wider lower profile tyres likely to that much of a contribution or is this just down to the stickiness of the tyres?

 

@Cbiggs - You are aware that EU "tyre performance data" is all self-certified? Did you realise that you're probably fitting heavier wheel+tyre combinations which will hurt acceleration, braking and fuel consumption?

It may be worth checking the speedo calibration was not changed. Are the wheel/tyres the same effective radius? This could affect your measured speed. Also are you going by the consumption figure given by the car's computer? These can be misleading also. 

Sometimes the measurement error is bigger than the effect  

There have also been tests performed on different size wheels with as close to the same model tyres. Sweet spot for economy seams to be between 16 and 17. Wider may make it worse but your experience with the difference will probably be a combination of weight, width and tyre deformation. That last one is a huge one and is what makes the different models of tyres change the economy. iirc the actual tread makes little difference unless comparing off-road to slicks etc.

24 minutes ago, TDIum said:

It may be worth checking the speedo calibration was not changed. Are the wheel/tyres the same effective radius? This could affect your measured speed. Also are you going by the consumption figure given by the car's computer? These can be misleading also. 

Sometimes the measurement error is bigger than the effect  

Overall they are the same effective radius, the car coasts much better on the 16” than the 18” which leads me to think they are just stickier!

1 hour ago, Cbiggs said:

I appreciate that the 18” tyre is wider and therefore more contact with the road but I am surprised and the significant difference between the two. 

 

Has as anyone else experienced this drop, I’m in two minds whether to sell the 18” wheels and tyres (although the do look better) and go back to the 16” or change the tyres for the B rated that I should have bought in the first place!

 

Is the wider lower profile tyres likely to that much of a contribution or is this just down to the stickiness of the tyres?

 

 

Absolutely. Averaged 57mpg over my time with Mk2.5 Focus with 1.6tdi  Several years later bought a mk3 Titanium with many fuel saving devices - better aerodynamics, active grille, stop/start etc - 50mpg over my time with it (I believe the mk3 was lighter too). Not only was fuel worse, the car would tramline and had a much worse turning circle. Our car had the upgraded fancy 18" alloys.  Just b4 I traded it in, we needed a rental car for a month - they gave me an identical car only in Zetec S trim with 17". Over that time I averaged 62mpg. The car rode more smoothly, was quieter and handled like I expected a Ford to handle. And no more 5 point turns to get the car in/out of my garage!

 

Lesson learned. Not only do 18" tyres generate a greater rolling resistance, they're significantly heavier too.

 

PS - what do I have on our SUV? 18"  Why - because despite being better, the 17" wheels look too far small. (19" fill the car much better). They're on the car for no other reason than vanity.

Edited 13 July, 20187 yr by Guest

don't forget tyre pressure in the equation.

Dropping the pressure can have a noticable effect on fuel economy also.

I guess you should run a slightly higher pressure on a larger wheel to give similar deformation where the rubber contacts the ground....

16" are usually eco tires, plus they are way narrower then 18" and 225. Plus, 18" are usually UHP tires, where grip and performance are parameters above fuel economy, noise and price of course.

 

Yes, type, size and diameter of wheel affect the fuel consumption, sometimes significantly. I even have quite measurable difference between 18" winter set and 19" summer set. 

 

Conclusion, if you're concerned about economy, go back to 16". If you want more precise steering and more grip, 18 it is.

Thanks, my annual mileage has just increased significantly so economy is having to take preference over looks and handling!

 

i hadn’t really expected the difference to be as much as I have found. 

 

Back to the 16” for me and a set of Skoda Elbrus 18” alloys up for sale!

On my Qashqai (18”) I swapped the Front Continentals at 29k for Avon ZX7 to save £60. I lost 9mpg and my “saving” had disappeared after 12 fillups.

Awful tyre, noisy and soft sidewalls for such a high load rated tyre.