JG Pasterjak
JG Pasterjak Production/Art Director
2/17/20 8:31 a.m.

[Editor's Note: This article appeared in the December 2013 issue. Some information may be different today.]

Story by J.G. Pasterjak • Photography as Credited

Friction is what makes tires fun. The more they generate and the more grip they have, the more smiles they put on our fa…

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iceracer
iceracer UltimaDork
2/17/20 10:50 a.m.

By going to a wider tire, you increase the footprint and the frontal area, both increasing drag .

Vigo
Vigo MegaDork
2/17/20 1:40 p.m.

There is a ton of anecdotal data about this out there if you look at drag racing. Drag slicks are well known to 'eat mph' and if you know your race weight and before and after trap speeds it's pretty easy to ballpark some power consumption numbers. Now in that case a lot of it comes down to sidewall deflection and the very stick compound is probably in 2nd. In street tire terms I think the mpg loss is MOSTLY attributable to aero impacts from the front tires with actual rolling resistance being secondary. 

Another stark way to find the losses from tire 'upgrades' is to see the kind of range that EVs lose when you put 'autox tires' on them. It's considerable..

ShinnyGroove
ShinnyGroove Reader
2/17/20 3:51 p.m.

Wider tires can cost you top speed due to increased drag and turbulence, but a lot depends on the individual car.  Miatae (in stock form anyway) have almost no front bumper or fender coverage of the tires, they just hang out in the wind.  Other cars are better considered in this regard and probably pay less of a penalty at high speeds.

freetors
freetors Reader
2/17/20 7:47 p.m.

My s2000 with 255 Bridgestone re71r tires and an aggressive autocross alignment loses about 3-4 mpg on the highway compared to normal tires and a modest alignment. The effect is real.

KyAllroad (Jeremy)
KyAllroad (Jeremy) UltimaDork
2/18/20 12:58 p.m.

It also doesn't appear you weighed the tires to see what effect that would have.  Heavier tires take more energy to spin up to speed (remember, all cars have 5 flywheels:  one on the engine and one on each corner)

It seems a better test would have been to stay as close as possible to the same tire size and weight and only adjust the compound.  Introducing two extra variables isn't very scientific.

aw614
aw614 Reader
2/18/20 1:45 p.m.

I never noticed the mpg loss on my integra, it seems to get a solid 25-27 mixed mpg with autocrosses and occasional commuting, but I am wondering, how much of an affect if any do sticky tires affect dyno tuning on a roller? 

Cedricn
Cedricn New Reader
2/3/21 11:43 a.m.

Would have been nice with some correlation to the logs from the track, to see if it's a measurable difference on the straights 

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
2/3/21 5:23 p.m.
Vigo said:

There is a ton of anecdotal data about this out there if you look at drag racing. Drag slicks are well known to 'eat mph' and if you know your race weight and before and after trap speeds it's pretty easy to ballpark some power consumption numbers. Now in that case a lot of it comes down to sidewall deflection and the very stick compound is probably in 2nd. In street tire terms I think the mpg loss is MOSTLY attributable to aero impacts from the front tires with actual rolling resistance being secondary. 

It's a rule of thumb that going from a limited slip diff to a spool will make a car run about a tenth slower.  This kind of boggles my mind because tires are always running under a slip percentage when under load, so you'd think that any minor circumferential differences would get lost in that, but enough people have noted the effect that it is hard to ignore.

 

wspohn
wspohn SuperDork
2/4/21 10:49 a.m.

It would be an interesting data point if you could take a narrow tire and a wide tire of the same make and model, to isolate exactly what the difference in fuel mileage was due to frontal area.  Just run the car in a straight line  on a long highway to eliminate cornering effects.

I used to run a very stock race class on tracks with long straights and while the competition always squeezed on every bit of rubber width they legally could, I felt that wider tires might impair top speed more than they would result in saved cornering times and could actually reduce lap times. 

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