Gas mileage loss with wider tires?
 

I am looking for new wheels and tires for my 2000 V6 mustang. I found some for a good price but they are very wide. They are 275 wide compared to the stock tires of 205. They will be summer tires and not the M/S I normally run in the summer. They will be 17" wheels verses the 15" I now run meaning total weight will be less. I was wondering if anyone had any real would experience on wider tires and fuel mileage?

actually, unless you have already weight them, the probably weight more.
And unless the are a little taller, your screwed.
they are stickier so they wont roll easy.

There has been some information posted stating that wider tires have a lower coefficient of rolling resistance (i.e., lower rolling resistance than their narrower counterparts), but I'm not sure how that translates into real world mpg. Your mileage is affected by aerodynamics more than rolling resistance, so having a wider tire might still cost you mileage despite the decrease rolling resistance.

That being said, the composition of the tire is more important, and M/S and summer tires are probably equally bad on mileage. Most of the good LRR tires are A/S. Also, if the tires are taller, you'll gain a few % just based on fewer rotations per distance traveled.

While wider tires have less rolling resistance, the effect is small compared to the differences between tires. At 275 width, you're in the range where RR is not the desired attribute and the tires don't have good RR - and summer tires will be worse than all season tires.

With the 15" tires, you are much more likely to find tires that meet your excpectation for fuel economy/traction/treadwear, all 3 of which are tradeoffs.

Choose wisely.

If you've been happy with M/S (didn't you mean A/S ?) tires in summer, I'd say you don't need 275 wide tires.

A dedicated, decent summer tire will outperform the all seasons, and Mud and snow variety.

Even sporty tires can't escape the current trend towards greener tires with less RR, so you can nowhave tires that combine good performance with reduced RR to get good mileage.

Unsprung weight will most likely increase with bigger wheels, unless you've deliberately chosen lighter wheels.
Lower profile tires on the 17" wheels will be heavier per inch of rubber they add to the diameter, so that's another weight increase.

Thanks for the replies. The reason I am getting new rims is to prevent the rush to get studded snow tires put on/taken off when the law allows. If I can do it myself it would be a lot easier.

Buying used wheels for my car seems impossible, the places I go say that they are all damaged from hitting curbs. I guess there are a lot of bad drivers out there. I have not found any after market 15" wheels I can afford, If I could that is what I prefer to use.

I see now that these tires are probably way too wide to not effect aerodynamics. I am going to install splats but I didn't want them to stick out from below the car.

Paul

Paul,

sometimes 'opprotunities' arise and we have to weigh the choice.
Decissions are not always as clear cut as someone looking from the outside says it is.

For example: I REALLY want clear flat wheel covers BUT I have factory alloy rims and I'm not going to drill holes in them to hold the clear cover on. Nor am I going to change to a steel rim and do flat wheel covers.

But atleast you have some more information than you had before.

I would find some nice piece of higway and do an 'a' test now and then a 'b' test with the new setup.

Go look for "take off" wheels. These are the OEM wheels that some owners have removed (and trade in) when they buy a set of fancy new wheels for their new car. You can often get them next to new for very low prices since they are OEM and aren't considered "cool" by the automotive performance crowd.

if your wheels are toast. I have a set that would work with only 13k miles

they are not 15s. there 18X7s +45 with 225/55-18 they should be the 2005+ mustang diameter if not slightly larger. and prob much more efficient then 275s.

let me know if yer interested and you can test em out.

I picked up 19s and im getting 16s for winter so these will be of no use they were the oem they have a nice flat lip for a lexan wheel cover.

btw. if you dont mind me asking whats your budget? I can atleast help you source some 15s

http://pictures.topspeed.com/IMG/cro...-20_460x0w.jpg

The main factor is increased aerodynamic drag from the larger frontal area, not rolling resistance.