straightaxle

Alright, so we all know that weight, diameter, width and tread type reduce performanc and mpg, but what is the biggest factor? Reason I am curious, is I am looking to add bigger aggressive tires, but trying to determine if a lighter or narrower tire would make the "least" amount of impact. For insatnce;

Cooper STT: 35x12.50x20, actuall dimension of 34.7, 12.5" width, and about 65 lbs.
Toyo OC Mud: 275/65/20, actual dimension of 34.1, 10.8" width, and about 71 lbs.

So, the Toyo is shorter and narrower (less rolling resistance, more effective gear ratio), but weighs 6lbs more. Will the benefits of the shorter narrower tire be eaten up because it is slightly heavier? Or am I just over analyzing, because it seems that anything bigger than a 275/60/20 highway tire nets about the same mpg loss, 2-3 mpg.

Lastly, where will the big mpg hit come from, City driving or highway? My truck gets pretty abismal City mpg (like 12 mpg with a very light foot) but great highway mpg (21 mpg at 75mph) so I cant see the City get much worse, but if it did......I should have kept my Superduty!!

Anyone have any experiences, either way?

F-250,LD

A larger tire will effectively give you a higher final gear.
A higher final gear will be harder to accelerate from a stop and will hurt gas mileage.
A higher final gear will lower your highway RPMs. This can give you better mileage except if it is too high then the engine will have to work harder which requires more fuel.

No matter what, a heavier tire takes more energy to get and keep spinning which will hurt acceleration and gas mileage.

straightaxle

So, you think the weight is the biggest factor??

sullyman

Between the two, it's probably a wash. If anything, the bigger tire might use a 1/2 mpg more.

Get which one you like the most. Between the two, I'd go with the Cooper.

ernierob130

Stt actually weighs 71 lbs.. But any size to size toyo is going to be much much heaver

BassAckwards

The weight has far more affect in MPG in my opinion. Width would be pretty negligible when you think of the actual percentage increase of total surface area touching the ground unless you go to something ridiculous like 275mm wide (10.82") to a 14.50" wide tire.

Going from a P-Metric Tire to an LT-Metric tire it's not hard to increase weight by 50%+ depending on your size increase from stock.

ernierob130

The lightest 35" tire by 20" rims is the Goodyear Duratrac at 67 lbs..of all my research ,can anyone find a lighter one?

straightaxle

Good info, as its hard to find anything accurate on the net, and cooper doesn't list on their site.

sullyman

Updated, see below.

sullyman

BFGs in 315/70/17 weigh less at 64 lbs. in S speed rating, and only 62 lbs in an R. And the Duratracs are lightest at just 60 lbs each.

http://www.tirerack.com/tires/CompareTires.jsp