Bumping up one tire size/expected loss in mpg?

SLong · March 13, 2013

Guys, I have a 2011 Silverado Crew Cab Z71, 5.3 V8, 65,000 miles, 1.5" front level kit. I currently still have the OEM Bridgestone Dueler A/Ts on it, which are 265/65 R18. I've pretty much decided on the Cooper A/T3s as my next set of tires, and I'm thinking of bumping up one tire size. The A/T3 isn't a real aggressive A/T, and the next size up is 275/65 R18. These A/T3s are 32.14" tall, and the stock Duelers are 31.5" tall. Do any of you guys have an idea of what I should expect to lose in MPG? I do a lot of highway driving and the truck gets great gas mileage down here in South Louisiana on our level roads with the stock tires. I average 18.4 to 19 MPG for a tank of fuel with the stock tires. I don't want to lose a lot in MPG since I drive a lot but the truck would really look good bumped up one tire size. Any help is appreciated.

MS3DALE · March 13, 2013

I did the same thing your doing,I have a 1.5" front leveling kit,and went from 265/65R18's up to 275/65R18's,I didn't lose any MPG.

SLong · March 13, 2013

Thanks for the feedback. I appreciate it. I'd also appreciate any feedback from any guys out there who bumped up one tire size, specifically with the Cooper AT3. Seems to be a pretty popular tire with good reviews, so maybe there is someone out there who did the same thing I'm thinking of doing.

flyboyron · March 13, 2013

I have the stock 20" wheels and low profile tires on my truck and would like to go up one size in height, but what I am worried about is most places here in California, they will only install the factory size tire on the vehilce. I am thinking of taking the wheels off and then taking them to a shop and having what I want put on.

I would hope that with a bigger tire size, the engine would be turning at a slightly lower rpm and I should get better mpg.

Then again, I have the 3.73 rear end so it may not do anything to my mileage.

elite0259 · March 13, 2013

bigger tires take more energy to get rolling and keep rolling, as far as MPG loss, since I put leveling kit on my truck and went with 285/65/18 BFGoodrich A/T's I'm at about 1 MPG loss overall, I barely hit 13 MPG a week, sometimes 14/15 if I do mostly highway.

Edit: When I was running the stock tires I would usually pull off 15/16 MPG

TooTall1 · March 13, 2013

bigger tires take more energy to get rolling and keep rolling, as far as MPG loss, since I put leveling kit on my truck and went with 285/65/18 BFGoodrich A/T's I'm at about 1 MPG loss overall, I barely hit 13 MPG a week, sometimes 14/15 if I do mostly highway.

Edit: When I was running the stock tires I would usually pull off 15/16 MPG

Did you have your speedometer adjusted for the new tire size? The bigger tires may take more energy to get going, but shouldn't require any more energy to keep them rolling. When I had my '99 Silverado 5.3L, 3.73 gears, I actually got better mileage with the 285s.

SLong · March 13, 2013

A lot of guys don't realize that, but when reading 70 on the speedometer on my old truck, I was actually going 73 on a gps. This is going to cause your trip meter to read less than you actually traveled on a tank of fuel. Not a far stretch to say 20-25 miles off for a tank of fuel if you do a lot of hwy travel. If you don't factor in those miles, it would seem like you were getting worse mileage than you actually are when you divide the miles driven by the gallons it took to fill back up. I was mainly interested in seeing if guys had first hand feedback with my particular truck/engine and how it responded to bigger tires. The bigger the tire, the longer it takes to make one complete revolution. If you travel for an hour on the hwy and the speedometer is reading 70, but you're really going 73, you went 73 miles in that hour, but the trip will read 70 miles traveled. I've been through this with other trucks but it sounds like 1 size bigger won't affect my Silverado with 3:73 gears. Thanks for the feedback guys.

elite0259 · March 13, 2013

I didn't, but I factor in the 3% size change when I calculate my mileage. Everything I've learned in dynamics class says more mass, more energy. Granted its a tiny change, and its probably more in the way I drive it than anything else, but that's what I've noticed. It's probably because most of my driving is city so its more accelerating and stopping.

I have 3.73 gears too, the AFM doesn't kick on as much on the highway.

TJay74 · March 14, 2013

I have a 2010 Sierra AT, leveled out with 275/65/18 NItto Terra grapplers. My city mileage is 15-16 and the highway us 18-19. Speedo is off by less than 1mph with this setup.

Blue2500CC · March 14, 2013

I have a set of 275/65/18 A/T3's on my '10 5.3/6spd/3.42 4x4. It's been a while since I actually checked mileage, but haven't noticed the gas usage being any more! Unless the trailer is hooked up!

I think I have about 5k miles on them or so now, been pretty happy. 1st real snow test was last month heading up to the in-laws cabin in Ont. Did pretty good, pulling the 10' clamshell snowmobile trailer.

moab11 · March 14, 2013

Thanks for the feedback. I appreciate it. I'd also appreciate any feedback from any guys out there who bumped up one tire size, specifically with the Cooper AT3. Seems to be a pretty popular tire with good reviews, so maybe there is someone out there who did the same thing I'm thinking of doing.

I just put these on this fall and so far I am loving them, I went with 275/75/17 load range C tires, the ride is still good, and I maybe lost a little mpg, but my driving varies too much to accurately keep track.

Ryan00TJ · March 14, 2013

After I had my setup recalibrated by Justin for the larger tires it averages around .5-.7 mpg loss vs the stock 245/70/17's. I like the AT3's, though they will be gone by 30K miles. Currently at 15K miles and half tread. Rotated every 5K and proper air psi.

SLong · March 14, 2013

Ryan, surpirsed to hear that you're getting bad results on tread life on the AT3s. I've always had good luck with the old Cooper ATs and ATRs. Those were warrantied to 50K miles and Cooper bumped the warranty up to 55K miles on the AT3. Have you informed the tire shop where you purchased the AT3s? I've read nothing but good reviews on the AT3 so far. You've got me rethinking them now.

Ryan00TJ · March 17, 2013

Ryan, surpirsed to hear that you're getting bad results on tread life on the AT3s. I've always had good luck with the old Cooper ATs and ATRs. Those were warrantied to 50K miles and Cooper bumped the warranty up to 55K miles on the AT3. Have you informed the tire shop where you purchased the AT3s? I've read nothing but good reviews on the AT3 so far. You've got me rethinking them now.

Upon buying these tires I was curious about treadwear. Brothers ATR's were worn to the wearbars at 25K miles on his Wrangler. I know they have a prorated 55k warranty, but that will only be a discount applied to a new set which I likely won't be buying. Other than treadware I am very pleased with the tires' performance.

Dans09Max · April 14, 2013

Hi Guys,

I have a 2009 4x4 crew, with the Max Trailering package (6.0L, 3.73, the heavier rear axle, rear disc brakes, aux coolers, all that jazz). The truck has about 42,000 miles on it, and has an overall MPG average of 14.3 counting every tank since I bought the truck at 6000 miles. That includes some towing at the rated limit (over 10,000 lbs trailer) in hilly terrain. Actually probably more like towing 13,000 lbs.

Last weekend I changed out the factory Goodyear ATS in 265/70r17, standard load rating, for some Cooper Discoverer AT3, in 285/70r17, but in E-rated (10-ply).

I also have HP Tuners and have the speedo calibrated within 1 mph at 60. So, no need to calculate for extra miles traveled.

I feel like I'm getting BAD mileage with the Coopers. The last fillup was one complete tank with the new tires, my normal commute for a few days, no towing... It was 13.0 mpg. I'm chalking it up to combination of larger tire and the E-rated tire being heavier, and colder weather again (around 0F).

I also notice it takes a LOT more throttle to hold speed on level ground.

For anyone wondering about fit, these just barely hit the mudflaps, if I turn while backup up. The Bilstein 5100 leveling struts are on the way.

I paid $1138 installed in Fairbanks, Alaska.

Anyhow, time to break out the Aveo again. 30mpg when I don't need a truck sure is nice.