Anyone else with 255/70/17?

[bowhunter53]

Ok, I put Cooper Discoverer ATR's on my 03 Sport 4x4 v8 about 20K miles ago. I immediately noticed a decrease of 1.5 to 2 MPG. It was winter when I installed the tires, so I thought winter gas may be playing a role. Needless to stay it never improved.

Now, I totally understand that I have a very heavy SUV with a v8, so please dont pile on and tell me it is what it is.

Im just having a very hard time believing that the new tires could cause such a drastic change. below are my stats;

exterior - bone stock, aside from tires.
engine - bone stock, just replaced plugs, air filter, cleaned MAF, Castrol Synthetic oil, 94K.
previous MPG - 15-16/city - 19-20/hwy with Grandtrek AT20
current MPG - 13/city - 17/hwy with the Coopers.

I get MPG envy when i hear people posting that they are getting 17 MPG city with their v8's ?!?!?!?!??!

Any ideas/suggestions?

P.S. on a hopefully non related note, i had the blinking A/C light issue around the same time that I replaced the tires. I replaced the relay with a NON toyota part, could that be playing a role in this?

Sorry for the long post, any help or suggestions are greatly apprecited.

 

[CGuava]

I run BFG 255's and get ~17 hwy. The tire is bigger, so you should see a decrease in MPG.

 

[bowhunter53]

so do you think the size plays a bigger role than the tread pattern? The Grandtrek's were much more all season, and the ATR's are much more agressive, with a much deeper tread depth.

 

[luvmyt4r]

Another thing to take into consideration is the weight of the tires. Takes more power to turn a heavier tire. Also....Are these hand caculated or by the Lie-o-meter on the dash?

 

[CGuava]

so do you think the size plays a bigger role than the tread pattern? The Grandtrek's were much more all season, and the ATR's are much more agressive, with a much deeper tread depth.

Size is probably the biggest factor. The fact that the ATR's are knobby, and have more tread void will also cause a decrease in mileage. Both of them combined will cause a drop in MPG, I don't think there's anything wrong with your ride, just the tire size and type decreased mileage.

 

[bowhunter53]

Thanks, those numbers are hand caluclated, and I run them between 38-40 psi. I guess I will just have to suck it up and wait until they wear out. Although, after 20K they look almost brand new! On a positive note, they are absolutely awesome tires in any kind of weather.

 

[IS_350]

How are you calculating distance traveled? It would have to be GPS-based with the new tires in order for it to be accurate.

The odometer and computer will read less miles traveled using the oversized tires vs stock tires, hence it will skew your calculation saying you're getting worse mileage. 1 mile on the odometer is not 1 mile traveled. Multiply that error out by a full tank of gas and 2mpg low is about right.

 

[bowhunter53]

good point IS, looks like I will have to hook up the GPS and get some "real" numbers.

 

[samslmmr]

I have a 2004 SR5 V8 with a set of 2011 P265/70 R17 tires on my truck. I average around 15.5 MPG city and even with a passenger and full load of gear I still average around 21 MPG on the highway - and that is driving through the hills of PA.

 

[bowhunter53]

What kind of tires?

 

[samslmmr]

Also, the difference between the two tires is roughly 5.2%. Calculate your mileage by taking your stock mileage and adding 5% then divide it by the amount of fuel it took to fill up(assuming you reset the odometer right after filling up in the first place).

The difference should be minimal honestly - the difference in weight between my stock tires and new tires was roughly 3 lbs per tire - not enough to change things too much.

 

[samslmmr]

Grandtrek AT20 - fresh off a 2011 4runner.

Dunlop Grandtrek AT20

 

[bowhunter53]

The Cooper Discoverer ATR's in 255/70/17 weigh 45.7 lbs each

The Grandtrek AT20 in 265/65/17 weigh 36 lbs. each

so Im looking at 9.7 lbs more per tire. That, plus the more aggressive tread, I think I just answered my own question.

I dont remeber the weight difference being that much when I was doing my research.

 

[JB.]

I dont remeber the weight difference being that much when I was doing my research.

Don't know if you meant to but it sounds like you got LT255/70/17.

ATR is no longer on Cooper website but using AT3 as a proxy, P255/70/17 weighs 38lbs. LT265/65/17E weighs 46lbs.

 

[stanleybb50]

Don't know if you meant to but it sounds like you got LT255/70/17.

ATR is no longer on Cooper website but using AT3 as a proxy, P255/70/17 weighs 38lbs. LT265/65/17E weighs 46lbs.

I was just on their website, but couldn't find the weight of the P rated Cooper Discoverer AT3 in 265/70/17. Where'd you find it at? I feel like an idiot... lol

 

[teampwr2]

I Run BFG KM2 Mud Terrain 255/ 85/ 16 And It Killed My mileage .and I drive like a granny Went From getting about 370 miles a tank to 325 a tank avg. and I have a V6

 

[bowhunter53]

Now I feel dumb. I dont see any designation on the tire. There no "LT" or "P" in front of the 255/70/17.

The speed rating is 112S if that matters.