cooper tires and crappy gas milage

[nwoods]

Also the taller Coopers have changed the relative aspects of your gearing ratios. Though it's not really perceptible, your engine has to work slightly harder to turn those meatier tires. That reduces efficiency. You never hear about the great mileage those rock crawlers on 40" tires get, right?

 

[huelsmma]

If I average 17.5-18.0 mpg right now on 255/60/18 continentals. What do you think it would drop to with the cooper 285/60/18? Have been debating switching to cooper or gy silent armor since I need new tires. I have read nwoods several posts and even the other thread he has.

 

[blackforestham]

Based on tires sizes 255/60 and 285/60 with an average of 17.5mpg's, you get a 4.7% difference netting you an estimated loss of .786mpg. Add .500mpg rolling resistance (guess) and expect close to 1.286mpg (16.2mpg) loss at an unadjusted speedo reading. Remember, this is not "true" mpg loss. For every 100 odometer miles driven, your actual miles equal 104.7...if my math is correct??

 

[Boaz]

Umberto (as usual) is right. About half is the misread in the computer being off due to the larger size (you're going farther than it thinks you're going). The other half is the wider footprint and friction. Here's a link to the best tire size comparison calculator on the web. Should answer all your questions.
http://1010tires.com/TireSizeCalculator.asp

 

[davidfkon]

that IS a nice calculator!

 

[BldrRover]

I average about 16 mpg in mixed commuting from Louisville to Boulder. On roadtrips to Durango, I see 19 to 21 depending on what's on the roof. That is based upon the trip computer readout, which has to be adjusted by ~ +6%. I am probably average on the acceleration (don't floor it or granny it). I have noticed about a 1-2 mpg boost since the switch from winter gas to summer gas. I use premium almost exclusively. I have to say that I am pretty happy with that mileage. Out 06 Grand Cherokee is much smaller and gets substantially worse gas mileage.

 

[CMGRover]

My Rover is the economy vehicle in my house old.

 

[di_LR3_co]

bldrvr ---> matt ?

you running 285/65 or 285/60?

 

[BldrRover]

Kelby, that is me. I am running the 285/60/18 Coopers.

 

[di_LR3_co]

ahhh... hmmm... when we gonna hit the trails again?