Tire Question

SLong · March 22, 2013

Guys, I'm about to buy a new set of Cooper AT3s and have gotten some good feedback from guys on here. I've got one more question. I've narrowed it down to 2 sizes: 275/65/18 (32.14" tall) and 265/70/18 (32.63" tall).

The stock tires on my Z71 were 31.5" tall when new.

The AT3 in 275/65/18 is 32.14" tall and has a tread width of 8.73".

The AT3 in 265/70/18 is 32.63" tall and has a tread with of 8.4".

I'm a little hesitant to go with the 32.63" tall tire out of fear that it will knock down my mpg a good bit from stock, but will the narrower tread width decrease the rolling resistance (in comparison to the 265/75) and keep it close to the 275/65 as far as mpg loss? The 275/65 is shorter but a little wider. I drive 36K miles a year so mpg loss is a concern. I know I'll lose some. Just don't want to lose a ton by getting close to a 33" tire if I go with the 32.63" tall one. Thanks to all of you have responded to my different questions lately.

FYI, either size I go with will be a P metric, so the weight won't be a factor.

Daryl LBZ · March 22, 2013

I put on the Cooper AT3 P265 70 R18 and my mileage hasn't gone down any. I had a 265 70 R17 stock.

SLong · March 22, 2013

Good to hear. Sounds like you upgraded to the 18" wheels and went with the 265/70R18. My concern was that the 1.13" bigger tire would knock the mpg down a good bit. Thanks for the reply.

Big Whiskey · March 22, 2013

I really think the MPG will be the same with either size. It really just comes down to personal preference. Which one do you think looks better? One is a little taller, and the other is a little wider. The taller tire may have slightly more effect on your speedometer and holding 6th gear on the highway...because it will lower your RPM's at cruising speed. However, these changes/differences will be very small because we're only talking fractions of an inch in difference.

SLong · March 22, 2013

Thanks guys. I'll post some pics once I put the ones on.

Silverado4x4 · March 22, 2013

Thanks guys. I'll post some pics once I put the ones on.

Well its been almost 3 1/2 hrs since you posted this, where's the pic's

SLong · March 23, 2013

Stopped this evening and put both size tires up against the stock tires on the truck. Going with the taller one (265/70) in the morning. The taller one is stock width, the shorter one slightly wider. I like the idea of a little more height. Will post pics. Thanks for the feedback.

SLong · March 25, 2013

Went with the 265/70R18s (32.63" tall). Truck looks like a Z71 should now in my opinion. Thanks for all the input. Averaged 18.7 mpg on 45 mile commute to work this morning, and it was pretty windy. Apparently very little effect on interstate mpg. I do think the effect on city driving mpg is a little more, but not enough to worry about.

FYI, I got on side of my wife on the interstate yesterday and had her set her cruise at 70. She's in a new Toyota Highlander so I know her car is accurate. I was reading 66-67 staying right on side of her on a long flat stretch. When I increased to 70 I passed her up. I'd say it's off a solid 3 mph at that speed.

Didn't have time to take any good pics this weekend. Will post some later on. Thanks again.