New Tires for my 99 Suburban: Std or Upsize


Old 10-05-05, 06:16 PM
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Join Date: Feb 2005
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New Tires for my 99 Suburban: Std or Upsize

I just bought a 99 Suburban 4x4 and it needs new tires. The OEM size is 245/75R16, but it has 265/75R16 on it right now. The rear axle ratio is 3.42. Is there any advantage to remaining with the oversize tires or should I go back to the OEM size. I've had dealers tell me I'll get better fuel economy with the larger tires (due to their larger diameter) and another tell me the vehicle was engineered for the 245's and I'll get better mileage if I go back to the original component size. The fuel economy is only 15 mpg at present so anything I can do to improve it is welcome. As I occassionally tow a heavy trailer I was looking at the Michelin X Radial LT tire, a load range E, 10 ply tire which is available in both sizes. Any knowledge or experience you can share is much appreciated.
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Old 10-22-05, 07:35 PM
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I had the same issue with my 96 Dodge truck. I went back to the original tire size 245/75/16 and it made no difference whatsoever in gas mileage or otherwise. I put Bridgestone Revo's on mine on the recommendation of a very good tire guy. Absolutely the best tires I've ever had on a truck. They channel water great and got me through an 18" snowfall blazing through driveways that were still plowed in. But don't just take my advise he's a link.
Old 10-24-05, 10:10 AM
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Actually, you'll get better fuel mileage with the larger tires, but you will not notice it because your odometer is lying to you.

Your odometer is geared for the smaller tires, so if your odometer gear travels 50,000 revolutions the odometer will show x number of miles travelled regardless of which tire size you are using.

Since the larger tires have a larger circumstance, each rotation actually moves you farther down the road. AKA - better fuel mileage with the larger tires.

The only way to know for sure how much better fuel mileage you get with the larger tires is to have the speedometer/odometer re-geared to match the larger tires. Or travel a route where you know the exact mileage.


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