tire question

[bow hunter]

I had 245-75-16 from factory changed to 265-75-16, what percent to I add to figure fuel mileage

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98. 5 SLT Q/C L/B intense blue loaded 3. 54 5 speed straight exhaust,isspro boost egt dual pillar, bullydog stage II injectors NRA MEMBER

 

[Ted Constantine]

http://www.4lo.com/gearspeedo.htm

 

[Loren]

Bow Hunter,

I suspect that different manufacturers have different specifications, but Goodyear publishes the following: The Wrangler AT/S is available in LT245/75R16 with 679 revolutions per mile and in LT265/75/R16 with 654 revolutions per mile.

This means that your new tires are turning 654/679 = 96. 32% slower than your old ones. If you read 100 miles on your odometer, you actually traveled 679/654 = 103. 82% more than that, or 103. 8 miles. To calculate fuel mileage, apply the correction to the miles you have traveled, then divide by gallons used in the usual manner.

If your speedometer was correct before, it will now read 96% low. Your 65 mph indicated is actually 67. 5 mph. This is probably not enough to get you a ticket, but be aware of it.

By the way, Dan Richter of Rickson Truck Accessories (the 19. 5" wheel guy) has been installing correcting gears and electronic boxes to fix speedometer/odometer errors caused by tire changes for quite some time. If you want to install something so you don't have to do the math every time you buy fuel, call Dan. Phone number is 800-587-7633.

Loren

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2000 Quad Cab, 4x4, short bed, six-speed: U. S. Gear exhaust brake, MileMarker Select Drive viscous coupling, Velvet-Ride spring shackles, Painless Wiring circuit box, Optima yellow-top batteries, Super-Glide 5th wheel hitch, Reese folding ball gooseneck hitch, Drawtite front hitch receiver, Tekonsha Sentinel brake controller, Westin nerf bars, Clarion sound system
1995 Standard Cab, 4x4, long bed, automatic: Firestone Ride-Rite air springs, torque converter lock-up switch, 4" cat-back exhaust, Reese 20K 5th wheel hitch, Reese gooseneck hitch, Hayes Micro Control trailer brake controller, 100 gallon bed-mounted fuel tank with 12 volt electric pump & fill nozzle, Swiss Cap fiberglass cap

 

[Joe G.]

Bow Hunter,

You should check to see how much your speedometer is off. I increased the size of my tires and it's closer than it was before. It was reading too fast with factory tires and it's now reading a little slow but a lot closer to the correct speed.

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Joe George
Eureka, CA

'95 2500 CC auto 4X4,3. 54,Combo EGT/boost guage,custom switch panel,PacBrake,TST #5,Automatic motorhome steps on both sides,Foldacover hard bed cover,Cummins chrome kit,Black steel grill guard,Front hitch receiver