MPG question

[907DAVE]

Do you guys recalibrate your speedometer when using taller tires?

Reason I as is because with the larger tires you are actually traveling farther than what your speedometer shows, thus lowering your calculated fuel mileage.


Its is surprising how far off they can be. I had changed from the stock 31'' to 33'' , and during a fairly recent road trip(7,800k) I kept a very close eye on actual miles traveled via mile markers, and my trip counter. Now keep in mind I would watch this every day of the trip, and kept a log on it, and it would consistently show that every 10 miles my trip would only count 9 miles. Doesn't sound like much but over a tank of fuel, roughly 350 miles(on the trip), I actually traveled 385. Figure the mileage on 26 gallons, which would show 13.5 mpg, when actually it was closer to 15mpg.


Just an idea........

[Longshot270]

Well they probably aren't that far apart in weight when you consider I have the brush guard, stereo/radio equipment and a fully loaded tool box and your truck is probably naked. Trucks are heavy, I just used it to my advantage. Instead of powering up hills and around corners I would just let it coast and let the weight pull it through (until it got below 5 mph of my regular speed). Like I said, there was a lot of fancy pedal work involved. I need to see if I can get it weighed because I've just been going on estimates. I'm guessing 52-5300# for my truck (4800# curb + 150# grill guard + 100# stereo/radio equip + 200plus# tool box...that sucker is heavy when fully loaded like it is) and I've seen numbers for your truck that range from 5200 for 2wd to 5600 for 4wd. But the road I took has a magical effect on mileage.

And 907dave makes a good point. Until you have your tire size dialed in, your mileage is going to be off. It will be better if the number is smaller and worse if the number is larger. If you dont have a GPS or some decently spaced road markers just go to a parking lot with a marker. Mark the tire and the street, roll one full turn and get a tape measure to measure. The measurement will probably be really close if you drove for more than 5 miles to warm the tires up. It would be funny if driving to a parking lot could increase your mileage.