Engine/Transmission (1994 - 1998) 4.10 rear end gear

[Loren]

Near as I can tell I have changed tire sizes and the mileage doesn't change

i started out with 245 and went to 305 and the 305's slowed the engine down but the mileage was a little worse short trips with the larger tires. I know a guy who had 354 then went to 373 then to 410's, and mileage didn't change.

Just my 2 cents

Dennis

Dennis,



Lots of drivers change to a larger tire with the hope of increasing fuel mileage and find that their mileage has actually dropped. This is usually not entirely true.



If your odometer was correct before the tire swap and you don’t adjust the reading for the change in tire size, your mileage calculations will be incorrect.



If your original tires turned 630 revolutions per mile and your replacement tires turn 600 revolutions per mile, your truck will read only 95. 2 miles on the odometer when it has traveled an actual 100. 0 miles. If you burned five gallons of fuel to travel that distance, you will calculate fuel mileage of 20. 0 mpg with your original tires but only 19. 0 mpg with the new tires.



In this scenario, your actual fuel mileage hasn’t changed. You traveled the same distance and burned the same amount of fuel. The difference is the distance you measured.



Be sure to adjust your odometer readings before blaming tire size for a change in mileage. This is also true for a change in differential ratio (for trucks that do not measure mileage at the wheel).



Loren

 

[Dbonzi]

I was using a gps to track mileage in both cases.

I have 4. 10 and the truck came stock with 245 tires.

I got between 19 and 20 on the gps for mileage on trips staying at 55mph

when I would push it on the freeway at 70 it would drop to 15-16

I now have 4. 10 and 255 85 16 which are just over 33inches and mileage hasn't changed

other than around town. The only thing it can acdount it to is the tires are larger and it takes a little more torque to get them moving.

Sorry I should have mentioned the Gps.

I thought for sure I would improve my mileage putting larger tires on and having the engine turn slower but just not the case with my truck.

A diesel will only burn the amount of fuel it takes to do the work. RPMs don't seem to matter that much.

just my observations.

I could be all wet.

Dennis

 

[98rammer]

Dennis,

Be sure to adjust your odometer readings before blaming tire size for a change in mileage. This is also true for a change in differential ratio (for trucks that do not measure mileage at the wheel).



Loren

you also have to figure in the extra rotating mass with bigger tires (and possible extra air resistance, though probably not really a factor). i don't know how much more, seeing as a lot of bigger tires have a lower air pressure rating. i dunno if it would be worth mentioning