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-   -   MPG drop due to tire change (http://www.ramforumz.com/showthread.php?t=37296)

02ram47 12-11-2008 12:00 PM

MPG drop due to tire change
 
I have an 02 Ram 1500 SLT with 245 17inch tires. I put on my winter tires which are 265 17's and felt a drastic drow in my mileage. I didn't expect this much or a drop staying with 17 inch tires. Should the computer be adjusted or is a 2 to 4 mpg drop normal.

Marcelo 12-11-2008 09:53 PM

Take into account that the overhead console calculates MPG as an average fuelflow/distance rate. And that distance is measured upon standard diameter wheels. If you put larger wheels, "distance" won't be the same. So the quotient fuelflow/distance varies also... ;)

boostjunkie1 12-11-2008 10:16 PM

http://www.miata.net/garage/tirecalc.html

Go here and you will see the size difference. Take that difference in % and multiply that by how many miles you drive before filling up. This will be around 4% by what I can tell. Add what you get to your total mileage and that is the actual miles you have drove.

Example: You drive 250 miles before empty and then fill up at 19 gallons.

250 miles X 4% = 10 miles...... So that gives you 260 miles.

260 miles / 19 gallons = 13.68

Instead of: 250 miles / 19 gallons = 13.15

Little better. You also have to take into consideration the rolling resistance of the new tires + the weight difference + the fact that you have now numerically lowered your gear ratio. Around town bad ====== Interstate Good.

:smileup:

Oldy but goodie 01-12-2013 10:58 PM

Quote:

Originally Posted by boostjunkie1 (Post 45197)
http://www.miata.net/garage/tirecalc.html

Go here and you will see the size difference. Take that difference in % and multiply that by how many miles you drive before filling up. This will be around 4% by what I can tell. Add what you get to your total mileage and that is the actual miles you have drove.

Example: You drive 250 miles before empty and then fill up at 19 gallons.

250 miles X 4% = 10 miles...... So that gives you 260 miles.

260 miles / 19 gallons = 13.68

Instead of: 250 miles / 19 gallons = 13.15

Little better. You also have to take into consideration the rolling resistance of the new tires + the weight difference + the fact that you have now numerically lowered your gear ratio. Around town bad ====== Interstate Good.

:smileup:

another thing after they play with what they call winter fuel you will lose fuel ecomny even if you don't do anything different. The combination change your ging to see a change in your fuel milage.


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