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2002 rodeo wheel/tire change now poor mpg

2K views 6 replies 4 participants last post by  fstr 
#1 ·
Hello. I'm going back to the experts on this one. I needed new tires. I was happy with the last set. They were 245/70R/16. I had two bent stock steel rims on the right side from froading. I couldn't find any at the dismantlers. I did find some identical sized aluminum rims however. I bought them figuring not as strong but got to get this done. When I went to get tires they were out of the original size but had 245/75R/16. I bought them. Same tire. Same rim size. Slightly larger diameter. 70 aspect ratio to 75. They don't rub. Cool. Except now I get 14-15 MPG instead of 17-18. I drive 25-30K miles a year. Unacceptable. What did I do wrong? I realize the Speedo is off by a couple miles but 3 MPG? Could it be the additional weight of the tire? Could the aluminum rims be heavier than the steel ones? I didn't weigh the rims before the tires were mounted but they were aluminum after all. Thanks in advance.
 
#2 ·
That does not make sense. You put tires on that are 1 inch larger diameter and your getting less gas mileage. Actually there should be a slight difference, but should be in the other direction.
 
#3 ·
Is your 02 a 4 cylinder? is it a 5 speed or auto? You shouldn't have that big an impact, and yes normally getting a larger tire will improve mileage at the expense of power.

I've had issues going with bigger tires that were 10-ply and felt like the truck lugged around and I had to change the way I drove it to keep my mileage. I was constantly giving more gas to get moving. So I was losing my mileage with stopping and starting. I ended up regearing and it solved my issue.
 
#5 ·
Make sure your wheel bearings are in good shape and brakes aren't dragging or something. You should be fine with your drivetrain as is, I only got in trouble with lack of power when I went bigger than 265/75r16s.
 
#6 ·
I'll repack the wheel bearings this weekend. I can weigh one of the new tire/wheel combinations versus the spare (which still has the stock rim & tire) when I have them off the truck. I went through the brakes a couple months back but I will check them. Thanks. I'll post back on Monday.
 
#7 ·
I have a '99 trooper that I put 10 ply tires on last summer. I have replaced the fuel filter, thermostat, throttle positioning sensor, O2 sensors and still am only getting 13 to 15 mpg. The tires are the only thing I can figure is dragging it down.
My other '99 trooper was getting 18 to 19 mpg before taking it off the road to have engine rebuilt.
Any thoughts?
 
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