Hello all.
Now that I have my Bronco running smoothly I was looking into a new set of tires for her. It came with 205/75-15's it now has 215/70-15's. I was looking into a set of 235/75-15's. How much will this affect my gas mileage? I'm hopeing for some feedback from people who have run or are presently running this size tire. Not really intrested in going bigger or lifting the truck because this is gonna be my "gas-sipper" commuter truck.

 

It will not make much of a difference at all, if you could find a way to measure it because your speedometer will read slower.

It might seem like it effects your MPG, because the speedo is turning slower for every mile traveled, it really doesn't for that small of a tire increase with that computer system in the truck.

 

When im calculation MPG i dont know how many miles to add to my odometer,can you give me an equation or basic idea of how many miles to add for 31 10X50 r15 tires. Say for every 10 miles add 2 or something similar.

 

Sometimes going bigger might hinder your gas mileage. It did on my f-150 when I went from a 245 to a 285. Seems the truck has to work harder to turn the bigger tires. Also acceleration might suffer a little. Just a thought.

 

Not sure exactly what you are asking, but, you can figure out the close/true speed of your speedometer here.

http://www.4lo.com/

If you want to figure out your MPG in an accurate way, then put a GPS in your vehicle. I have been using a Garmin GPS-72 for my vehicles stuck on thr dashboard.

Once I know 45 mph = 55 mph - I write it on a sticker and stick it on the dash You can add a reprogrammable speedo from Dakota Digital

http://www.dakotadigital.com

that will pretty much solve all the problems of larger tires.

 

Thanks for the info rebocardo. Hopefully my speedo wont be off too much with shuch a small increase in height. Standing side by side the 235/70-15's and the 205/75-15's have about 3/8" diffrence in height. so the 235/75-15's should be a bit taller, hopefully keep it within half to three quarters of an inch overall diffrence.

 

I got up to (by dumb calculations -- I'm guessing my speedometer was recalibrated with a new gear on the transmission end of the cable... if you need info for that, let me know...) 23 mpg with 235/75R-15s on my '87 with the stock 3.45 gears (at least I haven't verified if the tags are correct as far as what gears are installed). These little trucks don't have a whole lot of neck-jerking power anyhow... but I didn't notice that big of a drag on mine as far as acceleration. Just beware that larger tires do affect braking and brake wear.