if i have 32 inch tall whells and I am getting 11.5 mpg with my truck, what is that equal to if i had stock tires?

So i need to know stock tire height and a formula for finding my current tire size, and if your really good at math.... i beg you to do the problem for me!

my truck is a 88 302 aod bronco

 

I tried to link another websites tire calculator, but then it deleted my entire post. Now I have to do it all over again. Does anyone know what is up with that? I have done it a million times before. Do a web search for the diesel garage. On the left hand side they have a tire calculator. It does several things.

I'm not sure what exactly you are asking. A stock 235 75 15 tire is about 29 inches tall. A 32 11.50 15 is about 31 inches tall. If you have 32 inch tires with 3.55 gears the characteristics should be like the stock tires with 3.08 gears. If you want the behavior of 3.55 gears with stock tires, you will need 4.10 gears with the 32s. I have 32 inch tires with 3.55 LS. My truck is 5.0 AODE. I get around 15 mpg overall. So its probably about 12 in town and 17 on the highway. If you truck has 3.08 gears then I suppose mileage could be bad. Almost all of these trucks 4.9 5.0 5.8 auto or manual get about 15 mpg. Thats combined city and highway driving. I have had 3 of them and they are all about the same. If you are really getting that bad and have at least 3.55 gears, I would do a tune up. Also, an upgraded performance exhaust could help along with a K&N and upgraded ignition coil. The Bronco is a little heavier so that my be why it doesn't get as good.

 

if you use 29 for stock height, and 32 for current height. Your speedometer and odometer are off about 10%. 32/29=1.10 1.10x 11.5= 12.6 MPG actual

 

I see what you were trying to figure out. Aren't 32 inch tires really only about 31 inches tall though? So it would be 1.06 times 11.5. Thats 12.29. I guess its about the same thing. I would think your truck would get better than 12.3 mpg. It should get at least 14 mpg I would think. What gears are in the rear end?

 

something else, am i really going 100 miles when my odometer says i have gone 100? so maybe that may change the equation? no idea about the gears, stock.

 

wait. so if i have 31 inch tires my speedo is off?

 

When you have gone 100 miles you have really gone about 110 miles. For the other question, with 31 inch tires your speedo is off by a few miles per hour at highway speed. In town it is probably only 1 or 2 mph. Any tire other than stock will throw off the speedometer. A smaller tire will make the speedo read faster than you are going and a larger tire will make it read slower than you are going. This is height, it has nothing to do with width.

 

Thanks. So i probably dont need to spend the time or $ on recalibrating my speedo if its only off by 1 or 2pmh, i dont drive he highways in my truck. Thanks again.