Hey I've got 33's and would like to be able to calculate my MPG, but don't I have to divide something by a percent since the tires size is altered? Could someone tell me how to figure my mpg now? I'm sure its gonna be horrible, I've about a third of a tank of gas and I've only gone 180 miles..

 

Was it ever regeared? What was the factory tire size?

http://www.4lo.com/4LoCalc.htm

http://www.grimmjeeper.com/gears.html

 

Find how big your tank is, fill it up, drive till empty and record your miles traveled. Divide your gallons into your total miles.
Simple math

 

He's trying to figure out how many miles he is traveling, because the odo is not accurate.

 

get on the interstate and when you pass a mile marker note your tripmeter down the .10 of a mile. once you figure out how far off it is (ex. 1.2 miles per actual mile driven) finish off your tank then multiply the 1.2 by the number on your trip.

 

1) Get a GPS from a friend

2) Look in manual to see how much your tank holds

3) Fill the tank

4) Set GPS trip to 0, go drive for a while

5) Fill'er up, and see how much it takes to fill

6) Using trip mileage, and how much gas you needed to fill your 15 gal tank (or whatever it is) calculate your mileage.

 

Correct your mileage be figuring the difference in the circumference of the tires. For example, if your truck came stock with 31" tires that gives a circumference of 97.34" (Pi x diameter). A 33" tire has a circumference of 103.62". Divide 103.62 by 97.34 and you get 1.06. This is your correction value. If you multiply your odometer reading by 1.06 you will get closer to your actual mileage. So if your odometer reads 250 miles on a tank, you really went closer to 265 miles (250 x 1.06 = 265). This is how I do mine.

 

So now that everyone has explained the math, let me explain why it doesn't matter...

The odometer is off from the factory. It is VERY possible that your speedo/odo is MORE accurate now than it was then.

The ONLY reason to do the correction for the diameter is to compare your mileage now to what you got then. Realize that you're just comparing numbers then, and that neither of them are truly accurate.

There are only 2 ways to truly know the distance/speed:
- Stopwatch between mile markers
- GPS (and there is plenty of reason to question these readings too)

 

Well I had some dumb metric tire size like 225/75/15 or some crap on it when I got it, either way I went from 28" tires to 33" tires..

 

you went up in tire size by almost 18%. multiply the miles your odo says by 1.18. thats how far you have actually travelled.

 

Is there a product out there that plugs up to your rig to calibrate this?

 

^Doubtful. I think our speedos are just mechanical, you'd have to change a gear or something.

 

What's considered a standard/stock tire for these trucks? I have seen them come stock with the smaller tires and also come from the lot with 31's.

Mine had BFG 31's on it when I bought it so I have no idea what it had stock.

But I doubt Toyota uses a diiferent speedo gear for say the 225's or the 31's, so which one is considered "stock"?

 

Toyota changed the diff gearing. Small tires, manual transmission, you likely have 4.10, 31's with the manual you have 4.56. For automatic, those numbers are 4.30 (I think) and 4.88 (for sure)

 

I know for a fact is has 4.10 ring an pinion, oh and is there any way I could use 4.88 toyota brand gears in my truck seeings as their cheep? Iwant some cheap 4.88's, I could live without them, cause I haven't noticed any power loss or difference in clutch feel so.. But I'd like to have correct gearing.

 

You would have to swap the whole 3rd member due to the offset pinion with the factory 4.88's.

http://home.4x4wire.com/erik/diffs/

 

Sounds kinda gay... Any way I could run an aussie locker and do that? I'll probably just get some other 4.88's..