figuring out MPG..

[Artemis Entreri]

With oversized tires?

Is there a mathamatical way to figure out how many miles im driving based on what the odometer says, and taking into consideration my 33 inch tires?

Trying to get a MPG without actually altering the board that tells me the right mileae based on tire rotations, will do that once I get her lifted and with 35s on.

Thanks
-Steve-

 

[4X4HIGH]

Just find a mile marker on the freeway and then pay attention to what your odometer says compared to a measured mile (mile marker). Now you'll now how far off the odometer is and you can then calculate MPG

 

[Artemis Entreri]

Would that work with a gps also? I assue they would be more accurate? Maybe not though..

 

[4X4HIGH]

Yes, a GPS would work as well. All you need to know is the difference between your odometer and an actual mile.

 

[sloth]

new tire diameter / old tire diameter = correction factor

odometer mileage * correction factor = corrected mileage

speedometer * correction factor = corrected speed

so, for example:

35/31 = 1.13
300 miles * 1.13 = 338.7 miles
65 MPH * 1.13 = 73.4 MPH

***Note: this is assuming you did not change your ring and pinion ratio and you should try to use the actual tire diameter, not what is stamped on the sidewall.

Hope that helps,
Mike

 

[Artemis Entreri]

Thanks, I will try that, just looking for a rough, but more accurate rating right now.

 

[Artemis Entreri]

Well even with 33inch tires, according to my GPS I am traveling exactly one mile and my odometer is flipping saying one mile, that was easy.

That means, if my math is correct, I got roughly..15.8mpg on the high way, eek, not what I was looking foward too, but I guess its not too bad.

 

[4X4HIGH]

If you're actually getting almost 16mpg you're doing real good. Is you truck stock? When mine was bone stock i was only getting 14mpg on the freeway. My truck came factory with 31's and 3.73's.

 

[Artemis Entreri]

Yea stock minus the 33x12.5x15 tires

 

[4X4HIGH]

Yea stock minus the 33x12.5x15 tires

What gears are in the truck?

 

[Artemis Entreri]

I still have to go and look in my glove compartment, which of all those numbers am I looking for to tell me my gear ratio?

 

[Artemis Entreri]

Are these the numbers im looking for??

 

[Thunder]

GU6 is your gear ratio. = 3.42

 

[Artemis Entreri]

Ok so how does 3.42 gear ratio like my tires, and are these smaller gear ratios better for the highway or no?

 

[AJMBLAZER]

They'd be better for highway use. You want something like a 4.10 ratio to run 33's with an OD transmission but 3.73's would work as well.

Could be worse, you could have 3.08's or 2.73's.



As far as the GPS goes the best way to do it is to switch it so that it shows your ground speed (or find one that has this function) and then while maintaining (say) 50mph indicated read the GPS's indicated ground speed.
My truck's speedo is showing about 45mph when I'm actually doing 55mph according to the GPS.

 

[454k30]

WOW!!! thats fantastic mileage! I'm getting half that with my rig!