tripometer reading with bigger tires.

[sapogmxr]

I just put some 33's on my truck and my gas milage has suffered but it feels like im driving the same distance and the gas gauge is were it should be. Did putting bigger tires on my truck make my tripometer move slower? It looks like it. If thats the fact id be happy cause then i will not be loosing the more than 2 gallons of gas differnence from 31's. I didnt think it would be that much of a difference but it is. 25miles i lost!!

 

[03ExplorerSPT]

Yes the tires effects the trip odometer, the total milage odometer and the speedometer. Everything will read less with bigger tires.

 

[Opera House]

For this year you can still get gears

I believe the standard for the 4WD is 19 tooth. You can get replacements from 16 to 21. Each change in tooth is about 5%. Make sure you figure out your true speed before the blue lights do! Easy to change and about $7.50.

 

[Hokie]

By my calculations, going from 30" to 32" tires means that my trip will read 19 miles less per tank than actual distance driven (assuming 1 tank = 300 miles).

I can post the derivation if you want to see it

 

[Hokie]

Originally posted by sapogmxr
I didnt think it would be that much of a difference but it is. 25miles i lost!!

All things equal, you should "lose" approximately 18.2 miles per tank when going from 31's to 33's (36 when going from 29's to 33's). But 33's also weigh more, and are most likely more aggressive than the 31's so that explains the other 7 miles/tank lost. By lost I mean, if the speedo is left at stock calibration, your odo will read X amount of miles under the actual distance traveled.

If you could keep all things except for diameter equal (rolling resistance, weight, amount of gas used during acceleration, etc) and properly regeared your speedo, you would actually see a mileage increase on flat, constant highway driving. But alas, we don't live in a perfect world and those assumptions don't work...

The formula I am using comes down to a very simple...

(old distance traveled/tank)(old diameter/new diameter) = new distance traveled/tank

I went through and derived it the long way first >> finding new and old revolutions per mile based on the circumference of the tires, but since it is a linear relationship for all of the equations (C=Pi*D), you can just simplify it to the equation listed above.

 

[sapogmxr]

this is great news. so how do i find out what gear i need to put my speedo back in check along with my odometer? Is it just one gear for both?

 

[Hokie]

Originally posted by sapogmxr
this is great news. so how do i find out what gear i need to put my speedo back in check along with my odometer? Is it just one gear for both?

Yes, your odo is based off the speedo cable, so you will fix your now off speedometer and odometer. As for which gear to use, do a search. I think Robert posted on this topic. I know this has been discussed plenty. I can't regear b/c in '99 they went to an electronic speedo/odo reader so I will have to get my cpu reflashed.

 

[Alec]

Hokie, Superlift speedo corrector, www.truckperformance.com.

 

[Hokie]

Originally posted by Alec
Hokie, Superlift speedo corrector, www.truckperformance.com.

It only costs $90 at the dealership... Those superlift things are like $200

 

[huskyfan23]

Would switching from stockers to 31's change the odometer also? How do you fix that, like what gears to use?

 

[Hokie]

ANY time you change tire size (increase/decrease) from the stock size (what the speedo was calibrated for) you will alter the reading. How much, obvioulsy, is dependant on the ratio increased/decreased. Whether or not you want to bother with it, is up to you.

How do you fix that, like what gears to use?

Originally posted by Hokie
As for which gear to use, do a search. I think Robert posted on this topic. I know this has been discussed plenty.

 

[sapogmxr]

For 4x4's these are the gears. I searched and found my answer. Now i just have to go under my truck and look to see what gear i got.

teeth color code
16 wine codz-a
17 white c3dz-c
18 yellow codd-b
19 pink codz-b
20 black c1dz-a
21 red c402-a


The formulla is New Teeth= (Current teeth * Speedo Reading)/ Actual speed.

To find your actual speed you can go to www.4lo.com

 

[dgibson]

I got pulled over out here and the cop told me I was doing 81 in a 65. I went and had the x calibrated and when the speedo says 65, I'm actually doing 62. So my 35's didn't hurt that much.

 

[huskyfan23]

So the dealer will calibrate it for you? How do they tell how off it is?

 

[dgibson]

I don't know about the dealer, I went to a place that a buddy of mine knew about.