Speedo/Odo Error with 31X10.5 Tires

[farmtruckman]

Has anyone calculated the Speedo/Odo error with installing 31x10.50 tires on their X? I just did on my 95 (and it looks great by the way) and was wondering if anyone has already checked out the error. I did it years ago and then, AAA used to do speedo checks for free. I remember it being about 10% off on the odo and the speedo being about 5MPH at 65. Any help appreciated.

 

[Silver X]

Try this:

http://www.paspeedo.com/calculator.htm

Should get you close to the actual speed.

 

[X6StringerX]

Another good site is:

http://www.1010tires.com/TireSizeCalculator.asp

 

[farmtruckman]

Speedo Gear Swap

Thanks, both of you guys. Both sites are awesome! Has anyone heard of swapping out the speedo gear drive to a different unit to get back close to original. Meanwhile, I better slow it down a little!

 

[Albino 94LTD]

I've been too lazy to swap out the gear. I just run a Garmin Etrex VistaC on the steering coloum. I'm consistantly 10% off, both speed and odometer.

 

[farmtruckman]

Albino 94LTD,

I am too cheap for the Garmin and as you know, the State Patrol loves to site around the curve from you on I90 where it changes from 70 to 60 to pick off people before you get to Sammamish coming west. Almost been caught there numerous times going to west side. Think I would get smarter as I get older but not the case. Meanwhile, I'll just keep it a margin below and tell myself that I am getting better mileage this way. FTM

 

[rwenzing]

You can change the gear to correct it on 97 and earlier Explorers. Here's a short explanation:

http://www.therangerstation.com/tech_library/Speedogear.html

The "tire revs per mile" value for 31x10.50R15 BFG A/Ts is 677.

 

[Albino 94LTD]

There, the Fall City Dip, and between Olallie Park and Edgwick RD.

I'm old enough to know better but not young enough to do it anyway. No need to hurry things anymore so 2-3mph above is fine for me.