Callibrating Speedometer for 33" Tires

[Snooze]

I think you can do this via re-programming the computer. Not sure though. I need to do this cause it is driving me nuts not knowing how fast I am driving with my new tires.

 

[Dallas Starr]

yes... it is done via computer... i have the same problem, but am going ot get this fixed when I buy the xcal2.... If WFOY stays as a supplier.

 

[Todd Z]

There are other devices as well that you cut into the VSS wire and it will recalibrate for any thing you want, larger or smaller....

I had to do this on my 98 v6 stang when i put the 4:11 gears in it because you could not re calibrate via the computer... I think the box was under $150 and took about 1 hour to install..

Todd Z



P.S I spoke to Wayne today, he said he will be posting tonight....

 

[Adam Cat]

Superlift sells a recalibrator that does it. I forget how much it is though. I have 33s and I just go with that my speedometer is about 5mph slower than I am actually going.

 

[Chet 02]

If the speedometer is off from changing wheel / tire sizes, doesn't that change the rate on the odometer too?

 

[Dallas Starr]

yup

 

[Terry Schultz]

Yes - do the calculations. The circumference (sp) of the new tire divided by the old. This is the ratio of the speed increase per speedometer.



Example: 1:1.1 ratio = 10 mph = True 11 MPH

40 mph = True 44 MPH



It is not a set number for higher mph at any speed !



Terry

 

[Chet 02]

Thats true. But in calculating gas milage it would have an effect due to the odometer being off, right?

 

[Terry Schultz]

Chet:

Mileage calculation is:

Take miles driven times ratio = true miles divided by the gallons added.



Terry

 

[Snooze]

Thank you for all the input. Really helps out seeing what others have to say and are doing. I think I like the option of re-programming the computer. I just wanted to know if there were any short cuts around it to save money.



When I was driving my old Explorer with 31 inch tired I got pulled over and the police officer stated I was going just shy of 80. I didn’t have my speedometer calibrated and I had the needle at 65! I was shocked. Of course the guy gave me a ticket, but he understood that tires made a difference and I had not known the difference. So he ticketed me for 10+ That is another reason why I am a little scared to drive around without the calibrated speedometer.



Once again thank you for your time.

 

[Chet 02]

True Terry....that;s my point. I don't have the true miles driven because my computer has not been recalibrated for the change in tire and wheel size, thereby making my odometer inaccurate.

 

[mookie]

Check this out:

 

[Sean M 2]

Excellent page Mookie, I just put 33's on my ST and had no idea that the speedo was over 13% off. 60mph=53mph without calibration. The difference only gets greater was speed increases as it is a percentage of total speed. I better be careful

 

[Hal S]

You can usually get pretty close by just reprograming the parameters. All dealers have the equipment and I suspect that if you found the right person at a Auto Zone type of store, they could access that area (progamable parameters) also.

 

[Snooze]

Hal. Great Idea. I didnt think about that. Im going to have to look around for that option. On Sunday night I was driving and was guessing that if I was driving 65 that my true speed was 75. So I was about right.



Mookie: That is a really good site. I didnt know something like that was around. Thanx