Speedometer Calibration?

How does one go about doing this to our cars when changing the diameter of the tires?
 

Alin

Diehard Car Enthusiast!
Subbed out of curiosity about the answer.
 
Yea I want an official answer, I've searched around but no one seems to care much for the speedometer being off.
While "places" that are unnamed take like an hour or so to calibrate the speed? Shrugs* Can the Subaru dealer program it?

I want to go from
245/40/18x8.5 (stock)
to
255/40/18x9.5

I was going to do 265/40/18x9.5 but they said it would rub on stock suspension(fenders would need to be rolled) and also it would rub on 255/40/18x9.5 unfortunately.

From 40 to 35 the speedometer would read about 3mph faster than normal and I would believe the odo would also be going up on a faster rate as well which nobody should want! lol
 

HolyCrapItsFast

Drinks beer!
I looked in the tuning software suites I have and there is nothing for calibrating the VSS.

Sounds like another Arduino project to me! :lol:

My idea is to intercept the VSS signal and alter it by simply applying a multiplier and then output the modified signal. Very simple to do.
 
Interesting lols
Does ours have the VSS or was that eliminated and is now controlled by the ABS computer/speed sensor there? [MENTION=9]HolyCrapItsFast[/MENTION]
 
It still has a VSS. Actually it now has three... a primary, secondary and front wheel sensor.

Now that sounds complicated! lol. Then something like this I'm guessing wouldn't work? can skip to 6:10
 
Hah okies, someone needs to make a import version lol. I can't believe there's no actual thing to fix this, you would think false odo would be a bad thing.
 
Welp I give up lol, after hunting around the official wheel/tire fitment threads people are saying 255/40/18x9.5 will clear stock suspension.

245/40 to 255/40 has a smaller diameter difference from stock(almost not noticeable) than 255/35 which is noticeable on the speedometer.
One would think this would be easier to correct as people change tires and wheels all the time in this day in age.
 
Top