Speedometer calibration and Tire size

[TymeKeeper]

I just put in a 21 tooth gear to replace the stock 19. Works great, I have 235/60's instead of the 235/75's.. the 21 tooth gear was red..

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Jim
'92 Eddie Bauer Explorer
Dual 2.25 exhaust, no Mufflers
Drilled AirBox
Bosch Platinum plugs
Low Temp Pro Thermostat
Cobra 148GTL W/K40 Mag
235/60's

 

[Kenneth Walsworth]

I recently purchased a 95 Eddie Bauer Explorer. The shop I bought it from put new tires on it before they sold it. They obviously used a smaller tire than what the previous owner had on because it reads 65 when im going 55. Luckily ford sells gears for the VSS (vehicle speed sensor). They are color coded for each model (RH/LH long or short) I had an 18 Tooth gear on mine. Now I have a 21 tooth gear on and the speedo is right on (w/in 1 mph). This is the calculation.

Current Teeth X Indicated Speed
New Teeth = -------------------------------
Actual Speed

You can also do the same for tire size.

Current Teeth X Current Diameter
New Teeth = --------------------------------
New Diameter

To figure out your diameter use this..

Diameter = Wheel Size + (2 X Sidewall)

Sidewall = Tire Width X Aspect Ratio X .0394

.0394 is conversion of millimeters to inches

255 70 R16 would yield
Tire Width = 255mm
Aspect Raio = 70% (.7)
Wheel Size = 16"
Sidewall = 7"

I know this is old hat for some of you pros out there, but it helped me out a lot.

-Ken
Overall Diameter = 30"

 

[Kenneth Walsworth]

Isnt there a way to also calibrate the speedo by adjusting the settings in the computer? I know that my buddy has a Corvette and he has a hypertech power programmer and he can adjust the gear ratio ect to adjust his speedo. Any smart guys know anything about this with late model explorers that dont have an actual speedo cable but rather a VSS instead?

 

[GJarrett]

Some Ford dealers can reprogram the VSS if they have a computer-savvy guy in their service dept. It cost me $105 to get it done. It's the ONLY way to recalibrate the newer models. They don't have a mechanical gear to change.

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Gerald
"Nerves of Steel; Brain of Chipmunk"
~~~~~~~~~
'99 Eddie Bauer 4x4 4.0L SOHC aka "The Jeepeater"
Mods listed in my Explorer Registry post 7/8/99
Dead Link Removed "What the heck is he doing out here in that thing?"

[This message has been edited by GJarrett (edited 04-06-2000).]