speedometer calibration because bigger wheels/tires?

CruizinKev · October 3rd, 2008, 11:17 AM

like topic says, are there any speedometer calibration issues when going any bigger tires/wheels?

when going with some 15" welds on the rear with 275/60-15 tires the speedometer will be going wrong and will display wrong speed.

how you guys fixed that?

is it true with the Xcal its possible to adjust that? ..also heard about some speedometer gears things but dunno much bout that..

-Kev (1998 mustang auto)

yojoe600 · October 3rd, 2008, 11:32 AM

im pretty sure a xcal can fix it

Patrick@LCR · October 16th, 2008, 02:43 PM

Your speedo will read about 10% lower than your current speed.

If you have an Xcal2, look to change your Tire Revs Per Mile.

If you had a V6, I believe it came stock with 205/65/15's (my 97 v6 did), and that calculates to 80.1 inches of total wheel circumference, and at 63360 inches/mile, gives you 791 revolutions per mile.

Your new tires 60 aspect ratio (changed from 65) gives you an 87.9" circumference, and that divided into 63360 gives you 720 revs per mile.

Set that, and you should be dead on from here on out.

October 3rd, 2008, 11:17 AM	#1
CruizinKev Regular 98 V6 Auto Join Date: Nov 2007 Location: GERMANY Posts: 81 iTrader: 0 reviews	speedometer calibration because bigger wheels/tires? like topic says, are there any speedometer calibration issues when going any bigger tires/wheels? when going with some 15" welds on the rear with 275/60-15 tires the speedometer will be going wrong and will display wrong speed. how you guys fixed that? is it true with the Xcal its possible to adjust that? ..also heard about some speedometer gears things but dunno much bout that.. -Kev (1998 mustang auto) __________________ => my 1998 Mustang.. (click)

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October 16th, 2008, 02:43 PM	#3
Patrick@LCR Regular 97 Mustang, 98 Cobra pretty darn fast Join Date: Oct 2008 Location: San Diego, CA Posts: 69 iTrader: 0 reviews	Your speedo will read about 10% lower than your current speed. If you have an Xcal2, look to change your Tire Revs Per Mile. If you had a V6, I believe it came stock with 205/65/15's (my 97 v6 did), and that calculates to 80.1 inches of total wheel circumference, and at 63360 inches/mile, gives you 791 revolutions per mile. Your new tires 60 aspect ratio (changed from 65) gives you an 87.9" circumference, and that divided into 63360 gives you 720 revs per mile. Set that, and you should be dead on from here on out.

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