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 speedometer calibration for tire size
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kelvin
Garage Guru

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Posted - Feb 26 2012 :  08:59:03  Show Profile  Send kelvin an AOL message  Reply with Quote
16" tires are no longer being made in a 245/45/16 size or even 265/45/16, however there are many still made in a 50 aspect ratio. If I bought a set of 265/50/16 is there a way to correct the speedometer to read faster? I know there is a sensor on the diff, mine is currently a 3.25lsd big case. What would happen if I took the sensor out of a 3.46 or 3.64? would it make the speedometer read faster or would I be able to correct the signal elsewhere. I appreciate the input.

cliffo
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Posted - Feb 29 2012 :  17:33:55  Show Profile  Reply with Quote
the sensor in the diff reads a signal from a toothed chopper wheel inside the diff, so changing the sensor wont alter the signal.
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kelvin
Garage Guru

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132 Posts

Posted - Mar 02 2012 :  05:53:45  Show Profile  Send kelvin an AOL message  Reply with Quote
Ok, thats good to know. I found some 245/50/16 tires that will read only a little slower. I have heard german cars read too fast to begin with, hopefully this is true.
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greg_mazur
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Posted - Mar 08 2012 :  04:43:05   View greg_mazur's Photo Gallery  Show Profile  Reply with Quote
Myself I would not be concerned, keep your eyes on the road/tach/temp gauge & the mirrors....and drive on.
But there are specialty firms that do speedo repair and adjustments.
I would bet there is a variable potential resistance screw on the cluster somewhere for factory setting. Problem would be setting up a bench situation to allow adjustment. Would be a pain to drive, pull cluster, adjust, drive again etc. Would be nice to know in case you get a speedo that is way off true reading. In your case....drive on.
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