Big tires mess up speedometer?

[khoeysr]

I use radar detectors that can calculate and display my speed. They are always right on no matter what vehicle I am in UNTIL I put them in my Gladiator equipped with 37 inch tires. I notice a 5 mph difference between the radar detector and the truck speedo, with the truck always lower.

Anyone know of this?

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[CFLgladiator]

Have you recalibrated your speedometer since installing larger tires? Otherwise It'll read wrong.

 

[rr11]

Larger tires will make the speedometer read slow. You can have the dealer adjust it or you can use a mini taser to make the correction. I have the Rubicon wheels and tires which gives me a 2 MPH slow reading per my GPS.

 

[BlueScapegoat]

I use radar detectors that can calculate and display my speed. They are always right on no matter what vehicle I am in UNTIL I put them in my Gladiator equipped with 37 inch tires. I notice a 5 mph difference between the radar detector and the truck speedo, with the truck always lower.

Anyone know of this?

The bigger tires have a larger rolling circumference. For each rotation of the tire you're traveling further than with the stock sized tire.

 

[Rocksalt]

yep recalibrate either with tazer or jscan... make it right

 

[Freebooter]

YES.............recalibrate! My dealer did it for $100. I bought my wheels and tires from them also, would have been nice if they did it for free but....................

 

[Jeeperjamie]

Recalibrate as other have stated. Your MPG's on the computer will thank you for it.

 

[SargeDiesel]

Recalibrate as other have stated. Your MPG's on the computer will thank you for it.

I just upgraded to 37's also.. glad you mentioned MPG.. I have not calibrated with my TAZER yet ( just installed them) but I was getting sick on the way home looking at the mpg... ha ha would be nice to see some improvement, hopefully the calibration will help.

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