according to the calculator on 1010tires.com the speedometer difference between the 255/75R17 (32") my Jeep is programmed for, and the 35x12.50R18s spinning under it is 8.475% too slow

It claims that at 60 mph actual my speedometer says 55.3mph.

 

My damn head is hurtin after readin this thread.

 

just wanted to make sure that i got this
bigger tires and same gears means spedo will read slower than you are going

bigger tires,say 35s and taller gears like 5:13s,depending on the size of the tires that you get will make the spedo read a little bit faster than you are going

so when you upgrade both tires and gears the same time you should be close to the original speed on your spedo,give or take a little


my head hurts,o well

 

unlike the tj where the speed sensor/speedo gear was in the transfer case, the JK has sensors at the wheels. This means that the tire size alone changes the speedometer reading. Where the TJ changed from tires and or gears. Larger tires on the JK no matter the gear ratio means speeds will read slower than actual.

 

Quadratec sells new speedometer gears look under speedo gears they have a chart in the catalog but i cant find it on their website. I am going to be in the same boat going to 40's soon


thanks
Mike

 

Yeah but NOT for a JK!
BTW I use to live in Cranford.