King2010

I'm wanting to put a leveling kit on my truck with some 33 inch tires. My concern is that my tire shop said I need a turner to control transmission shift points and to get my speedometer to read correctly. I have also read on here a little bit about the larger tires throwing the nav system off but has anyone found a fix for this yet?

northlight labs

iTrader: (1)

...to correct speedometer and shift points.

Hypertech Speedometer Calibrator can be purchased to correct speedo by inputting diameter of new, larger tires.

This unit can also be purchased with performance tunes, too.

I used the calibrator to correct for the 34" LT275/65-20" Bridgestone Revo2 tries I put on to replace the stock 275/55-20 tires.

Northlight

King2010

Would a tuner be needed for going with only 33 inch tires? How much would my speedometer/odometer/nav system be off?

Bulldoggy Daddy

I'm running 33s and my speedo is dead on now per GPS. I tow and haven't seen a change in anything.

STingray1300

+1

I just put on LT275/70R18s (33.2" diameter) and my speedo is dead-on now according to *2* of those speed carts the police use around town.

Go figure...

blacklion

That's good to hear...I am getting ready swap the Wrangler SR-A for a set of LT275/70R18s and I have been looking to see how much the speedometer would be off.

WH-7

+2

I put on 285/70/17's which are exactly 33" and my speedo is dead on as well measured with gps. Shift's just like it did before, haven't noticed any issues. Nav unit hasn't changed either.

jumpseat82

I just put on 33" tires 275/60/20 and guy at tire shop said when I read 40 it's actually a tick above 41 i believe. Doing 80 is almost 2 mph off. Nothing for me to worry about until I get a tuner. I had the stock Pirelli's 275/55 before.

blacklion

I still have the stock 275/65R18s used Ulysse Speedometer app last night. It matched up with the speedometer on the truck exactly all the way up to 80. This is the only baseline I've done so I don't know how accurate it is...going to try to test with an actual GPS.

NastyFFX4

iTrader: (1)

Typical most modern Ford vehicles are roughly 2-3 mph slower than the speedometer registers.