Damn Dirty Ape

iTrader: (1)

Can a speedometer on a 14 fx4 be recalibrated? I just got some '23 wheels that have 275/60/20 on them and mine are 55's,. Just curious if so and what I'd need.

marshallr

Not enough difference to worry about. Theoretically you'll be off by about 3 mph at 90. Even less at slower speeds. Even from the factory about 3 mph is as close as they can make them anyway. That is because your tires get smaller as they wear, and your speedometer is not accurate all the time. As the tires wear and get smaller in diameter the speedometer changes. The 55's are about 1" taller when new, but after 40,000 miles they will be about the same height as the 60's were when new.

Paul-g

always a good thing is get your gps going and see what the speed it's saying on there verse what speedo is reading, just be sure set cruise at like 70mph and give it a bit so you gps is up to speed with no delay

Laminar

Forscan

KRUISR

With Forscan you should be able to get it within 1-2 mph. Let us know what you are seeing on your speedo and what a gps speedo says.

Spiky

I just speed up til I see flashing lights, then I slow down a little.

mikeru

Yes the speedometer can be re-calibrated on a '14. The 2014 Limited I bought used in early December came with oversized tires so the speedometer was off by more than 5 mph at 60 according to my GPS app on my phone. The Chevy dealership that sold the truck to me was able to re-calibrate the speedometer before I took delivery. In my case the truck threw a code (P0720) for the transmission within about 30 miles of that adjustment. I quickly learned that usually means it's time to replace the lead frame, but I reset the codes on the off chance that the speedo re-cal caused it. It's been four months now and the code hasn't come back.

KRUISR

In Forscan when you change the tire size and gear ratio values in the BCM (that's how you calibrate it) you need to do the PCM Relearn process for the new values in the BCM to be accepted by the PCM, otherwise it will throw codes.

jhanna

I'd get on the interstate, if you have one around, and drive exactly 10.00 miles, accorging to a gps app, or mile markers, then see what the odometer says.

more actuate than trying to use speedo.

KRUISR

My experience has been that the speedo and odometer are both out the same amount (as a percentage). Using GPS speedo is easier in that you don't need mile markers and can get a result at any speed and within a couple miles driving at a steady speed (so that GPS speedo can settle in). You could check before you swap to bigger tires to see how much it is out to start with in current state. Then going from 275/55/20s to the 275/60/20s you will add another 3% error over whatever you have now.

I swapped from stock 275/65/18s to 275/65/20s and my speedo was out 6%. So cruising at 100 km/hr (62mph) I was actually doing 106 km/hr (about 66 mph). After adjusting my tire size and gear ratio with Forscan in the BCM I am less than 1% off (I can't see a difference between speedo and GPS speedo at any given speed).