The manufacturer stated diameter is often incorrect when calibrating the speedometer. They can only account for the diameter as produced but can't account for the diameter at different air pressure and different vehicle weight. There is a thread that attempted to log the different OEM tire diameters and the actual diameter used to calibrate the speedometer. In that thread was a post by @HoosierDaddy that mentioned to take the manufacturer diameter and multiply by .967 for an adjusted diameter to use for the speedo.
I have a base and switched to Badlands wheels and tires. When my speedo is 30 it's actually 32 according to the speed cameras. After 30 mph, it's 4 mph over. Haven't checked over 60. I adjust my speed to suit, hopefully.
My speedo was off by 2.5% from the factory. I am sure they all are. In fact, only my Audi S4 had an completely accurate speedo. My wife's prior car (the Bronco is hers) was a Porsche Macan, and that was high by something like 5%.
typically, the factory reads a little bit high to prevent folks complaining about getting tickets. some jurisdictions practice zero tolerance over the posted speed limit.
My MKVII GTI is spot on, my Mazdas always ran about 5% fast. I’m guessing this bronco showed faster on the Speedo than actual speed also. On the stock tires.
It's at any speed higher than 25. I may have to try that.
Awesome will do that, thank you!
You didn't lose MPG, it's just using corrected data for calculation. However much you adjust your speedometer is how much of an MPG change you'll see.
