tak4ff

Has anyone changed stock 275/65/18 to 285/75/18 without being "close" or "off" on the speedo? In other words, what did you do to get the exact results? Are you satisfied with the change? And what are your biggest pro's and con's to making this change. I understand there are a ton of posts on this issue, but ZERO info from Simone who actually made this change on a 3.55 and did it correctly to yield true results. Thanks.

05CrimsonTide

I did 295/70/18 which is pretty close to your tire in question and according to GPS and the police radars on the highway, my speedometer is accurate within 1 mph. That's on 3:55 gears and stock wheels. Ecoboost by the way.

kevin7898

The stock speedo setting reads faster than what your actually going. I believe a taller tire brings that close and you might get it accurate. Its also late and i might be over/under thinking it haha

DirtDawg

Not true on my truck as verified by two separate Garmin GPS units. If off at all, maybe less than .5mph at slower speeds and dead-on higher up. So being **** as I tend to be, I ordered same size LT275/65R18 Toyo Open Country A/T2 which will be installed tomorrow. BTW, I really wanted to go to prox 33" diameter but not at expense of losing current speedo accuracy. As they say, "your mileage may vary"...

klumb15

My speedo was fast from the factory. I have 34.5" tires and need to select 33.25 in my programmer to make my speedo accurate at highway speeds.

harrison14allen

I have 285s on 18s. My speedo was off by 1 mph at 70 so I didn't worry about it.
2011 FX4 ecoboost with 3.73 gears

Bonesoftitanium

Id be more worried about the odometer being off more than the speedometer. With my 33" duratracs my speedo was dead on and odometer about 5-10% off before a programmer and even then my speedo is 3mph off to get the odometer dead nuts.

Jbar1972

Is a front end lift required to fit 285s without rubbing??

harrison14allen

Mine did not rub at all. I ended up added a leveling kit later just for the heck of it