Been reading all the tire/wheel threads. I've seen conflicting info and some good points.

BUT IS ANYONE RUNNING 3.31 gear and 20 inch wheels without the CEL?

I've got a set of factory 20's that needs tires and I'm really wanting to run them on my truck. But I don't want to shell out the big $$$ for rubber and then not be able to use them.

I understand that the tuck knows it has 3.31 and therefor can't have 20's so the tech can't program it think it does. I have the 275/70/18 right now and I know there isn't much difference in tire height to the 275/65/20 (less than an inch I think)

The speedo reads fast right now. 60 MPH is 56 on the gps and side of the roadway "your speed is" radar.

May look and see if I can make a friend that would let me use a set of factory 20's and try them out.

Any ideas are welcome Please post

 

The check engine light comes on when you try to program your new wheel size into the computer, problem being it was not a factory configuration. You can put them on your truck no problem, its just going to change the speedo readings accordingly. Which as you stated, will probably make it more accurate.

 

is their anyway the dealers can program in a different size without the engine light? I didn't even realize you could do that much your self on these trucks, thats good to know.

 

You can't do it yourself.(reprogram) The dealer needs to do it. However, if they try to set a wheel combination that was not available from the factory for your configuration it will throw a CEL. (ie 20" wheels with 3.31 axle)

Been there with this. I had the same tires the OP had. I put on 295/70/18 Nittos. The 275/70/18 is the largest 18" wheel setting available. Fortunately my speedo read about 3mph fast before I changed the tires and now reads exact without re-programming anything. (Although I did try to see if the dealer could do anything and as predicted they selected a 20" wheel and it threw a CEL.)

 

I have a 2011 FX4 that has 3:31 gears and the truck came with 17 inch wheels and 265/70/17 tires. I purchased a set of stock 20 inch wheels and 275/65/20 tires. I had the dealer set the speedo for a size 18 inch wheel and 295/70/18 inch tire.......The speedo is 2 clicks fast over 65 mpr but at low speeds it almost dead on.......This is reflected by my GPS.....good luck and keep us posted

 

Doesn't the programming just tell the computer the revs per mile? Or the inches diameter, not the actual width/aspect by rim size? In which case, you can just have them tell the computer the size without mentioning wheel diameter? Just askin.

 

Apparently they are listed like you would see ordering your truck.....275/70/18 etc. There is not a selection for just say 35" tires. This has been an issue from day 1. I have not seen anyone come up with a solution around it as of yet.

Although one person did actually find a way. He had them also change his axle 3.55 allowing them to select a 20" wheel. Not sure if that is a good idea or not.