switching tire sizes, what do i need to reprogram the speedometer?

I am switching from 255/55/17 (30" tire) to 275/65/18 (which is probably a 33" tire) if memory serves me correct.

I could just remember in the summer I have the big tires on and pay better attention to the speed, or use my gps to keep track of current speed, but I'd rather buy whatever I need to readjust the speeds manually.

I have seen several devices people have hooked up to their trucks, but I don't know what each one does. I am not looking to change anything about my truck's performance, I would be afraid of screwing something up with the engine and I am going to have this truck for atleast 10 years, just looking to adjust the speedometer.

Can anyone help me with if I need is something like an Edge Programmer or is there something less expensive I can buy to do this?

Thanks...:

I'd rather buy something than have the dealership change it for me because I am changing back to my stock tires in the winter, and changing back and forth, I might as well just do it myself!

 

I just did a cursory Google search for something like you are asking for, and, I don't really think it exists. You see, to change the Tire Size (TS) information in your PCM (to correct the speedometer) you ARE actually "reprogramming" the PCM. So, I would advise getting one of the less expensive programmers, with "canned tunes" that offer this feature.

Ones from SCT and DiabloSport seem to be a good choice to me. There may be others. DiabloMike is providing a lot of good support in this forum for DiabloSport products, so you may want to talk to him. I doubt he'll try to sell you anything you don't need.

- Jack

 

Thank you sir!

I would definitely suggest you look into the Predator...you can find them for real cheap these days (under $300) and not only will it allow you to easily change tire size, you can also choose to add one of the performance tunes for a nice pick up in performance and mileage while your at it.

The Predator also allows you to read and clear trouble codes, and will even datalog the truck should you ever want or need to do so.

Let me know if you have any questions.

Thanks
Mike

 

Hello OP.

If you just wanted a device for this purpose, and no tuning, have a look at this:

http://superchipsmicrotuners.com/ind...rchips+TirePaq

Model = 1846

$199 or less if you shop around.

For $100 - $200 more you can get a performance-enhancing programmer - canned or custom ( preferred ) - Diablo, SCT, Superchips, Edge, Gryphon ...

Just fyi, buddy.

Cheers & good luck sir!


MGD v5.0 - The Orginal.

 

Way to go, MGD! I might have known you'd find "exactly" what he was asking for!

But, as you point out, $200 is a lot to pay for something that corrects your speedometer and does nothing else. I'd certainly move to the next step for $100 more.

- Jack

 

275/65/18 is the stock 4x4 size on an 18inch rim. Its a 32 inch tire. To go 33 at the same width you would need 275/70/18.

www.4lo.com has a tire size calculator.

For a tuner, get your revs per mile for the tire. According to BFG, my tires weres 608 revs per mile, tuner had an option 610. Viola - spedo is more accurate than stock according to two independent gpses.

 

Drove it with the gps, speedo isn't off by more than 1-2 mph at 65mph, so it didn't change enough for me to feel its necessary to buy a tuner. Thanks for the help guys.

 

The truck speedo is nearly always 2 mph faster than actual speed at 60-65. Ford builds them that way.

 

Agreed. Mine was that way stock as well. Verified it time and time again.