medicchief

I know, I could have gone the Forscan route, or purchased a real tuner, but I didn't have the time or money.....That being said, I purchased the Rough Country Speedometer Calibrator, in order to reprogram the speedo on my 2013 F-150 FX4 Ecoboost. I went from stock (275-55-20) tires to 34.1 inch Michelin LTX A/T2's (275-65-20). Bottom line is the calibrator worked but the tire sizes on the calibrator are not close to being right. I can understand a quarter inch difference, but not a 1 inch difference. I started with their 34 inch tire setting and my speedo was off (over) by 4+ mph. I had to reprogram my truck 5 times, before I finally got it right (display is in .25 inch increments). I ended up using their 33 inch tire program. Basically my axle to ground height is greater by 1 inch (stock 32 inch compared to 34 inch) and that's what I would recommend a person using to recalibrate their speedo. For example, if you're going to a 4 inch taller tire, chose a 2 inch taller setting displayed on their calibrator (at least to start with). At 80 mph (the faster you're going, the more off a setting will be), the speedometer is now dead on. I couldn't find a review on the Rough Country speedometer calibrator anywhere , so I just thought I would share my experience.

DavidFX4

Now that you are recalibrated, do you want to sell it? I'm about to get bigger tires on my 2013 FX4 Ecoboost and I really want my speedo to be right, I often drive at 10 over the speed limit, so being off by 5 MPH is going to cost me a lot!

bkjohnson63

Typically once you use a tuner or calibrator it becomes linked to that specific VIN because it saves all of the stock data in the tuner until you return the vehicle back to the stock settings.

DavidFX4

I was afraid of that, I think I saw that on some of the other 'tuner' threads, so I just ordered my own brand new one. I guess for $150 I'll have it for next time I change tire size. I wish I was not terrified of blowing my engine with a tuner - it seems a waste to spend $150 to just fix the speedo when for $400 I could get a whole tuner. But I'm pretty sure I'd screw something up with a 'real tuner' - so I just have to think of this as 'speeding ticket prevention'. I may intentionally program this to read 'higher' than my actual speed, I bet I'd tailgate less

bkjohnson63

I know what you mean. I recently bought the Hypertech Speedometer Calibrator for my truck whenever I changed the tires on it. For what it does compared to a tuner, it definitely doesn't seem worth the price. Usually unless you are putting a bunch of aftermarket performance parts on your truck, the canned tunes that come with the tuners are decent.

DavidFX4

I received mine yesterday, the day after I got my tires. I did the chalk-line measurement and my 275/65R20 tires came back at 103.5 inches circumference, so only 32.95" - I set the size at 33" diameter. Programmed for that, and I think my speedo reads about 1 MPH high at highway speeds. I'm going to stick with that, so I can set my cruise 10 over the speed limit and still be a little safe

DavidFX4

So I was just looking at the paperwork that came with this, and it says to return the 'stock programming' before any service on the vehicle? Is this serious? I have only used this to correct tire size, do I need to screw with this thing every time I take the truck to the dealer? how about if I take it to a regular garage?

Thanks.

bkjohnson63

I don't think I would worry about reprogramming it to stock every time just for updating the tire size. I didn't when I took mine to the dealer for service. If you had it tuned that would be a different story.