Speedometer Calibration on JKs

After installing larger wheels and tires on my JK, I’d prefer to correct the speedometer for the error I now have due to tire size - from a 225/75/16 to a 255/75/17. After perusing You Tube and the internet, it appears that dealerships perform this update in the US, but not in Canada for JKs. Only for JLs, go figure. I haven’t found a garage that will do this in my area. So, that means doing it myself, which I was trying to avoid. Has anyone on here done this? Also, of the many devices out there that will do this, do some work better than others! A calibration tool runs around $300 in Canada, so if I buy one, I may as well get one that is easy to use and does the job with a minimum of hassle. Thanks.

 

Interested in this myself. With 37's, I know Im going 60 while my speedometer says 45.

 

Form what I’ve learned so far, a Superchips Flashcal 3571 is what Jeep guys use. I’m still trying to find a shop to do it though. The devices set themselves up for your specific VIN on start up, and so it’s a lot of money for a one time use. If I understand it correctly, if you reset your vehicle VIN back to factory default, it will let you use it on another vehicle. But it only works on one vehicle at a time.

 

Yeah, I hate to swallow that kind of money just for a single use benefit. I'd rather guess at speed than spend over $400. Now, 100-150 bucks I'd definitely go forward with it.

 

I use a GPS for the speed meter

 

You guys need to check out this website

http://jscan.net/jeep-wrangler-jk/

 

Sorry I was at work but this is the website

http://jscan.net/

 

I use this.

https://www.quadratec.com/products/superchips-flashcal-f5-programmer-7-18-wrangler-jk-3571

 

I think that’s what I’ll have to do, @JKBob 25 - how does that programmer work, ease of use, performance. The only thing I want to alter is tire size, and it seems to be the simplest device out there for JKs. I guess I could use it to turn off my TPMS, and solve my sensor problem without spending any money. I’ll have to think about that, though. Thanks!

 

Very easy to use just plug in to your OBD and every thing shows up on the hand held. It downloads all your vechiles info and you just follow the prompts. You can also clear codes with it.

You just have to play with it when it comes to adjusting your tranny shifting points, tire size. Not all tires measure what is on the side wall. Just watch your Rpms and go from there.

 

Do you enter your actual measured tire size or the spec size?

 

@Justanotherjeeper . No, it's a list on the screen from 22.5 to 42" tires in 1/4" increments. Set it to the tire manufacture spec. Test drive it. And then just go either way, up or down, to fine tune it. I'm running 35's. And I remember correctly. I have it set to 34.75. And I get 19+ on the highway and 17 around town. But I have a lite foot.

 

Ok, I decided to get a Superchips flashcal F5. I got my speedometer reset with it, however, it wasn’t as plug and play as I would have liked because the unit I bought from 4 WD Parts didn’t arrive with the preloaded software installed in it. So, it didn’t recognize my Jeep right away, frustrating. I phoned the tech help line of Superchips, and after waiting awhile finally got a guy who was super helpful. He diagnosed the problem from the serial # of my device, and fixed it on line. It worked!
I double checked my speedometer reading with a gps on my cell phone, and it’s now perfect. That’s a big reset too, going from a 29” tire to a 32.1”. I’m glad I put up with the hassle and got it all corrected.

 

I had a similar issue with mine awhile back. And I had used it several times prior. Turned out it there was an update that apparently went in my junk mail and I didn't see it. Same as you @Justanotherjeeper . Called them they sent me the update again. And it's been fine since.
Happy yours worked out for ya.