Huge Favor To Ask - FORScan - Speedometer Calibration

[Glocker]

I just arrived in New Jersey after 13 hrs on the road. Tomorrow I'm getting new tires 275/70R17 put on my truck. I brought my laptop and cable for FORScan just in case. Can anybody give me a simple step by step on how to adjust my tire size in FORScan? I'm really new to it and won't have time to play with it before I drive back to GA. Thank you!!!

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[Adventure Ranger]

I just arrived in New Jersey after 13 hrs on the road. Tomorrow I'm getting new tires 275/70R17 put on my truck. I brought my laptop and cable for FORScan just in case. Can anybody give me a simple step by step on how to adjust my tire size in FORScan? I'm really new to it and won't have time to play with it before I drive back to GA. Thank you!!!

I believe it is in the Instrument Cluster, look for tire size. it is measured in mm. adjust accordingly. Tire manufacturer will have tire circumference listed in mm, change the figure to that number and you'll be very close. I fine tuned mine by setting up 2 separate GPS units on the dash to make sure I had a accurate speed reading, then fine tuned the size so that my truck is 100%. Hooked up laptop in cab and went for a Sunday drive checking the speed and modifying as req'd.

 

[Glocker]

I believe it is in the Instrument Cluster, look for tire size. it is measured in mm. adjust accordingly. Tire manufacturer will have tire circumference listed in mm, change the figure to that number and you'll be very close. I fine tuned mine by setting up 2 separate GPS units on the dash to make sure I had a accurate speed reading, then fine tuned the size so that my truck is 100%. Hooked up laptop in cab and went for a Sunday drive checking the speed and modifying as req'd.

Thanks! I hope it's as simple as you made it sound! LOL

 

[Glocker]

I believe it is in the Instrument Cluster, look for tire size. it is measured in mm. adjust accordingly. Tire manufacturer will have tire circumference listed in mm, change the figure to that number and you'll be very close. I fine tuned mine by setting up 2 separate GPS units on the dash to make sure I had a accurate speed reading, then fine tuned the size so that my truck is 100%. Hooked up laptop in cab and went for a Sunday drive checking the speed and modifying as req'd.

I think I'm going to leave it alone for now until I can look more into how it is adjusted. I'm 2mph off.

 

[RangerPNW]

Only responding as i just finished going through all this today, but just adjusting the tire circumference in Forscan (under the body control module) didn't provide me with an accurate speedometer reading when i went from my 265/65/17 factory Hankooks to 265/70/17 Goodyear Duratracs. Using the revised circumference of the Duratracs in the computer, i found that my speedo was about 4% off, so 60mph on the speedo was closer to like 57. Ended up using a gps app on my phone to determine the difference, and then revised the circumference measurement in the computer accordingly. So the basic math was (current tire circumference times actual speed according to gps) divided by the speed reading on the speedometer. So instead of the 2529mm circumference on the Duratracs (based on their listed diameter of 31.7"), I ended up using 2437mm. A quick drive down the highway confirmed that this was a hell of a lot closer and good enough for my purposes.

Hope this can be of some help.

 

[Fawnbuster]

Dumb question here, but do you have to pay for the license to be able to use the software (like an activation code etc) or are there a few things you can do minus the code cost? I need to adjust my speedometer for the most part. Already have a login and the cables but that's as far as I've gotten. Used GPS to figure out that with my new tires mine reads 5mph slow.

 

[RangerPNW]

Dumb question here, but do you have to pay for the license to be able to use the software (like an activation code etc) or are there a few things you can do minus the code cost? I need to adjust my speedometer for the most part. Already have a login and the cables but that's as far as I've gotten. Used GPS to figure out that with my new tires mine reads 5mph slow.

You'll need to get a free 2 month license for forscan. It takes a bit for the code to come through, so you'll want to get that going before you try adjusting anything. even if you have to pay, i recall the pricing being very reasonable, like 10 bucks for a year up to 30 bucks for a lifetime license.

 

[Fawnbuster]

Thanks! I did the yearly one.

 

[Big Blue]

Only responding as i just finished going through all this today, but just adjusting the tire circumference in Forscan (under the body control module) didn't provide me with an accurate speedometer reading when i went from my 265/65/17 factory Hankooks to 265/70/17 Goodyear Duratracs. Using the revised circumference of the Duratracs in the computer, i found that my speedo was about 4% off, so 60mph on the speedo was closer to like 57. Ended up using a gps app on my phone to determine the difference, and then revised the circumference measurement in the computer accordingly. So the basic math was (current tire circumference times actual speed according to gps) divided by the speed reading on the speedometer. So instead of the 2529mm circumference on the Duratracs (based on their listed diameter of 31.7"), I ended up using 2437mm. A quick drive down the highway confirmed that this was a hell of a lot closer and good enough for my purposes.

Hope this can be of some help.

Yea,the effective circumference of the tire will always be less than the measured or calculated circumference. This is because the tire flat spots due to the weight of the truck. Using the GPS method will take this into account and be more accurate.

 

[MinuteMan]

I believe it is in the Instrument Cluster, look for tire size. it is measured in mm. adjust accordingly. Tire manufacturer will have tire circumference listed in mm, change the figure to that number and you'll be very close. I fine tuned mine by setting up 2 separate GPS units on the dash to make sure I had a accurate speed reading, then fine tuned the size so that my truck is 100%. Hooked up laptop in cab and went for a Sunday drive checking the speed and modifying as req'd.

Would you mind expanding on this?

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