Ok I just got an edge evolution and I have 295/70/18 trail grapplers. When I input the correct tire size in mm, my speedo is still off by 3 to 4 mph off. I have tried a few different calculations but its still off. Does anybody have this tire size that has there speedo dead on? This is driving me nuts, what input in mm did you use? Thanks in advance.

 

im running 285/70/17 and i have mine set at 2450 and its about 2mph off

 

Mine is 1 MPH off...you can mess with it til its perfect.

 

X2, eventually i just decided that would be good enough.

 

What I don't understand is my speedometer is about 2-3 mph faster than both my Gryphon and GPS, which by the way the Gryphon and GPS match up perfectly. Weird... shouldn't the speedometer be slower than what I'm actually going since I got bigger tires?

Yesterday I returned it to stock, and my speedometer and GPS match perfectly. I don't get it...

 

I had the same problem with 305/70 r 17's. I just kept adjusting it in small increments until I was about two mph off. Speedo said 70 actually doing 68. I did this to try to keep from getting another speeding ticket. Ha Ha!

 

I have those same tires and size. I think I used the input of 2730mm the other day. It made the shift points work waaaay better. My truck was shifting out of Overdrive all the time before, and now it's back to normal. As for the speedo, the truck is 2-3 mph off, but I just end up using the Edge. I guess it doesn't really bother me that much now that the truck shifts right.

What input did you use?

 

It's fairly normal in our trucks for the speedometer gauge itself to not be accurate. The PCM is correct, just the gauge is wrong. If you are calibrated incorrectly for your tire size, the speedometer will get further and further off the faster you go. If it is a consistent amount off regardless of speed, then your gauge is just wrong.

My speedometer reads a consistent 3mph faster than what my PCM reports.

You can tweak the tire size to make the speedometer read correct at a certain speed, but it will still end up being slightly off when you're going faster/slower. It will also make your odometer read wrong since it uses the PCM speed, and in turn will effect gas mileage calculations.

The only other options are to either live with it or find a shop that can fix the problem.

Personally, I just live with it. I know it's off so just adjust my speed accordingly, and I'm perfectly happy with anyone else who drives my truck driving a little slower.

 

Well today, I tweaked it a bit as I read somewhere to use 2600mm as you have to consider the squish factor? I also had to "load previous settings" on the evo as it was reverting back to stock size everytime I wanted to change the size of the tire. At 2600MM the speedo was dead on with GPS but noticed a 1mph difference as I changed my speed below 30mph. Also the reason the factory speedo is usually 3mph off is due to the spring used in the needle which is mentioned in the evo guide. I can live with it now and really like the edge programmer. Thanks all...

 

Man with my truck.... with stock tires and all, the darn things was 4mph off. Not sure why. I had to back up from 2450 per say, to 2365mm and its right on. Just kept messing with it till i got it close to the gps. I with a cdl dont need no speedin tickets