Im running level 3 custom tune on my Edge, the Edge's display is showing that the MPH on the screen is slower by 2-3 MPH than the speedo on the truck. I did set the value on tire size for 33's. Has anyone here had that problem? Any ideas? Which of the two would be the accurate reading?
Thanks

 

I've got the same thing, except even my Edge is 2 mph faster than what it really is so my speedometer is actually about 5 mph off. I'd go with what the Edge reads if you want the closest speed.

 

Same thing with me. Im not sure what to do. I was thinking about adjusting the tire size but it might screw up the performance.

 

My truck's speedo reads 2mph faster than the edge. The other day I went past one of those side of the road radars with the speed displayed. The edge was right, the ford...was wrong. I did do the edge tire size by the roll three times, measure and calculate method...seems to be dead on.

Bill

 

Thanks for the replys guys

Is your Edge slower or faster? and by how much? I just dont want this slight difference to affect my shifting or anyother performance values. Also makes me wonder how accurate the performance test 0-60 & 1/4 mile test are

 

the edge says about 62 when my spedo reads 65

 

Exactly, but my actual speed according to the police radar-trailors was 60 mph.

 

dang. I thought at least one of thoes was right but now its neither.

 

The variance between the needle and the edge, ScanGauge, etc. is in the way the needle is setting on the dial. The actual reading is the one from the CAN bus. In other words, if the needle was on perfectly, at 60 mph both would read the same.
They are both reading the exact same signal, from the same source.

I've swapped clusters in several of these and no two speedometer needles were on exactly the same. They only apparently try to put them to plus/minus three MPH. Which makes sense when you consider how hard it is to adjust the needle...?

Use the mile markers, roadside radar or a GPS (my favorite) to get your actual speed. My present cluster is off by about two miles an hour 60 at 58, while the ScanGauge says 57, or less than one mile per gallon. The last cluster was off the other way. The Can bus didn't change, of course.
Chris

 

Unrelated to an Edge but directly related to the Speedo difference -- I've ALWAYS noted a 2 or 3 MPH difference between my GPS and my speedo. Like has been mentioned, I've noted the same 2 or 3 difference with the roadside speed sensor displays... The truck reads 2 or 3 faster than the other instruments.

I suppose Ford intended the guage to be 'close' but not 'dead on'? Kind of a form of an idiot guage for the operator? *shrugs*

 

My speedo & GPS are within 1 MPH of ea other

 

I rode with a ford mechanic with the diagnostic tool plugged in and it was reading the same as the edge reads about 2 miles an hour slower than the speedo. His explanation was basically that, Ford built it into the speedo to read a couple of mph faster than you are actually going. I don't know if this is 100% true but it is what I was told.

 

I've heard that about speedometers being deliberately set to read a little high all my life.
Nope. That would be unlawful. And boy, would it cause some really great class action law suits.

I've tested every vehicle I've owned and lots of other peoples and it is really not true.

Speedometers are set to an average, and they are not a precise meter. They are mass produced, and to calibrate them even close would cost more in man hours that the IP costs to build.
And it wouldn’t help a bit.
Tires change over three percent in normal driving from heat.
So if they were dead on when you start out, they are off by 3 percent when you return.

Two miles off at 60 is about 3 percent... If they are reading 3 percent high on the freeway, they were probably exactly right a block from your house...


The digital ones are the most accurate, but even those are subject to tire size changes.

Setting a needle is like adjusting barrels on a shotgun. Easy to get close, almost impossible to get exact. You can adjust the needle with your fingers if you really really wanted to. I wouldn't recommend it...

So if you set them, where would you set them to? Warm? Cold? Halfway in-between?
I had a very precise digital in a 92 Caddy. I replaced the tires at 50k miles, and whoops, it was off by three percent... Seems Michelin allows about 3 percent on their different tire runs. That makes them pretty accurate compared to others.

Even if you trued the tires, calibrated the gauge to exactly on at a certain tire temperature, it wouldn't matter in three months.
Like any other gauge, it will drift. Not much, but enough to be off under some conditions.

I used to sell fairly precision instruments (torque wrenches, dial micrometers, every sort of engine monitoring gauge) and sorta precision things like tire pressure gauges. They all drift.

Anyone that works in a lab would laugh at the idea of any instrument being set 'perfectly' a month after it was calibrated.

This, by the way, is a common and often successful defense against close speeding tickets. Another reason they will almost never pop you for less than five over. And 99% of speeding tickets are for 15 or more over.

If it really bugs you, you can have a speedometer shop set it ‘perfectly’ for about 40-60 bucks. But read the paperwork when you sign. It says 2 percent error is normal even after calibration…
Chris
Whoops, forgot that you have to allow for a 2-3 percent change due to tire wear also.

 

Before I custom-tuned my edge to include the correct tire size the speedo was about 7+ mph higher than the Edge. After I corrected the tire size (to 2559 I think) then the speedo was only 2 mph off. However, my GPS is different too.

speedo 63
Edge 61
GPS 59 (1.5 - 2 mph slower that the Edge)

From reading the Edge manual I understand the speedo may be off but I would have though the Edge and my GPS would both be right on. In the past I've tested my GPS so i know it's right on.

 

You missunderstand. The Edge is only reporting what the truck says to the speedometer. Period. There is no 'tracking device' in the Edge. It just presents a digital readout of the same signal that the needle gets. That is all.
Your GPS, assuming it is a good one with a good signal, is about right.
The signal from your VSS is 61. The needle on the Speedo is off slightly because the needle is off on the pin slightly. It could be adjusted on the pin, but is not worth the cost/effort.
The speed of 59 is what the truck is actually doing.
The speed of 61 is what the truck THINKS it is doing.
You could adjust the VSS signal till the Edge exactly matches the GPS for maximum accuracy, but of course the needle will still be off 2 mph.
Chris