Difference in Speed reading on iGO and real gauge

**yousef** · 18th April 2015, 01:48 PM

Dear Friends,

I notice that there is exactly 10 km/h between the reading of speed on iGO while driving and the real gauge in the car.

for example on iGO 90 km/h and the actual speed is 100 km/h

can anyone help to identify what is the problem???

**G-ulash** · 18th April 2015, 07:30 PM

Are you sure the real speed is 100, thus IGO is wrong?
Isn't it the other way around? I think it is, since speedometers in cars are legally (obliged by law) showing faster speeds than the real speed
Also tyre pressure is of influence, and the tyre size, and ...

**yousef** · 18th April 2015, 07:50 PM

Originally Posted by G-ulash

Are you sure the real speed is 100, thus IGO is wrong?
Isn't it the other way around? I think it is, since speedometers in cars are legally (obliged by law) showing faster speeds than the real speed
Also tyre pressure is of influence, and the tyre size, and ...

I guess there is something wrong with iGO settings or number of satellite involved for the car position and speed is not enough. actually we need some expert here to identify what is the problem!!!
about the speed yes I'm sure about the difference.

**Boki** · 18th April 2015, 09:42 PM

Well, trust me, very much chance is that car speedometer is wrong. It is old story.
You don't need experts, you need only proffesional equipement. Reporters from car magazines do tests all the time. I remember some of german big test where noone car showed no real speed! Some of theme made mistakes for more then 20km/h! Bigger speed. No one shows less.

**yousef** · 19th April 2015, 06:57 AM

Originally Posted by Boki_Srb

Well, trust me, very much chance is that car speedometer is wrong. It is old story.
You don't need experts, you need only proffesional equipement. Reporters from car magazines do tests all the time. I remember some of german big test where noone car showed no real speed! Some of theme made mistakes for more then 20km/h! Bigger speed. No one shows less.

Well, I will test the speedometer and I will return back to tell you what happend.

**yousef** · 20th April 2015, 04:26 PM

Originally Posted by Boki_Srb

Well, trust me, very much chance is that car speedometer is wrong. It is old story.
You don't need experts, you need only proffesional equipement. Reporters from car magazines do tests all the time. I remember some of german big test where noone car showed no real speed! Some of theme made mistakes for more then 20km/h! Bigger speed. No one shows less.

The problem from the car speedometer, you are right 100%.

**trebil** · 19th April 2015, 07:28 AM

Flat road at a constant speed the GPS is correct.

**Midnight Blues** · 24th April 2015, 04:54 PM

There are few things that is good to know:

Tolerance for car instruments is 10% (max), so at 100 km/h it is about 10 km/h.
This is not error only from instrument, tires can be new or old, pressure can be higher or lower, and so on..., which influence the result.

To avoid error in such way that someone is driving faster then allowed (when instrument is showing that speed), all instruments are set to show about +10% (max).

Result is that ALL car instruments are ALWAYS showing speed somewhere between actual speed and +10%

So when navigation is showing LOWER speed than car instrument, it is likely that actual speed is shown by navigation.

**G-ulash** · 24th April 2015, 05:50 PM

In short, see post #2

**k1w1_123** · 9th June 2015, 08:06 PM

A friend of mine used to work for Volkswagen a few years ago. He tells me at that time their design target was for the speedometer to read actual road speed +7%