Possibly an incorrectly calibrated speedometer

GPS should read between 3-7mph slower than the speedometer (the speedometer should always read fast)

OBD speed should also be pretty much spot on what the GPS is reading as well (when travelling on a straight road, at a constant speed)

If the OBD Speed is reading higher than the speedometer and GPS, then it’s possible that your ECU is setup wrong, or you have a wheel speed sensor issue – I’d get the dealer to take a look as it may be that the vehicle has a fault, or it’s subject to a known issue that the dealer should be able to fix for you if the vehicle is still in warranty

are you using tires with lower diameter than original?

what are the size of original tires and the the size of you’re using now?

Assuming that GPS speed reading is correct, on Torque settings you can adjust speed value given by ECU (using a multiplier) if you are running on tyres with out of specs diameter.

At the dealer you can ask if is it possible to adjust tacho readings accordling to tyre size.
But that is not possible for all cars.

you cannot modify ECU, but you can adjust the value shown by Torque

Under “Vehicle profile” options you can set OBD speed multiplier.
By default is set = 1, this means that if the speed given by the ECU is 50 mph Torque app will show 50 mph.

If you set the multiplier =1.1, the speed given by the ECU is 50 kph Torque app will show 55 kph

If you set the multiplier =0.9, the speed given by the ECU is 50 kph Torque app will show 45 kph

The speedometer bias is NOT a fixed value, its a percentage that is put there by the manufactuerer.

First reason, in some countries (mine for starters) a speedometer must never read less than the actual speed, while its allowed to read up to 10% more than the actual speed.

Second is the safety factor, while most ppl do risk factor calculations based on the size of fine theyre facing if they get caught speeding, they tend to speed less <10% because they mostly wont get fined for that, so they see it as “legally speeding”.

My car for instance, running standard size (225/45-17) wheels, would give me 105 kmh on the speedo when actually doing 100kmh (62mph).

Then comes to mind, the cars odometer, because that would make the service intervals shorter in relation to how far the car has truly travelled?

Well they thought about that and made it so only the instruments show the false speed, the ECU (in my car) showed +/- 0.5mkh compared to the gps speed (using torque).

So the ECU reads correct though…..however it became such a nuissance for me with the massive overread on the speedometer, that I ended up fitting tires that increased the circumference of the wheel by 4%, so now my speedo overreads by less than 1% which is fine.