Speed vs tires

[gazz]

HI you all
I was driving today and I was using GPS and it did show almost 8 km less speed than the meater in the car
I have 255/70 16" tires on
What is the problem ?

 

[Boggert]

HI you all
I was driving today and I was using GPS and it did show almost 8 km less speed than the meater in the car
I have 255/70 16" tires on
What is the problem ?

Mine is the same, but shows 8mph more. 8O

 

[(RIP) PLANK]

ther have been threadson this before with my tomtom it allways seems that the vehicle speedo (in several different vehicles) reads a couple of MPH faster than the tomtom, though the difference does vary with vehicle speed.

the concensus seems to be to reply on your GPS

 

[JonathanM]

HI you all
I was driving today and I was using GPS and it did show almost 8 km less speed than the meater in the car
I have 255/70 16" tires on
What is the problem ?

GPS speed will nearly always be less than speedo displayed speed, yours isn't too bad actually, when I drive at an indicated 110km/h, my GPS speed is 98km/h. Manufacturers usually have an indicated speed higher than the real speed, as legislation permits a speedo to over read but not to under read.

You say you have 255/70 R16's, thats an unusual size (standard is 235/70 R16) and abigger tyre will also effect speedo reading.

 

[dinky]

Mines the same x2 as ive got 235 75 15 atr and a set of 255 75 15 mt tyres get different readings at 40 mph on speedo on local speed camera display.

 

[gazz]

The label on the drivers door say it is 235 x 70 16R.
But I am confused here then the meater is all wrong
I have to ask the police to radar me :lol:
I thougt the GPS was on spot
I was driving in Germany some months ago and the GPS on the rent a car did read 206 km and the meater in the Passat the same

 

[(RIP) PLANK]

I think it is accepted that the police radar is the worst and most inacurate measure of speed! it will allways show in their favour :wink:

maybe as i said there is a speed at which the car speedo is accurate and at certain speeds less accurate, there is of course benefits to the speedo in the car reading faster than you are acctualy going!

it makes the service intervals closer, and reduces wear to mileage ratio!

saves litigation in speeding cases

and effects fuel economy and acceleration times etc.

 

[gazz]

Are you all driving on 235X70 R16 ?
That is the correct tire isen´t it ?