Got a tomtom last week, but which speed do i believe? I got standard steels on me polo, but my dash speedo is about 10% out all the time - 30 on dash is 27 on tomtom 80 on dash is 74/75 on tomtom...

Olly,

tom tom is more correct.. speedo's can be out from the factory

Speedo's generally read 10% above the actual speed you are going.

Its the same situation in my golf.

TomTom all the way

Got a tomtom last week, but which speed do i believe? I got standard steels on me polo, but my dash speedo is about 10% out all the time - 30 on dash is 27 on tomtom 80 on dash is 74/75 on tomtom...

Olly,

tom tom is totally accurate. i use sat navs all the time, and I've used them in 3 different cars and all the speedos were out. the car speedo should always tell you your going slightly faster than you are. on vauxhalls the speedos are all to fuck though, and this is how you get astra GSI drivers saying they have "done the clock" where actually the clock is wrong.

Construction and use guidelines for manufacturing cars allow car speedos to be out by around 10%.