according to ....... blah, blah, blah..........my tyres are 9.26% bigger than standard and my speedo will be out by the same

Not at all true, as there is almost zero possibilty that your speedo is 100% accurate with stock, factory tyres. According to ADR 18/03, when your vehicle is travelling at an actual 100 km/h your speedo is permitted to show anything between 100 to 114km/h. To avoid liability issues (ie driver's getting speeding tickets when an inaccurate speedo makes them believe they are under the limit), car manufacturers will invariably design their speedos to show the vehicle travelling at higher than actual speed.

Not at all true, as there is almost zero possibilty that your speedo is 100% accurate with stock, factory tyres. According to ADR 18/03, when your vehicle is travelling at an actual 100 km/h your speedo is permitted to show anything between 100 to 114km/h. To avoid liability issues (ie driver's getting speeding tickets when an inaccurate speedo makes them believe they are under the limit), car manufacturers will invariably design their speedos to show the vehicle travelling at higher than actual speed.

Fitting larger tyres will sometimes bring the speedo closer to reading accurately, but accuracy should always be checked by other means than relying on just the speedo.

not sure where you plucked that much variation from, but i can assure you that is well above the prescribed acceptable limit, even by territory standards.

Lot's of legal mumbojumbo in here about ADR 18/03 http://www.comlaw.gov.au/Details/F2006L01392

not sure where you plucked that much variation from, but i can assure you that is well above the prescribed acceptable limit, even by territory standards.

http://en.wikipedia.org/wiki/Speedometer#Australia

after 1 July 1995 (or 1 January 1995 for forward control passenger vehicles and off-road passenger vehicles) must conform to the previous Australian design rule. This specifies that they need only display the speed to an accuracy of +/- 10% at speeds above 40 km/h, and there is no specified accuracy at all for speeds below 40 km/h. All vehicles manufactured in Australia or imported for supply to the Australian market must comply with the Australian Design Rules.
[8] The state and territory governments may set policies for the tolerance of speed over the posted speed limits that may be lower than the 10% in the earlier versions of the Australian Design Rules permitted, such as in Victoria.[9] This has caused some controversy since it would be possible for a driver to be unaware that he is speeding should his vehicle be fitted with an under-reading speedometer. [10]

The speedo CANNOT read less than the actual speed, but the upper limit is 10%+4km/h, so at 100km/h the speedo is permitted to read 100+10+4=114km/h.

Speedometers are manufactured to be accurate to within 15% which is a pretty big margin and will most likely show u to be traveling faster than u actually are

Speedometers are manufactured to be accurate to within 15% which is a pretty big margin and will most likely show u to be traveling faster than u actually are

There is no +/- tolerance. The speedo can't read less than actual speed in any circumstance, but can read 10%+4 km/h over.

So before Joel jumps in, where do you find the 15% figure? The ADR clearly says up to 10%+4km/h.

10%+4km @100km = 14% by stating 15% i was simply rounding off

Its not even 14%.... From what i can read as per 303zuke said... its 10%+ 4km/ph at any speed. Not just 100km/ph (which was the example)

So.... 14% and 10% + 4kms/ph are completly differnet at other speeds other then 100km/ph?

So you're still wrong?

welcome to the interwebs

At the end of the day try telling the police who have just pulled you over for doing 110 in a 100 zone that your speedo read 100 and is ADR compliant cause it's within the 14%..