Speedo Inaccurate

[AdamD]

I made a quick spreadsheet here: https://spreadsheets.google.com/ccc?...gE&pli=1#gid=0

If anyone with larger tyres wants to fill in some of the details then let me know. Otherwise hopefully you know what your offset %age is by now (just drive at 100kph with a reliable portable GPS unit on the FWY).

Just bear in mind that the error margin does vary from car to car, not just between models and tyre configurations. There's the ever-present tyre inflation issue (and pressures vary depending on if the tyre, road and air temps are warm or cold), tyre age (treadwear affects rolling diameter)... and that's before considering the possibility of an actual speedometer error.

Caveat emptor! And don't get booked guys!

[Corey_R]

Yeah - those are my feelings too AdamD. Best to just give the knowledge to the forum members on how to determine the inaccuracy % themselves, and then let them decide what to do with it. Providing a spreadsheet with a "model / wheel / tyre size" lookup seems to be just asking for trouble :/

[Ryan_R]

I agree and will remove the mentionings of that. Although for someone to come along and just assume what they read on the Internet is true in realation to something like that without checking a few things out for themselves is also asking for trouble

[Corey_R]

pfft!!!! assumption is the mother of invention!

No wait... something's wrong there

[Ryan_R]

Give me a few hours to work that one out

[MkVIGTI]

Here in VIC the law allows us 3% of leeway but I've seen signs on the freeway that says we are allowed a maximum of 7%. They must allow an additional 4% for margin of error in their radar guns

[Corey_R]

I think what VIC tells you is the "law" and what they do is different. All the news reports I've seen says that their fixed cameras give you a 2km/h leeway - not a 3%. Thus 113km/h in a 110km/h zone gets a ticket.

[Ryan_R]

Last time I watched ACA they said they no longer advertise what the leeway is since their last revision of the law, and fair enough, but best guesses were that NSW was 2% and VIC was 3%. (or was it 2kph and 3kph - I've confused myself now)

I've driven down EastLink at up to 110 (102) kph no problems (cruise control + downhill slope)

[Corey_R]

Yes, but whilst VICROADS and the RTA may not disclosure the leeway (that'll be changing in NSW if you believe Barry), when you start rounding up people who have been fined and look at their notices, that is when you can determine what the leeway is.

Hence the 3km over = booking in VIC (at least the last time I looked). And whilst NSW might play hardball when they tell people what the situation is, the reality seems to be much different, with people not being booked until they're about 6% over on fixed cameras and 10% over on mobile.

[Glennb]

according to "authorities" here in VIC, going 5km/h over the limit will automatically cause you to spear off the road and into a tree....