Thread: What it is the error tolerance in a LR speedometer?

Originally Posted by PhilipA

I do not know where this idea of +-10% accuracy of speedos cpomes from.

I am sure that ADRs specify that speedos must have an accuracy of 0 to +10%.

Only from about 2006 - prior top that the ADRs were +- 10% - that is where it came from - so in theory cars built prior to 2006 can have a designed discrepancy`+- 10%

Garry

Inaccurate Speedos in Court

The current ADR prohibits any under-reading:
"5.3. The speed indicated shall not be less than the true speed of the vehicle. At the test speeds specified in paragraph 5.2.5. above, there shall be the following relationship between the speed displayed (V1 ) and the true speed (V2).0 ≤ (V1 - V2) ≤ 0.1 V2 + 4 km/h." This formula means that the vehicle's actual (true) speed must not be greater than the displayed speed. (Displayed speed minus true speed must be greater than or equal to 0, and less than or equal to 4kmh plus 10% of true speed). This means that if your vehicle's actual speed is 100kmh, the displayed speed is permitted to be anywhere between 100kmh and 114kmh.
Prior to July 2006 the ADR allowed ±10%. This means that cars sold new prior to 1 July 2006 could comply with the ADR even if the speedo under-read by 10%. Despite this being theoretically possible, due to the testing procedures and the reasons stated below it is unlikely to occur in practice.

Originally Posted by Numpty's Missus

Just as well ours reads 5km over then

The S1 is interesting as it reads 10mph over IIRC
The 2a is pretty accurate

Converting mph to kph is an interesting task for me
In the S1 because of the 10mph error I multiple the kph speed limit by 8...and that gives me close to what mph the speedo should be reading.
In the 2a I multiple by 6
Of course this all only gives a rough guide

At least out on the open hwy there is no way I'd be doing over 100kph in the series LR's

So lets see - 60kph speed limit X 8 = 480 mph
Yep I reckon you're pretty safe in the series


Martyn

Originally Posted by Chucaro

If the GPS have history storage, you have a clean records and have a history of faulty radars used by the authorities you can have some weight to defend yourself in Court.
The court can order to inspect the radar in question.
I remember few years ago a light post in Hobart was detected of doing over 100 kph

Or you could just... I dunno.....

NOT Speed

Its a voluntary tax after all.....

How they can justify to book a person going at 53 kph on a 50kph zone in a car buit before 2006

My point is that if they are going to implement a law like this, the roadworthy certificate should include an inspection of the speedo.

Lots of innocent and law obedient drivers are going to be book with the existing or proposed law, further more these type of laws should be standard across all the States

Originally Posted by Chucaro

How they can justify to book a person going at 53 kph on a 50kph zone in a car buit before 2006

My point is that if they are going to implement a law like this, the roadworthy certificate should include an inspection of the speedo.

Lots of innocent and law obedient drivers are going to be book with the existing or proposed law, further more these type of laws should be standard across all the States

You've missed my point. They already can pull you over for doing a couple over the limit. And do in WA and Vic.

How many cars out there with the right tyres and wheels read under anyway - pre or post 2006? I've never seen any!

Originally Posted by Chucaro

How they can justify to book a person going at 53 kph on a 50kph zone in a car buit before 2006

My point is that if they are going to implement a law like this, the roadworthy certificate should include an inspection of the speedo.

Lots of innocent and law obedient drivers are going to be book with the existing or proposed law, further more these type of laws should be standard across all the States

This is not a new law, motorist can and are being booked for 1k over the limit now. The proposal is that for 1k over you will lose 1 demerit point, now you lose 3 points for the same offence.

With an older second hand vehicle there is another reason why the speedo might be pessimistic - non standard parts (other than tyres and such obvious things).

My Series III had standard 750x16 tyres and as far as I could tell, the diffs were standard.

However my speedo read 90 kph when I was really doing 100kph. The odometer read 93 with brand new tyres or 94 km with old tyres for every 100 I traveled. I checked it several dozen times including over hundreds of km on the Stuart Highway and always got the same result.

My best guess was that it had some speedo parts out of a LR that was intended to have about 650x16 tyres.

Since the engine in it when I bought it was from an early 1960s LR, I always thought that was a reasonable assumption.