180/55/17 on the ST1300

[alans1100]

It seems that ADR 18/00 sets the rules for speedos and odometers. The latest version I can find is 2006. http://www.comlaw.gov.au/Details/F2007C00025/Download

Indicated speed can be +/- 10%
Indicated distance can be +/- 4%

That -10% on the speed is amazing , how can that be allowed when you can be booked for +5% on the speed limit?
Would be interesting in court if your car speedo does read -10% but as mentioned above I think most manufacturers paly it safe by having their speedos read high.

I found the same info as JC and that was the case up until July 2006 so there should be a later edition somewhere but from RACQ.

http://www.racq.com.au/motoring/cars/car_advice/car_fact_sheets/speedo_accuracy

"From 1 July 2006 newly introduced models of a vehicle available on the market must comply with ADR 18/03. Also, from 1 July 2007 any newly manufactured vehicle (excluding mopeds) must comply with this rule.

This new rule requires that the speedo must not indicate a speed less than the vehicle’s true speed or a speed greater than the vehicle’s true speed by an amount more than 10 percent plus 4 km/h. Significantly, this change means that speedos must always read 'safe', meaning that the vehicle's true speed must not be higher than the speed indicated by the speedo.

That is, at a true vehicle speed of 100km/h the speedo must read between 100km/h and 114km/h. An alternative way to look at it is; at an indicated speed of 100km/h, the vehicle's true speed must be between 87.3 km/h and 100km/h.

Significantly, this change means that speedos must always read ‘safe’, meaning that they are not permitted to read lower than the actual speed of the vehicle.
Additionally, there is now no requirement to have an odometer, and therefore there is no accuracy requirement."

[JC]

JC do you realise that Winstons Kumho is a car tyre?

Yes, but I didn't believe there was enough room for tyres that wide.

[JC]

http://www.racq.com.au/motoring/cars/car_advice/car_fact_sheets/speedo_accuracy

"From 1 July 2006 newly introduced models of a vehicle available on the market must comply with ADR 18/03. Also, from 1 July 2007 any newly manufactured vehicle (excluding mopeds) must comply with this rule.

This new rule requires that the speedo must not indicate a speed less than the vehicle’s true speed or a speed greater than the vehicle’s true speed by an amount more than 10 percent plus 4 km/h. Significantly, this change means that speedos must always read 'safe', meaning that the vehicle's true speed must not be higher than the speed indicated by the speedo.

That is, at a true vehicle speed of 100km/h the speedo must read between 100km/h and 114km/h. An alternative way to look at it is; at an indicated speed of 100km/h, the vehicle's true speed must be between 87.3 km/h and 100km/h.

Significantly, this change means that speedos must always read ‘safe’, meaning that they are not permitted to read lower than the actual speed of the vehicle.
Additionally, there is now no requirement to have an odometer, and therefore there is no accuracy requirement."

It seems that ADR 18/03 over-rides the 18/00 requirements. http://www.comlaw.gov.au/Details/F2006L01392/Download

Motorcycles are listed as ADR Class LC

The applicable section of ADR 18/03 seems to be:

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

which seems to allow car speedos to read up to 4.1% fast at 100km/h (≤104.1) and 6.8% fast at 60km/h (≤64.1)........but for motor cycles in class LC/L3, motor cycles with sidecars class LD/L4 and motor tricycles class LE/L5, there seems to be a relaxation to +8 km/h in Annex 3.

2. Requirements
The production shall be deemed to conform to this Regulation if the following
relationship between the speed indicated on the display of the speedometer (V1) and
the actual speed (V2) is observed:
In the case of vehicles of categories M and N:
0 ≤ (V1 – V2) ≤ 0.1 V2 + 6 km/h;
In the case of vehicles of categories L3, L4 and L5:
0 ≤ (V1 – V2) ≤ 0.1 V2 + 8 km/h;
In the case of vehicles of categories L1 and L2:
0 ≤ (V1 – V2) ≤ 0.1 V2 + 4 km/h.

This probably explains why the speedos read about 108km/h at a true 100km/h.
From reading various articles, it seems that GPS readouts may well have <1% error at highway speeds (100km/h?)