Monday, Oct 21, 2013 at 21:22
TBH, I'd be inclined to fit "standard" tyres.
Check the user manual, or the tyre placard in the vehicle, if you can find it.
That way, the speedo will be using the settings it was designed for - weird, I know, but that way the speedo might give you a reasonably accurate reading, at least within design parameters (ADRs require speedos to be within +10%, -0% - ie indicated reading must be higher than true speed and may indicate up to 10% higher than true BUT NOT LESS than true.)
Extract from ADR 18/03 Section 5.
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
(Bold emphasis is
mine!)
That last bit specifies that the indicated speed cannot be less than the true speed, but may be up to 10% + 4km/h. So, at 100kph the speedo must indicate between 100 and 114 kph.
AnswerID:
520138
Follow Up By: Member - johnat - Monday, Oct 21, 2013 at 21:24
Monday, Oct 21, 2013 at 21:24
I had bolded the words "shall not be less than the true speed of the vehicle" but it seems not to carry through to the page, even though it showed up in preview.
FollowupID:
800542