From:
http://www.transport.qld.gov.au/qt/driver.nsf/files/images/$file/Vehicle-Modifications.pdf
I've put relevant stuff in
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Alternative Rims and Tyres
Many vehicle owners wish to replace the original vehicle’s
rims and tyres with replacements of different width, diameter
and profile characteristics.
The following sub-sections outline the legal requirements for
replacement rims and tyres fitted to a passenger car or
derivative or an off-road passenger car which will ensure
your vehicle continues to comply with Queensland legislation
while allowing for your individual preferences.
Low Profile Tyres
It is common practice for manufacturers to fit low profile tyres
to high performance motor vehicles as standard equipment.
Low profile tyres (50, 60 or 65 series), replacing standard
profile tyres (70 series or above), are normally fitted in
combination with rims of larger than standard diameter to
maintain the correct overall diameter of the wheel.
A diagram of this concept appears below.
The rim diameter may be varied from the standard size
but the overall diameter of the tyre must not vary by more
than +15 mm or -26 mm.
These limits have been set for a number of reasons. Varying
the overall diameter of tyres affects ground clearance, centre
of gravity, brake effectiveness, steering geometry,
performance and speedometer accuracy.
Generally, to meet these limits, 60 series tyres are fitted to rims
with a diameter increase of 26 mm larger than standard and
50 series tyres are fitted to rims with a diameter 50 mm
larger than standard.
General Conditions for
Alternative Rims and Tyres
The rims and tyres must not protrude beyond the bodywork
of the vehicle, including flares, when viewed from above and
when the wheels are facing straight ahead. If the vehicle was
originally constructed with a portion of the wheel protruding,
the wheels must not protrude further than originally constructed.
The tyre to rim fitting and the tyre to rim combination must
be in accordance with the Tyre and Rim Standards Manual
published by the Tyre and Rim Association of Australia.
Reputable tyre retailers should have this information
and be able to advise on the correct combinations.
All rims fitted to an axle must be of the same diameter, width
and offset. They must not have a circumferential weld other
than that which attaches the outer rim to the centre.
All rims must have stud hole pitch circle diameters appropriate
to the hub. Wheel nut tapers must be appropriate to the wheel
and must engage the thread of the wheel studs for at least the
same length as the nuts provided by the vehicle manufacturer.
Slotted and elongated stud holes are not permitted.
The fitting of spacers between wheels and hubs, additional to
those provided by the vehicle manufacturer, is not permitted.
The tyre and rim must not foul wheel arches or suspension
components under any conditions. Steering limit stops should
not be adjusted to reduce the turning circle in order to allow
the fitting of the tyres and rims.
The tyres must have a tread depth of at least 1.5 mm on every
part of the tyre that touches the road and not have any
apparent defect that is likely to make the vehicle to which
they are fitted unsafe. It is not permitted to fit tyres that have
been treated by recutting or regrooving unless the tyre has
been marked by the original manufacturer as “suitable for
recutting or regrooving”.
Tyres
The maximum tyre width must not be more than 1.3 times wider
than the vehicle manufacturer’s widest optional tyre. However, in
the case of off-road passenger vehicles fitted with front and rear
beam axles, the maximum tyre width must not be more than
1.5 times larger than the manufacturer’s widest optional tyre.
The nominal width of the narrowest tyre fitted to a vehicle must
not be less than 70 percent of the nominal width of the largest
tyre fitted and never less than the vehicle manufacturer’s
narrowest optional tyre as indicated on the manufacturer’s
tyre placard.
Speed and Load Ratings
The speed rating of all tyres must be:
(a) a speed of at least:
(i) for an off-road passenger vehicle - 140km/h; or
(ii) for another car (sedan, station wagon etc.) up to 9 adult
seating positions or a car derivative - 180km/h; or
(iii) for another motor vehicle - 120km/h; or
(b) the vehicle’s top speed, if lower.
Load ratings of tyres must be at least equal to those specified
by the manufacturer on the tyre placard fitted to vehicles made
after 1972. For other vehicles, the load rating of a tyre must
be capable of carrying the part of the vehicle’s gross mass
carried by the tyre.
Tyre Construction
Tyre thread compounds, patterns, ply ratings and performance
characteristics vary. Tyre construction (e.g. radial) and size must
be the same on the same axle. Although it is recommended
that the tyres are identical (i.e. same brand and tread pattern),
this is not mandatory.
Vehicle Track
Track is measured at ground level from the centre of the tyre
on one side to the centre of the corresponding tyre on the
opposite side of the vehicle. Front and rear track differs on
many vehicles.
The wheel track must not be reduced to less than the standard
track specified by the vehicle manufacturer for the particular
model of vehicle.
The track of a car or car derivative may be increased by up to
26 mm beyond the maximum specified by the vehicle
manufacturer for the particular model of vehicle. Off-road
passenger vehicles fitted with front and rear beam axles,
may have an increase in track up to 50 mm beyond the
maximum specified by the vehicle manufacturer for the
particular model of vehicle.
Wheel Marking
Vehicles built on or after 1 July 1985 must be fitted with
original wheels or replacement wheels which are indelibly
marked in accordance with approved standards.
These include:
• Standards Australia;
• Wheel Industries Association (Australia);
• Technischer Uberwachungen Verein; and
• Japanese Industrial Standards.
Markings must include diameter, width, offset and the
manufacturer’s trade mark or logo and be located so that
they are readily visible when the wheel is correctly installed
on the vehicle.
Composite Wheels
The use of composite wheels (two or three-piece) is
permitted. They must be manufactured and marked in
accordance with the standards described above if fitted
to vehicles manufactured after 1 July 1985.
Repairs to Tubeless Tyres
Permanent repairs can only be made when the tyre is
removed from the rim. The tyre must be examined to ensure
it is structurally sound. The damaged area must be prepared
on the inside for a patch or mushroom headed plug to be
fitted and vulcanised into position. Any repairs to a tyre must
be sealed to prevent moisture or contaminants from entering
the tyre casing or structure.
CAUTION: Plug repairs can only be made in the tread area
of the tyre and not in side walls or where the tread and
side wall meet.
Punctures in tubeless tyres must not be repaired from the
outside or without removing the tyre from the rim as this
method is prone to failure.
Vehicle owners with doubts on tyre repairs should contact
a reputable tyre dealer for proper repairs.
[Edited on 28-2-2005 by MikeM]
