Tyre speed rating

[Kitbags Junior Member Find all posts View Profile Close Kitbags]

Toyota designate a S (180km) speed rating for Prado 120 models. The legal requirement is that replacement tyres are required to have the same S rating or a higher rating.
The load rating and speed rating are combined on tyre specifications eg 121Q.
All tyre manufacturers I have checked eg Cooper, Pro Comp, Mickey Thompson rate their All Terrain at S. All tyres in their range with a more aggressive tread are rated Q.
The lower Q rating renders them illegal to fit on a Prado 120.

Yes we all know there are a lot of 4x4's fitted with Q rated tyres running around.
Have there been any changes as to the illegality of this situation? If so please quote the ADR in your post.
Kitbags

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For passenger vehicles, the minimum speed rating is S - 180km/h.

For off-road vehicles, the minimum speed rating is N - 140km/h.

[Kitbags Junior Member Find all posts View Profile Close Kitbags]

Thanks I did not know that. The ADR I looked up does not mention that. Where do I find that?

[photoprado Avid PP Poster! Find all posts View Profile Close photoprado]

Have you read ADR 24?

I think that is where it is...

[Kitbags Junior Member Find all posts View Profile Close Kitbags]

Thanks amts and photoprado for your help and info. For others who want to check it out:-
Google ADR 24.
Go to VSB 14.
Go to Section 4
Tools Tyres rims suspension & steering on page 18
4.1Basic mods without certification

Paragraph marked B is the one that allows those Q speed rated tyres to be fitted to a Prado with OEM S rated tyres.

4.1 REPLACEMENT TYRES ON STANDARD (OR MANUFACTURER’S OPTIONAL) RIMS
Some tyre sizes have become obsolete and are no longer available. Equivalent replacement
tyres with different size designations may be fitted without specific certification under this
Section.
Every passenger car manufactured after 1972 (ADR 24) is fitted with a tyre placard that
contains information on original and optional tyres and rims for that vehicle model.
A motor vehicle under 4.5 tonnes GVM which is required to comply with ADR 24 may be
equipped with tyres other than those listed on the tyre placard provided that:
 the load rating of the tyres is not less than the lowest load rating listed on the tyre
placard of the vehicle or equivalent variant of that model vehicle;
 the speed rating of the tyres fitted to a passenger vehicle is at least 180 km/h (S) when
the tyre placard requires a higher speed rating than S;
 the speed rating of the tyres fitted to vehicles with special features for off-road use of at
least 140 km/h N when the tyre placard requires a higher speed rating than N; and
 for all other vehicles a speed rating of at least 120 km/h.
 In special circumstances, the speed rating may be less than the ratings specified above
if the speed rating of the tyre is more than the vehicle’s maximum speed. This will
need to be confirmed with the Registration Authority.

[r4ndll Avid PP Poster! Find all posts View Profile Close r4ndll]

What AMTS said.

Prado is MC category vehicle under the ADR's. Off road passenger vehicle: MC - OFF-ROAD PASSENGER VEHICLE - A passenger vehicle having up to 9 seating positions, including that of the driver and being designed with special features for off-road operation.

Speed and load ratings The speed rating of all tyres must be at least:
•for an off-road passenger vehicle – 140km/h
•for another car (sedan, station wagon, etc.) with up to nine adult seating positions or a car derivative – 180km/h
•for another motor vehicle – 120km/h
•the vehicle’s top speed, if lower than the speeds referred to above

[ Source: Department of Transport and Main Roads, G19.6 released March 2014, updated Feb 2016 ]

The original speed rating of the tyre casing must be at least:

For vehicles with a GVM of 4.5 tonnes or less with four or more wheels, the lesser of:

140km/h for a passenger car with special features for off-road use such as 4WD;
180km/h for any other passenger car;
120km/h for any other motor vehicle not descrbed above; and
the vehicle’s top speed.
[ Source: Vicroads VSI 26 ]



Note:
ADR 24 ceased to have effect for new vehicles as from 9 December 2003, the requirements have been incorporated in ADR 42/….

[brogers Advanced Member Find all posts View Profile Close brogers]

I'm not completely convinced, yet, and I'm certainly not starting an argument dear folk, but rather just thinking out load.... I'm happy that a 4wd vehicle, with special features for off road use, when being used for off road purposes can have a tire load rating of at least 140km/hr... as indicated in the threads below... but I just wonder if, when that same vehicle is now being driven on the highway (ie no longer off-road) if the tires now need to meet (or exceed) the tire placard minimum standard of "S" rating? Just wondering, because that would make sense...it would be a bugger... but it kind of makes sense.. somewhat.

[Kitbags Junior Member Find all posts View Profile Close Kitbags]

I had read where ADR 24 was replaced with ADR 42 but thats where I got bogged down trying to find the reference in ADR 42. It was after that when photoprado suggested I may find what I was looking for in ARD 24. I seemed to be going in circles so I phoned Qld Deptment of Main Roads Vehicle Standards Ph 07 31145844. They are only too happy to answer queries about this or any other matter relating to ADR's and VBS's. There are similar depts doing the same in other states They supplied the information I posted regarding VSB 14.
I did make an error by referring to ADRs in my post. At that point in time I was unaware that ADRs refer to new, not previously registered, vehicles only.
Modifications to existing vehicles are covered in Vehicle Standards Bulletins VSB's not Australian Design Rules ADR's. This particular topic is covered in VSB 14 National Code Of Practice For Light Vehicle Construction and Modification Section LS Tyres, Rims,Suspension and Steering.

Fellows please phone Vehicle Standards 0731145844 or their equivalent in your state if you need verification as
VSB 14 concludes with the message
"Queries regarding VSB 14 should be directed to your local Registration Authority".

Thanks for your input. One way or another we have established that Q rated tyres are legal on a Prado 120.

[r4ndll Avid PP Poster! Find all posts View Profile Close r4ndll]

I'm not completely convinced, yet, and I'm certainly not starting an argument dear folk, but rather just thinking out load.... I'm happy that a 4wd vehicle, with special features for off road use, when being used for off road purposes can have a tire load rating of at least 140km/hr... as indicated in the threads below... but I just wonder if, when that same vehicle is now being driven on the highway (ie no longer off-road) if the tires now need to meet (or exceed) the tire placard minimum standard of "S" rating? Just wondering, because that would make sense...it would be a bugger... but it kind of makes sense.. somewhat.

Its not the onroad/off-road driving its the tire construction. You're allowed to run lower rated tires which are thicker but can't handle the heat from higher speed running if you want. You can also run the higher rated tires if you want. They just won't be as good off road.

"However, offroad tyres are stronger (thicker) construction and are not typically rated for high speeds. Therefore, as 4WDs were developed a problem arose where 4WDs had top speeds the offroad tyres couldn’t handle, and the tyres became increasingly offroad-weak as they had to handle greater and greater heat dissipation. That is why every Australian road authority permits offroad vehicles (MC) to run N rated tyres, irrespective of the placard, in a very rare example of actual government thought and intelligent design on behalf of real-world users."

https://practicalmotoring.com.au/voi...-mc-offroader/

[brogers Advanced Member Find all posts View Profile Close brogers]

Its not the onroad/off-road driving its the tire construction. You're allowed to run lower rated tires which are thicker but can't handle the heat from higher speed running if you want. You can also run the higher rated tires if you want. They just won't be as good off road.

"However, offroad tyres are stronger (thicker) construction and are not typically rated for high speeds. Therefore, as 4WDs were developed a problem arose where 4WDs had top speeds the offroad tyres couldn’t handle, and the tyres became increasingly offroad-weak as they had to handle greater and greater heat dissipation. That is why every Australian road authority permits offroad vehicles (MC) to run N rated tyres, irrespective of the placard, in a very rare example of actual government thought and intelligent design on behalf of real-world users."

https://practicalmotoring.com.au/voi...-mc-offroader/

Convinced...thank you very much.


This time around (primarily due to price but there have been some good reports) I'm about to try Hankook Dynapro RF10 AT LT Tires, coincidentally with a speed rating of "S".
Last Time I had BF Goodrich AT LT (which also have a speed rating of S)..so the speed rating its not an issue for me.