Tyre rating - should I worry?

[Gullible]

Time to look for new tyres.

The hand book says 105 H. As I understand it 105 is the load rating and H is the speed.

A lot of the tyres that people say they are using only have a speed rating of T.

Is this a problem?

Do the boys in blue care?

[Homestar]

Not a problem unless you plan on driving over 190KMH...

H is 210KMH speed rating
T is 190KMH speed rating.

Speed rating of the tyre should exceed the maximum speed on the vehicle. IMF your talking about a Landy here, your probably fine. :)

105 is 925Kg per tyre as the load rating.

[Slunnie]

I'm not sure about Canberra, but I'm pretty sure in NSW the tyre speed rating only need to be 140kmh which is people can run muddies etc which all have low speed ratings. There are conditions where you can have down to 120kmh but these need tagging etc. this is because the max speed on the roads in NSW is 110kmh. With load rating you must have as a minimum what is on the tyre placard.

[mick88]

Pay to check with your Isurance Company that you are covered with the lower rated tires on.

Cheers, Mick.

[101RRS]

The minimum speed and load ratings that have to be complied with or on the tyre placard mounted on the drivers door - for my RRS this is 106 H. My General Grabber AT are H rating so are legal. If you can go to T ratings etc the tyre placard would have indicated that.

Garry

[isuzurover]

Slunnie is correct.


Australian Vehicle Standards' rules state that a 4WD manufactured with off road features must have a tyre speed rating of N (140 km/h) or greater. It is not a legal requirement to match the tyre placard's speed rating so long as it is not less than N (140 km/h). The speed rating must be stamped on the tyre.

Load rating on the other hand must be the same or higher than the tyre placard.

Cooper Tires - Load and Speed Ratings (http://www.coopertires.com.au/index.php?page=load-and-speed-ratings)

[101RRS]

Slunnie is correct.

Load rating on the other hand must be the same or higher than the tyre placard.

Cooper Tires - Load and Speed Ratings (http://www.coopertires.com.au/index.php?page=load-and-speed-ratings)

Well why does the tyre placard not show that information - it is an Aussie document.

Sort of defeats the purpose of a tyre placard.

Garry

[Slunnie]

Well why does the tyre placard not show that information - it is an Aussie document.

Sort of defeats the purpose of a tyre placard.

Garry

It was probably a broad based ADR written 45 years ago which had supplementary guidelines added when faster 4wds made them unworkable. It would have meant in practice that very few 4wds could use tyres designed for harsh conditions with the fitment of anything other than HT tyres. The tyre placard is still relevant because it has size, load and tyre pressure data which is important.

[Dougal]

Pay to check with your Isurance Company that you are covered with the lower rated tires on.

Cheers, Mick.

So you're covered when you crash from a blowout at 192km/h?

[101RRS]

It was probably a broad based ADR written 45 years ago which had supplementary guidelines added when faster 4wds made them unworkable. It would have meant in practice that very few 4wds could use tyres designed for harsh conditions with the fitment of anything other than HT tyres. The tyre placard is still relevant because it has size, load and tyre pressure data which is important.

I don't disagree but why not have the tyre placard reflect that? Why not have the current annotation with another that says where offroad tyres are required tyres may be fitted with a minimum rating of N and with a max allowable vehicle of 140kph where permitted.

That is a generic question rather than one targetted at you.

[isuzurover]

I don't disagree but why not have the tyre placard reflect that? Why not have the current annotation with another that says where offroad tyres are required tyres may be fitted with a minimum rating of N and with a max allowable vehicle of 140kph where permitted.

That is a generic question rather than one targetted at you.

Tyre placards are only intended to state the tyre size and rating originally fitted to the vehicle (and recommended inflation pressures).

You are allowed to fit different size tyres (e.g. wider/taller) too. Should this also be included on the placard???

[London Boy]

I don't disagree but why not have the tyre placard reflect that? Why not have the current annotation with another that says where offroad tyres are required tyres may be fitted with a minimum rating of N and with a max allowable vehicle of 140kph where permitted.

That is a generic question rather than one targetted at you.
You're probably getting into questions of product liability and so on. There is also a jurisdictional component, since not all the states have adopted all the design rules and codes of practice.

[Gullible]

OK, now I'm really confused.

One tyre place I was talking to was telling me it has a lot to do with the heat build up in the tire. That is, lower speed tyres build up more heat when under load or when running at lower pressures - like when on sand.

[PhilipA]

One tyre place I was talking to was telling me it has a lot to do with the
heat build up in the tire. That is, lower speed tyres build up more heat when
under load or when running at lower pressures - like when on sand.

Many tyre places I have found have a very sketchy understanding of tyres.
Perhaps he meant
"Tyres with a lower speed rating usually have large chunky treads as they are M&S and these treads are usually about 12MM deep compared to 9MM deep for high speed rated tyres. It is for this reason mainly that they have a low speed rating as the mass of the deeper tread would cause the tyre to break apart at very high speed"
Lower speed rated tyres usually also have a higher load rating especially LT rated tyres as the construction is heavier in the sidewalls etc, and this also could cause failure at very high speed due to centrifugal force.
So work out what you want : High speed rated tyres that have a lower load rating, thinner tread , and are more flimsy than lower speed rated tyres or the opposite.
I choose lower speed rated tyres every time.
BTW last time I looked in NSW the N rating was only allowed for M&S rated tyres . Also when I last looked you had to print out a warning label and stick it on your dashboard which nobody in the history of the World has ever done. This was about 10 years ago so it may have changed.
Regards Philip A

[Grumbles]

I checked this matter with my insurance company a couple of years ago. They said that my comprehensive cover would remain valid provided the tyre load rating met or exceeded the vehicle specs but that the speed rating could come down by one level.