Goddamn tyre thing again!!!

There is some truth in it. A higher load rating means a stronger tyre.

Have you ever seen one of those old cheap nasty 31 x 10.5 R15 tyres of yesteryear when it's not on the rim. You can squash the tyre down with your hands and the sidewalls are so soft it is a wonder they will hold up a 4WD at all.

Compare that to a modern high-load rating, high-speed rating tyre of similar size which is rather stiff and heavy.

Just using the word 'ply' does not mean much really. What are the ply's made of? Rayon, cotton, steel, kevlar ? Also what thickness is the ply material?

Hi Axle
That word ply can be very interesting. To me the most important ply is in the side wall ply, as when you are travelling off road, most of the punctures are side wall punctures. On a new set of LT's recently, they were rates as 10 ply, but when you check to side wall ply, the same tyre is only 3 ply. When will tyre maker give greater protection to the side walls. With a greater ply rating, the load rating will go up, as a stronger tyre will be able to carry a greater load.

Stephen

Yep - my BFG's are load rating D - very meaty walls too - I have been amazed at how thin the shoulders on some passeger tyres are - this contributes greatly to the smooth ride I'm told, but its a dead set crime to encourage people to go bush on the standard issue tyres that some 4bies leave the showroom with.
May be of interest...... Wheel and Tire Bible

The legality or otherwise of tyres would all be easily answered if we knew if the National Code of Practice issued by DOTARS had been adopted, found at this site is the information on suspension tyres and wheels, NCOP 11 from Feb 6th 2006 deals with the allowable tyres and wheels . Does anyone know the outcome of all this?

Site Link

From what I can work out, 'ply' rating comes from the old cross plies, when there were actually 8 plies, or 6 plies, or 10 plies in the tread and side walls. And they were plies of cotton or something similar.
This gave an indication of load rating for the tyre, since the load rating index we have now didn't exist.

As mentioned above, radial construction, steel belts and an official load rating index has changed all of that, but some people still like to refer to the number of 'plies'.

As far as I can see, to achieve the load rating, rather than increase the number of plies in the walls, more rubber (and there are also various types of rubber) is added. MT tyres can have wall thicknesses from 8mm to 13mm thick by all reports, all being 2 ply or 3 ply walls, and the 3 ply tyres may only have 9mm rubber walls.

Now to confuse the issue even further, some 'R' rated racing rubber have 4 steel plies in the tread and 2 steel plies in the wall. You can run them at 20 psi and the walls and tread don't deform too much and still give grip when cornering hard.
'R' rated racing rubber have a minimal tread and are road rated for running on road registered cars in road events such as the Qld challenge, or Targa Tasmania. Racing rubber which has a wear rate of about 200 to 300, while normal street tyres have a wear rating of about 50. Nice and sticky, worth about 2 seconds a lap at Willow Bank or Morgan Park, but will only last 200 to 500 kms. No good off road with roacky trails though, the rubber would get ripped off, it is so soft.

So the point is, yep, 'plies' don't really mean that much. Load rating is a better indication (note - indication only) of tyre strength!

Hello Axle,
Oldplodder has summed up what I was told years ago quite well.
If you read it quite literally it says, "Ply Rating" a rating in this case is an equivalency to something else.
The way it was explained to me by a tyre dealer is in the old days cross ply tyres really did have that many canvas belts. 3 ply had 3, 8 ply had 8 and so on.
Now days we use a different construction method and a load rating index to identify tyres.
The way it was told to me a tyre with an 8 "Ply Rating" in new speak was roughly the equivalent of an old canvas 8 Ply in toughness and rigidity. Even though the newer tyre may contain far fewer than 8 Ply's.

Geoff.

Tyre construction is a complex subject not reflected entirely by numbers, and certainly, not a simple subject.

As with other complex consumer purchase decisions, not all sales outlets are equal in their ability to give professional, unbiased, informed, experienced and relevant advice.

For example, many tyres will have similar number for construction but be build differently for different priorities and thus may work differently in different circumstances.

Know the application and priorities for your purchase.

Ensure that the dealer and the consultant you are working with knows their bacon and has real experience with the tyres and application you are envisaging, and you will be getting the best outcome, baring a lot of education.

An example, I run Cooper Tyres. I purchase them at Jack Baker Tyre Centre in Adelaide. Jack Baker and a number of his staff have a number of 4x4s that they use from time to time to experience real-world performance of Cooper tyres. They know their stuff, and have plenty of education from Cooper on the tyres they sell.

I also know that Cooper have a good program of testing new tyres in Australian conditions prior to introduction and that this experience gets fed back to the development of new tyre constructions, patterns etc. When they specify an application it is not a theoretical thing.

Ciao for now
Andrew.

Ply ratings and load are derived from denier strenght of the cord. BFG have three ply sidewalls at 1000 denier, Bridgestone, Cooper are two ply sidewalls at 1500 denier same load less friction for heat.
cheers
Charlie