KM2's going, Advise on A/T LT tyres

Tyre ply rating has absolutely nothing to do with sidewall plies or the denier of of the construction material but a measure of load carrying rating. It is an anachronism from the days of the early pneumatic tyres when the carcass was made of layers of canvas. The more layers, the greater load the tyre was rated to carry; thus 6, 8, 10, etc ply literally meant layers of canvas, the more canvas the less deformation under load. Modern ply rating of the tyre is the manufacturers equivalence relating the tyre to layers of canvas. Bias ply tyres, in relation to the discussion of sidewall strength, have angled and stronger cords than radial but it shows that multiple side cords, or plies, does not necessarily mean stronger puncture protection; it's only part of the equation. If sidewall strength was the only consideration, we would all be using bias ply tyres.

According to Michelin:

"A radial tyre allows the sidewall and the tread to function as two independent features of the tyre.
A bias tyre consists of multiple plies over-lapping each other. The crown and sidewalls are interdependent. The overlapped plies form a thick layer that is less flexible and more sensitive to overheating.

RADIAL TYRE
Sidewall flex is not transmitted to the tread. The footprint only lengthens. There is little transverse slip. The radial tyre allows the machine to transfer more power to the ground.

BIAS TYRE
All sidewall flex is transmitted to the tread. The footprint deforms and there is an increase in tyre slip.
The tyre does not contact as much ground as a radial tyre, leading to a loss of engine power transmission and greater ground damage.

RADIAL TYRE
Lower fuel consumption.
Less ground compaction and damage.
Greater productivity. More of your machines power is actually used.
Reduction in tyre replacement thanks to the longer service life of radial tyres.
Thanks to the flexibility and strength of the tire, the tire absorbs shocks, impact and bumps. The result is a better ride and better operator comfort.

BIAS TYRE
Due to the stiffness of the tyre, it does not absorb bumps on the ground. All impact and shaking is felt by the driver and machine.

PLY RATING
Before load ranges were adopted, ply ratings and/or the actual number of casing plies were used to identify the relative strength with higher numeric ratings or plies identifying tyres featuring stronger, heavier duty constructions.

Today's load range/ply ratings do not count the actual number of body ply layers used to make up the tyre's internal structure, but indicate an equivalent strength compared to early bias ply tyres."

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Originally Posted by MLD

...The Yokahama Geolander also scored well in that test review by 4wd Action.... I want a tyre that is road orientated but will hold up to punishment in the desert where MT's don't work as well as an AT.

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My Geolanders LT245/70-17 have been good although I haven't had the opportunity to test their 3 ply sidewalls on sharp desert sticks and rocks, only fast gravel roads and bits of old farm fencing wire that's lying about everywhere. They've done 60K and look as though they'll see close to 100K. I have a set of Duratracs to try in winter and will see if their better sloppy stuff traction is worth the anticipated extra noise and poorer road manners.

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Originally Posted by Babs

I looked into every one else's suggestions the Pirelli, Generals, Maxxis, could not find info on sidewall protection, so I'm assuming they are not a 3ply side, and confused to wether or not they are a LT construction.

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Some Maxxis LT tyres use a three ply sidewall, most are two ply, and FWIW when we've compared the two ply versions to an equivalent BFG the Maxxis sidewall seemed thicker yet were more supple. eg. I need more air pressure in my 255/85 Maxxis two ply sidewall 762's at a particular load vs the older BFG MT KM's I used.

From what I've seen a stake in the bush is no respector of tyre brand, cost or sidewall claims, they all seem to stake the same.

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Originally Posted by ugu80

Don't fall for the sidewall propaganda. Sidewall strength and thickness is not only a function of ply numbers. Most manufacturers keep their carcass manufacturing process an industrial secret. Some are (rightly) proud of their construction and openly advertise it (e.g. Coopers ST Maxx/STT). Ply thickness is measured in denier (As per Coopers above, 2x2000 denier ply and 1x1000 angled denier ply = 5000 denier total). I have read unconfirmed reports that some BFG 3 ply are 3x1000 ply, so, just for example, a 3 x 1000 ply sidewall will be thinner and weaker than a 2 x 2000 ply sidewall (Perhaps thats the case with the Bridgstone Babs mentioned). Don't forget the original Baja Claw, which achieved an enviable reputation for toughness, has a one ply sidewall (which must be very thick and tightly wound). On top of the ply there is simply how thick the outer rubber moulding is, the quality and construction of the materials used, etc.

Heat build up is another factor as to why manufactures stick to 2 ply as movement in the tyre produces less friction (two plies rubbing together instead of three). Also, all denier being the same, three plies are not 33% stronger and more puncture resistant. Probably more like 10%, and that's being generous.

In short, although having a 3 ply sidewall is a good marketing tool, its not the be all and end all. Personally, I think all tyres should have their ply numbers and the denier of each ply displayed.

It will be written on the sidewall, somewhere, the plies of the tyre, but not the denier.

I learnt a bit about tyres when I was involved with tyre choice for my work fleet when the bosses got a bit worried about OH&S liabilities and I had access to and discussions with various tyre company engineers. I also have a tyre fetish.

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Thank you for that insight, you have confirmed what I have suspected. After researching the D697LT I started doubting the whole 3 ply sidewall hype, with regards to heat build up thickness and wether or not a 10 ply carcass.

Very useful info you have provided there, thanks for that. This is the type of info we don't normally get.

So from what I can gather on the D697LT they have a thick and stiff sidewall which when you let your pressure down won't bag out, it will still flex over rocks etc. just won't bag out or heat up. So they claim. I'm starting to change my whole understanding on tyre set up. Interesting.

Funny, we all get deceived by the marketing on sidewalls, from now on I'm looking at LT construction, speed and load ratings.
The Coopers I notice along with the D697LT have the highest speed and load ratings in a 4wd LT tyre.

But I suppose horses for courses I guess. I've come to realise the muddies obviously don't suit my touring needs.

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Originally Posted by Bush65

I doubt all Coopers use the same plies as suggested. Some are 8 ply rating and some are 10 ply rating, for all I know some may be less than 8 ply rating. Those with the same ply rating probably use the same denier.

Don't assume a 2 ply construction, which has a 10 ply rating has only 2 plies of the same denier as some other 10 ply (or 8 ply) rating tyre with 3 plies.

Most people would/should know the difference between 10 ply rating and the actual numbers of plies (2 or 3). As pointed out it comes down to the denier used in the 2/3 plies.

The real advantage I see in 3 plies is the change in bias angle of the 3rd ply.

The original Baja Claws are cross ply, so it is silly to bring them up in a discussion on radial ply tyres.

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Your right not all coopers are a 10 ply you have to choose specific sizes, same goes for the D697LT. Fortunately the standard size for Deefers come in a 10 ply with high speed and load ratings.

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Originally Posted by ugu80

Tyre ply rating has absolutely nothing to do with sidewall plies or the denier of of the construction material ...

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Rubbish!

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Originally Posted by Bush65

Rubbish!

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"PLY RATING
Before load ranges were adopted, ply ratings and/or the actual number of casing plies were used to identify the relative strength with higher numeric ratings or plies identifying tyres featuring stronger, heavier duty constructions.

Today's load range/ply ratings do not count the actual number of body ply layers used to make up the tyre's internal structure, but indicate an equivalent strength compared to early bias ply tyres."

It's a load rating and relates to construction only in what has been done to give the tyre the appropriate strength to gain such rating. It does not denote any particular number, thickness, type or arrangement of the plies in the carcass. Perhaps reading all the posts on the matter would have been helpful.

Also, again if you bothered to read the post properly, there was no suggestion that all Coopers have the same construction, just certain models. Maybe your spectacle prescription needs updating.

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Originally Posted by Babs

The Coopers I notice along with the D697LT have the highest speed and load ratings in a 4wd LT tyre.

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Be careful, I think you're drawing a very long bow there, all brands have commercial/LT tyres with high to very high load ratings and you may end up with a hugely impressive load rating tyre that rides like a solid tyre and doesn't flex over any imperfection at all.
Match the tyre to what you are doing.

Speed rating can be leading you astray too, eg. look at the Michelin XZL fitted as stock to a 130.
Possibly one of the highest load rated 7.50-16/235/85-16's yet a relatively low speed rating, yet no one denies they are one tough outback tyre.

Horses for courses.

[edit] As an example I've been running 255/85 tyres for maybe eight or nine years now, two sets of BFG's and now on my second set of Maxxis 762's.
The car is used daily for work (I'm a tradie and do breakdown service) and the load rating of both brands is lower than the original 7.50/16 XZL's (umm aaah, very naughty !)
The 130 mostly tares out at around 3000kg, day in, day out and is driven over a variety of roads from rough farm tracks to highways and I've never experienced a load related issue and only run the tyres around the 40psi mark (maximum load 1380kg @ 65psi)
I only used around 34psi in the BFG's and if doing predominantly gravel/dirt, only 26psi.

If I tared out at around the maximum 3500kg I'd use 235/85's with a higher load rating and obviously more pressure, but I don't, I've only every been near that a couple of times hauling firewood and the current size/load tyres coped OK aqnd are still well below the rated maximum load for those tyres.
A 110's GVM is a more than a couple of hundred kg below a 130. ;)

Excellent advice Rick. Sounds like you are after an all terrain. I have a friend with a Pajero who does a lot of bitumen and some dirt. He does lots of kms and has had a number of brands, different brand at every replacement. He maintains the best he has had were the Pirelli Scorpion, if its any help (he has never had Coopers). He's been through Yokohama, Maxxis, Pirelli and now Hankook AT's. He rates the Hankook up with the Pirelli on all but road noise.

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Originally Posted by rick130

Some Maxxis LT tyres use a three ply sidewall, most are two ply, and FWIW when we've compared the two ply versions to an equivalent BFG the Maxxis sidewall seemed thicker yet were more supple. eg. I need more air pressure in my 255/85 Maxxis two ply sidewall 762's at a particular load vs the older BFG MT KM's I used.

From what I've seen a stake in the bush is no respector of tyre brand, cost or sidewall claims, they all seem to stake the same.

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Best way to reduce this is run lower pressures. I STILL hear from people who go on about 'keep those pressures up in the rocks mate, you'll save your tyres'...:o
M55

i have these, 12,000km and VERY happy so far. I have also recommended them to numerous customers about to go touring/ travelling, who are also VERY happy with their puncture restistance and wear/ load rating, too. I have deflated mine for rocks and sand as low as 20psi, and they do bag out reasonably well IMO. I currently run them at 36 f and 38 r, upping to 45 r when towing.

JC