Tyre info BFG AT 245/70/16

Nope, pressure was still at 36psi, centre of the tread area 'bulged' outwards and separated from the belt.

Other 3 tyres appear OK.

They have been (since new) like driving on ice as soon as the bitumen gets moist.

Tried different pressures but it made no difference.

Spin, slide & understeer so bad it used to scare the wife driving it.

Here is a bad blue by Holden, there are only about 4 choices of tyre to fit LEGALLY to the new Rodeos (at least in Qld). The BFG AT, a Continental AT (which is what is now on it), the original Bridgestone AT (a truly terrible tyre) and another all bitumen type of tyre.

The LOAD rating is where the bad judgement has been made, plenty of choices of tyres in the right size, but Holden have specified a weird load rating which drops the choices to the few above.

That's amazing, I wonder who got the under-the-table payment to make the load rating decision???

I have found my BFG's to be most excellent, on a wet road, short of redlining and dumping the clutch, I have to try hard to spin them up.(Allow me to get in first... If I had a real 4by with some real power, instead of a "sale proof" Triton, I may not have that problem)

Are you happy with the Continentals??

Too soon to tell, 2nd day with them on and dry weather abounds lol.

Funnily enough the guys at the tyre place also joked about under the table payments, it makes the woeful Bridgestones the only real choice if the majority of your work is on the black stuff.

For me I do maybe 20% on dirt/rocks at a coal mine so the Bridgestones only lasted 35k and they were chopped to pieces. The BFG ATs had 45k on them and although they were cut up pretty bad they had maybe 30% tread left.

I got 37k out of my stock Bridgestones, all on the black...

Keep us informed about the Conti's, it's a name that doesn't often rate a mention here.

Can't see how lower pressures help because a wider profife is more likely to aquaplane.

exakery. Aquaplane speed is proportional to the square root of the tyre pressure x 17 (km/hr) e.g.:

36 psi tyres, aquaplane speed is 102 km/hr.

Note that "breakthrough speed" - that speed at which the tryes will resume grip in the road surface is square root tyre pressure x 13 (from memory!)

36 psi tyres - 78 km/hr.

So you have to scrub off 24 km/hr somehow before you get the vehicle under some semblance of control. This is where you become a passenger rather than a driver.

Now some say - hell I go way faster than that - and I do not aquaplane. And F1 cars don't aquaplane. Well, let me tell you they will and they do. These formulas are based on aircraft tyres which have little tread - I think that there would be a co-factor somewhere that would relate to tread patterns and the ability of the tyre to pump water. There is also a relationship to the *thickness* of the water film on the road surface.

But one thing for sure - drop your tyre pressures for wet driving is inviting a dance with the devil - if you do aquaplane if will be at a lower speed; whats more you try and get the car to slow down to breakthrough speed without hitting something. I have seen some specatular accidents from this happening - and a court case...

/viz

Where did you get the formula "Aquaplane speed is proportional to the square root of the tyre pressure x 17 (km/hr)"

Where does tread pattern and softness of rubber come into this?

All I can think of is that a higher tyre pressure reduces the contact patch to such a small area that it easier to lock up the wheels.

However I do agree that there is a midrange pressure where further reduction in pressure will havethe reverse effect and increase aquaplaning.

I don't know the science behind it, but I know it works.

Maybe with radials, the lower pressure allows the radial to distort more and lets the tyre grip better (less slip angle), which I understand is basic radial technology as compared to cross plies.
Have you noticed the difference between cross plies and radials?

Lowering the tyres by about 5psi delays lockup on wet roads.

dropping it from 38psi to about 32psi does work.

I hold a commercial pilot licence and the formula for aquaplaning comes from that - in reference to aircraft (square root of the tyre pressure x 9 for knots). Aircraft aquaplane all the time, but they have a bloody great big tail that they can steer with which helps until the aircraft passes break-through speed and the nose wheel becomes active...

However there is a wealth of information off the net - a quick google gets this:

aquaplane speed

From personal experience and the knowledge of how tyres work on water, I would *never* drop tyre pressures for wet roads... You might as you say, improve grip, but you seriously increase the danger of aquaplaning at normal highway speeds. Do not confuse the two conditions.

/viz

No idea, the vehicle is a lease and tyre rotation is done at the service intervals.

But they are not a uni directional tyre so theoretically it shouldn't matter.

For what I chose them for (cut resistance) I too was very happy with them.

Hi Dennis;
I'm pretty sure that it doesn't make any difference if the tyre is a directional tyre or not. As it has been explained to me in the past that tyres (directional or unidirectional) "bed-in" with rotataion and gain a memory for this. If there is a change - rotation from side to side this upsets the memory and can cause the delamination. In theory this sounds OK to me and I have rotated tyres front to rear only and have never had a problem. Perhaps I have been lucky or this has actually saved me this grief.

Cheers.