Thread: D4 19inch COOPER Zeon LTZ 255 55 19

re temperatures, I know my Tyre Dog system has warnings for both temp and psi - what should the temp warning be set at on LTZ's? Assume if you hit a certain temp - then maybe pressure is too low??? is that right? ie tyre is working too hard?? you just pull over and let them cool for a while and maybe add a few psi?

I regularly saw 60 degrees on the rear tyres. The fronts struggled to get over 40 degrees most of the time the 2.5T single axle trailer would also only get to about 50 degrees with LT tyres. The pressures didnt seem to make much difference to temps. I could run down to 30 psi on the fronts at speed and still only got to 40 deg sames as I would with 38 psi in them. The rear tyres on vehicle though would rocket to 50 plus deg very quickly and then slowly keep creeping up to 60 deg almost regardless of pressure I.e no difference between 40 psi and 50 psi cold. Temps seemed more related to ambient than tyre pressures. Whilst the pressures just seemed to effect how quicklt tyre came up in temp. There must be some science on this somewhere but I haven't seen or read anything as yet.

Rear tyres have a hard time when towing especially when the trailer is as heavy as 2.5T even without considering a loose or rough road surface where front tyres throw more rocks and gravel at the rear tyres.

Why are we paying over $400au for these ( 255/55R19 111H Cooper Zeon LTZ All-Terrain ) but you can get them in US for $217us !?

http://tirecrawler.com/tire/cooper/zeon-ltz/c01410/

Originally Posted by tony_j_dean

Why are we paying over $400au for these ( 255/55R19 111H Cooper Zeon LTZ All-Terrain ) but you can get them in US for $217us !?

Cooper Zeon LTZ Tires C01410 255/55R19 111H BLK 520 A B

It's called the Australia Tax.

Prices are crazy high here,look earlier in the thread
Though and people are getting them for close to $300.
Usually grey imports, I got my 18" Zeon ltz for $280 a corner on flea bay, from a tyre outfit near Sydney .

Originally Posted by PaulGOz

I regularly saw 60 degrees on the rear tyres. The fronts struggled to get over 40 degrees most of the time the 2.5T single axle trailer would also only get to about 50 degrees with LT tyres. The pressures didnt seem to make much difference to temps. I could run down to 30 psi on the fronts at speed and still only got to 40 deg sames as I would with 38 psi in them. The rear tyres on vehicle though would rocket to 50 plus deg very quickly and then slowly keep creeping up to 60 deg almost regardless of pressure I.e no difference between 40 psi and 50 psi cold. Temps seemed more related to ambient than tyre pressures. Whilst the pressures just seemed to effect how quicklt tyre came up in temp. There must be some science on this somewhere but I haven't seen or read anything as yet.

There's plenty of science out there, but the only stuff I've read up on is for competition tyres, where you are trying to acheive slightly different aims.

I've never really thought too much about actual temperatures in road tyres. Thought about it a lot in rally tyres, but then it's the tread temperature that's important. You choose compounds to suit the temperatures so that the tread will work correctly - soft enough to provide grip but not too soft so the tread blocks break down and you lose the edges.

On the road I've always worked on the theory that if the tyre is too hot to touch, you have a problem. I haven't been able to find anything on what the max safe operating temperature is on these tyres, but I would be very surprised if 60 degrees was a problem.

The cause of heat in tyres is friction, both externally through the interaction with the road and internally from deflection of the rubber in the carcass. The amount of friction and therefore heat generated is proportional to the forces acting on the tyre. The magnitude of these forces is determined by speed, the weight of the vehicle and roughness of the road.

From cold, a tyre should gradually heat up until it reaches an equilibrium point where the rate at which heat is being created is equal to the rate at which it is being dissipated. The harder a tyre is working, the higher this temperature will be. Obviously, if the ambient temperature is high, you will be starting from a higher temperature and therefore the operating temperature will be higher. This is only a problem if the maximum temperature of the tyre is exceeded.

If a tyre continues to heat up, then it is not coping with the current operating conditions. You need to either reduce the rate at which heat is being created, or increase cooling.

Reducing the rate at which heat is being created is done by reducing friction, either through increasing pressure to reduce flexing, travelling on a smoother road, or reducing speed or load.

Increasing cooling is more difficult, but things like large, full width mudflaps can cause problems here, reducing airflow across the tyre.

From Boyles Law we can calculate that for an increase in temperature of 10 degrees Celcius, pressure will increase by 1psi. This can give you an idea of what temperature your tyres are. For example if you measured your pressure when cold at an ambient temperature of 20 degrees and they increase by 4psi after running, then they are at 60 degrees. This is the temperature of the air inside the tyre though, not the tyre itself. It is important to remember this too when checking cold pressures, as a pressure measured at 5 degrees will be different to one measured at 15 degrees.

Cheers,
Jon

My tyre guy just classified my only punctured tyre as "non-repairable". The hole (tear) was just too big. Considering the weight I had on the rear of the vehicle and the condition and size of the rocks, I'm not surprised I got a flat eventually. Every rock out there has a name on it. The rears were very cut up from rocks being lifted/ thrown at them from the front tyres. The sill of the car are like you spent all day poking at them with a sharp knife. The front tyres faired well. But as the tyre guy said, if that's the only thing that broke on the trip then I got away fine ($400 for the tyre - $6K for the total trip) - I tend to agree with him.
And yes, its a completely different mindset driving on low profile tyres. This was on a very fully laden D3.
Matti