352 wrote:
Does anyone have any information from the tire manufacturer why we should use trailer tires instead of truck tires on trailers? If all the side wall ply and tread ply are the same, what is the difference?
My conclusion is that, whatever the tire- and traler-makers advice, its better to use LT tires for Trailers or if keep using ST tires, calculate the pressure and determine the maximum load needed for ST tires with same criteria as LT tires.
Special trailer tires have lesser profile mostly because milage is generally lower and with lesser profile the cooling down of inside of treath is a bit better.
Also reinforced sidewalls wich makes them stiffer is done.
But this makes the tire produce more heat , and thats the problemm.
That is why Special trailer tires often give tire-failure.
They are calculated in their maximum load for more deflection allowed.
But this more deflection gives more heatproduction.
The lesser profile makes it cooldown a bit better, but the stiffer sidewalls makes it produce even more heat .
Probably when you drive 65 m/h and with maximum load on it and AT pressure in it , the heatproduction is so that no spot of the rubber of tire gets above the temperature at wich the rubber hardens and crackes in next bendings of that rubber so deflections of tire.
But a little overloading in combination with a bit to high pressure reading will give more deflection so more heatproduction so the rubber gets to hot and damages .
In next example I will give an idea of how bad it can get,
You can scipp that if its to technical.
Example: Say you have axles weighed at 5000 lbs each with single load so 2 tires on one axle.
Tires 2500 lbs AT 50 psi on sidewall written ST tires.
Then simple maximum load per tire so needed pressure 50 psi you would think.
But now the loaddivision is 49/51% on the axle ( 47/53 often weighed) and your pressure measurement device gives 5% to high pressure.
Then weight on "heavyest"tire 2550 lbs and real pressure in tire when measured 50 psi is 47.5 psi.
47.5 psi is then for loadcapacity aproximately 2380 lbs.
Real weight on tire 2550 lbs . so surface on ground aproximately 2550/2380=1.07 times what is allowd , and I found out that deflection of tire is quadratical to surface on ground aproximately.
Then squaire 1.07=1.145 times as much deflection and I asume also 1.145 times as much heatproduction a cicle of tire.
This would need 1/1.145= 0.87 times as much cicles an hour to give the same heatproduction so heat of rubber the same .
Asuming number of cicles to be the same as speed ( wich it is not but close) then 0.87 x 65m/h= 56.5 m/h critical speed at wich rubber gets to hot so tire damage begins.Using now an LT tire wich is calculated in its maximum load for lesser deflection so speed of 99m/h mostly , gives the tire more reserve for misreadings of pressure-devices and unequall loading.
Then I am not even talking about estimating the loads on axles or tires , wich makes the deviation even more.
Best is to calculate the needed pressure for a ST tire with the same reserves as for LT to give it lesser deflection and so lesser heatproduction.
Then still acceptable shockabsorbing of tires, the same as LT tire would give.
This could lead to a higher pressure then the here 50 psi AT pressure/maxloadpressure, but is often allowed by the tire-maker up to 10 psi extra. Adviced for higher speed then, but you can use it for what you want.
Topic of mine about the relation between maximum speed and maximum load of tire
here
