Tire Air-Presure Preparation: timing
Silly question: We are getting ready for a short journey tomorrow afternoon; is it okay to check and fill the air in the trailer tires today; or, should I wait until tomorrow? Does it really matter?
Forum Discussion
Stated already that the rubber of tire must stay below a sertain temperature, but what is that temperature?
I dont know either, but the man from Vredestein told me that the tires are "backed" at 170 degr C /338 degr F?. This sets the sulfurbridges at that rate that the rubber is flexible but not hard.
My suspicion is that this hardening already begins at lower temp.
So as long as I did not hear it for shure , I will keep it at 130 gr C /266 degr F?.
Then if we calculate with this, and say that higher temp differences give more heatransfer, its lineair.
So example : outside ( O) temp 65degr F, Inside tire temp ( I) 115 degrF, hottest part of rubber ( R) 265 degr F.
Then temp difference R/O 200 degr F and R/I 150 degr F.
Now new situation O= 90 degr F, I = 140 degr F, R must stay below 265 degr F.
Then temp differences , R/O=175 degr F , R/I= 125 degr F.
Then differences between situations.
R/O 175/200=85% of heat-energy possible to transport in new situation then in old.
R/I 125/150=83% transport possible per second in new then old.
Now I state that for instance half of deflection gives half of heatproduction a cycle, so also linear.
So roughly the tire must produce 84% of heatenergy in new situation the old , and so must have only 84% of the deflection in new then old situation. Then heatproduction is in balance with Cooling down of rubber, so rubber reaches in new situation also 265 degr F.
Now its gets even more complicated, howmuch lesser deflection does the tire get in new situation versus old. Lesser deflection gives lesser heatprocuction, and when constant temps in and out tire and rubber, the heating up and cooling down is in balance.
We could calculate the loadcapacity for the new pressure , wich would give again a ratio between old and new surface on the ground, and you could determine the new deflection for that.
Will spare you the calculation, because I have to find it out myself first.
But this all made me suspect that within a sertain range of outside temps,, and same speed, the heating up and cooling down of rubber is in balance so hottest part of rubber stays below 265 degr F.
You will understand that if outside temp is 265 degr F , the rubber can never cool down that much that it stay below 256 degr F, because temp differences are zero then .
Luckyly we dont drive at these extreme outside temps.
But mayby and outside temp of 110 to 120 still keeps the heating up and cooling down in balance ( because of the lesser deflection by the higher tirepressure) so rubbber stays below 265 degr.
And again if I determined this 265 degr F right to be the temp at wich hardening begins.
I dont know either, but the man from Vredestein told me that the tires are "backed" at 170 degr C /338 degr F?. This sets the sulfurbridges at that rate that the rubber is flexible but not hard.
My suspicion is that this hardening already begins at lower temp.
So as long as I did not hear it for shure , I will keep it at 130 gr C /266 degr F?.
Then if we calculate with this, and say that higher temp differences give more heatransfer, its lineair.
So example : outside ( O) temp 65degr F, Inside tire temp ( I) 115 degrF, hottest part of rubber ( R) 265 degr F.
Then temp difference R/O 200 degr F and R/I 150 degr F.
Now new situation O= 90 degr F, I = 140 degr F, R must stay below 265 degr F.
Then temp differences , R/O=175 degr F , R/I= 125 degr F.
Then differences between situations.
R/O 175/200=85% of heat-energy possible to transport in new situation then in old.
R/I 125/150=83% transport possible per second in new then old.
Now I state that for instance half of deflection gives half of heatproduction a cycle, so also linear.
So roughly the tire must produce 84% of heatenergy in new situation the old , and so must have only 84% of the deflection in new then old situation. Then heatproduction is in balance with Cooling down of rubber, so rubber reaches in new situation also 265 degr F.
Now its gets even more complicated, howmuch lesser deflection does the tire get in new situation versus old. Lesser deflection gives lesser heatprocuction, and when constant temps in and out tire and rubber, the heating up and cooling down is in balance.
We could calculate the loadcapacity for the new pressure , wich would give again a ratio between old and new surface on the ground, and you could determine the new deflection for that.
Will spare you the calculation, because I have to find it out myself first.
But this all made me suspect that within a sertain range of outside temps,, and same speed, the heating up and cooling down of rubber is in balance so hottest part of rubber stays below 265 degr F.
You will understand that if outside temp is 265 degr F , the rubber can never cool down that much that it stay below 256 degr F, because temp differences are zero then .
Luckyly we dont drive at these extreme outside temps.
But mayby and outside temp of 110 to 120 still keeps the heating up and cooling down in balance ( because of the lesser deflection by the higher tirepressure) so rubbber stays below 265 degr.
And again if I determined this 265 degr F right to be the temp at wich hardening begins.
