Max tire pressure
Playing off my other post, if a tire says “max cold pressure 80psi,” what can you safely run that tire at? If you already run this at 80psi cold and other post shows up to 25% increase in psi at high...
Forum Discussion
Once read from Tireman9 or Capriracer , that tires have teststandards, so they have to stand a pressure of 2 to 3 times the pressure behind AT.
So your 80 psi can rise to 160 to 240 psi before they blow.
I would not try this at home, if tire is already damaged by using to low pressure once, so overheating has happened long enaugh, it will blow sooner.
But gives an idea that only for the tires, you dont have to be affaid of putting for instance 120 psi in it ,if its undamaged.
In old PDF I have from Semperit ( Continental Group) they prescribe 140% of that pressure behind AT( official reference-pressure, but will call it AT-pressure furtheron). Then the tire is allowed 2 times the maximum load when speed zero so standing still.
Continental group in Europe gives on many tires 2 pressures.
1. The pressure behind AT but without AT in front of it right behind the service-descriptions ( example 255/70R16 121/119R 65psi)
2 on the other side behind the maxload information "maximum inflation pressure of 10 psi higher then 1 (so then 75 psi).
, and this is also cold pressure .
Also old documents of Goodyear gave for ST tires a 10psi higher pressure for 75mph.
Nowadays, if not given on tire-sidewall, you may not fill cold pressure higher then AT-pressure.
In earlyer days it was allowed.
Cold pressure is when inside tire airtemp is outside/ambiënt temp, that simple.
But sun can heat up the tire inside even when standing still.
Also exaust pipe yust in front of rearwheel can make that tire hotter .
Cold pressure advice and also AT-pressure is meanth for 18or20degrC/65or68degrF.
So you can always argue when filled fi 90 psi on AT80psi tire, that you filled it at freesing point( 0degrC/32degrF), and the pressure has rissen to that 90 psi now its 65 degr F.
Suppose you fill at freesing point of 32 degr F your tires with 1,4 times the AT-pressure , and in use the temp in tire goes to boiling point of water so 212 degr F, Then the pressure in tire will rise to a small 2x AT-pressure , so still within the test-standards of 2 to 3 times AT. Boiling point of water it can incidentially get in the tire, when descending the mountains and using the brakes to often.
Then heat of brakes is transported trough the rimms to the tire inside.
I suspect tiremakers to sometimes fi put a D-load designed tire( AT 65 psi) in the market as E-load ( AT 80 psi) , because especially american market asks for it.
But then the 2 to 3 times higher then AT wont go anymore.
Mayby thats the reason why they standard dont allow higher then AT-pressure anymore.
For P- tires , only maximum cold pressure is given on sidewall, of 44 to 51 psi , and for XL sometimes even 60psi.
The AT-pressure of a standardload P-tire is USA system 35 psi always, and EUR system 36 psi with exeptions to lower.
XL/reinforced/EXtraload USA 41psi always, EUR 42psi with exeptions to higher and lower.
So for P- tires its normal standard to allow higher cold pressure then AT.
So your 80 psi can rise to 160 to 240 psi before they blow.
I would not try this at home, if tire is already damaged by using to low pressure once, so overheating has happened long enaugh, it will blow sooner.
But gives an idea that only for the tires, you dont have to be affaid of putting for instance 120 psi in it ,if its undamaged.
In old PDF I have from Semperit ( Continental Group) they prescribe 140% of that pressure behind AT( official reference-pressure, but will call it AT-pressure furtheron). Then the tire is allowed 2 times the maximum load when speed zero so standing still.
Continental group in Europe gives on many tires 2 pressures.
1. The pressure behind AT but without AT in front of it right behind the service-descriptions ( example 255/70R16 121/119R 65psi)
2 on the other side behind the maxload information "maximum inflation pressure of 10 psi higher then 1 (so then 75 psi).
, and this is also cold pressure .
Also old documents of Goodyear gave for ST tires a 10psi higher pressure for 75mph.
Nowadays, if not given on tire-sidewall, you may not fill cold pressure higher then AT-pressure.
In earlyer days it was allowed.
Cold pressure is when inside tire airtemp is outside/ambiënt temp, that simple.
But sun can heat up the tire inside even when standing still.
Also exaust pipe yust in front of rearwheel can make that tire hotter .
Cold pressure advice and also AT-pressure is meanth for 18or20degrC/65or68degrF.
So you can always argue when filled fi 90 psi on AT80psi tire, that you filled it at freesing point( 0degrC/32degrF), and the pressure has rissen to that 90 psi now its 65 degr F.
Suppose you fill at freesing point of 32 degr F your tires with 1,4 times the AT-pressure , and in use the temp in tire goes to boiling point of water so 212 degr F, Then the pressure in tire will rise to a small 2x AT-pressure , so still within the test-standards of 2 to 3 times AT. Boiling point of water it can incidentially get in the tire, when descending the mountains and using the brakes to often.
Then heat of brakes is transported trough the rimms to the tire inside.
I suspect tiremakers to sometimes fi put a D-load designed tire( AT 65 psi) in the market as E-load ( AT 80 psi) , because especially american market asks for it.
But then the 2 to 3 times higher then AT wont go anymore.
Mayby thats the reason why they standard dont allow higher then AT-pressure anymore.
For P- tires , only maximum cold pressure is given on sidewall, of 44 to 51 psi , and for XL sometimes even 60psi.
The AT-pressure of a standardload P-tire is USA system 35 psi always, and EUR system 36 psi with exeptions to lower.
XL/reinforced/EXtraload USA 41psi always, EUR 42psi with exeptions to higher and lower.
So for P- tires its normal standard to allow higher cold pressure then AT.
