The tire and loading information placard on my 2001 Wrangler Sport/4.0L that came original with 215/75R15 tires states 33lb per tire TJim. The information you got from other posters above is probably more accurate!
Tire Pressure Advice
- Thread starter TJim
- Start date
I once got hold of the official european formula to calculate pressure for a certain load.
People who calculate lineair, dont do it bad.
But is also speedrelated, for lower speed lower pressure is still safe.
And on track , and in mud/sand, you can even go much lower.
For on road, the goal is not to overheat any part of tire.
Lower speed, lesser cycles a second, so deflection of tire is allowed more, so more heatproduction a cycle. Then still same heatproduction a second.
So give weight and speed and terain, and tire- specifications, and I will calculate, and show how.
My dangerous prediction here is 18 psi on road even.
People who calculate lineair, dont do it bad.
But is also speedrelated, for lower speed lower pressure is still safe.
And on track , and in mud/sand, you can even go much lower.
For on road, the goal is not to overheat any part of tire.
Lower speed, lesser cycles a second, so deflection of tire is allowed more, so more heatproduction a cycle. Then still same heatproduction a second.
So give weight and speed and terain, and tire- specifications, and I will calculate, and show how.
My dangerous prediction here is 18 psi on road even.
OP
Hey!
Terrain: on road (just for daily driving and highway)
tires: goodyear wrangler adventure all terrain with kevlar 235/70r16 (max psi=51, max load=2094 pounds) https://www.tirerack.com/tires/tire...rrain+Adventure+with+Kevlar&partnum=37TR6WATA
I dont go very fast, never above 70mph.
Weight:
I have a TJ 2.4 2004 with hardtop. thw gvw is around 2000 pounds.
Factory recommended tire pressures for all trim levels and available OEM tires sizes for the 2004 Jeep Wrangler can be found here:
https://tirepressure.com/2004-jeep-wrangler-tire-pressure
According to that webpage the recommended pressure for the 215/75R15 tire size on a Jeep Wrangler is 33 psi regardless of vehicle trim level.
Googled the sise and found XL 106T
This is maxload 2094lbs AT 42 or 44 psi, wich is standard for XL / reinforced/Extraload, upto 99mph.
The 51 psi is the maximum allowed cold pressure, and difference with the 44psi referencepressure, as it is called, and maxcold of 51psi, is used to highen up the referencepressure, for higher speed , but also for camberangle above 2 degr( no issue for Yeeps).
But your given 2000lbs total weight, seems low to me. This weigt can be carried by one tire. Can you also give Gross vehicle weight rating and gross axleweight rating( GVWR, GAWR) .
Back of the sigarbox methode is.
First add 10% reserve to weight on one tire.
Substract first 100lbs from weight +10% on tire and maxload of tire.
Yours 2090 lbs -100 lbs= 1990lbs.
Say weight on tire +10%=1095-100 = 995 lbs . Devide 995/1990= 0,5 ( coincidence no) x referencepressure of 44psi= 22 psi.
This then is for on road upto 99mph.
I determined that for 99mph and 10% reserve gives highest pressure, so with max reserve, and still acceptable comfort and gripp and reasonable fuelconsumption.
Equally devided this would mean axleweigt of 1810 lbs, more realistic weight to my opinion, but correct me if wrong.
Give the additional info ,and I calc it for you.
This is maxload 2094lbs AT 42 or 44 psi, wich is standard for XL / reinforced/Extraload, upto 99mph.
The 51 psi is the maximum allowed cold pressure, and difference with the 44psi referencepressure, as it is called, and maxcold of 51psi, is used to highen up the referencepressure, for higher speed , but also for camberangle above 2 degr( no issue for Yeeps).
But your given 2000lbs total weight, seems low to me. This weigt can be carried by one tire. Can you also give Gross vehicle weight rating and gross axleweight rating( GVWR, GAWR) .
Back of the sigarbox methode is.
First add 10% reserve to weight on one tire.
Substract first 100lbs from weight +10% on tire and maxload of tire.
Yours 2090 lbs -100 lbs= 1990lbs.
Say weight on tire +10%=1095-100 = 995 lbs . Devide 995/1990= 0,5 ( coincidence no) x referencepressure of 44psi= 22 psi.
This then is for on road upto 99mph.
I determined that for 99mph and 10% reserve gives highest pressure, so with max reserve, and still acceptable comfort and gripp and reasonable fuelconsumption.
Equally devided this would mean axleweigt of 1810 lbs, more realistic weight to my opinion, but correct me if wrong.
Give the additional info ,and I calc it for you.
Last edited:
OP
I am sorry, my bad!
The GVW is 4409.25 pounds (it is 2000kg), the GAWR I am not sure but it must be :
| GAWR Front/Rear (lbs) |
| 2200/2650 |
Filled in in my made motorhome, pressure calculator, wich I even can use for airplanes, gave for 2200lbs axleload front and back 24 psi all around. If bacj really fully loaded to 2650 lbs, it would need 30 psi.
Now lets use the BOTSB method
2200lbs+10%= 2420 lbs = 1210lbs a tire - 100= 1110 / 1990 x44psi = 24,54 psi. The not rounded with my spreadsheet was 23,88 psi so 0,7 psi lower only. To high pressure is never unsafe.
The tricky parts in this all is , determinig the reference- pressure( if daubt, use the highest) , and determining the real weigts on tires.
I forgot to write that I dont use the official european foemula anymore.
The same weigt +10% would give 22,2 psi with that official formula.
If calculated with the american formula for P-tires of before 2006, it would give 14.74psi. In 2006 America stepped over to the European formula, wich used here for decades , for all kind of tires .
America used different formulas for P- and LT tires , and only changed for P-tires.
The same weigt +10% would give 22,2 psi with that official formula.
If calculated with the american formula for P-tires of before 2006, it would give 14.74psi. In 2006 America stepped over to the European formula, wich used here for decades , for all kind of tires .
America used different formulas for P- and LT tires , and only changed for P-tires.