Tire pressure
Senior Member
Joined: Nov 2011
Posts: 758
Likes: 1
From: Tampa, FL & DC/MD infrequently
Year: 2000
Model: Cherokee
Engine: 4.0L I6
Example of why not to use sidewall (on tire) psi.
I picked up a 2012 Ford Focus rental (great car btw). The guy at the rental place said he hated the stupid TPMS (tire. monitor). He said he puts air in the tire but the tire indicator is always on. I'm like, OK. I drive it a short distance to my house load up, leave. I notice the dash board screen warning.
Before I get far, I stop at a local station with an air pump, and check the psi on the tires with my guage (a nice quality one). What...50 psi...that isn't right. I do notice on the tire it does show a max. Psi of 51. But as per convention I check the door jamb, 34 psi. I match the tires to that pressure....and low and behold....the tire pressure monitor says everything is good at that point.
Anecdotal of course, but I think a good one of tire vs. manufacturer specified pressure. Does not address non factory sizes though.
I picked up a 2012 Ford Focus rental (great car btw). The guy at the rental place said he hated the stupid TPMS (tire. monitor). He said he puts air in the tire but the tire indicator is always on. I'm like, OK. I drive it a short distance to my house load up, leave. I notice the dash board screen warning.
Before I get far, I stop at a local station with an air pump, and check the psi on the tires with my guage (a nice quality one). What...50 psi...that isn't right. I do notice on the tire it does show a max. Psi of 51. But as per convention I check the door jamb, 34 psi. I match the tires to that pressure....and low and behold....the tire pressure monitor says everything is good at that point.
Anecdotal of course, but I think a good one of tire vs. manufacturer specified pressure. Does not address non factory sizes though.
Herp Derp Jerp
Joined: Nov 2011
Posts: 18,251
Likes: 17
From: Parham, ON
Year: 1999
Model: Cherokee
Engine: 4.0L OBD-II
CF Veteran
Joined: Nov 2008
Posts: 7,874
Likes: 100
From: Northern Ontario, Canada
Year: 1990, 1999, 2000
Model: Cherokee
Engine: 4.0
the door jam rating is only for stock sized tires. it should also tell you what the stock size is along with the tire pressure.
the side wall rating is for max pressure as used in a much larger vehicle than what that tire might have been used as stock.
example, your door jam says 32psi and the tire size says 225/75/15 but you're running on 31s, but the sidewall says max 50psi (think of what vehicle would run 31's as stock), i would start airing to 28psi only because the tire is much larger than the stock 29" tire.
but the 31 would come on say a ford f350 which might be three times the weight of a cherokee, so if you use 32psi on that truck, the tire will be soft, so you would have to choose a pressure between 32 and 50, but 50 might be too much for an empty f350, but loaded pulling a loaded 5th wheel, it may need 50psi.
i run 26psi in my 33" radial mud tires on my xj and tj. seems fine, but 32 is way to harsh, now 50 would just wear the tires uneven and possibly damage the belts.
once you start changing stock components on your jeep, you will have to keep in mind the rating will also change. you just gotta know which way to adjust for optimal performance.
the side wall rating is for max pressure as used in a much larger vehicle than what that tire might have been used as stock.
example, your door jam says 32psi and the tire size says 225/75/15 but you're running on 31s, but the sidewall says max 50psi (think of what vehicle would run 31's as stock), i would start airing to 28psi only because the tire is much larger than the stock 29" tire.
but the 31 would come on say a ford f350 which might be three times the weight of a cherokee, so if you use 32psi on that truck, the tire will be soft, so you would have to choose a pressure between 32 and 50, but 50 might be too much for an empty f350, but loaded pulling a loaded 5th wheel, it may need 50psi.
i run 26psi in my 33" radial mud tires on my xj and tj. seems fine, but 32 is way to harsh, now 50 would just wear the tires uneven and possibly damage the belts.
once you start changing stock components on your jeep, you will have to keep in mind the rating will also change. you just gotta know which way to adjust for optimal performance.
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
the door jam rating is only for stock sized tires. it should also tell you what the stock size is along with the tire pressure.
the side wall rating is for max pressure as used in a much larger vehicle than what that tire might have been used as stock.
example, your door jam says 32psi and the tire size says 225/75/15 but you're running on 31s, but the sidewall says max 50psi (think of what vehicle would run 31's as stock), i would start airing to 28psi only because the tire is much larger than the stock 29" tire.
but the 31 would come on say a ford f350 which might be three times the weight of a cherokee, so if you use 32psi on that truck, the tire will be soft, so you would have to choose a pressure between 32 and 50, but 50 might be too much for an empty f350, but loaded pulling a loaded 5th wheel, it may need 50psi.
i run 26psi in my 33" radial mud tires on my xj and tj. seems fine, but 32 is way to harsh, now 50 would just wear the tires uneven and possibly damage the belts.
once you start changing stock components on your jeep, you will have to keep in mind the rating will also change. you just gotta know which way to adjust for optimal performance.
the side wall rating is for max pressure as used in a much larger vehicle than what that tire might have been used as stock.
example, your door jam says 32psi and the tire size says 225/75/15 but you're running on 31s, but the sidewall says max 50psi (think of what vehicle would run 31's as stock), i would start airing to 28psi only because the tire is much larger than the stock 29" tire.
but the 31 would come on say a ford f350 which might be three times the weight of a cherokee, so if you use 32psi on that truck, the tire will be soft, so you would have to choose a pressure between 32 and 50, but 50 might be too much for an empty f350, but loaded pulling a loaded 5th wheel, it may need 50psi.
i run 26psi in my 33" radial mud tires on my xj and tj. seems fine, but 32 is way to harsh, now 50 would just wear the tires uneven and possibly damage the belts.
once you start changing stock components on your jeep, you will have to keep in mind the rating will also change. you just gotta know which way to adjust for optimal performance.
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Seasoned Member
Joined: Nov 2010
Posts: 361
Likes: 2
From: Nazareth, PA
Year: 1996
Model: Cherokee
Engine: 4.0L High Output
Originally Posted by caged
the door jam rating is only for stock sized tires. it should also tell you what the stock size is along with the tire pressure.
the side wall rating is for max pressure as used in a much larger vehicle than what that tire might have been used as stock.
example, your door jam says 32psi and the tire size says 225/75/15 but you're running on 31s, but the sidewall says max 50psi (think of what vehicle would run 31's as stock), i would start airing to 28psi only because the tire is much larger than the stock 29" tire.
but the 31 would come on say a ford f350 which might be three times the weight of a cherokee, so if you use 32psi on that truck, the tire will be soft, so you would have to choose a pressure between 32 and 50, but 50 might be too much for an empty f350, but loaded pulling a loaded 5th wheel, it may need 50psi.
i run 26psi in my 33" radial mud tires on my xj and tj. seems fine, but 32 is way to harsh, now 50 would just wear the tires uneven and possibly damage the belts.
once you start changing stock components on your jeep, you will have to keep in mind the rating will also change. you just gotta know which way to adjust for optimal performance.
the side wall rating is for max pressure as used in a much larger vehicle than what that tire might have been used as stock.
example, your door jam says 32psi and the tire size says 225/75/15 but you're running on 31s, but the sidewall says max 50psi (think of what vehicle would run 31's as stock), i would start airing to 28psi only because the tire is much larger than the stock 29" tire.
but the 31 would come on say a ford f350 which might be three times the weight of a cherokee, so if you use 32psi on that truck, the tire will be soft, so you would have to choose a pressure between 32 and 50, but 50 might be too much for an empty f350, but loaded pulling a loaded 5th wheel, it may need 50psi.
i run 26psi in my 33" radial mud tires on my xj and tj. seems fine, but 32 is way to harsh, now 50 would just wear the tires uneven and possibly damage the belts.
once you start changing stock components on your jeep, you will have to keep in mind the rating will also change. you just gotta know which way to adjust for optimal performance.
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