General question re tire pressure. I read the sticky note on the front page but it didn't really answer my question. I was told that the pressure listed on the tire was max pressure and the pressure listed on the door jamb was recommended pressure (for passenger cars), and is based in part of comfort of ride. With the Ford Explorer/Firestone tire debacle of a few years ago, which do you go with? I have been told that if they are not the same than you just split the difference. I am about to buy my first non-car (an '02 Excursion 7.3l) and was wondering what to do.
tire pressure
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Depends on your priority and if you have a compressor. Comfort, go with sticker. Max. tire life or heavy loads max. press. cold. I run mine at max. press. cold. I have to mention this, when I say cold, I mean cold. The way my truck sits in my driveway the sun will shine on the driver side first thing after it gets up over my neighbors house (8-9A.M.). Ten pound diff. btwn. pass. and driver side. If you want to run max. cold and don't have a compressor, air up at a gas station on your way home, 15 over max. then bleed down in the morning to max. cold. HTH BTW get a GOOD gauage
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[ QUOTE ]
I was told that the pressure listed on the tire was max pressure and the pressure listed on the door jamb was recommended pressure (for passenger cars), and is based in part of comfort of ride.
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Not exactly.
The pressure on the tire sidewall is the max pressure you should ever put in the tire.
The pressure on the Federal Certification Label on the lower doorpost behind the driver's door is the PSI needed only when the the vehicle is loaded to GVWR. For a pickup, that's the most you should ever put in the tire - but again there's an exception. LT tires (when loaded to the GVWR) can have up to 10 PSI more than that, and LT tires should always be overinflated by 5 PSI more than the PSI indicated in the load/inflation table for sustained high speed cruising of over 70 MPH.
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With the Ford Explorer/Firestone tire debacle of a few years ago, which do you go with?
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Neither one. Both those are maximum PSI. The PSI you should go with depends on the weight you have on each axle. Divide the axle weight by two to get the weight on each tire (or by 4 to get the weight on each Dooley tire). Then apply a load/inflation table. All load/inflation tables are identical for identical size of tire, so use any tire manufacturer's table for your size tire.
For example, when running around unloaded, I inflate my tires to about 50 front and 40 rear. When loaded for bear, I pump them up to 55 front and 65 rear. I never need the max of 80 PSI on the sidewall. My Cert sticker says 60 PSI front and rear, but I overload my F-250 by a few hundred pounds so I need the 65 per the load/inflation table. /ubbthreads/images/graemlins/blush.gif
Here's a quickie load/inflation table:
http://www.goodyear.com/truck/pdf/LoadInflLTMetric.pdf
Here's a comprehensive load/inflation table:
http://www.goodyear.com/truck/pdf/databook/loadInflation.pdf
Michelin hides theirs, but I found it. Note that the loads are per axle instead of per tire - unlike most other load/inflation tables:
http://www.michelintruck.com/michelintruck/other/Reference.jsp - then click on “Truck Tire/Lt. Truck Data". Save the PDF file on your hard drive for future reference without having to download it again.
I was told that the pressure listed on the tire was max pressure and the pressure listed on the door jamb was recommended pressure (for passenger cars), and is based in part of comfort of ride.
[/ QUOTE ]
Not exactly.
The pressure on the tire sidewall is the max pressure you should ever put in the tire.
The pressure on the Federal Certification Label on the lower doorpost behind the driver's door is the PSI needed only when the the vehicle is loaded to GVWR. For a pickup, that's the most you should ever put in the tire - but again there's an exception. LT tires (when loaded to the GVWR) can have up to 10 PSI more than that, and LT tires should always be overinflated by 5 PSI more than the PSI indicated in the load/inflation table for sustained high speed cruising of over 70 MPH.
[ QUOTE ]
With the Ford Explorer/Firestone tire debacle of a few years ago, which do you go with?
[/ QUOTE ]
Neither one. Both those are maximum PSI. The PSI you should go with depends on the weight you have on each axle. Divide the axle weight by two to get the weight on each tire (or by 4 to get the weight on each Dooley tire). Then apply a load/inflation table. All load/inflation tables are identical for identical size of tire, so use any tire manufacturer's table for your size tire.
For example, when running around unloaded, I inflate my tires to about 50 front and 40 rear. When loaded for bear, I pump them up to 55 front and 65 rear. I never need the max of 80 PSI on the sidewall. My Cert sticker says 60 PSI front and rear, but I overload my F-250 by a few hundred pounds so I need the 65 per the load/inflation table. /ubbthreads/images/graemlins/blush.gif
Here's a quickie load/inflation table:
http://www.goodyear.com/truck/pdf/LoadInflLTMetric.pdf
Here's a comprehensive load/inflation table:
http://www.goodyear.com/truck/pdf/databook/loadInflation.pdf
Michelin hides theirs, but I found it. Note that the loads are per axle instead of per tire - unlike most other load/inflation tables:
http://www.michelintruck.com/michelintruck/other/Reference.jsp - then click on “Truck Tire/Lt. Truck Data". Save the PDF file on your hard drive for future reference without having to download it again.
[ QUOTE ]
LT tires (when loaded to the GVWR) can have up to 10 PSI more than that, and LT tires should always be overinflated by 5 PSI more than the PSI indicated in the load/inflation table for sustained high speed cruising of over 70 MPH.
[/ QUOTE ] This stuff about adding pressure for higher speeds with LT tires only relates to "65 mph-rated tires". Or "non speed rated tires". Years ago these were common. This would not apply to any modern radial LT tires as I believe that the lowest speed rating you will find is "Q". Q=99 mph. NOTE : some Truck and Bus tires are still speed rated at 65 mph today. Others are 75 mph. There may be some that are higher. And there may be some Bias Ply LT tires that are 65 mph-rated also. This "inflation pressure increase" for speeds above 65 would apply to those tires.
LT tires (when loaded to the GVWR) can have up to 10 PSI more than that, and LT tires should always be overinflated by 5 PSI more than the PSI indicated in the load/inflation table for sustained high speed cruising of over 70 MPH.
[/ QUOTE ] This stuff about adding pressure for higher speeds with LT tires only relates to "65 mph-rated tires". Or "non speed rated tires". Years ago these were common. This would not apply to any modern radial LT tires as I believe that the lowest speed rating you will find is "Q". Q=99 mph. NOTE : some Truck and Bus tires are still speed rated at 65 mph today. Others are 75 mph. There may be some that are higher. And there may be some Bias Ply LT tires that are 65 mph-rated also. This "inflation pressure increase" for speeds above 65 would apply to those tires.
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2,572 Posts
[ QUOTE ]
The pressure on the Federal Certification Label on the lower doorpost behind the driver's door is the PSI needed only when the the vehicle is loaded to GVWR.
[/ QUOTE ]
Correct me if I'm wrong, but is not the pressure on the label to meet the GAWR (axle weight rating)? Combined axle weights will usually exceed GVWR.
The pressure on the Federal Certification Label on the lower doorpost behind the driver's door is the PSI needed only when the the vehicle is loaded to GVWR.
[/ QUOTE ]
Correct me if I'm wrong, but is not the pressure on the label to meet the GAWR (axle weight rating)? Combined axle weights will usually exceed GVWR.
Joined
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18,824 Posts
[ QUOTE ]
Correct me if I'm wrong, but is not the pressure on the label to meet the GAWR (axle weight rating)? Combined axle weights will usually exceed GVWR.
[/ QUOTE ]
I'm not the expert on this stuff. Maybe we can get toalpi to chime in with the straight scoop. /ubbthreads/images/graemlins/cool.gif
But here's my take:
You're probably right. /ubbthreads/images/graemlins/warmsmile.gif
Use my pickup as an example.
GVWR 8,800
Front GAWR 4,850
Rear GAWR 4,970
Combined GAWR = 9,820
Ford says 60 PSI front and rear. For my stock tires, 60 PSI results in 2,485 pounds capacity per tire, or max of 4,970 per axle. 4,970 is the same as the rear GAWR and slightly more than the front GAWR. But 55 PSI is a tire capacity less than the front GAWR. So it has to be 60 when loaded to the GAWR. /ubbthreads/images/graemlins/grin.gif
But on a practical note, when I'm overloaded to 9,620 GVW and 15,960 GCW, my front axle carries 4,440 pounds and the rear is 5,180. So I'm nowhere near the GAWR on the front axle, but overloaded on the rear axle. That's why 60 PSI in the rear tires is not enough for my rig when loaded for bear. /ubbthreads/images/graemlins/blush.gif (And if those numbers look funny to most of you, remember that I have a 4x2 with around 400 pounds less road-hugging weight on my front end. /ubbthreads/images/graemlins/cool.gif )
Correct me if I'm wrong, but is not the pressure on the label to meet the GAWR (axle weight rating)? Combined axle weights will usually exceed GVWR.
[/ QUOTE ]
I'm not the expert on this stuff. Maybe we can get toalpi to chime in with the straight scoop. /ubbthreads/images/graemlins/cool.gif
But here's my take:
You're probably right. /ubbthreads/images/graemlins/warmsmile.gif
Use my pickup as an example.
GVWR 8,800
Front GAWR 4,850
Rear GAWR 4,970
Combined GAWR = 9,820
Ford says 60 PSI front and rear. For my stock tires, 60 PSI results in 2,485 pounds capacity per tire, or max of 4,970 per axle. 4,970 is the same as the rear GAWR and slightly more than the front GAWR. But 55 PSI is a tire capacity less than the front GAWR. So it has to be 60 when loaded to the GAWR. /ubbthreads/images/graemlins/grin.gif
But on a practical note, when I'm overloaded to 9,620 GVW and 15,960 GCW, my front axle carries 4,440 pounds and the rear is 5,180. So I'm nowhere near the GAWR on the front axle, but overloaded on the rear axle. That's why 60 PSI in the rear tires is not enough for my rig when loaded for bear. /ubbthreads/images/graemlins/blush.gif (And if those numbers look funny to most of you, remember that I have a 4x2 with around 400 pounds less road-hugging weight on my front end. /ubbthreads/images/graemlins/cool.gif )
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