air pressure question

Messages
17
Location
Mackay, Idaho
This sounds like a silly question, but what air pressure recommendation do you follow? My owner's manual specifies one pressure, but the tire has another pressure on it specifying maximum air pressure at maximum load. Which one do you follow? Thanks. trinket
 
Messages
2,703
Location
Lincoln, NE
I go with the one listed in the door jamb/owners manual. The one listed on the tire is the absolute maximum pressure that particular tire (not car) can handle - and stuffing that much air into it could cause funky wear and handling issues; depending.
 
Messages
12,385
Location
Northern CA
The pressure molded onto the tire is the maximum do not exceed when cold pressure for the tire and wheels designed to go with that class of tire. It has nothing to do with what is the correct pressure for your car. Start with the ownwers manual recommended pressure. It's usually a bit low for max economy or handling. Car manufaturers like to pick a pressure the gives the smoothest ride they can without completely ruining tire life. Once you get used to what the owners manual recommends, try 4 psi higher and see if you like that better. It's generally not a good idea to go much more than 4 psi higher the owners manul recommendations.
 
Messages
235
Location
Ar
If I followed the pressure listed on the door jam, my tires would be almost flat. I went from stock 195/70/14 tires to 205/55/16. The new ones list 44PSI max, and I run them at 40 cold (front) and 27 cold in the back. If I run any less than 40 in the front, they squat. Gotta love FWD. Follow what gives you the best results, just don't exeed the max pressure listed on the tire. [Smile]
 
Messages
2,533
Location
Pittsburgh, PA
I always go higher, up to the max on the sidewall sometimes, because I think the mfg's recommended psi is based more on having a smooth ride than performance and tire life. My truck calls for 30 all-around but I run 34f/30r, her car calls for 30 all-around but I run 35 all-around, my van is old and you can barely read the sticker plus I have bigger tires and wider wheels so I run 35f/32r. Basically just see how they wear and adjust accordingly, but in my experience using the recommended psi usually results in faster wear on the edges.
 
Messages
1,565
Location
palm beach
i awalys run my tyres at the maximum listed on the sidewall. who cares what the car manf says. higher tyre pressure means more fuel economy, better tyre life, less tyre heat, and improved handling.
 
Messages
1,187
Location
Southern Vermont
In 40 years of driving, the rule of thumb I follow is to start at around 32-35 cold, and then adjust as appropriate. It is usually down, but I almost never wind up below 30. What is an appropriate pressure in any particular circumstances, as a fraction of maximum pressure, depends in part on how much load the tire will see in relation to its maximum load rating. As many others have said, the pressure on the tire sidewall is the maximum recommended for the tire by the tire manufacturer, and represents the maximum pressure to be used when the tire carries a load at or near its rated maximum. If you are carrying a full capacity of passengers with their luggage, increasing pressure for that journey is a good idea. An investment in a good tire gauge is wise.
 

trinket

Thread starter
Messages
17
Location
Mackay, Idaho
Thanks for all of the good information, everyone. Most agree to inflate above the car manufacturer's number, but below the maximum molded into the tire. Do you folks who inflate higher than the manufacturer's amount lower your pressures for winter road conditions?
 
Tried and true procedure for getting your tires on your car or truck at the optimum pressure for traction and wear. Draw a straight chalk line across the tread of each tire. Roll the vehicle a few complete tire revolutions and stop. Check the chalk line for wear pattern. If the chalk wears evenly across the tread. record tire pressure. If wear is center to the middle of the tread, tire is over inflated, let out a couple of lbs and start over again. If wear is on the outside near the edges of the tire and the chalk in the middle still shows, tire is under inflated, add a couple of lb's and start over. When you get the chalk line to wear evenly across the tread you’re done. Record tire pressure for each tire and L/F, L/R and R/F and R/R. Then as long as you use the same pressure gauge you used for this procedure you will easily be able to maintain the proper pressure for the life of the tire. I check every 2 months (cold tire) The principle is a tire that is over inflated will mostly contact the pavement at the center of its tread, being too full of air, and a tire that is under inflated will ride more on the outside tread while the center tread will bulge (concave inwards) slightly due to not enough pressure to fully contact the pavement. I have done this for over 30+ years of driving. I have never had a tire blow out and always get at lest the minimum miles of wear for any given tire. On passenger cars I rotate the tires every 10K, on trucks every 5-6K Note;if wear is uneven or one sided you need to get that tires alignment checked, possible rim damage, something is causing the tire not to roll smoothly over the pavement. If its worth doing, DO IT RIGHT THE FIRST TIME. [Patriot] [ September 20, 2004, 07:02 PM: Message edited by: Steel Blue Wind Rider ]
 
Messages
2,387
Location
Chicago area
Take a close look at the maximum pressure given on the side of the tire. It has a corresponding maximum weight allowed, as well. No one ever seems to notice the other half of the statement.
 
Messages
8,711
Location
Nothern USA
quote:
Originally posted by Steel Blue Wind Rider: Tried and true procedure for getting your tires on your car or truck at the optimum pressure for traction and wear. Draw a straight chalk line across the tread of each tire. Roll the vehicle a few complete tire revolutions and stop. Check the chalk line for wear pattern. snip.... Note;if wear is uneven or one sided you need to get that tires alignment checked, possible rim damage, something is causing the tire not to roll smoothly over the pavement. If its worth doing, DO IT RIGHT THE FIRST TIME. [Patriot]
ey, that sounds like a great way to check to see if you need an alignment. The toe in can be a way off and you will never know it until the tire is ruined.
 
Messages
2,077
Location
Cordelia, CA
I bump them to the max, then start letting out until the tire scrub is seen reaching the arrows on the sidetread. Course, I "Drive it like I stole it." Steel Blue Wind Rider's method is good for more sedately driven vehicles.
 
Messages
40,715
Location
Great Lakes
quote:
Originally posted by cryptokid: higher tyre pressure means more fuel economy,
True.
quote:
better tyre life,
Umm... no. All you're going to achieve this way is uneven tire wear. The center of the tread will wear out faster than the sides and you'll have to replace your tires sooner.
quote:
and improved handling.
That's a questionable one at best. Yes, you get quicker steering response by having stiffer sidewalls, but on the other hand you lose grip because the more you inflate it, the smaller the contact patch surface. As for me, I follow the owner's manual. I find that if I go up even a few PSI, the centers start to wear out too fast, and with high perf. summer tires which wear out pretty quickly anyway, you don't have to wait long to notice it. [Smile]
 
Messages
40,715
Location
Great Lakes
quote:
Originally posted by trinket: Do you folks who inflate higher than the manufacturer's amount lower your pressures for winter road conditions?
If anything, you should add a few PSI more air in your tires just before winter (if you don't check it often that is). That's because for every 10 degree F temperature drop, your air pressure will go down by 1 PSI (approximately). So, let's say it's 50F today, and you decide to inflate your tires to 35 PSI. Then, one month later when winter hits and it's now 10F outside, you'll only have about 31 PSI in your tires. Of course I recommend checking the air in your tires more often than that, but even I sometimes get lazy. [Big Grin]
 

JHZR2

Staff member
Messages
46,137
Location
New Jersey
steel blue: nice method, Ill be using that! What kind of chalk do you use? Is it powdered? big sticks of sidewalk chalk? Doesnt seem to me that the typical 'blackboard' type chalk (maybe its polymeric low-dust?) would work well. Thanks, JMH
 
Messages
3,939
Location
Somewhere in the US
I am surprised no one has commented that inflation pressure = load carrying capacity, so it is important that the placard inflation pressure be used as a minimum. The placard inflation pressure is based on many things and load carrying capacity is one of them. However, there isn't agreement between vehicle manufacturers about how this pressure should be calculated. Some manufacturers include a certain amount of overcapacity (we call it reserve capacity) and some don't. It's the ones that don't that make this whole issue of inflation pressure kind of scary - which is why the placard inflation pressure ought to be considered a minimum. Hope this helps.
 
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