Tire Pressure: What Constitutes "Cold Tire Pressure?" (vehicles, 2011, auto)
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In the winter time your TPMS might come on untill the tires warm up.
In this case, they are under-inflated. As noted, they should be filled to the correct pressure at ambient air temperature without driving. So, in the winter, you'll need to add air so that they are the proper temperature without warm up. Obviously, no one is going to add/subtract air ever day, and in the example given by Vannort where it is 50 degrees one morning and -5 the next, you would get the light on the -5 day, but you should make seasonable adjustments.
The door sticker is for the cheapo factory tires. You should alway inflate to the tire manufacturer's recommended pressure, which is usually higher than the car maker's cut rate tire pressure.
The door sticker is for the cheapo factory tires. You should alway inflate to the tire manufacturer's recommended pressure, which is usually higher than the car maker's cut rate tire pressure.
So, in your opinion, what should I have inflated the tires to on the Jeep Wrangler Rubicon that I used to have, that came from the factory with Load Range E tires?
The Jeep sticker said 33 PSI.
The door sticker is for the cheapo factory tires. You should alway inflate to the tire manufacturer's recommended pressure, which is usually higher than the car maker's cut rate tire pressure.
This is correct semantically only. Almost every tire manufacturer (other than some specialty tires) recommendation is to use the door sticker for stock sizes. If you change the size of the tire, the reccomendation changes by tire size (not tire manufacturer). What the tire manufacturer tells you (on the sidewall) is the maximum safe inflation that you should not exceed. This is not the recommended pressure. You can find the above information confirmed on any reputable tire manufacturers web site or manual. Again, specialty tires (off road, racing etc....) may be different, but otherwise you should be using the door/owner's manual.
Cold tire pressure refers to the pressure when the tire is cold, which means at the ambient air temperatures. It doesn't mean cold as if the tire feels cold, but cold as opposed to being hot due to running. The ambient air temperature is as cold as the tires can get sitting outside. Ambient temperature changes, so it's best to measure in the morning at the lowest temperature. If you have a heated or cooled garage, you should measure the pressure at outside temperatures, since those are the temperatures at which the tires run on the road.
The maximum pressure given on the tire sidewall is the maximum, not the recommended. The tire manufacturer does not know what vehicle each tire will be put on, so they can't give a pressure recommendation, since that's based on the tire/vehicle combination. The vehicle manufacturer knows its vehicle and specifies certain tires, so they give the pressure recommendation. The only reason to be concerned with the pressure limit on the tire is that it needs to be at least, and preferably above, the pressure recommended by the vehicle manufacturer.
Tire pressure naturally drops when temperatures cool, but pressure also drops due to use. All tires leak, most very slowly. As the rubber flexes when the tires turn, air molecules slip through. The rubber is not the solid wall it looks like, but under a microscope actually looks like strands of spaghetti. The strands move around as the tire turns, and air molecules slip through. This effect, however, is very small. In my experience, adding air in winter to counter colder temperatures and maybe once or twice per year besides will compensate for the small leakage. I drive a lot, so this natural leakage may be more for me than for those who drive less.
So, in your opinion, what should I have inflated the tires to on the Jeep Wrangler Rubicon that I used to have, that came from the factory with Load Range E tires?
The Jeep sticker said 33 PSI.
Did you read the owner's manual? My Grand Cherokee specified minimum tire size and load range C for towing, with a recommended inflation of 55 PSI, the same number that is marked on the typical load range C tire. The Rubicon is a light duty puddle jumper, so load range E tires were silly. I bet it was jacked to the point of being a rollover hazard too.
When checking your tire pressure considering buying something better than a pencil gauge.
I was using a pencil gauge when I was enjoying my motorcycle at the race track. I checked the pressure and it was good. I got on the track and instantly knew something was very wrong with the bike. Got to the pits and borrowed a nice gauge made by Quick Car. The pencil gauge was wrong and I over inflated my tires by about 12 psi.
I got a quality gauge and it has been with me for years.
All tires leak, most very slowly. As the rubber flexes when the tires turn, air molecules slip through. The rubber is not the solid wall it looks like, but under a microscope actually looks like strands of spaghetti. The strands move around as the tire turns, and air molecules slip through. This effect, however, is very small. In my experience, adding air in winter to counter colder temperatures and maybe once or twice per year besides will compensate for the small leakage. I drive a lot, so this natural leakage may be more for me than for those who drive less.
No they don't. The only places they can leak is at the bead, where they contact the rim, and at the valve stem. I was in Automotive for 40 years, and tires do not leak through their walls, unless punctured.
The "strands" you speak of, or "Belts" in a tire, are molded in rubber casings, that do not leak. or pass air.
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