Tire Pressure Questions

[zey]

I have a couple of questions about tire pressure issues:

1) How often do you need to pump your tire in order to meet factory specification?

2) Approximately how much of air pressure in terms of PSI (or kPa) drop per month?

3) A difference in environment temperature of 1 degree celcius will cause how much of air pressure difference in the tire? For example, during the day time, the temperature is 36C, and at night it's 22C, will it affect the air pressure in the tire?

I think that's all at the moment...thanks!

[Aurora40]

1) as often as it takes. The tire should always be at or above the factory spec.

2) this depends greatly on your tire, wheel, valvestem, and how well it was mounted. Some tires seem to hold air indefinitely, while some leak a few psi a month or more. You need to check your tires often to find out how they hold air.

3) 10F drop in temp will cause a drop of roughly 1 psi in a tire. I guess that's about 5 1/2 degrees C?

Low tire pressure can cause instability in the car, and can lead to tire failure at higher speeds and under load. It's much better to be a couple of pounds over the recommended pressure than to be a couple of pounds under it.

[zey]

Aurora40, thanks for your swift response. If all four of my tires have air leak of 20kPa over a month, is there any problem? I think it's very unlikely all four tires have defect at the same time.

[HellrotCi]

I just read an article about tire pressure. It was written based on direct input by several tire manufactures. What they said is it's better to be 10 psi over inflated than 2 psi under inflated. Check your tire pressure during the coolest period of the day and use the vehicle manufacturer's recommended tire pressure. I check my tires every 2-3 weeks. I find that I'll need to add a couple of pounds of air to 1 or 2 tires every 5 to 6 weeks. I don't worry about the ambient temperture changes that occur on a daily basis.

So to answer your questions:
1. about once a month
2. a couple of pounds
3. don't know the exact amount, but cooler temps will reduce your tire pressure.

[zey]

Thanks HellrotCi, I think you have answered my questions well. I'm using metal valvestems now, I hope it's better than rubber valvestems. I have heard people saying if the car is not being driven for long time (such as 2-3 weeks), the air pressure will drop even more. Is that true?

[HellrotCi]

Honestly, I don't know, but from my own experience it doesn't seem to matter. I've got a S10 p/u that I drive less than 1k miles a year and those tires never seem to lose pressure. I only drive it a few days in the spring and the fall to get some yard supplies. Basically it sits in my driveway 360 days a year.