How much does tempeture affect tire pressure? I've noticed that the pressure in my tires has been fluctuating quite a bit recently. The weather here in Michigan has been below zero at times but then will go up into the twenties later in the week. I keep my tires at around 33 and I've noticed them dropping to like 28 or so. Sometimes even lower. Is this normal in cold weather?
Thanks.

 

Temperature ushually changes pressure 4 pounds or so either way unless your in an enviroment that goes from one extreme to the other,the important thing is to set pressure when tires are cold on an average day 55-75 degrees.I would check tire pressure once a month unless it changed drastically or something then I would check weekly

 

It's become a saturday morn'n ritual ..for years... regardless of the car I own :smile:
I keep my tires at 34..it's my personal preference.
Temp swings as stated does effect pressure.... it's what it is :smile:
Peace,
D

 

Do you guys know of a good portable/home tire pump to buy? I'm tired of going to the gas station and paying to fill my tires up. Any suggestions?
thanks

 

i use a 12v cigarette lighter plug air compressor which i purchased at the local
auto store. It was like may be $25 or so. very convenient. I keep it in the
boot. :smile:

yep, 34psi for me too in the winter. i check about once a week but
check each tire visually before driving the car each time.

1psi changer per 10F increase/decrease in ambient temp.

 

Campbell Hausfield (Check Home Depot) makes a little plug in wall mounted compressor you can mount anywhere in your garage. Does tires, basketballs, footballs, and other smaller compressor tasks, even compressed air for blowing stuff off. Around $80.00

 

Check your local Costco. They have an electric pump that plugs into the lighter. I think it's under $20.

 

Camping stores will have cig-lighter-powered pumps (for blowing up air mattresses & the like.) Check sports authority, target, etc.

Bike (motorcycle or cycle) shops also stock really small portable pumps, if you want to take with. RiderWearhouse has a couple of them, but a quick google will find what you're looking for.

I use just a full size bike floor pump. For the small amount it takes to raise it a few PSI it's faster than tangling with cords!

Jeff

 

Thanks everyone. I love this forum.

 

I have an old Whisler "Air Command" system, not the fastest to fill up- but durable. I think it's about 10 years old. I check my tire pressure monthly, unless I'm driving on excessively bad roads, then shortly after the drive, and always before/after long trips (ie +3 hrs.).

I've found with drastic temp changes, your pressures can vary a few pounds.

 

p1*v1*t0=p0*v0*t1

If I remember my high school years that is the ecuation to pressure temperature volume, and if you change one of them and the others remain constant one variable will change.

More temperatura more pressure if the volume remains constant.

In this case the temperature is lower and the volume remains constant, that is why the pressure is lower.

If we have some phisics or chemestry majors please confirm the theory, no to make a debate just to learn more about it.

 

I check 2x a month, once when rotating.

Ken was right 10 Deg F is 1 PSI.

Bear in mind that "most drivers" will loose 1 psi a month in usage and the related heat cycles, not air temp related.

Alex

 

As I understand it, all manufacturer recommended pressures are based on tire and ambient temp. of 70 F. A 10 degree change will equal a pressure change of 1 lb.

Therefore, you should check pressures on a cold tire (not driven for couple of hours) and not having sun shining on one or more tires as this will increase the tires temp. If you want 34 lbs. pressure (this is what I use) and its 50 degrees out, put pressure at 32 lbs. If its 80 degrees, set pressure to 35 lbs.
I make it a point to check pressures everytime I wash the car. As we all know, in the case of the Mini, that could be several time s a week. I admit thats a bit more often than needed but, once you make it a habit its no big deal and only takes a couple extra minutes. More time to spend with your baby

 

>>As I understand it, all manufacturer recommended pressures are based on tire and ambient temp. of 70 F. A 10 degree change will equal a pressure change of 1 lb.

Manufacture recomeded pressures are based on the ambient air temperature of the conditions. Meaning that if its 20 degrees out, set your pressures when the vehcle has been undriven an exposed to those temps for 4 hours minimum.

Alex

 

I check mine before each autocross, which is about every other month.

 

Alex: I'm confused with your last comment. Surely you don't mean if temp. is 20 degrees ambient and you haven't driven for 4 hours, you would set pressure to 33 lbs. if that was the pressure you wanted! I think 70 -20= 50. 1 lb. per 10 degrees = 5 lbs. Therefore I'd set pressure at 28 lbs. Otherwise, if you set at 33 lbs. with temp. of 20 degrees, pressure would increase to 38 lbs. when ambient reached 70 degrees, even if you haven't moved the vehicle... Am I correct?

 

Set your air pressures to OE specs once the vehcle is not driven for 4 hours, and rests in the outside ambient air temps you intend to drive in. OE pressures are based on "cold temp" meaning before the tire has warmed up due to deflection while rolling.

Alex

 

So, what is the recommended tire pressure for an S with 195/55 x 16 tires. I'll be damned if I can read the chart on the door pillar? For "spirited driving" or better/crisper handling?

Also, what is recommended for aftermarket tires, like a 215/45/17, assuming I go that route with non-runflats

Charlie

 

33 PSI is you best bet on an S.

I have recomeded 34 F, 39 R for agressive driving, but it will wear your tires quickly.

Alex

 

I check my pressure every other week. Got a dial guage from Moss Mini as a "bonus gift" when I ordered my saddle bags. It's great and accurate. I purchased a small compressor off of E-bay a few months ago - I just went back and looked and couldn't find it listed. It is small enough to fit in one of side boot compartments and has a digital read-out guage, that stops the compressor when it reaches the set pressure amount. It was about $25.