My brother is an incredible wealth of knowledge about anything and everything I have ever asked him. The cool thing about getting instruction from him is that he never assumes I have a 'baseline of knowledge'. He teaches from scratch. I'm posting most of our entire chat just in case it can help someone else out there like me. I'm sure I'm not the only one on the planet who doesn't know about tire pressure! So, here is our chat about tire pressure and how to work the air machine:
Serena said: Sooooo..... how do you put air in your tires?
Michael: ? How do you put air in your tires? What do you mean? Is this a metaphor?
Serena said: Um.....no. I truly don't know how to do it. Check out my blog.
Michael: 'Somewhere written on the tire is a number followed by PSI...' The number on the tire is the MAXIMUM the tire should be run at. The specs for your vehicle are on a sticker on the driver's side door. Open the door, look down along the side that would be impossible to see when the door is closed, and there it is! It’s probably 30 or 32 psi.
Serena said: You know, I found that, but disregarded it because it wasn't on the tires. It said 33 psi.
Michael: Good. That is the pressure the car was designed to operate at, for maximum fuel economy and handling characteristics.
Serena said: Ok. Now. 3 of my tires said 28, and one said 30. They are all supposed to be at 33. How do I get them up to 33? I know I have to use one of those machines at the gas station, but I don't know how they work. And what happens if I get too much in? Will they blow up?
Michael: Don't worry about the light - the car won't blow up.
When the pressure is mismatched, you lose a very small amount of fuel economy, it might not corner that great, and it might cause a little extra wear on the CV joints.
“A little extra” is a 1.) function of how low the pressure is (tires will still run with as little as 10 lbs pressure), and therefore how great the mismatch between tires, and 2.) how long you leave the problem unattended.
At the gas station, there will be an air pump that will probably cost you $0.75 to use for two minutes of air.
Uncap the valve stem on your tire, put the money in, press the nozzle TIGHTLY to the valve stem. You’ll know if it isn’t tight enough, because you’ll hear hissing of air escaping.
Many stations have a gauge built into the nozzle – you release the handle WITHOUT LESSENING THE PRESSURE AGAINST THE VALVE STEM and the gauge pops out with the tire pressure. Continue filling until you hit the number you are after (33).
Another note:
Tires get hot as they run, so 33 psi is a cold temp. Try to use a station nearer to your house. If you have to drive a long distance, put in 34 or 35 lbs (as long as the number on the tire sidewall is at least 35 psi), go home, check your pressure in the morning after the car cooled all night, and bleed off the excess until you get to 33.
Really, though, that is being reeeeeeaaaallly fussy about it. The exact pressure is not as important as getting all the tires as close as possible to the same number.
Don’t forget to put the valve stem cover back on. It keeps road dirt out of the valve.
Serena said: Okay. It sounds like I can do this. :)
Michael: Come to think of it, its winter, everything in Buffalo is close by – just fill ‘em to 33 and don’t worry.
Serena said: LOL! It's 19 degrees right now!!!
Michael: Yeah. That is TRULY cold temp.
Now. If the pressure falls a long distance in one of the tires, say to 20 lbs, you will notice pulling to one side of its in the front, or a feeling that the car is trying to skew sideways a little if it is in the back. The point? A mismatch affects handling, and can cause loss of control in sudden responses or slippery road conditions.
Again, don’t be paranoid, just understand that there is a reason to pay attention to this maintenance detail.
Serena said: Yeah, the idiot light being on really frightened me.
Michael: One more thing about tires – improper pressure causes uneven wear. If you run them a long time underinflated, they wear out on the edges before the center. If you run them overinflated, they wear out in the center of the tread before the edges.
The second scenario is easy to visualize – overinflation makes the tread balloon out, or bulge.
Low pressure also allows the tire to fold over (collapse) on hard cornering.
Use a gauge. Trust science.
You need to get your father to teach you how to change a tire. Seriously, he’s good at it. Back in the day, before steel belted tires were invented, tires were “bias ply” with fabric belts. Flats were very common, so most everybody learned how to change a tire.
Even if you have AAA, it is something you need to understand – you might have a flat at a time or in a place that you just cannot wait four hours for the AAA tow truck to appear out of the mist.
Serena said: True. Something AAA is doing now is asking if you are in a safe place when you call. In my case, I tell them I am with a child, and my wait time has never been longer than 20 minutes when Ian is with me. It's not something I'd like to count on, though.
Michael: You bet. And Ian will not always be with you. ;-) Besides, it’s a chance for bonding with your dad. :D
You asked, ‘what happens if I get too much air in the tires? Do they pop like balloons?’
On the rare occasions when tires fail, the nearest grease monkey is either killed or horribly injured.
The good news is that this hardly ever happens, and I’ve never heard of a case happening when ordinary folks are properly doing routine maintenance.
http://www.automotivetraveler.com/index.php?option=com_content&task=view&id=225&Itemid=119
We didn’t cover tread depth. The tread should be at least up to the top of Abe’s head when you stand a penny in the groove.
Serena said: Why?
Michael: Insufficient tread - HYDROPLANING!!!! WHEEEEEE!!!!
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=51
Serena said: Oh.
Michael: http://en.wikipedia.org/wiki/Hydroplaning_(tires)
http://www.engr.pitt.edu/ssc/images/clip_image001.gif
Hydroplaning = “there’s a little brown spot in my shorts today”
(Sung to “There’s a little black spot on the sun today” Sting)
Serena said: LOL! Wow. Okay. Does air pressure in the tires affect the tread depth?
Michael: No. Tread depth is a direct function of wear.
That is why tires are rated by miles: 15,000 mile tires are cheaper than 80,000 mile tires because they will wear out faster.
Serena said: Ah haaaaaa. And the 80,000 tires are probably the more expensive.
Michael: Of course. They are made with more expensive chemicals & processes, and more complex design.
Did you know that roads are covered with a bacterium that lives on the rubber shed by tire wear?
Serena said: Eeuuu.
Michael: That is why the roads are not full of black eraser crumbs.
Serena said: Good heavens.
Michael: I know. You don't really think about it, but all that rubber has to be going SOMEWHERE!
Serena said: How do you know this stuff?!?!
Michael: I am Obi-Wan.
Serena said: How different our conversations would be if it weren't for Star Wars!
Michael: LOL! You bet!
Plus, I lived next door to a tire salesman – he told me all kinds of stuff that I have not even gone into – the 300 chemicals it takes to make tires, the belts in the sidewalls to prevent failure, blah, blah, blah. It’s an entire universe of knowledge.
