Quick, what does your vehicle ride on?
If you said tires, you’re not quite there. Your vehicle rides on air. The tires are there primarily to hold the air in. When you look at tires that way, it makes it easier to understand why it’s so important to ensure your tires are at their optimal inflation pressures.
First, the dangers of low tire pressure
Low pressure creates uneven wear, it generates sidewall-killing heat and turns your vehicle’s handling to mush.
Excess pressure creates uneven wear, it increases the chance of a blowout and turns your vehicle’s handling to mush.
Low pressure allows the sidewalls to flex too much, generating heat, and it also increases the odds of wheel damage when you hit a pothole. The softer sidewalls are more likely to crush on impact to the point your wheel takes a hit.
It also turns the rolling surface concave, putting more wear on the treads on the sides than on the centre. Because the tires are flexing so much, your handling suffers, too.
Too much pressure turns the rolling surface convex, putting more wear on the centre treads than the sides, and because it’s riding on the centre instead of the entire tread, you don’t get the turning power or traction you should.
How to check your vehicle’s tire pressure: a quick look
When your vehicle has just been driven, the air inside your tires will be warm. Warm air expands, so check your tires now and you’ll get a false reading. It’s best to check your tires when your car has been at rest for at least an hour.
Using either an electronic tire gauge or old-fashioned stick type, place the end of the gauge on the tire nozzle (remove the cap first, of course) and seat the rubber on the gauge on the nozzle and then press and hold until you get a reading. If you hear air escaping around the nozzle, pull the gauge off and start over.
So, what should my tire pressure be?
Your tires are at the correct pressure when the gauge shows the same numbers as on the tire pressure sticker on your driver’s door jamb or in the manual. Ignore any numbers you see on the tire itself, as those represent maximum pressures.
Usually, the front tires will have slightly different recommended pressures than the rear tires. That’s OK. Some engineer who has forgotten more about tire pressures and suspension systems than most people know has arrived at that number after some careful calculations. Go with those stated numbers and ignore anything else you might hear.
Tires will gradually lose pressure even when in top condition. It’s usually a loss of air through the sidewalls. If your tire loses pressure rapidly, there’s usually an issue, either a puncture or an issue with the valve stem.
3 types of tire pressure gauges to know about
There are three types of gauges you can buy. The cheapest, and good enough for most applications, is the stick type that resembles a ballpoint pen. These run around $10.
Are digital tire gauges better?
A digital gauge will be more accurate, and is only $6 to $10 more. The other advantage is these typically have backlit LCD screens, making them good choices if you’re checking pressure in low-light situations, such as your garage.
A dial type has a face that resembles a watch, which can make it a bit easier to read than a stick, but these aren’t necessarily any more accurate and can be susceptible to permanent loss of accuracy when dropped. These sometimes come with a hose for attaching to the wheel, which means they require two hands to operate and are more awkward.
In all cases, protect your gauge from impact, such as dropping it, and keep it at room temperature rather than leaving it in your glovebox. Electronics work better at room temperature and any lubrication on mechanical gauges will be at a better viscosity, too.
Whichever type you buy, consider that you’ll need to check the pressure in a compact spare, if your vehicle is so equipped. These are typically inflated to 60 psi, so make sure your gauge goes to at least 70.
Keeping the Air in Those Tires
Air compressor is the way to go
Since bicycle tires are usually inflated more than car tires, even a bike pump can be used for your vehicle’s tires. Most people will want to use an air compressor, however. Gas stations that offer service sometimes leave a hose out near one of the service bay doors but more common are units that require payment to operate.
Where to inflate them
If you long for the days when air was free, remember that the air hose left out for you was simply supplying surplus air from the compressor used to drive the station’s power tools. If a station doesn’t have service bays, then it will have had to purchase and install a compressor for customer use alone, so don’t necessarily begrudge the need to pay. Some stations offer free air for even a small purchase, as well.
Summer tire inflation
In summer, inflating tires is as simple as putting the end of the hose on the valve and holding it on until the tire is inflated. If it sounds as though most of the air is going into the tire, you’re doing good. If you hear a lot of air escaping, simply reposition the hose on the valve until it stops. Pull the hose off and recheck the pressure and keep inflating and checking until the tire is at the specified pressure. Most tire gauges also have a little nib you can use to press in on the valve stem to deflate the tire if you go above the specified pressure.
Winter tire inflation
In winter, consider the compressed air might have a bit of moisture, or there could be moisture on the valve stem. Either way, it’s possible this moisture might freeze in the valve stem and hold it open, causing a slow leak. A little spritz of water-displacement fluid (such as WD40) on the valve prior to and after filling can help avoid this.
Make sure you replace the valve stem caps, as these keep dirt and moisture out of the valve.