Growing up I was always told that the only thing between me and the road were my tires. This has always stuck with me and I have valued this advice since I was 16 years old.
However, today's cars almost feel like they are nagging at us all the time. So I decided to embrace the safety feature because I do understand the importance of correct tire pressure and now I would like to debunk and provide you with the appreciation of understanding it too.
This article is from the Porsche Club of America, however it applies to all tires on all cars. I liked this article because it explains the what, the why, and the how. Whether you are a novice or an expert on tires, there are good explanations and nuggets to use and remember.
Did your low tire pressure light come on last week? | PCA Tech Tips posted by Manny Alban #PCATechTips Tuesday December, 27, 2022
tags: #tiredamage #techtips #diy #porsche
In the past few days, I saw a unique site at gas stations around the county I live in. A line not at the gas pump but rather at the air pump. I thought to myself, “Technology is forcing people to be safer.” Since September 2007, the US government mandated that all passenger cars come equipped with a tire pressure monitoring system. Did your light come on in the past few days?
I’m sure most if not all the cars in line had low tire pressure sensors that alerted them. After temperatures plummeted around the country, many people discovered that their tire pressures were less than recommended. Personally, I try to be on top of this throughout the year. Probably because years ago I didn’t realize that a tire was low on pressure and I ended up blowing out the sidewall on the highway. When you don’t have a spare, this makes for a bad day. My daily is a 1997 model, so I have to check my pressures manually. It’s something I do on a monthly basis.
So why does your tire’s air pressure drop when it gets cold? With apologies to my high school physics class teacher, here’s the part of Boyle’s Law that applies to our topic: The volume of a gas (including air) decreases when temperature is lowered and increases when temperature is raised. In the confined space of a tire, the air pressure changes depending on the temperature of the air. The rule of thumb is that a tire will lose between 1-2 pounds per square inch (psi) of air pressure for every 10° Fahrenheit drop in temperature. If you haven’t added air since the summer, you likely have lost air pressure in your tires.
Can I check the tire pressure when I fill up at the gas station? Yes, but it’s preferable that you check it in the morning before you get on the road. As you drive, the tires will warm up due to friction and the heat will raise tire pressures. To get an accurate reading, you want to check pressures before you start driving and also before the sun has had a chance to warm them up. If you notice one tire with significantly less air than the others (5 pounds of pressure or more), I would suggest looking for a nail that may have punctured the tread, damaged sidewalls (inside and outside), a crack or bend in the rim (check inside and outside, especially if you’ve hit a memorable pot hole recently), or a worn out valve stem. If you can’t find anything wrong with the tire or rim, add air, take note of the pressure, and check the pressure a few hours later or the next morning. A slow leak might even take days to reveal itself, and can be caused by corrosion of the wheel where the tire is mounted
How do I know what pressures to fill the tire to? Check your driver’s side door sill. There should be a decal from the factory that lists the recommended cold pressure. For Porsches, the front and rear tire pressures may differ across model lines, trim levels, and wheel sizes. Check your owner’s manual if your car does not have this decal, or Google the question and you’ll easily find the answer.
Should I carry a tire pressure gauge even if I have a TPMS (tire pressure monitoring system)? Yes. Tire gauges are not very expensive and can fit into your glove compartment. While tire pressure monitoring systems are very helpful, they can fail when the battery in a sensor goes bad. This can turn on your TPMS dash light. A tire pressure gauge will show whether or not the tire is really low on pressure or if you have a dying battery on your sensor. While I prefer to use a quality gauge, a simply pen-style gauge that you can find at Walmart is better than nothing (yes, I keep these in all my cars for emergencies). It’s worth noting that TPMS sensors may display different air pressures than your air pressure gauge. For example, a coworker’s Cayman has sensors that always read 2 psi below his Longacre Racing gauge yet are otherwise accurate. And different air pressure gauges sometimes give conflicting data, whether due to quality or damage. This is why it’s worth purchasing at least one quality air pressure gauge to double check against TPMS sensor readouts as well as to make sure all your other cheaper pen-type air pressure gauges are functioning properly.
I also recommend purchasing a quality air compressor to fill up your tires at home. These are now compact and can be preset with the pressures the manufacturer recommends. You can buy one with an automatic shut off for less than $30 at most Home Depots, Lowes, Walmart, or Amazon. A quick look at online reviews and features will help you determine which one fits your needs. These can also serve as a tire pressure gauge. Here are a bunch of options on Home Depot's website.
Running over a pothole or debris can damage not only the tire but also the wheel, especially if tire pressures are too low. The inside sidewall of the above tire is damaged and will need to be replaced. Look closer and you'll see that the wheel is also cracked. Be sure to check both the inside and outside of a tire for sidewall or wheel damage. Because Porsches often come with a bit of negative camber, the inside of the tire or wheel is often what makes the first and hardest contact with the edge of a pothole.
What does keeping the tire pressures at the correct level do besides keeping the TPMS light off? As I said in the beginning, it’s just plain safer. A tire at the recommended pressure will keep it and the vehicle operating as the manufacturer intended. It also improves gas mileage. A tire running too far below the vehicle manufacturer-recommended pressure runs the risk of being damaged (which is unsafe) and creates more drag, reducing fuel economy. Low pressure can even lead to a damaged wheel. Conversely, running a pressure that’s far too high is also bad, so do not think that adding extra pressure to hedge a drop in temperature is a smart move.
Of course, the alternative is to simply move to a warmer, stabler climate. But even relatively mild seasonal temperature changes can mess up tire pressures. The video below is from a television news station in the very cold state of Minnesota. They know all about tire pressures dropping in the cold weather. (the video would not load, but you can google it).
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