This Sub-topic is for discussing the article listed above, which can be read here. Please add your thoughts and reactions to the article.

In response to your recent article concerning proper tire inflation you advise drivers that "Under loads, inflate tires according to the manufacturers recommendations, NOT the maximum pressure listed on the sidewall."

As an instructor and owner of Control Driving Skills in Smiths Falls, Canada, our classes are taught to keep their tires at the "Maximum" air pressure indicated on the sidewall at all times for safety and vehicle control reasons. I agree that under "normal loads" the manufacturer's recommended pressure is sufficient. "Normal loads" only apply when everything is under control. During emergency situations it is not uncommon to load an individual tire with 10 - 20 times the normal load if heavy braking or aggressive steering is undertaken. Now you need and want maximum pressure to ensure the tire will stay on the rim. You will not have time to stop and increase your pressure before you complete the exercise.

Maximum pressure is compared to an insurance policy—you hope you will not need it—but if you do ... you'll want it NOW!

Stiffer side-walls give better steering response, as well as better braking response, cornering control, and keep the footprint properly placed on the road surface for maximum traction. Softer tires wear out quicker, hydroplane at lower speeds, and roll more with lateral pressure.

Also, air pressure loss due to temperature drop is not as critical, not to downplay the practice of constantly checking air pressure. We tell our students that especially during the fall, winter, and spring to check their tires every two weeks.

When I get told that harder tires result in uncomfortable ride, my response is that 90% of comfort is the result of the vehicles suspension system and the thickness of the seat you are sitting on. But if they insist, I tell them that they have to sacrifice a little comfort for better control.

High performance cars have low profile tires at high pressure for performance and handling which I interpret as safety. If you watch most races you will hear about a crew altering tire pressure by ½ pound in one tire to affect the handling of the vehicle. In emergency situations on the roads, our vehicle control and response is every bit as critical if not more so than on a safe race track.

Thank you for your time and interest.

I am interested in Bob Joynt's comments on tyre pressure. He states that he advises people to drive with the maximum pressure in their tyres. How does this affect the wear and tear of tyres? At our driving school (Safe-T in Brisbane, Australia) we advise our clients to put an extra 4-5 psi in their vehicle tyres and 10 psi in the spare - above the vehicle manufacturers recommended pressure. That is what we use and it gives good control, comfort and wear and tear.
Tony Everett

I don't understand why people insist that they know better than the teams of tire engineers and rubber scientists at the car and tire manufacturers. If you advise clients to put more air in the tire than recommended by the company that MADE the vehicle and then they crash and are injured or die--what evidence will you provide to back up your advice when they sue you for negligence or causing them harm?

I ask this to get you to think hard about your advice, and what science it is based on. Over or under-inflation are well-established as dangerous practices. Recent tire recalls have shown us the incredible folly of the wrong combination of tire and vehicle and pressure. Regardless of the final outcome of the Firestone/Ford controversy, what should be clear is that tire pressure can be seen as the source of blame in lawsuits. Even if the manufacturers of either the Explorer or the tires in this case were giving bad advice or practicing bad engineering, one of the things I learned from the experience is to make sure I follow the instructions on the door jamb of my car.

There may be different regulations and hence different labelling practices in different countries. In Australia the label on the door jamb shows a recommended pressure that is probably biased slightly toward greater ride comfort rather than braking and handling performance. Therefore, most tyre (sorry, tire in the US) manufacturers and retailers and motoring organisations recommend pressures 4psi or so above the labelled recommendation for better braking and steering response, because with higher pressures come stiffer sidewalls and less movement of the tyre relative to the rim - as mentioned by Bob Joynt above and in the original article.

Some also suggest raising pressures higher again when doing an extended run at highway speeds, as distinct from driving around town. This is because tyres at higher pressures will run cooler, and tyre life will be extended.

On my car the recommended pressure is 32psi; I run mine at 36. I do a lot of highway running and use those pressures all the time.

Tyre pressures are a compromise between ride comfort on the one hand and better braking/handling etc on the other. If you run your tyre pressures higher you might experience a harsher ride although this is probably hard to discern for most purposes at about 4-5 psi above recommended pressure. At pressures above that you probably will feel the difference in additional vibration, especially on rougher surfaces.

There is room for experiment and for all owners to try different pressures for themselves to find the compromise that suits them best. I personally would not favour going to maximum pressure as Bob Joynt suggests: you would get optimum braking and handling but for my money the ride would be too harsh for the benefit gained.

What is without doubt is that owners should not run at lower than recommended levels because braking and handling will be compromised and tyre life degraded: to put it shortly it's less safe and more costly. Over-inflation is also dangerous because it reduces the size of the tyre contact patch on the road, and will lead to greater wear on the centre of the tread. But that occurs at much higher levels than 4-5psi or so.

To construct a tire they use extreme heat. To de-construct a tire drive underinflated. That is the story of steel belted radials. Underinflation allows maximum belt flexing and heat build up. Feel your tires after a highway trip. You can burn your hand.

The question I have to ask is why can't I buy Kevlar belted tires? My experience at a time when I was busy with my life, 60 and 70 hours weeks, was a total ignoring of liquid levels, belts, and tire pressure. My Kevlar tires never gave me a problem. They protected the sidewalls from nail and stone damage, and when underinflated did not blow. Not so my Michelin tires, on the outgoing trip tire pressure was checked, a brief business call, back on the road, and on the return trip the tire was totally destroyed. How many of us re-check our tires every time we stop and then go? It's good advice, but humans being what we are, I believe we are asking the impossible, when we ask people to check their tire pressure by the trip or by the day. Shouldn't tires be made 'idiot proof'? As well can we get the financially challenged to buy new tires? These drivers are putting used tires on the wrong side of their vehicles, and proper inflation will not stop the consequent overheat, and blow-out.

So, why won't the tire companies sell us Kevlar tires? Or is there something about these tires I don't know about? Is it because the steel lobby is better at marketing than Dupont? Or is it just because the tire companies and car companies do not care about safety for ordinary citizens unless legislated to do so?

What is BOB Joynt on!!!!

The maximum tyre pressure is just that - its the the maximum setting for maximum load. What do you think happens if you run the tyres at maximum which is set /checked at a cold setting AND THEN run the tyre for four hours or more? Heat /expansion, maybe. His students are either spending a fortune on tyres due to excessive wear or explosions! By the way - for security stuations - you need only run tyres at 5 psi above the manufactures recoommended pressure to ensure it stays on the rim. The only other reason to adjust it slightly - is to take into consideration extra cargo weight!

Interesting string! I've felt for years that the tire (tyre) pressure should be closer to the sidewall maximum. Ride is an issue, but I have used the wear of the tires as a better indicator. Using a tread gage on new tires, I find the pressure at which the tread wears evenly across the tire. I figure that gives me most effective footprint, minimum even wear, and yet most effective traction in the wet as well as in the dry. That number for me is about 3-psi LESS than the sidewall max, for the way I normally load my car.

I am an advanced driver instructor in New Zealand and the advice we give is similar to Bob Joynts- a 4-5 lb increase over manufacturers [minimum] figures which are unrealistic and unsafe especially on our course chip, high cambered roads. David Carter has it in a nutshell, a tyre should wear evenly across the tread, we generally find that wont happen with factory recommended pressures. We check all our clients cars before the course begins, in 5 years I and most of my fellow instructors have never seen a case of over-inflation whereas, underinflation is an epidemic. Vehicles with minimum pressures handle like pigs and I believe are the cause of many unnecessary deaths.

While I appreciate Brian and others who offer anecdotal evidence, and "beliefs", it still begs the question: whose advice would you rather take...that of current and former race car drivers and advanced instructors, or that of billion dollar companies with teams of tire engineers (and lawyers) who spend years researching tire technologies and vehicle safety?

It's really simple Doug, we're out on the coal face & they are not. If you're tyres are not wearing evenly all the way accross the tread, [ie. both shoulders are worn], alignment is correct & you are using factory specs then.....somebody has it wrong.

My cars have been tire-eating machines for years (uneven tread wear and tread separation). One of the cars is relatively new with 19,000 miles. The tires were always inflated as specified on the door placards, but they just kept wearing out quickly. I decided to try increasing the pressure 5 lbs above the placard specs on both cars, and the results have been amazing. The new tires on both cars have shown minimal relative tread wear, and the ride is still smooth. Perhaps living in a desert is a factor, but the increased PSI sure seems to help.

The vehicle placard is a very poor guide for the proper pressure to have in your tires. It is based on a certain tire at the time of its manufacture. At that time the tire may have been a maximum pressure 32 psi tire, or maybe a maximum 35 psi tire. There is really no way to tell. These days a max 44 psi tire is not that uncommon as a replacement tire for the same vehicle. If 30 was recommended for the tires then, do you put 30 in your 44 psi tire now ? Of course not. It would be severely underinflated. So, the lesson here is: Never use the manufacturer's placard as a guide, unless you are dealing with the originial tires (which as we all know are usually cheap tires that don't last too long anyway.

I haven't read where anyone has addressed the issue of frequent cornering. Most driving is done under varying conditions, one of which is driving on roads with many curves. Curves will put excess stress upon the sidewalls of the tires compared to straight roads. If the tires are below maximum pressure they will flex more which will result in poor handling, as well as excessive wear and tear. Maximum pressure does not detract from highway driving so there is no reason not to put maximum pressure in your tires. Tires are max psi rated at cold pressure so the extra pressure that results when your tires heat up is already taken into account. By the way, you are in greater danger from blowouts at lower pressure than at maximum pressure. Blowouts are caused by heat buildup, and heat builds up much faster in underinflated than in overinflated tires, since underinflated tires have larger footprints and this puts more stress upon the sidewalls.

Although of course it is not recommended for other reasons, one can put 10-15 psi more than the max pressure in a tire and not fear that it will "blow." Tires are manufactured to withstand tremendous pressures, up to double their max, without bursting. The continuing problem on the road today is underinflation, not overinflation.

The US based BMW Advanced Driving Course recommends BMW owners inflate to maximum recommended pressures for everyday driving.
Manufacturers pressures are minimum pressures for low speed round town driving and obviously still not enough.
For those over inflated scare mongerers ;-) why do racing cyclists utilise anything up to 130 psi in their tyres? My god! their wheels are bombs!