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My one nitpick would be with the contact patch comment. Tire pressure DOES have a tremendous amount to do with contact patch- one of the most important factors next to tire design- but there are numerous reasons why tire pressure is critical beyond that. For starters- air and most any gas will heat up and expand in a tire. Too high pressure or too low can cause a tire to slip off the bead- effectively dismount itself. But load and speed rating are actually the more critical factors in most people’s lives which tire pressure effects. A vehicle is rated for a certain load- including cargo, fuel and fluids, and passengers. This can usually be found on most passenger vehicles where you find the tire pressure.

But tires themselves are rated for a maximum load- how much weight each tire can support and function. Generally a manufacturer specified tire matches load ratings to the vehicle load and weight distribution, and manufacturer pressures are specified off of that. When you go to non OEM tires- you might have new load and speed ratings. A tire rated for 150mph will not be able to do that if it is over or under inflated because the tire pressure changes the behavior of a tire- notably, the heat the tire will see under any conditions. The same is true of load ratings.

Now- if you have a 2,000lb car- you may think that tires rated for 500lbs load are perfect- 2000lbs divided by 4 tires right? Wrong. Even amongst factory performance models that have not been corner weighted it is VERY uncommon a car will have perfect weight distribution front to back and side to side where each corner carries exactly 1/4 the weight. More over- a tank of gas can easily weigh over 100lbs- and just a driver is usually at least 100lbs- a 4 seat car with groceries can weigh easily 600lbs or more than the car alone weighs. And guess what? Say you have. perfectly Balanced car when full of gas etc and aren’t going to drive anyone else- that weighs 1900lbs and you weigh 100... those 500lb tires should work now right? No. Because you’re probably sitting towards the front of the car and to one side. That 100lbs won’t be divided evenly on all 4 tires.

Ok. Ok. So we have a car, that magically- all 4 tires at rest will always carry equal weight AND the car is balanced for all possible people and cargo you’d place in it and magically will never weigh more than 2000lbs total. So now it is ok to use the 500lb limit tires? No. Physics. When you turn, brake, speed up quickly- the cars weight is transferred. You ever felt yourself be pulled forward when a car stops quickly, or seen the front of a car “dip” when it brakes hard? Ever seen a dragster or a high powered remote control vehicle do a wheelie when the driver slams the gas? That’s the weight transfer. Same when you are pulled to the “outside” of the car or you see a car leaning in a corner. Centrifugal force and other factors are at play- but the effect is that parts of the car get lighter, and parts of the car get heavier. In hard braking, the rear gets lighter and the front gets heavier for example- hence the front of the car dips down.

Because of this- a perfectly balanced 2000lb car at rest- where the rear weights 1,000lbs and the front weighs 1,000lbs- under extreme braking the front might weigh 1200lbs or more and the rear suddenly weighs 800lbs or less. 1200 divided by two overwhelms what our 500lb limit tires are rated for no?

So usually you will want to have a pretty good reserve of load limit- more for vehicles like trucks and such- to deal with both passengers and cargo as well as forces of physics. Usually, at the extremes of physics is where you need your tires to be operating at their best or most reliable- and that is where a tire is most likely to fail if it any matched to the vehicle and conditions, and set up and cared for properly.

Now- contact patch is effected by tire pressure. More pressure usually means a smaller contact patch and less means a larger patch. Counter intuitively- sometimes a smaller contact patch is better for traction such as in some cases with mud or snow etc. smaller contact patch means less rolling resistance and generally less friction- often less heat to the tire, better fuel mileage or EV range (to a point) but it can also decrease the vehicles ability to response to inputs including braking on dry relatively smooth pavement. Lower pressures can often offer more grip in most common situations, most rain conditions, dry pavement. But it isn’t exactly the contact patch that is to worry about here- even though it is very important. It’s the only part of your car that touches the road after all.

Tire sidewalls. You can find neat videos of high speed camera footage of tire sidewalls at work. The side wall of a tire is a complex piece of engineering and you rarely if ever notice- but it is constantly flexing in all manner of ways and directions. I won’t get into skip angles and the math of how it is possible for a car with 4 wheels to turn. But the sidewalls are a large part of why that is possible. Your vehicles handling and basic function depend on the sidewalls and their ability to flex to some degree.

More over- the reason we use air in tires- one of the main reasons- is pneumatic cushion. Not only does a tire with air in it generally have a higher load capability than a solid tire- it will almost always offer a better ride quality. The air can move and compress and expand far easier than most solid compounds which are suitable for making a traditional airless tire.

This allows the tire to also contort and conform to shapes as it is smashed into every rock and road dimple by your 4,000lb car. Every pot hole is like dropping thousands of lbs on your tire. If tires couldn’t contort like this- not only would your ride be pretty tough for you- it would be rough on your car. Bolts and such being shaken and battered, metal being fatigued- and your poor wheels- usually steel, aluminum, or other alloys- you’d be quickly and easily bent or cracked (easier than they are with air.) not safe and not cheap replacing those regularly. But your side walls- not only can wrong pressure cause the tire bead (where the tire is held to the wheel) to come off- too low and your side walls can flex enough that the tire can rub on itself and effectively destroy itself, or the heat can cause the materials to lose their ability to do their job. Etc etc. too much and your side walls may not be able to flex enough and the tire, wheels, and your cat can be damaged.

Tires are very complex. There is ALOT I’m leaving out. The engineering of tires and the physics involved are complex. It is often difficult to give a primer on tires that is both in depth and brief enough to serve as a tutorial people can remember.

Most people just drive. They know little to nothing about cars and don’t generally want to. They often know little to nothing about physics or engineering- and even those who know these things often don’t think of cars in terms of how their behaviors are influenced or examples of certain principals. It’s good to know some things about... well... anything really. But especially with machines you operate. But... most people don’t have the interest or ability to absorb all the information they need to operate and maintain a vehicle with a functional understanding. That’s why for most people, it’s best to go with a competent mechanic and just stick to whatever the engineers who made the car say you should.

- i should have specified. Its not ALL the contact patch, but that's a big part of it.
- You'd have to have some really extreme low pressure to unmount the tire. Usually with very low pressure you worry a about poor handling and overheating the tire due to excess sidewall flex. High pressure worries about uneven wear, or blistering/bursting.
- Pretty much any passenger car tire is rated to enough weight that you dont have to worry about that.
- "speed rating" is mostly just the tire's ability to dissipate heat. As you go faster, it generates more heat from flexing. Part of the reason why hypercars like the Veyron need ridiculous tires for their speed runs.
I did waaaay too much research into tires with my 2012 miata. It came with some standard all-seasons. 205/45r17. It wanted its tires at 29psi and weighs about 2500lbs
My mazda 6 i had for a while wanted 33 and weighed about 3300lbs
My current nissan leaf wants 36psi and weighs about 3800lbs.

So yes, everything you said is true. Tires way more complicated than you think. The average driver should just stick to OEM tires as much as possible (although sometimes those can be more expensive than similar performing tires from different brands...).
My miata is a completely different car on its 205/45r17 all seasons that it came with, vs the 205/50r16 summer only tires i put on it during the warmer months

Oh yeah. The NC needs tires and sway bars to come alive. No disrespect to your vehicle- I’ve never liked the NC, too radical a departure from the formula of the nameplate, but as what is basically a short wheel base RX-8 as far as chassis and suspension design, they can be made to handle well. Like the 8- they are ok out of the box but some minor tweaks- staring with tires, can really transform them. And nothing you said was wrong either- I just wanted to clarify a little on the nuance of detail. As for the bead coming off.... nuance there too.

Depends a lot of the tire: a low aspect ratio tire such as 225/45 or some such will behave much differently in regards to bead sealing than a 225/75; and then we have to ask what the tire is doing. Is it being driven hard at high loads or high speeds? Is it carrying a lot of weight? Even the suspension of the car factors in. Overall I agree that tires coming off the bead are relatively rare. It CAN happen, doesn’t mean it will. As you allude to, this is more likely to happen when one has a puncture of some sort that allows air to escape unoticed. That said- with cars problems often form teams. Low initial pressure on a long trip for example- leading to sidewall damage, leading to a slow and unoticed loss of pressure. Low initial pressure reducing the time one has to notice the loss, and contributing to heat and damage in the tire... does the side wall give and the treads come off? Do you notice before then? Does the tire have a stiff sidewall or a long enough sidewall that under...

These conditions it slips the bead? The least common one would probably be slipping the bead. But it can and does happen. But that’s part of the problem of attempts to sum up automotive “guides” in easily digestible blurbs. You’re going to sacrifice accuracy. I mean- you seem to have owned a few Mazda’s- the Mazda Tributes could have an issue involving the cruise control that could cause the vehicle to seemingly spontaneously combust while running or not. Unlikely- but possible. But when explaining these things to people in general- you have to choose wether to present possible dangers, or omit the possible but unlikely. It’s POSSIBLE that if you run your brakes too long without service that the hub can weld itself and the entire wheel can come off. I’ve actually seen that happen on a relatively new car which wasn’t even grossly in need of service. Sometimes it’s a fluke- but sometimes it’s just one possible outcome that is rare... but possible. Most people don’t have the information..

.. and experience to make an informed decision. They can’t really “accept the risk” or not because they don’t, often can’t, actually understand the risk. So I mean... it’s nuanced. But it’s a good thing when people educate themselves as you do when you changed your tires out- the danger there is that a little knowledge can be more dangerous than no knowledge (I’m not saying in your case as you seem to have done good research and grasp the issues- but in the case of “knowledge blurbs”) as it can give a confidence that if a person had less knowledge, they’d trust an expert instead of trying to be an uniformed expert. I suppose there is some overlap with a general attitude we see a lot in society today that somehow it’s wise for people who don’t know about an issue to question fact...

My final comment in this reply has to do with load rating. You’re generally right I think. But.... well... a lot of people don’t like spending money on tires. I don’t blame them. They aren’t very glamorous, they wear out, and most people don’t notice a difference after putting new tires on vs. how their car behaved before. And tires are expensive, a good set of tires from 15”-17” is easily $1000+ retail out the door when the bill is settled. So a lot of people shop tires on one thing only- price. From the used tire guys and junkyards- up to the more suburban crowd who is “above” that but not “above” going to Costco and buying the cheapest tire that physically fits on their cars...

I’ve been around cars my entire life and I have seen so many things.... I’ve seen suburban dads living in the desert but snow tires because they were the cheapest option at Wally World- and then hate them for the noise and poor characteristics, before they wore out extremely prematurely since they aren’t made for everyday “summer” driving- then turn around and buy another cheap set to replace those- when for the same or less total cost and headache they could have bought decent tires that would have lasted longer and done better than the cheap sets they gave to keep replacing and or hate the whole time they have them.

I’ve seen people put trailer tires on cars because they were cheaper. Usually that’s the blind leading the blind. They go to someone with some experience but little knowledge and they too have enough “knowledge” to conclude that the name brand mainstream guys are ripping them off or charging them for more tire than they’ll actually use. Granted- you probably don’t need an S rated street slick on your stock 99 Camry- and it will probably do more harm than good. Even your average Miata owner (whichever generation) probably won’t get the full benefit of a DOT legal race tire in every day street driving- and would find it much more enjoyable on the balance of upkeep and costs and ride and such to choose a more mundane “performance tire.” So like most things- the most expensive one or the highest rated one usually isn’t the “best” one for most people-

I mainly mention weight rating because well... I’ve seen enough to figure it’s worth a mention, and it illustrates that tires are very complex and if you don’t know these things and don’t plan to learn them- you should probably trust the engineers who made the car. Of course- it’s also prudent because honestly- it’s very common for people to run cars overloaded. I’ve owned many Mazda RX-7’s of all years and types, street cars and race cars and... mixes of the two. And the RX-7 chassis can be overloaded (even a non 2+2) with two robust Americans. My basic principle is that most people don’t read the manual, don’t care, and couldn’t understand it anyway. But for all the cars driving around overloaded and under maintained- rarely does any bad come of it. The odds are that most people can get away with it. If you miss an oil change it’s unlikely the average car will blow it engine before the next one- or even have significantly shorter life because of it. But.... it can happen. CYA.

You also must remember that where a tire sidewall meets the tread is called the “shoulder.” The shape of the shoulder changes the tires handling characteristics as well as other factors, and tires with different shoulder shapes may even be unable to safely fit a car that had that same tire size in a different shoulder shape.

Numbers not pictured or Keri ones include a date code- this code shows when the tire was made. It’s better to not buy tires that are very old, and no one should generally drive a car with tires that are older than about 6 years even if they don’t show signs of damage- as the tire materials have undergone certain changes as results of oxidation and other factors and can fail- and most certainly won’t offer the level of performance they were rated at new.

Also not pictured is the number showing tread wear rating. This is a numeric value showing how quickly the tires are expected to wear. Smaller numbers generally mean a tire is expected to wear out very quickly. Lower numbers GENERALLY correspond to better traction and grip characteristics in dry conditions on flat pavement. A high performance tire such as on a (real) sports car will commonly be between 100-160 treadwear. Trucks and economy cars often have tires 300,400 or even 600.

Do keep in mind:
1. These numbers ARENT UNIVERSAL. They can only be effectively used to compare tires from THE SAME MANUFACTURER. In other words- a Goodyear tire with a 600 treadwear will (under identical intended conditions) last longer in general than a Goodyear tire rated 300. However- if you compare a Goodyear tire rated at 300 to a “Brand ABC” tire rated at 500- the Lower rated tire MIGHT actually last longer than the 500 rated tire.

So you can’t really compare tire wear ratings across brands- although something rated like 60-90 (which is usually something like a special race tire) will almost always wear faster than a tire rated 250 regardless of the manufacturers. But it isn’t guaranteed.

2. Tire wear rating doesn’t mean anything specific. There’s no single standard, there’s no real tangible or quantifiable way to measure what it all means. It’s just... a number that sort of acts as a guide.

Holy fucking guest!
You are a phenomenon.

lol. Like a typhoon.

*blows away*