So…

You may be thinking to yourself that tires don’t matter as long as they have tread.  You don’t want to spend a ton of money on something that is just going to wear out anyway and dropping over $1K on a set of tires just doesn’t make any sense.  Or does it?

What you have to remember here is that regardless of how much power your engine will deliver to the wheels, how beefy your braking system is, or how stiff your suspension is… it all comes down to four rubber patches that make contact with the road.

There are a number of considerations that you need to work through in your head BEFORE you make a tire choice.  First, you need to figure out what the worst case scenario is in terms of where you drive your car.  What do I mean by that?  Just about any tire will do its job in normal day to day driving conditions on dry roads.  If that is all we ever subjected our tires to, then any old piece of rubber will do; however, this is rarely the case.  The fact is that our tires are subjected to any number of variables such as cold, wet, and slippery surfaces.  We expect that our tires will continue to do their job regardless of the environment… but the truth is that they won’t.  So think again carefully… do you need to do a panic stop?  Do you drive in the rain?  Do you drive when it’s below 40 degrees outside?  Do you get annoyed when your traction control kicks in and throws your head into the steering wheel?  If so, you may not have the right tires for the job.

If you have been doing any kind of tire shopping at all, you probably have noticed that there are a wide variety of tires out there.  Summer, All-Season, Winter, Performance, High Performance, Ultra High Performance, and R-Compound, just to name a few.  The question as to which tires you need to run really goes back to the paragraph above… what do you need your tires to do?  Let’s discuss some of the considerations.

The tire compound

What determines the amount of grip a tire provides in warm and cold weather is the compound that is used to produce the tire, as the compound will determine how much of the tire actually makes contact with the ground at a given temperature.

Winter tires tend to have the softest compounds that stay pliable in the cold weather. This allows the winter tire to better adapt to the road surface.  Additionally, you’ll notice that winter tire treads tend to be closer spaced so that the tire does not pick up and get covered in snow which can have a tendency to harden into ice over time while driving in snow.  Summer tires, on the other hand, are made of a much harder compound that can withstand heat. The warmer the tire gets as you drive, the better it grips the road. The cutoff to where summer tires are borderline unsafe and where winter tires have reached their usefulness is about 45 degrees Fahrenheit. The question as to what tire would work best when temps rise and fall between optimal summer and winter tires depends on where you live.

The most popular tire sold is the all-season tire.  This is because most consumers have been duped into thinking that this type of tire is going to provide the best all-around performance regardless of weather conditions.  Nothing could be further from the truth, and in actuality, all season tires are really a compromise between summer and winter tires and do neither function well.  They do not provide the grip that you get from a summer tire on warm pavement and they do not adapt well to cold weather environments.  What most do pretty well is extend the life of the tire over a longer period of time, and most also provide the least amount of rolling resistance which means an increase in gas mileage.  Because all season tires tend to be a compromise, they are not treaded to handle a large amount of water on the road and will tend to hydroplane much sooner than a dedicated summer tire.  In the winter, all season tires will harden in freezing weather.  All season and winter tires that are rated M+S are designed to handle snow a bit better than those that are not rated for mud and snow by actually picking up mud and/or snow and binding with the surface; however, take this with a grain of salt.  All season M+S tires only provide a nominal improvement over other all season tires in the snow due to the hardening of the rubber.

Ideally, you want a tire that will work for you in most driving conditions you will encounter… in reality, most of us cannot afford three different sets of tires, nor have the time or inclination to change our tires every time the weather changes.  So where does this leave us?  In most cases, you are going to need at least two sets of tires. All seasons will provide those in more temperate climates the best all-around performance; however, they are no replacement for winter tires when temperatures drop below freezing or there is frozen precipitation on the road.  Summer tires work well in the sunbelt where temperatures rarely fall below freezing; however, rapidly begin to lose their advantage when temperatures drop below 45 degrees Fahrenheit.  For daily driving, an extra set of all season tires for the winter may be best for folks who don’t often deal with snow.

Lastly, for those who may be interested in pulling every possible ounce of performance out of a tire, we have the R (racing) compound tires.  These tires work best in temperatures above 70 degrees Fahrenheit and provide the ultimate level of grip that you can get from your four rubber patches.  While they are very sticky, they will also wear very quickly.  Additionally, R compound tires tend to maximize grip on DRY roads.  Most road legal R compound tires WILL hydroplane if subjected to substantially wet roads (puddling).  If you decide that an R-Compound tire is right for you in certain situations, consider carrying them to where you need them and installing them before you drive…then remove them and replace them with your daily tires after you are done.  You’ll spend a LOT of money on R compound tires and it would be a shame to waste the tread doing your daily commute where you don’t really need that level of stickiness.

Diameter, width, and profile

Ever notice the numbers on your tire indicating the size?  They aren’t just random numbers and can tell you quite a bit about the tire’s dimensions.  Other than making sure they actually can fit on your wheel, there are performance considerations that go along with those numbers.

275/35R20 <~~~ the first number in the size spec indicates the width of the tread in millimeters.  That’s metric for those of you who are unfamiliar with the term.  A 275mm width is equal to 10.83 inches in width.  What you want to do is try to get the width of the tread approximately equal to the width of the wheel to create the largest contact patch you can get.  While you can go with a tire that is significantly wider or narrower than the wheel, you are always going to affect the size of the contact patch and how the tire sits on the road.

275/35R20 <~~~ the second number in the size spec indicates how tall the profile of the tire is in relation to its width.  In this example, the 35 indicates that the sidewall is 35% of the width of the tire or 96.25mm… or for you troglodytes… 3.79 inches tall. There are a number of things that the sidewall profile height affects in terms of performance.  First, is deflection… or the amount of give the tire has when subjected to lateral forces.  The taller the profile, the more give the sidewall will have.  If you have too much deflection in the sidewall, the tire will tend to fold over onto itself in hard turns… or a less technical term is that the tire will have a tendency to scrub on its side.  This is usually indicated by the amount of squeal that the tire gives off when it is laterally stressed. If you have too little deflection, you will maximize the grip of your tread; however, when it does release, it will do so with little or no warning beforehand.  Ideally, you want a little warning and a slow grip release rather than an all out release with no warning.  The second thing sidewall height will affect is the overall rolling diameter of your tire.  This can negatively impact your electronic stability control system if that system relies on wheel speed sensors to determine when to activate.  On the Genesis Coupe, it can change the aspect ratio from front to back and cause the traction control/electronic stability control to intercede when no actual slip is present.  You want to stay as close to the stock rolling diameter of the tires that came with your car as possible to avoid any ESC issues.

275/35R20 <~~~ the R in the tire spec is a left over from back when you could get radial (R) tires or bias ply tires.

275/35R20 <~~~ the last number in the size spec indicates the inside tire diameter. You don’t get much of a choice on this one as you must buy the tire that will fit your wheel.  Where you do have a choice is in the wheel itself.  Smaller diameter wheels have a lot of advantages over larger diameter wheels.  Smaller wheels tend to be lighter and they tend to have a better selection of tires made for it.  Larger wheels tend to look better and allow you to reduce the profile size of the tire without sacrificing the rolling diameter.  Smaller side walls mean less sidewall deflection and more grip.  You have to be careful with this as there are diminishing returns when you start getting into micro-thin sidewall profiles.

A note about weight…

The larger the wheel, the heavier the tire.  That kind of goes without saying.  So in addition to a heavier wheel, you will have a heavier tire to go along with it.  All this weight has to be turned by the engine which means that your engine has to work harder to move the wheel.  This will have the effect of reducing your acceleration times.  Additionally, a heavier wheel/tire combo also requires more energy to stop turning… which puts more wear and tear on your brakes and potentially have required a much longer braking distance than a lighter wheel/tire combination. Heavier wheel/tire combinations will also use more gas.  Overall, if you are interested in straight line performance, a lighter/smaller wheel/tire combination is your best choice.  If you are interested in increasing your lateral turning stability, a larger wheel with a lower tire profile may fit the bill.  From a performance aspect, it all comes down to how you drive your car as to what wheel you should choose.

Performance, high performance, ultra high performance

Now, keep in mind that the difference between these tires can only be used to compare tires in the same make/model/line since these are manufacturer ratings.  An ultra high performance all season tire will not provide the same level of grip as an ultra high performance summer tire when the road surface is warm.  Additionally, the higher the performance of the tire, the softer the compound and the faster the wear. It’s the trade off you have to live with when you are looking for a higher performance/stickier tire.  When looking for a performance tire, talk to people and don’t rely on online reviews or tire manufacturer descriptions.  Most online reviews are written by people who daily their cars to work every day and do not push their tires to their limit.  Tire manufacturers would have you believe that their tire is the best of the best.  If you want the best review, talk to people who drive their cars the way you do… and make sure they haven’t just owned one brand of tire in their lifetime.  You don’t talk to street beggars to learn how to be a millionaire, you shouldn’t talk to commuters and hard parkers to determine what type/brand of tire will work for you.

Final thoughts…

The last component on your car that you should consider compromising is your tires. Your tires are the only component on your car that actually touches the road, and they will determine how much torque you can apply, how fast you can stop, and how quickly you can safely turn.  No other component on your car and no modification can make your car faster if it cannot hold the road.  So, before you head off and purchase your Indonesia $50 bargain brand tires that will last 75,000 miles… think long and hard about what you are trying to accomplish.  If you are building your car to sit in a parking lot, it doesn’t matter what kind of rubber you wrap it in… but if you are intent on actually driving the car as it was designed, you may want to reconsider your tire choices.  The wrong choice could put you in a ditch… or worse.