Rubber 101: The Ultimate Tire Guide

Few parts have quite as much of an effect on the comfort and safety of your ride as your tires. While they’re often an afterthought for many of the less mechanically-minded out there, finding the best tires in Cincinnati can make all the difference. Not all tires are created equal, with each type offering its own advantages and disadvantages. It can be a lot to unpack, but learning a little about these subtleties can make a world of difference every time you get behind the wheel.

From tire size and construction to care and maintenance tips, we’ve compiled the ultimate tire guide in hopes of demystifying the whole process. At McCluskey Chevy, we’re not only one of the area’s most trusted dealerships, but we’re also a full-service repair and tire shop. We offer the best tires in Cincinnati, leveraging years of experience and industry connections to get you the best tires at a fair price. Read on to learn some basics and stop by anytime to experience the difference a new set of tires can make.

What’s All That Info?

For the uninitiated, the sidewall of the average tire looks like an unintelligible mess of seemingly random letters and numbers. While it might seem as if the team at Goodyear let the office cat walk across the keyboard and printed the results, these complex codes are actually an informative shorthand that tells you virtually everything you need to know about the tire. From the tire’s size and weight capacity to details on the tire’s construction and maximum air pressure, this information is vital in helping you to find the right tires for your specific vehicle and driving conditions and keeping them rolling for as long as possible.

All the information listed is relevant, but the average driver looking to find a replacement for their old, worn-out tires can usually get away with just paying attention to the tire size, which is encompassed within the first four abbreviations. Let’s use something like P195/60R16 as an example and break down exactly what that’s trying to tell us.

The “P” is short for “Passenger Car” and represents what’s called the tire’s class. When shopping for new tires, the average driver will almost always be looking for a tire class of either P or LT, which stands for “Light Truck.” Don’t let the term “light” confuse you though: LT tires are designed for pretty much any truck that doesn’t require a commercial driver’s license.

Other tire classes include Special Trailer (ST) and Temporary (T), with ST tires being used exclusively on trailers, not the vehicles themselves. These specialized tires have thicker sidewalls than average, giving the tires more load-bearing capacity while helping to prevent trailer sway. Since trailer tires don’t typically need to handle sharp turns, ST tires also have more tread in the middle of the tire. The T designation is pretty self-explanatory and can be found on that spare tire in your vehicle’s trunk. Hopefully, everyone knows this one, but temporary tires are no substitute for the real thing and should never be driven further than 50 miles or quicker than 50 mph.

Going back to our example, “195” refers to the width of the tire at its widest point, measured from the edge of each sidewall, as expressed in millimeters. Common tire sizes can range from 185 for subcompact cars up to the high 200s for full-size trucks and sports cars. Next up, “60” is the tire’s aspect ratio, a term that will be familiar to anyone who’s ever accidentally fiddled around in the settings menu of their TV. In this case, it refers to the height of the tire’s sidewall measured against its width. The smaller the aspect ratio, the shorter the sidewall, resulting in improved lateral stability, steering, and handling.

The letter “R” is shorthand for the tire’s construction type. These will typically fall into two categories, R for “radial” and D for “diagonal bias.” Modern tires are constructed of plies, internal layers constructed of steel, fabric, and polyester coated in rubber. In radial tires, these plies are constructed perpendicular to the direction the vehicle will travel, whereas bias-ply tires are designed with a crisscross pattern that approaches the road at more of a 45-degree angle. Compared to bias-ply tires, radial tires offer improved gas mileage, durability, grip, comfort, and lower rolling resistance.

Radials quickly became the industry standard after being invented by Michelin in 1946, owing to their many advantages over the older bias-ply construction method. Still, there are some applications for which drivers might prefer bias-ply tires, including being used for rugged agricultural purposes or as trailer tires where the bias delivers less sway and bounce. Vintage car enthusiasts will also often use bias-ply tires to match the original aesthetic of a restored vehicle.

Getting back to our example, the number “16” is the diameter of the wheel the tire was designed for. Every tire was designed to fit a specific size wheel, so you want to make sure these numbers match up. While you can often get away with tires that have a slightly different width or aspect ratio, wheel size is something that you can’t change without getting different wheels.

More Factors to Consider

That’s a lot of information, but it’s still just a fraction of the data splashed across today’s tires. In addition to size, tires will also display load index, speed rating, treadwear grade, traction and temperature scores, and date of manufacture. Let’s quickly define a few of these terms before moving on.

Load index: The weight each tire can accommodate. These numbers usually range from between 81 to 123, with a larger number indicating a larger weight capacity. The load index can be a little confusing as it’s not a linear function, so don’t just assume that a tire with twice the load index can carry twice as much weight. A tire with an 85 rating, for example, can carry up to 1,135 pounds, while a 120-rated tire can carry over 3,000. This number is always grouped together with a letter denoting the speed index.

Speed index: This alphabetical system categorizes tires by the maximum speed they should attain. High-performance supercars obviously require tires with a higher speed rating than the stolid family minivan, but most all-season tires will fall somewhere in the T (118 mph) to Y (186) range. While you might be thinking that you are never going to drive that fast in your car, it is important to have a higher speed rating than your actual top speed to take into account the added stress of acceleration and braking.

Treadwear grade: This number indicates how quickly a tire will wear out under normal use conditions. A higher number means a longer tire life, with a 600 treadwear tire lasting twice as long as its 300 treadwear counterpart. However, treadwear ratings are not uniform across manufacturers, so one brand’s 400 treadwear tire may last longer than another brand’s 450 treadwear tire.

Traction scores: Ranging from AA (best) to C (worst), this letter indicates a tire’s ability to stop in wet conditions. Traction and treadwear have an inverse correlation, as a grippier tire will wear out more quickly. Race cars generally use 200 treadwear and lower tires.

Temperature score: The tire’s heat resistance is expressed as a letter between A and C, with C representing the lowest rating allowed by the federal government. A-rated tires can withstand heat at speeds over 115 mph, while C-rated tires bottom out the scale with a maximum recommended speed of between 85 and 100 mph.

Manufacture date code: The “Sell-by” date for tires, represented as a four-digit code. It’s important to stay away from tires with more than a couple of years under their belts, so it’s useful to learn how to read this figure. If you see 1520, for example, it would tell you that a tire was manufactured in the 15th week of the year 2020. Tires should generally be replaced after no more than six years from the date of manufacture, even if they have tread left.

How to Check/Make Tires Last

Okay, so you’ve finally found the perfect new tires for your vehicle. Now: how do we make sure we can go as long as possible before going through that ordeal again? There are a few simple tricks for keeping your new tires in good shape, with a little preventative maintenance going a long way in prolonging their lifespan.

First off: how do you know when you need to replace your tires? There are a few easy ways to check, with the first and most obvious being to gauge the tire’s tread depth. This will likely be the cheapest maintenance you ever perform on your vehicle, costing a grand total of one cent. Just take a penny, slot it into the groove of your tire tread, and if you can see the top of Lincoln’s head, it’s time for new tires (and Honest Abe wouldn’t lie about something like that). Most tires have another built-in warning system – bars in the tread that will appear once the treads are less than 2/32″ thick, but you will experience a marked decrease in grip and stopping power well before then, so don’t let it come to that.

Occasionally inspect tires for cracks, cuts, bulges, splits, and punctures. If one seems a little low but isn’t obviously totaled, fill it back up to the recommended pressure and keep an eye on it. If it can maintain some decent pressure over the next couple of days, you might be in good shape, but a rapid decrease means there’s a leak somewhere. Tire repair is an option and can be surprisingly affordable, but that doesn’t apply to any damage to the sidewall. Just remember: Fix-a-flat and other emergency repair options are just that: a temporary solution to help you limp along to the next reputable service station, not an excuse for a cross-country road trip.

Tire Rotation and Wheel Balancing

Tires wear out, it’s just what they do, but they don’t always wear out in exactly the same way. Front-wheel drive vehicles see the front wheels wear out faster, and even all-wheel drive vehicles can wear down tires unevenly. A tire rotation means moving each tire to a new position, evening out wear, and extending the life of all four tires. Experts recommend a tire rotation every 5,000 miles, and a good way to remember is to have them rotated whenever you get an oil change.

Wheel balancing sees technicians measure the minute differences in wheel wear and weight on a piece of specialized equipment. By attaching small weights at prescribed points along the wheel, this process can not only dramatically increase the lifespan of your tires but also make for a smoother, more comfortable ride. Tire rotations and wheel alignments often go hand-in-hand, as removing tires for a rotation is the perfect time for wheel balancing.

Air Pressure

There are few parts of your car that you can gauge the state of just by looking at them, so there really aren’t any good excuses for poor tire pressure. While many contemporary vehicles have automatic warning systems that will let you know when tire pressure falls below a certain level, a tire gauge is a must-have for most drivers. Remember that the PSI listed on your tires is the maximum recommended amount, not what you should actually be driving them at. Refer to your owner’s manual or driver’s side door jamb sticker for recommended operating PSI, and be prepared to tweak it slightly given road conditions and loaded weight.

Pressure readings should always be taken before driving, as a “hot” reading will typically be 4 to 10 PSI higher than one taken before the tires have been in motion. While we often worry about tire pressure being too low, high tire pressure can be equally dangerous, risking a blowout and creating an uneven pattern of wear on the rubber. Tires that have been chronically overinflated will show higher-than-normal wear towards the center of the tire, whereas tires that are left too low will be worn more around the edges.

Any Questions?

We know that was a lot of information to take in, but if you have any questions about tires, just give us a call here at McCluskey Chevrolet. We work hard to ensure you enjoy the most comfortable and safest ride possible, and that starts with your tires. That’s why in addition to being one of Greater Cincinnati’s most trusted dealerships, we’re also a full-service tire shop. Whether you need new tires to replace the worn set on your car, truck, or SUV, a tire rotation, or repair, the team at McCluskey is here to help. From trustworthy winter tires to reliable all-terrain tires and everything in between, we carry a wide selection of tires from all the leading manufacturers. Tires are a complicated subject, but we have all the answers you need.