Where Rubber Meets the Road: The Secret Life of Tires…
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by Damien Heenan
13 min reading time
When dusting your bike off after a long Winter’s break, it makes solid sense to carefully inspect each and every part of your motorcycle. Engine, handlebars, brakes all deserve their time in the sun – but there’s nothing that directly affects your safety any more than your TIRES.
Depending on the tires you choose and their condition, your first ride of the season can be carefree, fun, and smooth – OR – in a worst-case scenario, rough and tumble and even life-threatening.
To make sure you’re rolling down the road safely and securely, it’s important to know some of the key factors about motorcycle tires and how they work.
Let’s Talk Tires – Basic Terminology
There are four essential terms often used when talking tire construction: carcass, tread, sidewall, and bead.
Carcass refers to the tire body and determines the type of tire you’re dealing with. The body can be radial or bias-ply. Radial tires feature steel reinforcing belts that run across the tire tread. Bias-ply tires instead use fiber cord, which not only are a different material, but a different structure.
Tread is the outermost part of the tire – the one directly in contact with the road. The type of tread determines whether a tire will be better suited for particular terrain types. A smooth tread will work well on dry and flat surfaces, while tires with deeper grooves will be ideal for off-road riding. Tread patterns may also be suited for the street, which includes wet roads, or dedicated to off-road rides (with variations for different types of terrain including sand to dirt).
Sidewall is a small but essential tire part. It’s the section of the tire that goes from the tread to the wheel. It’s largely responsible for handling and load transfer; essentially, the stiffer the sidewall, the better the motorcycle will handle. There is a trade-off, however, as shorter and stiffer sidewalls make the tire react to bumps worse, which can make the motorcycle harder to control.
Bead is where the tire connects to the wheel. The bead is made of steel wire with a heavy rubber coating. This is a relatively simple part whose only key feature is how snugly it fits.
Some Key Differences Between Radial and Bias-Ply Tires
When talking about motorcycle tire carcass, we mentioned the two main types: radial and bias-ply.
Radial tires are the newer of the two and are the more common tire type.
Radial tires have several advantages over bias-ply. First off, radial tires don’t heat up as much during the ride, which causes them to have a longer useful life. They are also stiffer in construction, making them more responsive.
In radial tires, the cords run across the tire, from one bead to the other. This type of construction allows the tire to support a bulkier sidewall with fewer body cords. As a result, the motorcycle grips the road better and the tires provide great feedback during the ride. These traits make radial tires excellent for performance motorcycles.
Now based on that, you may be thinking that radial tires are superior to bias-ply. Not so fast… bias-ply tires offer some advantages of their own. For example, bias-ply tires are generally a bit more affordable than radials.
A bias-ply tire has cords that run bead-to-bead, with cords positioned as alternating layers. These layers are angled relative to one another, i.e., constructed at a bias, giving the tire type its name. This form of construction makes the bias-ply tire carcass thicker, which prevents them from shedding heat as efficiently as a radial tire.
And bias-ply tires are generally softer, with a bit more “give” as you ride, which makes them better fitted for carrying bigger loads – a bias-ply tire will have a higher weight rating compared to a radial tire of the same size. That’s why bias-ply tires are a great choice for heavyweight motorcycles like baggers and cruisers.
When choosing tires, make sure to consider the overall construction of your motorcycle, as it’s equipped with particular suspension components and chassis specifications. These traits are fine-tuned for maximal stability when handling and braking, and they often require a specific tire type. It’s always best to go with the manufacturer’s recommendation.
NEVER put two different tire types on your motorcycle. These types of tires handle differently and may have completely opposite features. This means that riding a bike sporting one radial and one bias-ply tire will almost certainly affect your handling.
How to Understand Tire Markings
Everything you need to know about the essential features of a tire can be discovered reading its markings, what at first could seem merely a confusing string of numbers and letters.
Tire markings usually come in two formats: Metric and Alphabetical.
Metric looks like this: 130/90 – 16 67 H. Of course, the numbers and letters may be different – we’ve chosen these particular values as an example.
The first number – 130 – is the tread width expressed in millimeters. The width may have slight variations depending on the manufacturer and profile curvature. But if the variation is only slight, the tire should still fit.
The second number, 90, is the aspect ratio which represents sidewall height as a percentage of the first number. In other words, the height in our example is 90% of the width, which was 130mm.
The third number, 16, simply displays the diameter of the rim, expressed in inches. Similarly, the following number – 67 – is the tire’s load rating. You can find handy charts for load ratings online that explain what the rating number means in pounds. In our example, a rating of 67 translates to 677 pounds – the maximum weight the tire can carry.
Last - the only letter in this format, H, stands for the speed rating. Similar to the load rating, you can use a chart to figure out what the letter means in miles per hour. The letter from this example – H – means the tire is designed for a maximum speed of 130 miles per hour.
Alphabetical, the second format looks like this: M T 90 – 16 Load Range B. Again, the particular letters and numbers are for illustration purposes only.
The first letter, M, simply stands for “Motorcycle.” If you find a tire with markings that don’t start with M, you’re likely looking at a model designed for a different vehicle.
The next letter, T, marks the tire width. The letter corresponds to 130mm.
The following number. 90 represents the width-to-height ratio, just like in the first system.
The number, 16, here stands for the same thing as in the first example – it marks the rim diameter in inches. (As you might’ve noticed, it also shows up in the metric markings.)
Finally, Load Range B, unsurprisingly means the tire has a load range of type B. Load ranges for motorcycle tires come in three tiers: A, B, and C, with A being the lowest and C being the highest.
Tire Tread Considerations
When it comes to the design and pattern of the tread, you have a lot of options. The type of terrain you’re going to ride the most often plays a crucial role in selecting the tread.
First off – ALL types of tread have specific advantages and shortcomings. Generally speaking, the number of grooves will always impact traction. If a tire has more grooves, it will have less surface to grip the ground, and the opposite is also true.
Tires featuring larger treads perform the best off-road, on paths filled with loose dirt. Used on regular pavement, however, they’ll wear off quickly and have issues with traction.
Treads with open patterns are less aggressive and represent a better fit for your typical roads, highways, and byways. Tires with these treads are commonly found on adventure and dual-sport motorcycles. As you might expect, these tires will perform poorly on loose surfaces like sand, dirt, or mud.
A street tire will have the least aggressive tread. In other words, it will be specifically intended for precisely what the name implies – street use. The advantage of this kind of tire is that it has rain grooves, making it ideal for wet roads.
There are also tires built for use on both pavement and dirt. If you see a dual-purpose tire, it will have a designation that indicates the traction percentage for on- and off-road use. For instance, if a tire has an 80/20 marking, it means it has 80% traction on pavement and only 20% on dirt. Some tires may have a 50/50 designation, meaning they’ll perform the same on most surfaces.
The Importance of Maintaining Optimal Tire Pressure
Regardless of which type of tires you choose, the tire’s pressure will play a crucial role in how both that tire and indeed, the entire motorcycle performs.
Take your manufacturer’s recommendations for the optimal tire pressure seriously. While some believe those recommendations are made only to protect the OEM from potential lawsuits, they’re there for good reason.
When designing a motorcycle, the manufacturer factors in how much stress its tires can endure under different operating conditions. Optimal tire pressure recommendations are the result of careful engineering and numerous test rides. They’re made with performance and your safety in mind and. So, trust what the manufacturer says regarding tire pressure and take their advice.
In most circumstances, keeping tires at their recommended pressure ensures proper handling and action. But if you’re riding with a pillion or luggage, however, you can increase the pressure by 1-2 PSI.
In all cases, you should always have an accurate tire pressure gauge before you hit the road. Do NOT start riding until you check your tire pressure – and keep checking often. But don’t measure the pressure after the bike has been moving and the tire has warmed up, because you’ll likely get a false reading. Instead, to ensure accuracy, use the gauge at the beginning of a ride or after the bike has been idle for a while.
Knowing When to Replace Your Tires
Obviously, a FLAT tire should be replaced. But that’s not the only situation where you should consider putting on a new tire.
Punctures, of course, are a huge red flag. Any time you see a puncture on the sidewall – or indeed, any puncture bigger than a quarter of an inch – just consider that tire unsafe for use. Or if you notice a tire is sliced or cut, you’ll definitely be better off replacing it.
The same rule applies to any kind of damage that makes the tire impossible to repair.
Note that motorcycle tires can develop cracks due to weather or UV exposure. While this might not seem as alarming as a puncture, the cracks can represent a structural weakness. And you certainly don’t want to discover just how bad the damage was while taking a turn or just cruising down the road – ouch!
There’s a specific form of damage that can result from running your tires at too low pressure. It will appear as a rubbed-in circumferential ring on the tire. Seeing this mark should be a clear sign the tire has come to the end of its lifetime.
When the tread’s damaged, it will show obvious signs of wear. Tread blocks might even be missing. Remember, having good tire tread is critical for control and traction. If your tires start losing tread, it’s best to replace them with fresh ones.
Finally, if you see any alterations in the tire cross-section or deformations, like cupping or feathering, it’s best to ditch the tire and get a new one. Note that your front and back tires might not wear out evenly and that one tire might need replacing while the other could still be fine.
It’s also worth mentioning that the tread might wear out unevenly. That’s why it’s crucial you inspect the tire thoroughly from all sides.
How to Properly Break In Your Tires
When you install new tires on your motorcycle, you shouldn’t be taking them to the limit right off the bat. A tire’s tread surface needs to “scuff up” a bit for the tire to start functioning properly. This means that suddenly accelerating or braking – along with hard corners – isn’t a good idea until AFTER you’ve properly broken in your tires.
Doing so is simple. For the first 90-100 miles, just ride your motorcycle with a bit more caution. After that, the tires will develop a proper grip, and you’ll get used to how they handle and feel.
Some riders might find the break-in period unnecessary, and indeed, not all tires need it. However, if you’re not an experienced professional, it’s better to play it safe. You won’t lose much by being overly cautious, but things could go sour pretty fast if you aren’t.
One Common Tire-Related Mistake
The most common mistake riders make boils down to just not checking your tires often enough.
While this might seem like a relatively minor issue, it can have a disastrous effect on your tires and riding experience.
We’ve already mentioned tire pressure and how important it is to check it before every ride. But that’s not the only thing to consider. Always take care to NOT go over the recommended weight for your tires – any extra weight can impact everything from the structural integrity of the tires to the pressure inside them.
To make sure everything’s good-to-go before you hit the road, it’s not a bad idea to load your motorcycle with everything you’re taking along. Then measure the tire pressure to see how it looks with the bike fully packed - ideally, it should always be around 42 PSI, with a 10% offset.
By making sure your tires stay in optimal condition, you’ll be able to use them safely for longer. More importantly, they’ll remain reliable and efficient on their intended terrain. As a result, you’ll enjoy a smooth, safe ride every time you head off for adventure.
And when it comes to safe riding, don’t make the all-too-common mistake of hitting the road without proper gear. If your motorcycle is equipped with the best new tires, that same attention to detail should be paid to what goes on your body. Visit Eagle Leather and choose the right gear for your needs from a reliable and respected online store.
Comments
Good information,
Specific and clearly written.
Thank you
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