It’s essential to adhere to tyre specifications when buying new tyres. Tyre specifications matter because they help ensure that you have the safest drive possible. They also help to ensure your vehicle is able to perform at an optimal level, have enhanced fuel efficiency, and your tyres aren’t prematurely worn due to being the wrong fit.
In this article, we’ll cover the key tyre specifications you’ll come across when you consider buying new car tyres. Let’s firstly look at why car tyre specifications matter.
When cars are engineered, their manufacturers put a lot of work into determining the optimal tyre for that particular vehicle, and for the kind of driving it’s designed to do. A range of factors come into play in making the decision, including the tyre’s speed rating, pressure rating, its construction type, width, and more.
Once all these decisions are made, a tyre is either selected or manufactured to match the vehicle, and the tyre specifications are stamped onto the sidewall of the tyre. (Specifications will also usually also be printed in your vehicle’s owner manual, and you can also find this information through a car tyre dealer.)
When your tyres have seen better days and you start perusing new tyre sales online or in store, the general advice is that it’s best to choose a tyre that meets the tyre specifications as that of your original tyre (the ‘Original Equipment’, or OE, tyre). Doing this means you can be certain your new tyre will perform well when fitted to your vehicle. Secondly, adhering to specifications makes the business of buying new tyres much easier, as you have set parameters to work with—you know exactly the type of tyre your vehicle needs, and needn’t waste time at new tyre sales considering tyres that aren’t suitable.
When buying new tyres, here’s a list of specifications you should have on hand. Following these specs will help you to get the best new tyres for your vehicle, and save you wasting time looking at new car tyres that aren’t suitable.
Each specification matters, as it will have an impact not only on safety, but also on how your vehicle handles and performs.
The tyre width refers to the width of the tyre from sidewall to sidewall. It’s measured in millimetres. (In a tyre labelled 195/65R15 91V, the 195 represents the width.)
Tyre width has an influence on how safe your vehicle is on the road, with tyre width impacting braking, handling and grip.
Pros of wide tyres:
Cons:
Pros of narrow tyres:
Cons:
The ‘tyre profile’ or ‘aspect ratio’ is the height of the tyre’s sidewall, shown as a percentage of the tyre’s width. For example, in a tyre labelled 195/65R15 91V, the profile is 65, meaning the sidewall height is 65% of the tyre’s 195mm sidewall width.
Any tyre with a tyre profile below 50% is considered a ‘low profile tyre’. If it has a profile below 30%, it’s ‘ultra-low’.
The lower the profile, the better the tyre performs on corners, which is why these low or ultra-low profile tyres are often seen on high-performance cars. However, low profile tyres mean you will usually have a firmer ride, as the shorter sidewalls mean there’s less flexibility and cushioning in the tyre, and therefore, less shock absorption.
Higher profile tyres have more sidewall height, and greater flexibility, which means they absorb bumps better. This makes for a more comfortable ride. In addition, they’re better at protecting the wheel from damage on potholes, as there’s more give in the tyre.
The way a tyre is constructed will affect the comfort of your ride, vehicle handling, and tyre durability. The main types of tyre construction are bias-ply construction, belted bias construction, and radial construction, (the most common type).
Diagonal or Bias-Ply Tyres (‘D’): These tyres feature crisscrossing nylon belts. They have stiffer sidewalls, which provides better load capacity, however they tend to offer a rougher ride and reduced grip.
Radial Tyres (‘R’): These tyres have steel belts running radially across the tyre. They offer better fuel efficiency, improved handling, and longer tread life due to their flexible sidewalls.
Belted Bias Tyres (‘B’): These are a hybrid between bias-ply and radial tyres. They include extra belts for added strength. While better than bias-ply, they still don’t match the comfort or performance of radial tyres.
A tyre’s construction type is stamped onto the tyre’s sidewall. For example, in a tyre labelled 195/65R15 91V, the R refers to radial construction.
This refers to the diameter of the wheel or rim in inches. The tyre is designed to fit this diameter. (In a tyre labelled 195/65R15 91V, the 15 refers to the wheel diameter.)
How does wheel diameter impact vehicle performance and safety? Wheels with a larger diameter are better at handling corners and are more stable at high speeds. They can also accommodate bigger vehicle brakes, hence, better braking performance. On the downside, larger wheels reduce acceleration speed due to their larger rotational mass.
Smaller wheels with high-profile tyres absorb bumps well, and offer a smooth ride and good grip in rough conditions.
The load index indicates the maximum load the tyre can support when properly inflated. A higher number corresponds to a greater load capacity. (In a tyre labelled 195/65R15 91V, the 91 refers to the tyre’s load index, meaning it can carry 615kg.)
It’s imperative that you have tyres with a load index fit for your vehicle, as a tyre’s load index can impact safety and performance. For a start, tyres with a load index appropriate for your vehicle are better able to brake effectively, as their weight is evenly distributed. Conversely, if you have tyres that are with insufficient load-bearing capacity, you may overload them, which can result in longer vehicle stopping distance. Additionally, if the load-bearing capacity of your tyre is insufficient, your car won’t perform well during acceleration and on corners. Tyres with insufficient load-bearing capacity can also succumb to uneven treadwear, which means reduced traction over time.
Refer to the Tyre Load Index Chart on this Wikipedia page, to understand what tyre load index you need to follow when looking at new tyre sales. This page also includes a helpful tyre identification diagram, which you can refer to when looking at specifications on an actual tyre.
The speed rating represents the maximum speed the tyre can safely sustain under load. Having the appropriate tyre speed rating for your vehicle reduces risk when driving at high speeds.
Speed ratings are represented by letters ranging from L (low speeds) to Y (high speeds). (In a tyre labelled 195/65R15 91V, the V refers to the speed rating, which means it can travel at a maximum speed of 240 km/h). Refer to a Speed Rating chart to see the speed that corresponds with the speed rating letter you see on your tyre.
Speed rating can impact a car’s driving performance. Higher speed-rated tyres handle better at high speed. They have better stability and grip, perform better on corners, and brake better at high speeds. They’re also built to withstand the high heat that comes with high-speed driving.
Low speed-rated tyres are only designed for driving at low speeds. If driven on at faster speeds, you risk tyre blowout.
This is the recommended inflation pressure for the tyre to function optimally. This recommended rating will appear on your tyre’s sidewall, but also often in the driver’s seat door jamb, and car user manual.
Having the right tyre pressure for your vehicle and driving requirements is important for safety. Appropriate pressure enables you to brake faster, minimises the risk of blowouts and reduces uneven wear on your tyre.
Tyre pressure also affects performance. With proper pressure, you will experience better handling and fuel efficiency, whereas with underinflated tyres, you will have poorer grip on the road and poor fuel efficiency.
Read more on How to get ideal tyre pressure for your car?
These ratings provide information on the tyre’s durability, grip, and ability to withstand heat, and are usually marked on performance tyres.
Treadwear grading indicates a tyre’s durability, with a higher-grade tyre meaning a longer-lasting tyre. Lower grades may offer superior grip.
Traction grading measures how well tyres grip the road when braking on wet surfaces. Higher grades (AA, A) offer better stopping power.
Temperature grading rates a tyre’s ability to resist heat buildup at high speeds. Higher grades (A, B) offer better heat resistance and reduced risk of blowouts.
On the sidewalls of your tyres, you’ll see a set of letters and numbers. These tell you all you need to know about your current tyres, so that you can match them up when buying new tyres.
Example tyre markings : 195/65R15 91V
In this case, this set of numbers and letters refers to the following:
195 is the width in millimetres of the tyre, from sidewall to sidewall.
65 is the tyre profile or ‘aspect ratio’ (the ratio of the tyre’s cross-section to its width).
R – the tyre has a ‘Radial’ construction.
15 – is the wheel’s diameter, in inches.
91 – is the tyre’s load index, meaning it has a load index of 91 (it can carry 615kg)
V – is the tyre’s speed rating. (V means it can travel at a maximum speed of 240 km/h.)
Note that a tyre sidewall won’t always include information in this format. Also, tyre pressure rating and treadwear, traction, and temperature grades may appear on other parts of the tyre. It can also differ between tyre products. If in any doubt, refer to your vehicle’s owner manual for tyre specifications for your vehicle, or ask a tyre professional at Jim’s Mobile Tyres.
Tyre specifications aren’t too difficult to decipher, however if you have better things to do than look up speed rating and load index charts, then feel free to leave it to the professionals at Jim’s Mobile Tyres. We’re experts when it comes to matching vehicles with the right set of new car tyres. So rather than hunt around new tyre sales, just give us a call and we can relieve you of the headache.
We stock a wide range of car tyres from well-known brands, at competitive prices. Not only can we match you with the optimal new car tyres, but we offer convenient tyre fitting at your location. So ditch the online or instore car tyre sales and call Jim’s Mobile Tyres instead.
Other great services at Jim’s Mobile Tyres
We aren’t only a great source for new tyre sales. We also offer services like tyre pressure checks, tyre puncture repair, tyre rotations and emergency breakdown repair.
Related posts:
If you’re considering buying new tyres, you might want to read these articles before you check out the new tyre sales. It pays to do a bit of research before you make a purchase.