Having the correct tyres for your vehicle is essential for both safety and performance. As the only part of your car in direct contact with the road, tyres significantly impact handling, braking, fuel efficiency, and overall vehicle safety. Choosing the right tyre size and type ensures your vehicle maintains proper grip, responsive steering, and optimal braking distances in all conditions. Using tyres that are too small, too large, or of the wrong type can compromise your car’s stability and may even make it un-roadworthy. In this guide, we’ll explain how to find your tyre size, when to replace your tyres, and how to understand key tyre specifications like load index, speed rating, and manufacture date. Our aim is to give New Zealand vehicle owners a friendly, tyre size guide filled with practical tips on how to choose tyres, helping you find the right tyres for your needs. (If you ever feel unsure, remember that our friendly team is always here to help – don’t hesitate to contact us for expert assistance.)
How to Find Your Tyre Size
Knowing your tyre size is the first step in finding the right replacement. Every tyre has a code on its sidewall that indicates its size and key specifications. For example, a tyre might read 205/55R16 91V – this series of numbers and letters corresponds to the tyre’s width, aspect ratio, construction type, rim diameter, load index, and speed rating. Here’s how to locate and understand your tyre information:
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Tyre Sidewall Markings: Check the sidewall of your current tyres. You’ll find a combination of numbers and letters (e.g. 165/55R17 94H) molded into the rubber. This is your tyre’s size code which includes the tyre width (in millimetres), aspect ratio (height as a percentage of width), construction (e.g. “R” for radial), and the wheel diameter in inches. Following the size, you will see a number and letter (like 94H in this example) which indicate the load index and speed rating – we’ll explain those shortly. Make a note of this full code.
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Vehicle Placard: Car manufacturers usually list the recommended tyre specifications on a placard (sticker) somewhere on the vehicle. In many New Zealand cars, this placard is on the driver’s door jamb. It might also be located under the bonnet, inside the fuel flap, or in the glove box. The placard will show the ideal tyre size for your vehicle, as well as the proper load rating and speed rating. Compare the tyres currently on your car to these factory recommendations (If a previous owner fitted a different size, you’ll want to know and possibly revert to the correct spec for safety.)
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Owner’s Manual: Your vehicle’s owner manual will also list the approved tyre sizes and specifications for your model. This can be a helpful double-check to ensure the tyres on your car match what the manufacturer deems safe. If your current tyre sidewall code doesn’t match the manual or door placard, it may be time to get advice on the correct size.
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Ask an Expert: If you’re still uncertain about reading the sidewall or finding the placard, feel free to contact our team or use our online tyre finder tool. We can quickly help you identify the right tyre size for your specific vehicle – making the process of choosing tyres simple and straightforward.
Pro Tip: Sticking to the manufacturer’s recommended tyre size is important. Changing to an improper tyre size can affect your odometer, fuel economy, and even your vehicle’s Warrant of Fitness (WOF) status. Always double-check any new tyres against your car’s specifications to ensure a safe fit.
What are the different types of tyre patterns?
There are three main types of tyre patterns: directional, non-directional/symmetrical, and asymmetrical.
- Directional tyres are designed to rotate in only one direction, and their tread pattern is characterized by a V-shaped pattern with grooves that point in the direction of travel. These tyres are typically used for high-performance vehicles and provide excellent traction on wet roads.
- Non-directional/symmetrical tyres have a tread pattern that is the same on both sides of the tyre and can be mounted in any direction. They provide a smooth and quiet ride and are commonly used on family cars.
- Asymmetrical tyres have a different tread pattern on the inside and outside of the tyre, providing a balance between wet and dry handling. They are typically used on sports cars and provide better handling and grip than symmetrical tyres.
It is important to note that when replacing tyres, they should match in terms of pattern type. For example, if your front right tyre is asymmetrical, your front left tyre must also be an asymmetrical.
When to Replace Your Tyres (Tyre Replacement Timing)
Tyres don’t last forever. Knowing when to replace them is critical for staying safe on New Zealand roads. Here are the key signs and guidelines for when you should fit new tyres:
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Tread Depth is Low: Regularly check your tyre tread depth. New Zealand law requires a minimum tread depth of 1.5 mm across the principal grooves of your tyre for it to be roadworthy. In practice, waiting until 1.5 mm is not recommended – by this point your wet grip and braking are greatly reduced. Many safety experts advise replacing tyres once the tread wears down to about 3 mm for optimal safety. Deeper tread helps channel water and maintain traction in the rain, reducing the risk of skidding or hydroplaning. You can check tread depth using the tread wear indicator bars moulded in the tyre (when they’re flush with the tread surface, you’re at the legal limit) or try the simple 20c coin test – insert a 20-cent coin into the tread groove; if you can see the entire number “20”, your tread is around 2 mm or less and it’s time to consider new tyres.
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Uneven or Excessive Wear: Pay attention to how your tyres are wearing. If one side of the tread is worn much more than the other, or if you notice patches of bald tread, it could indicate alignment or suspension issues. Uneven wear can compromise grip and is a sign to have both the tyres and your car’s alignment checked. Remember that rotating your tyres periodically can promote even wear over their lifespan.
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Cracks, Bulges or Damage: Visually inspect your tyres for any cracks in the sidewall or tread, cuts, or bulges (air bubbles) under the rubber. Such damage often results from age, UV exposure, or impact with potholes/curbs. Cracks can weaken the tyre and lead to blowouts, while cuts may penetrate through the tyre’s layers, risking a failure. A bulge indicates internal structural damage (like a broken cord or belt) and means that tyre could fail suddenly. If you spot any bulges or serious cuts, do not continue driving on that tyre – replace it immediately for safety. Driving on a damaged tyre is not only uncomfortable but dangerous, especially at highway speeds.
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Persistent Vibration or Noise: Unusual vibration in your steering wheel or loud humming/whumping noises from your wheels can hint at tyre problems. While vibration can also be caused by wheel imbalance or suspension issues, it’s smart to have it checked out. It might mean a tyre is out of balance, cupped (unevenly worn), or has internal damage. If your car is shaking on smooth roads, have a professional inspect the tyres (and alignment). Timely intervention could prevent a small issue from ruining a tyre.
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Tyre Age (Old Rubber): Tyres deteriorate with age, even if you don’t drive many kilometers. The rubber compound hardens and cracks over time, reducing grip. Most tyre manufacturers recommend replacing tyres every six years or so, regardless of tread wear. In fact, aged tyres can be past their prime even if they look fine on the outside, because the internal materials lose elasticity and strength as years go by. If you know your tyres are around 6+ years old, treat that as a signal to start shopping for replacements. As a rule of thumb, tyres older than 10 years should be replaced outright for safety – they’ve simply been on the car too long. (You can check your tyre’s exact age by reading the manufacture date code, explained in the next section.)
Safety tip: Don’t wait until your tyres are dangerously worn out. Driving on bald or damaged tyres greatly increases the risk of accidents. If you’re unsure about your tyres’ condition, drop into our store for a free tyre inspection or contact us – we’re happy to check your tread and make honest recommendations. Ensuring your tyres are in good shape is not just about passing a WOF, it’s about keeping you and your family safe on the road.
Understanding Tyre Load and Speed Ratings
Besides size, tyres are classified by their load index and speed rating. These ratings are critical to choosing a tyre that can safely carry your vehicle’s weight and handle your driving speed. You’ll find these values as a number and letter at the end of your tyre’s sidewall code (for example, a tyre marked 205/55R16 91V has “91V” as the load index and speed rating). Here’s what they mean:
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Load Index: This is a number that tells you how much weight each tyre can safely support when properly inflated. The higher the number, the more weight the tyre can carry. For instance, a common load index 91 means the tyre can support about 615 kg max load. It’s essential to use tyres with a load index that meets or exceeds your vehicle manufacturer’s recommendation. Never install a tyre with a lower load index than specified for your car – overloading a tyre beyond its rating can lead to excessive wear, poor handling, or even tyre failure (e.g. a blowout when your car is fully loaded on a summer road trip). If you frequently carry heavy loads (towing a trailer or a boot full of gear), consider a tyre with a higher load index for an extra safety margin.
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Speed Rating: The speed rating is indicated by a letter (or letter+number) that corresponds to the maximum speed a tyre can sustain under load. Common speed ratings include T (190 km/h), H (210 km/h), V (240 km/h), and higher for performance vehicles. Importantly, you should choose a speed rating that at least matches what’s specified by your vehicle manufacturer – usually this will far exceed New Zealand’s legal speed limits. For most everyday driving, a tyre rated T or H is more than sufficient. Higher speed-rated tyres (like V, W, Y) typically have stiffer construction for heat resistance at high speeds. If your vehicle doesn’t require them, you won’t gain any benefit from an excessively high speed rating. Always match or exceed the manufacturer’s recommended speed rating; do not go lower. Using a lower speed-rated tyre than recommended could lead to overheating or faster wear if you drive at high speeds, and it may even affect your insurance or WOF. (One exception: dedicated winter tyres sometimes have a lower speed rating, but that’s generally not an issue in NZ’s mild climate.)
When buying new tyres, check your car’s handbook or the door placard to confirm the minimum load index and speed rating required. We stock a wide range of tyres that meet the needs of everything from small hatchbacks to 4x4s – you can explore our tyre options or contact our experts for help selecting the perfect match. Choosing the correct ratings will ensure your new tyres can handle New Zealand road trips safely, whether you’re cruising down the Auckland motorway or exploring winding South Island highways.
Checking the Tyre Manufacture Date (Why It Matters)
Tyres have a “birthday” too! Knowing when a tyre was made can tell you if it’s approaching the end of its safe service life. Tyre rubber and internal structures degrade over time (even unused tyres gradually dry out). To find the manufacture date of a tyre, look on the sidewall for a small oval or rectangular stamp that begins with the letters “DOT”. This is followed by a series of letters and numbers. The last four digits of the DOT code indicate the week and year the tyre was made. For example, a code ending in “1219” means the tyre was produced in the 12th week of 2019. If you see a three-digit code, that means the tyre was made before 2000 – by now any such tyre is far too old and unsafe to use!
How to read the DOT code: Let’s say your tyre’s DOT marking is DOT ABCD 3419. The highlighted “3419” would mean the tyre was manufactured in the 34th week of 2019 (around August 2019). Another example: 0222 would mean the tyre came off the factory line in the 2nd week of 2022. Once you know the week/year of production, you can judge the tyre’s age.
So, why does the date matter? As mentioned earlier, tyres older than about 6 years can start to harden and crack, even if they have plenty of tread left. By the time a tyre reaches around 10 years old, it’s considered unsafe to use. It’s a good habit to check the DOT code on any new tyres you purchase as well, to ensure you’re not being sold old stock that’s been sitting on a shelf for years. We make sure our tyres are fresh and meet all safety standards. If you’re unsure how to interpret the code, we’re happy to show you – just ask during your next visit or contact us for advice.
Hint: When checking tyre age, also look for any signs of dry rot (small cracks in the rubber surface). That’s a visual clue the tyre is aging. Replacing an old tyre (even with good tread) can dramatically improve your vehicle’s safety, especially in wet weather where fresh rubber grips much better.
Always Match Tyres by Type and Rating Across Each Axle
A key rule for maintaining balanced handling and control is to use matching tyres on each axle. This means the two tyres on the front (and the two on the rear) should be the same size, construction, and preferably the same tread pattern and brand. Mixing different types of tyres on the same axle can lead to unpredictable handling – the car might pull to one side or become unstable during braking or cornering. In New Zealand, it’s actually required that tyres on the same axle have the same size and construction (for example, you can’t mix a radial tyre with a bias-ply tyre on one axle), and it’s strongly recommended they are of the same type and performance rating. For instance, do not pair a heavy-duty 4x4 all-terrain tyre with a standard passenger tyre on the same axle.
Car manufacturers and the NZ Transport Agency also advise replacing tyres in sets of four (or at least in pairs on the same axle) to maintain consistent handling. If you fit one new tyre and one worn tyre on an axle, the imbalance in traction can affect the car’s stability. Always aim to replace tyres two at a time (both fronts or both rears) so that handling remains predictable. And if you’re changing tyre types or brands, do so across the entire axle (or ideally the whole car) for uniform performance.
Equally important is matching the load index and speed rating on each axle. Both tyres on the front should have the same ratings, and likewise for the rear. It would be unsafe to have, say, a high-speed-rated tyre on one side and a lower-speed-rated tyre on the other – the lower-rated tyre could overheat or wear out faster under stress. The same goes for load capacity: each tyre on an axle should be able to carry the vehicle’s weight safely.
Consistency = Safety: By keeping tyres matched, your vehicle will behave predictably during braking, acceleration, and emergency maneuvers. You’ll get better traction and more even tyre wear. It also ensures you remain compliant with WOF requirements and the vehicle manufacturer’s guidelines. So when it’s time to replace tyres, plan on doing two or four at a time. Our technicians can help you pick a matching set that suits your budget and driving needs – just get in touch with us for personalized help.
Maintaining the right tyre size, type, and specifications on your vehicle is one of the best things you can do for safe driving. With the tips in this guide, you can find the right tyres with confidence – and remember, we’re here to assist with any questions. Whether you want advice on reading your tyre sidewall, help checking your tread, or recommendations on the best tyres for New Zealand conditions, feel free to contact our team. Safe driving starts from the ground up, so give your tyres the attention they deserve and enjoy peace of mind on the road!
