What Tyres Do I Need

If you have a new car (or even a current one in need of a change), you may well ask yourself: "what tyres do I need?”. It’s a good question for a number of reasons: your tires are an integral part of your vehicle’s structure - they’re what connect you to the road - and most importantly, they help you to stay safe while you’re on it. To help you get on the road safely, here’s a guide covering everything you need to know about choosing the right tyres for your vehicle.

Size

When choosing your tyre, it can help to consult a trained technician who can offer guidance on finding the best type for your style of driving and budget.

All the information you need to determine which size of tire to purchase can be found on the sidewall of the OE, or “orignal equipment” tyre - in other words:  the tyre specifically made for your vehicle when it was constructed.

OE Tyres

Since the previous tyre used may not have been the best fit  (this can be possible in cases of second-hand vehicles), the best place to start when looking for information on the best fit for your vehicle is to look at the OE tyre.

A Quick Guide To OE Markings By Brand

-     AO = Audi

-      = BMW, Mini

-      MO = Mercedes

-      MO1 = AMG

-      N0, N1, N2, N3, N4 = Porsche

-     RO1 = QUATTROVO = Volkswagen

What to Look For

Look for three key markings to make note of so that you can use them as a reference when taking them to your local tyre supplier. These are usually seen in the following order:

1. Tyre Width - the overall width of the tyre, or “section width” measured in millimeters from the widest point of the tyre on the outer sidewall to the widest point of it’s inner side wall.

2. Aspect Ratio - or “profile” (compared to the tyre’s width). The lower the aspect ratio on a tyre, the smaller the height of the sidewall - this usually equates to better cornering, but is less suited to drivers seeking a smoother ride.

This  is usually calculated as:

H ÷ W X 100 (Where “H” represents the height of the tyre’s sidewall and “W” represents the width of the tyre)

3. Diameter - represented in inches, this indicates the diameter of the wheel on which the tyre is meant to fit.

4. Load Index - this represents the most amount of weight the tyres can carry at the speed shown on the speed symbol. Some variations of load capacity include:

-      Extra Load (XL) tyres designed to carry higher loads with higher inflation pressure. This will usually be marked on the tyer sidewall as Extra Load (XL), or Reinforced (RF).

-      “Run on flat”,  DSST  or run flat  tyres are constructed in reinforced sidewalls capable of carrying the vehicle in case of pressure loss, enabling the driver to continue their journey with a flat tyre for up to 50 miles at up to 50 miles per hour. This technology is also known as “self supporting” and is typically found on Minis and BMWs.

5. Speed Rating -  indicated by a letter showing a maximum speed at which the tyre can carry the load corresponding with the load capacity index, as seen below:

-      S  112mph or 180km/h

-      T  118mph or 190km/h

-      U  125mph or 200km/h

-      H  130mph or 210km/h

-      V 149mph or 240km/h

-      W(ZR) 168mph or 270km/h 

-      Y(ZR) 186mph or 300km/h 

-      ZR Above 149mph or 240km/h

Stay Within Your Limit

Purchasing tyres with a speed rating exceeding your vehicle’s top speed won’t allow it to move any faster - and doing so can be unnecessarily expensive, so when buying a new set of tyres, select those within your vehicle’s existing speed range.

Other Aspects

Other sizing aspects to consider may not be marked on the side wall, but are still worth noting:

Rim

This is the part of the wheel left after removal of the tyre. This may vary slightly from the width of the tyre itself (which is why these two dimensions are given separately).

Construction

An optional letter sometimes found on tyres relating to the internal construction of the tyre. These are usually of three types:

-   R (Radial) - most car tyres are radial, or radial-ply in construction, where a network of plies of cord are used to create the “carcass” of the tyre, giving it it’s strength and structure.

-   B (Belted or Bias Belt) - this is where the sidewalls are the same material as the tread, creating a more rigid drive

-   Diagonal - often found on classic cars, diagonal tires are made from nylon cord placed in the treads and side wall following a crosswire or diagonal direction of 55 degrees.

If none of these are visible, it may mean the tyre is a cross-ply tyre. This tyre type is common in older vehicles, with rigid sidewalls and little resiliency on bumpy roads.

Noise Rating 

While wider tyres provide better grip, they can create excessive amounts of road noise - something worth noting if you are looking for a quieter drive. Noise-efficient tyres can also be useful to help reduce noise pollution levels in our towns and cities.

Wet Grip Rating

Your tyres have an impact on the fuel efficiency of your vehicle, making up to 20% if it’s total fuel consumption.

High-quality tyres with decreased rolling resistance can help improve this: look for a tyre label indicating how fuel efficient your vehicle is on a  scale of A-G.

It’s also worth remembering that fuel efficiency can be affected by tyre pressure, so to ensure peak performance always keep your tyres properly maintained.

Season

Here’s where the rubber meets the road. The compound, or type of rubber tyres are constructed from will vary depending on whether it is a winter, summer or all season tyre.

When purchasing tyres, seasonal changes are important as they account for variables in the weather that could affect the tyre’s grip on different surfaces such as ice or hot tarmac.

The type you need will depend on the climate you are driving in - while warmer European countries tend not to require winter tyres (although colder regions may require them by law), the UK tends to have more inclement weather conditions.

Winter Tyres

These are constructed from a more malleable, elastic rubber compound, creating additional traction and grip in temperatures below 7°c. This tyre type also has specially designed sipes to help with winter precipitation to help ensure improved performance, shorter braking distance  and better traction come rain, snow or sleet.

Summer Tyres

In summer heat, the softer compound of those used in winter tends to degrade faster, which is where summer tyres come in. Constructed from a harder compound enabling them to perform in hot, dry and wet conditions, this tyre type allows for braking distances grip, handling and traction whilst on the road

All Season Tyres

This tyre type combines both design elements of both seasonal tyres to offer versatile, year-round performance. To ensure peak performance in all conditions, it is advsiable to have both a set of winter and summer tyres - but if you prefer the convenience of not having to change your tyres when the seasons do - an all season tyre can be a good all round option.

Wet Grip Rating

This refers to the ability of the tyre to maintain traction under wet conditions - essential when driving in the UK, which receives on average 133 days of rain or snow annually . The higher the wet grip rating, the quicker the car is able to stop on wet roads with full braking applied.

Minimum Tread Limit

A close to minimum tread depth not only means reduced grip and poor handling (especially on wet roads) - but it could also cause your car to fail it’s MOT or even result in a fine by the police.

Always check before purchasing to ensure your tread is well above the minimum depth of 1.6mm. In wet conditions, 3mm or less could mean a significant loss of traction on weather roads.

Snowy conditions require a minimum of 4.75mm - while shallow groove and lug depths may impede the tyre’s ability to grip the snow and to “clean out” any snow compressed into the tread.

Comparing Tread

When comparing different tyres within the same brand, use the UTQG (tread wear) ratings to determine value by dividing the tread wear rating by price: the higher the number, the better value it will be.

That said, this system may not help you decide between brands, as no standardisation currently exists for tread wear ratings. If you are looking to compare brands, reviewing temperature and traction ratings may be your best option, as these are standardised measurements

Vehicle Type

Certain types of vehicle such as 4x4s or SUVs may require specifically-made tyres. When choosing tyres for this vehicle type, seasonality is also important - however they must also be designed to take the additional weight of heavier cars while maintaining handling, traction and grip on the road.

Premium, Mid-Range And Budget Tyres

Depending on your budget and type of car, there are three main types of tyre to choose from - however it’s worth remembering that there may be specific types you cannot use, for instance if your car is a model requiring premium tyres only.

-     Premium - manufactured by big-name brands, these are usually the most expensive, offering benefits such as additional grip, durability, increased stopping distances and quieter performance on the road. These are generally available for every make and model.

-     Mid Range - a less expensive option, these tyres are popular with most drivers, owing to their great all-round performance and durability while offering value for money.

-     Budget Tyres - the cheapest option can be best for drivers on a tight budget - however they are unlikely to provide the same level of durability and performance as the other two options, requiring more frequent changes. That said, if you are unlikely to travel far and generally use your car to get from A-B, a budget tyre might be the best buy for you.

-     Part Worn Tyres - another option for those on a budget, part worn tyres may be shipped in from other EU countries, where the minimum depth tread is higher, allowing for greater longevity - and you may even b able to find premium or mid-range tyres at a good price point.

Part Worn Tyres: Tread Carefully

Purchasing part worn tyres carries safety risks, especially if you are unsure of their origin, how they’ve been used or whether they have had repairs made to them. 

If the tread has worn down, this can also be an issue: most part worn tyres will only last a couple of thousand miles, and may already be close to the minimum tread limit.

In general, it’s best to purchase the best quality you can afford to ensure longevity and value for money. The best way to do this is with another simple calculation:

TP ÷ DS (where TP relates to the total price of tyre purchase and DS relates to the distance of service (in miles or kilometres)

Determining Number of Tyres Required

Due to cost restrictions, some drivers choose to have premium tyres fitted on the front wheels only, as this is where tread tends to wear the fastest - allowing for the best grip when rounding corners - but there may be other reasons for choosing two tyres over four.

If you are replacing your tyres in pairs, it is advisable to also perform a tyre rotation as this can help to avoid alignment problems. When first fitting your new pair, it’s a good idea to first fit them to the rear so that you can drive to the condition of your tyres.

However, if your car is rear-wheel drive, the opposite applies and they should be fitted on the front. For further advice on tyre fitting, contact your local tyre supplier who will be able to help advise you on this process.

Where to Find The Right Tyres

In addition to checking the side wall there are a number of ways to determine which tyre is best suited to your car. You can do this by:

-      Contacting the original manufacturer

-      Referring to the manual (if this is not available as a hardcopy, copies can usually be found by searching online)

-      Online forums for your make and model of car - these can also be helpful for drivers looking to share tips, advice and impartial reviews on their experience of using different tyres types.

-      Checking for stickers featuring information about your tyres - these are usually  located either in the handbook for your vehicle or on a sticker positioned on the fuel cap or door jam.

-      Contacting your local garage or online tyre merchant for professional advice on mobile tyre fitting, wheel alignment and more.