When To Replace Tyres

when to replace tyres

How To Know When To Replace Tyres

As a vehicle owner or driver, it is up to you to observe the condition of your tyres to make sure that they are always safe for use. Recent studies show that damaged tyres cause about 10% of all car accidents. This is because many vehicle owners neglect to check their tyres until they swerve, fail to brake or go flat. To avoid tricky situations that could compromise your car and the safety of everyone in it, you will need to know how to check tyres for excessive wear, signs of damage, and dry rot. In this article, we will learn important information on when and how tyres wear or get damaged. More importantly, we will find out when to replace tyres to ensure that you will be able to remedy a bad tyre condition before it’s too late.

How Long Do Tyres Last?

There are a variety of tyres available that match what their vehicles are intended for. These tyres are designed for everyday passenger car use, boat trailers, agricultural vehicles, commercial transport, racing, and other more specialised vehicles. Although their internal construction may vary, the exterior of all tyre is a uniquely-blended rubber compound that allows airtight sealing, impact cushioning, and firm gripping on roadways and pavements. This rubber compound is made to deteriorate slowly in standard driving conditions. This implies that if you drive your tyres on rougher road surfaces, then wear or damage could be faster. This is also the reason why car manufacturers cannot stipulate replacement intervals. In typical conditions and circumstances, the average life of car tyres is around 20,000 miles. However, its construction, age, tread wear, tread depth and damages will greatly influence how often to change car tyres.

Tyre Construction

Modern passenger car tyres generally feature a steel-belted radial design. Better known as radial tyres, they hold a series of radial plies mounted across the tyre from left to right, perpendicular to the direction in which they travel. Unlike the earlier bias-ply tyres with plies laid out diagonally, radial tyres give better ride quality, produce less heat, and last significantly longer.


To continually maintain grip and have optimal control of your vehicle, your tyres will require grooves. These grooves take away water from the road to allow your vehicle to have a steady grip on the pavement. As the grooves allow you to drive through dirt, mud, or snow, they also take a bite into the slippery surface to push you forward. Many of today’s tyres come in highly developed and more effective tread patterns that provide adequate grip levels for both dry and soggy land.

Some tyre (racing slicks) have no grooves at all. However, they are only used on smooth tracks and for racing purposes. Driven on rougher or damper roads, these racing tyres would lose traction easily and may cause terrible injuries and damages.

Tread Depth

When figuring out when to replace tyres, tread depth is one of the things you need to carefully inspect. This is because checking tread depth is an important part of tyre care, ensuring better handling and safety when braking hard or quickly accelerating away from a threatening situation. Without proper tread depth, traction would be difficult. The hard bite usually provided by your tyre treads turns into a useless little nibble. In Australia, tyres are required to have a 1.6mm minimum tread depth. Anything below is considered unsafe for road use. Most tyre makers suggest changing tyres at around 3mm of tread, instead of waiting for the minimum admissible depth.

Treadwear Ratings On Tyres

The Uniform Tyre Quality Grade (UTQG) treadwear rating or treadwear grade is a number marked on the tyre sidewall, indicating its expected tyre life. The higher the rating, the longer the tyre life will be. A tyre with a 600 treadwear rating is known to last twice as long as a tyre with a 300 rating. It should also be able to run three times the mileage of a 200 rated tyre. Treadwear grades are tested under controlled conditions with the use of four vehicles that are fitted with test tyres. They run in convoy on a specified 640km road course repeatedly until reaching 11,520km. Tread depths are measured every 1,280km, which will be averaged to find the tyre’s projected wear-out life.

Tyre Age And Dry Rot

Driving on old tyres can be a major safety risk. Tyres are made with textile, steel, and rubber compounds which have properties that evolve. As tyres age, they tend to dry, harden, and crack. Dry-rotted tyre poses a serious threat because the strength of the bond between the rubber and the steel belts reduces as the rubber hardens. It can no longer be flexible enough to effectively hold things together. This could further result in tyre blowouts and shaking while on the road.

To minimise dry rot, tyre manufacturers blend waxes with the tyre’s rubber. Nevertheless, a tyre must be rotated and flexed so that these waxes will rise to the surface. Rarely used cars are more prone to dry rot and cracks. Five years after your set of tyres were manufactured, you should check for cracks. And, after about ten years, the rubbers would have hardened enough and your tyres must be replaced to avoid untoward incidents. These recommendations should be done regardless of how much or how often your vehicle has been used. Remember to check the spares as well.

How To Check Tyre Age

One of the important factors should you know when to replace tyres is to check the age of a tyre. Look for the 10 to 12 digit serial tyre identification number, found on the tyre’s sidewall. This identification number is usually preceded by the acronym DOT (Department of Transportation). This 4-digit number indicates the week and year the tyre was manufactured. For example, 1807 means that the tyre was produced during the 18th week of 2007. Most tyres will show this date code on the outside-facing sidewall, while others will have them on the inward-facing side.

Tyre Damage

Inspecting your tyre for damage signs is just as important as observing tread wear. Here are common damages you need to watch out for.

Sidewall Blisters

Sidewall blisters and bubbles are caused by impact damage. This happens when a tyre hits a deep pothole, curb, or a sharp object, and the speed of the vehicle is focused on the small area of contact. Following the initial impact that compresses the tyre against the rim, the inner lining of the tyre is cut. Air then starts leaking from the inner to the outer sidewall areas in a concentrated pocket, forming a visible bulge or bubble. If left mounted, they could blow out at any moment. It is impossible to repair a blister in the sidewall. If you see any sidewall blisters on your car, it’s best to change them right away.

Damage From Driving An Underinflated Tyre

If your vehicle has been driven while severely underinflated, you should carefully inspect your tyres for resulting damages. When a car is driven on an underinflated tyre, the sidewall becomes tattered all the way around. This is caused by friction between sections of the inner sidewall that rub together when the tyre has collapsed on itself. On its exterior, you could find a ring around the tyre. This is where the rubber has become visibly shredded. You could also see a cut line all the way around the outer sidewall. No matter how the damage appears on the outside, the tyre has become unfit for continued use. Get it replaced before you hurt yourself or further damage your vehicle.

Tyre Punctures

A plug and patch repair combination is a quick solution for most tread punctures. However, if your tyre has sidewall punctures, the only remedy is to get them replaced. There’s just no way for a plug to fill the punctured hole. The patch won’t hold, and it’s going to continue to leak on sidewalls where there are no tyre cords. Even if a patch has been successfully placed over a sidewall puncture, your tyre is already compromised and susceptible to a sudden blowout.

It’s also good to note that run-flat tyres also have difficulty holding plugs in because their harder rubber blend is not flexible enough. If your run-flat tyre has been punctured, you’ll need to remove it and mount a new one. Not to worry, tyre warranties for run-flat tyres usually cover replacement due to puncture. Contact your dealership for more information.


Replacing tyres can be stressful on your finances, especially since it’s necessary to replace your tyres in pairs or sets of four even if only one tyre is damaged. However, you need to remember that those four tyres keep you in control of the vehicle then driving through different road surfaces. You should always be sure that all four tyres will keep you safe and prevent you from getting into blowouts and other threatening circumstances.

By knowing when to replace tyres, you can avoid the inconvenience of calling for emergency roadside assistance or changing a tyre in horrendous situations. For more information on tyre replacement, get in touch with our professionals at Tyres Now. Our experience and expertise will help ensure you always have good-fitting tyres that offer consistent road safety. Check out our wide range of products and services through this website or call us at +61 39303 7116.

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