Let me ask you a simple question? How does the general person get to know his tyres are old and finished? If he's lucky, a mechanic might tell him when he's getting his car serviced, or honestly, as is the case with most people, he will just not come to know. Eventually, the punctures start to pile up, he starts losing mileage and only then does he think about replacing his tyres. All this when he could've simply checked his tread depth and gotten to know in 30 seconds (not a typo) if his tyres needed to be replaced. Yes! 30 seconds is all it takes.
Most automobile owners today are still not familiar with the concept of tread depth. Tread depth is to tyres what gasoline is to cars/bikes. It tells you how much more your tyres can run depending on how much depth is available and is probably one of the most important elements of your tyres that you should regularly check. It also means that as your depth reduces, your tyre performance goes down and the risk for accidents increase.
Tread depth is an important concept that is essential to ensure your safety and this is precisely why we're here today to make sure that you guys understand and keep track of your tread depth.
What is Tread Depth?
Depth here in simple terms refers to the vertical measurement from the top of the tyre's tread surface to the bottom of the tyre's deepest grooves. You see these grooves essentially help you get the grip you need on wet surfaces, snow and mud. When your tyres start to wear down, the depth of these grooves also starts to reduce which makes your tyres less efficient.
Tyres can lose their footing long before they're worn out, and, if a tread has worn down too far, they could become a serious safety issue.
New tyres typically start with a tread depth of around 8 -9 mm, with some off-road tyres topping 12 millimetres. New tyre tread depth is something that manufacturers usually give information about, however, please note than it is not the same as usable tyre depth. Tyres are considered worn out not when this depth reaches zero but when the depth is around 2.7-3mm. So, the usable tread depth is essentially just around 5-6mm. For example, if you start with a new tyre with a tread depth of 8mm, the actual usable tread depth is only around 5mm as the moment it reaches 3mm your tyres are pretty much worn out.
When tyres wear down to less than 3mm, they've reached a point where they’re unable to meet the challenges associated with driving on wet, slushy or snow-covered roads. They also become prone to heat damage in hot weather and are susceptible to flats, punctures or complete failure due to any or all of these hazards. In other words, when a tyre’s tread depth is less than 3mm, it's time to get new tyres. Don't wait.
For those who frequently drive in rain or snow, you may want to consider shopping for new tyres for your car or truck when the tread depth is closer to 3.5-4mm.
How To Check Your Tread Depth
1) Tread Wear Indicators
The best and the easiest way to check your tread depth is with the help of tread wear indicators. Tread-wear indicators (TWI) refer to the projections between the tread grooves that are specifically designed to give you a visual indication of the degree of wear of the tread. Here's what they look like:
Tread wear indicators are spaced evenly through the main grooves in the tyre tread. If the tread is at the same level as the indicators then its a sign that the tyre has reached its maximum wear and it should be replaced. The science behind tread wear indicators is that the indicators sit just two to 3mm above the bottom-most portion of the groove. Now, if you remember, we explained above how the actual tread depth is calculated 3mm above zero as this is the least amount of depth required for safety. Now since this absolute minimum requirement (3mm) is highlighted by the level of the indicators, all you need to do is make sure that your tyre tread/tread area is always above these indicators.
Also See: Tyre Blooming: Brown Coloured Tyres Explained
2) Tread Depth Gauge
Another way you can measure tread depth is by utilising a tread depth gauge. This is an instrument that uses a probe bar which when inserted in the grooves of the tyre with its shoulders flush with the tread is able to read how much depth you have left. Don't use the probe bar on tread wear indicators, you have to do this between the grooves where no indicators are present. Check the reading and as long as the depth is above 3mm, you're safe.
3) With a Coin Test
Instead of a tyre tread depth gauge, you can also estimate the depth with a 1 Rupee coin or any other coin for that matter.
Simply place the coin inside the groove of the tyre and use your fingers to mark the level at which the tread area meets the coin. This level, once marked, will indicate the depth of the grooves on your tyre. Once you have marked the level, use a scale or a tape to get an idea about the depth of the groove. Remember, you must mark the level perfectly in order to get a precise and accurate idea of your tread depth.
Important Note - If you do use any of these methods, be sure to check in various locations as a misaligned wheel can result in uneven tread wear. Keep an eye open for any areas that look more worn than the surrounding surface. The tyre's tread should be judged by the lowest depth you measured.
If you are uncertain of the measurements, take your vehicle to a service centre.
How Much Wear Is Acceptable
- 4.7 mm or higher: Your tyre's depth is sufficient.
- 4 mm: If snow-covered roads are a concern, you should consider replacing your tyres.
- 3.5 mm: If you frequently drive on wet roads, consider replacing your tyres.
- 3 mm: It's time to start shopping for new tyres. They are close to being worn out.
- 2.5 mm or lower: Your tyres could be legally bald. It's time to replace them.
Your tyres are responsible for maintaining the essential contact between your vehicle and the ground with its tread being the surface that interacts with the road. The tread grips the road as you drive, but if it's not deep enough, your car loses traction and suffers extended braking times. Shallow tread grooves also make it harder to control the vehicle in wet weather and the chances of aquaplaning increase. To ensure your safety, measure the tread depth as part of your regular vehicle maintenance.
Watch for Other Signs Of Tyre Damage
While measuring the tread depth, you can also look for signs of cupping, or scalloping. These are small scoops, or divots, carved from the tread. They can indicate misalignment or other problems with your vehicle. Also, watch out for bulges in the tyre tread or sidewall. If you spot any of these, get your tyres inspected by a professional.
Image credits: rusnakwestlakeporsche, supertyreswellwyn, z-onetoledo, carsguide.com.au, medium
