BPS JPT FOR YOU: How to Know when Car Tires Need Replacing

Wednesday, December 15, 2010

How to Know when Car Tires Need Replacing

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How to Know when Car Tires Need Replacing: "

Ever wonder when to replace your worn car tires? The performance of your car tires is critical to the safety, performance and efficiency of your vehicle; the NHTSA estimates that about 400 fatalities annually may have been attributed to tire failures.^[1] Most tires are designed to provide similar performance throughout their lives. However, at some point they start to lose performance in terms of their traction and braking ability. Here are a few tips that should help you decide if it is time to start shopping for a new set of tires and avoid spending more than you need to.

Steps

Understand that the primary function of tread on a tire is to divert water from beneath the tire to improve traction and avoid hydroplaning on wet roads.^[2] Tires become unsafe when they're worn, and once the tread is down to 1/16th of an inch (1.6mm), the tire is no longer safe.
The wear bars are the vertical bars between the treads in this photo.
Look at the tread pattern. All tires sold in the United States and other countries have what are called 'tread wear bars'. These are small bridges that form between your treads. Look at the tread pattern and you'll see the beginnings of these bars start to form between the treads, or running across the tires. As the tires wear, these bars will become flush (level or even) with the tire's tread. At this point, it's time to replace the tires.
Abe's hair, showing clearly.
Check the tread by using the 'penny test.' Take a penny, and place it upside down with Lincoln facing you in the center of the tread (at the thickest part of the tire).
- If you can see the very top of Lincoln's head or the copper above it, replace the tires immediately.
- If Lincoln's hair on the top of his head is partially visible, it is time to go shopping for tires.
- If you cannot see the hair on the top of his head (if the coin is inserted enough that the tire tread is at least as deep as Lincoln's forehead), your tires do not need replacing yet.
Use a tread depth indicator or gauge. Obviously, not everyone can get hold of an Abraham Lincoln penny. Either use the tread pattern test, or resort to using a special tread depth indicator or gauge tool to measure your tire's tread. If you don't already own one, the gauge is cheap to purchase from an auto parts dealer and it's easy to use.
- Alternatively, it might be easier to pop in to your regular tire place and ask them to check it for you; likely they'll do this for free if you're regular customer.
Know the legal requirements. Worn tires should be replaced as a matter of common sense to assure safety, but in some jurisdictions, there are also legal requirements to replace worn tires. In many US States, tires are considered to be legally worn out when they have worn down to 1/16' (1.6mm) of their remaining tread depth.^[3] In the UK, the minimum depth of the tread on tires (tyres) is 1.6 millimeters, across the central ¾ of the tread around the whole tire (tyre).^[4]
Make note of any irregular tread wear. This could indicate a wheel misalignment, the need for a tire rotation, or both. Uneven tread wear is a sign that you need to take your car in for servicing.
- If uneven tire wear is extreme or if tires wear out much faster than expected, have a competent tire workshop check your suspension and correct as necessary before replacing tires. Improper alignment or worn suspension parts can dramatically shorten a tire's life.
- It is a good idea to rotate your tires from front to rear in pairs. Take both front tires and move them to the rear and vice versa.
Replace the tires at least every 6 years. If you're not sure, the minimum replacement time that is recommended by the NHTSA is six years regardless of use, with 10 years being the maximum service life for tires. Check your owner's manual for specific recommendations related to your car. And always err on the side of caution if you suspect your vehicle has tires that are over six years of age.^[5]

Video

Tips

On 4-wheel-drive or all-wheel-drive cars you should replace all four tires if it is recommended in your service manual. Differences in tire diameter, even due to different states of tread wear, can permanently damage differentials.
If you see uneven wear on a front tire, chances are that the front end is out of alignment. You should have this checked and rotate the tires to the rear if possible (some vehicles have different sizes on front than the rear). The tires from the back should be fine and the uneven tires moved to the rear will start to correct themselves.
Tires do not wear perfectly evenly, so be sure to insert the coin at several points from the outside to the inside of your tires. Tires generally wear more on the inside but over-inflated tires will wear more in the middle.
Test all of your tires and if possible, replace them all at the same time. Mismatched tires will not provide the same safety, performance and efficiency as a matched pair will.
Keep your tires properly inflated.
Treadwear grades are an indication of a tire's relative wear rate. The higher the treadwear number is, the longer it should take for the tread to wear down.
Tire age is dated from the date of manufacture, not sale, as tires deteriorate even in storage.
Tires age faster in warmer climates.^[6]
A quarter can be substituted for a penny; just use Washington's head as the point instead of Lincoln's.

Warnings

Be careful to buy tires that are the right size and type for your vehicle and rims (wheels). Changing to low-profile tires may require you to buy larger rims so that the outer circumference of the tire remains unchanged. Incorrect tire size or mismatched tread can also cause a low tire pressure warning to come on if the vehicle is equipped with a Tire Pressure Monitoring System (TPMS).
Tires should never rub against your fenders or any other part of your car. If your new tires rub during turns or when going over bumps, they don't fit, no matter how cool they look. Fix this before you suffer a blowout and crash.
Be careful when rotating tires, and especially when moving tires to different rims. Many modern tires have a specific rotational direction and corresponding rotation method. Refer to your tire manufacturer or dealer for details.
If you happen to see wires on your tread or notice wear on the sidewalls of the tire, don't even bother with the penny – just get the tire replaced. The wire thing is rare, and even if Abe says the tread is still good, the wires indicate an immediate need for replacement. It happens and it's better to replace the tire than get the blowout as you're speeding along the road.
Hydroplaning is an increased possibility with bare tires. The risk of hydroplaning increases as the tire wears. This is true even if the tire is not fully worn out. A tire with 50% tread life may hydroplane in conditions where a tire with 90% tread life may not.