What Your Tyres Can Tell You About Your Car

How You Can Tell If Your Car is Fit and Well

The tyres of your car can tell you lots of information. For example, they can show you that your wheel alignment (tracking) is out of adjustment, that you have a worn wheel bearing that requires replacement, a shock absorber is defective, you have a suspension or a steering fault.

Your tyres can tell you if you have a brake problem, perhaps a brake is binding (sticking on), or you have a wheel balance issue. Talking of wheel balancing, if ever you find the steering of your car beginning to judder at a speed between about 50 and 70mph, wheel balancing is most likely the fault. Left for long and the persistant vibration will knock the life out of your steering joints and bearings, resulting in a very expensive repair bill.

Front tyres are the most revealing, although the rear tyres can tell you a lot also, and here’s what to do so as to tune into the information.

Give Your Tyres a Stroke as Often as You Can

Squat or kneel down at the side of your car next to one of the front wheels, and place the palm of one hand on the tread area at the 12 o’clock position. With very light pressure, stroke the tyre by running your hand around its circumference until you reach the ground, and then back the other way, passed the 12 o’clock position, until you reach the ground on the other side.

The tyre should feel the same when you do it in either direction, however if you feel any feathering of the tread pattern, like if you stroke a cat or a dog first the right way and then the wrong, this will tell you something is not right.

If you have patches of feathered tread blocks, instead of this condition being present all the way around the tyre, it can indicate that you have a shock absorber (damper) that is worn out and needs replacement, or perhaps a warped brake disc or drum.

Next, have a look at the tread on the tyres, and you can most easily do this by steering the front wheels onto full lock, to check one tyre, and then full lock the other way to check the other. Don’t do this whilst the car is stationary, as this will cause accelerated wear to your steering linkages. Always start the engine and move a little way forward or back whilst steering.

Watch Out For Unusual Tyre Wear Patterns

What you are looking for is any difference in wear across the tyre. Do you have deeper tread on one edge to the other? If so, this will indicate that your tracking is out of adjustment, making the tyres scrub on one side of the tread area.

Tracking is term that refers to the wheel alignment of your front wheels. Did you know that the two front wheels of your car are not supposed to be in equal alignment with each other? That’s right, they have either a built in toe–in or toe–out, but the difference to parallel is small.

Front wheel drive cars have the front wheel alignment set at toe–out, which means the leading edge of the front wheels are set up to turn out slightly, as in away from each other. This is because the engine is driving the front wheels, and when you accelerate, the torque through the driven wheels pulls them into near enough perfect alignment.

Rear wheel drive cars are set to the opposite, as toeing in they splay outwards as you drive. You can’t see any of this, of course, as the change in angle is only a small number of degrees.

Incorrect Wheel Alignment Causes Uneven Tyre Wear

The purpose of telling you this is that if the front wheels are toeing in or out by an incorrect amount, depending upon which it is, on one edge of the tyre the tread pattern wear badly, and if left long enough you will get a band of excessive wear around one edge, which is a characteristic of this condition.

In the diagram below you can see the two tyres are excessively worn around the inside edge, which means the wheel alignment is toeing out too much.

Toeing in too much will cause a similar band of wear around the outside edge of the tread area, and a trip to a tyre fitting centre will be needed to have the wheel alignment corrected, which is a 10–minute job.

Be Kind to Your Tyres

Wheels become misaligned if you hit a pot hole, or anything that gives the wheels a clout. Bumping up and down kerbs is a good way to mess up your suspension and steering, as will be driving over traffic calming humps too quickly. Don’t wait for the tyres to start telling you something is wrong, as that may prove expensive as well as harmful to your health.

As many vehicles today have independent rear suspension, and adjustable rear wheel alignment, so as to gain advanced warning that all is not well at the back end of the vehicle, give the rear tyres a stroke also.

Driving With Incorrect Tyre Pressures

If you ever find you have a band of wear around the middle of the tread area, this is usually an indication the car has been driven with the tyre over inflated, as in too much air pressure.

If you have deeper tread around the centre, but greater wear at both the outer edges, this can indicate the car has been driven with the tyre under inflated.

The importance of correct tyre pressures should never be under estimated, as to neglect them is a potential killer. You may not notice anything amiss when driving around town on your own, but if you add two or three of your mates to the car, and you get out on the open road, you could be heading for disaster. We’re not just talking about the risk of tyre blow–outs here, we’re talking severe loss of vehicle stability, and that can mean sudden and irretrievable loss of car control.

Complete a Thorough Visual Check At Least Once a Week

Checking the overall condition of the tyre structure is something that should be carried out on a regular basis, and at least once a week. When you do this you are looking for anything that is different from how a tyre will normally appear. Any odd lumps, bumps, splits or tears in the rubber, don’t ignore it. Get it checked. It is no good wishing you had done something after an incident, as that will not change history.

The Law Concerning Tyres

Cuts, Splits, Tears, Lumps and Bulges — Any cut in the tyre that has exposed the ply or cords of the tyre (cords and ply are the tyre body beneath the rubber) that exceeds 25mm in length, or represents more than 10% of the tyre width (whichever is the greater) shall be an offence. However, if there is any cut or split in the tyre that exposes the ply or cords, the tyre will be illegal no matter how small that split or cut may be.

Any tyre that has a lump, bulge or tear that has been caused by the separation or partial failure of its structure will not be legal for use on the road. It is also an offence to use a tyre whilst it is under inflated.

Minimum Legal Tread Depth — The legal minimum tread depth for car tyres is 1.6mm in a continuous band throughout the central three–quarters of the tread area width, and throughout the whole circumference. In other words, if you have a tyre that is 16cm wide across the area that will normally have tyre tread pattern, and you have a 12cm band of tread no less then 1.6mm deep with 2cm bald area on either side, that is the legal limit. However, this will be only if the band of tread pattern does not drop below 1.6mm deep for the whole circumference of the tyre.

However, whilst that is the minimum requirement, to allow a tyre to get to this condition, and still be driving on it, is foolish. As a general rule, do not let your tyres wear beyond 2mm in tread depth, and if you have any area less than that depth, change the tyre for a new one. NEVER fit second hand tyres.

Space Saver Spare Wheels & Tyres — Some modern cars carry a skinny spare wheel, or space saver spare wheel. These are intended to be get you home temporary equipment. If you have a puncture, and have to change your wheel to fit one of these, they have a maximum speed limit, usually being 50mph. This will be marked on the wheel on a big yellow label. Do not exceed the speed limit rating and change the wheel back again as soon as possible after the replacement of the punctured tyre.

Penalties

If you are stopped by the police, or if you have a crash, and you are found to be driving with an illegal tyre, even if it is not your car, you will be held responsible. The punishment is a fine and penalty points.

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This page was last updated
Sunday, 29-Jan-2012

Information About Tyres – Driver Education & Safety