Here's a sobering thought. Summer or winter, rain or shine, all that lies between you and a short, damaging trip into the scenery is the equivalent of the area of four shoe soles. Yes, every car tyre has a 'contact patch' the amount of its treaded area that touches the road. This area is only the size of an adult's footprint.
Let's say your car weighs one tonne. Nobody weighs half a tonne and the soles of his or her shoes do a pretty good job, expect perhaps on ice or snow. Translated into car tyre terms, the four-sole area has to do much, much more. It's unlikely, for example, that a road car could generate a cornering force of 1g. Under heavy braking, it's quite possible for such a force to be generated. Moreover, the forces generated during acceleration and cornering can be very high. Your car tyres and their contact patches do more than a 'pretty good job'. You don't usually expect your shoes to keep you from slipping in adverse conditions, such as on gritty or diesel-soaked tarmac in extremes of temperature. Your car tyres do this on a regular basis.
Legally, each of your car tyres must have a minimum of 1.6 millimetres of tread across ¾ of the width of the tyre's running surface. Not meeting this requirement can get you three penalty points on your licence, as well as a £2,500 fine…per tyre. So, four balding car tyres equals a lost licence and fines of up to £10,000.
In this context, the law could be called an ass. Why? Because just 1.6 millimetres of tread on a car tyre is cutting things fine when it comes to grip. The Royal Society for the Prevention of Accidents (RoSpa) put this to the test. They tried some emergency stops in a typical car on some typical surfaces. On smooth concrete, as some motorway stretches have, the car's barely legal tyres took a distance of 46.6 percent more to stop than an equivalent car with good tyres. Similarly, on hot rolled asphalt, the worn tyres needed 36.8 percent more distance to bring the car to a halt. There's no need to ask why RoSpa recommends a minimum tread depth of 3 millimetres.
This isn't the only scenario where worn car tyres will struggle. Tyres are designed to act like water pumps in wet conditions, they can clear surface water from their contact patches. When this fails to happen properly, the tyre will ride on a thin film of water. If this happens, you'd feel the steering lighten, which is an indicator of what's actually going on. When a car tyre is unable to cut through road water fast enough, it will aquaplane. Aquaplaning equals significantly reduced grip, as you might find out when you attempt to steer or brake.
Whilst it may seem to make sense to get the very most out of the treads on your car tyres, there is such a thing as false economy. Your car tyres have wear indicators, moulded into the treads. Take a look at them and, if the treads no longer stand proud of the tread wear indicators, it's new tyre time. Running your tyres down to the legal minimum could cost you far more than you think.
Article Resource
Merityre.co.uk are one of the leading UK independent suppliers of car tyres. Why not visit their website for an online tyre quote or contact your nearest fitting centre.
Wednesday, 21 December 2011
For Your Tyre Treads' Sake. Wheel Alignment
Wheel alignment? Surely your car's wheels are in line all the time? In fact, they aren't necessarily. Speed bumps, kerbing, speed pads and general wear and tear on a car's suspension and steering can put the wheels out of alignment. Misalignment may be felt as pulling to one side or another, and/or strange steering. In the longer term, your car tyres will suffer – bad wheel alignment can radically reduce tyre life.
So, how do you fix poor wheel alignment, thus making your car steer and brake better, as well as achieving maximum car tyre life? The good news is that car manufacturers provide a means of adjusting wheel alignment. The not so bad news is that you can't correct poor alignment yourself.
Cue a visit to your local friendly tyre man. Good tyre bays (and garages) have the equipment to check and adjust wheel alignment. All you have to do is watch (or not, depending on your preference) and pay for the work. Then, drive away secure in the knowledge that your car is shipshape in the wheel alignment department.
What happens in a wheel alignment session? Generally, three things are checked, and adjusted as necessary. The first check establishes that the car tyres are vertical, as viewed from the front or rear. Sometimes, the tyres may not be truly vertical. Some cars' tyres sit at a slight angle from the perpendicular. This is the camber angle, which can be adjusted to meet the car maker's specification.
The second check involves another angle, the castor angle. Does your car run on castors? Technically, yes, the castor angle permits the wheels and tyres to return to straight ahead when the car is rolling with no steering input. As you know, your front wheels turn from side to side in response to your turning the steering wheel. No matter how the wheels and tyres pivot, a line drawn through the centre of the axis on which they pivot won't be vertical. The line has to lean backwards slightly and if it doesn't, the steering will feel very odd. Again, this can be cured by adjustment.
The last check is on a figure called the 'toe'. All car suspension has a small degree of flexibility built into it. So, if the car tyres are parallel at rest, the drag between them and the road as the car moves would cause this flexibility to allow the wheels to splay very slightly. You wouldn't see this but your tyres would soon tell you all about it, by wearing out the inner edges of their treads. So, the wheels are usually set to 'toe-in', so they run parallel. If the tyres toe out, if the toe-in is too much or if the toe angle varies from side to side, the car tyres will wear out prematurely. Curing this is again a matter of adjustment.
Wheel alignment used to be checked with a special gauge that used a mirror and lens system. Nowadays, it's common for car tyre bays and garages to measure the angles involved using laser equipment. Yes, accurate measurement is necessary. In some instances, worn suspension or steering components mean that a problem can't be adjusted away. Then, the tyre man in question will tell you what needs repairing or replacing for accurate alignment to be achieved. It's also the case, especially on a car with independent rear suspension, for the rear wheels and tyres to be misaligned. Once again, adjustment is usually possible.
Is it possible to stop your car's wheels becoming misaligned and making the tyres suffer? In a word, yes. Don't kerb your car tyres. Avoid potholes and traverse speed pads carefully. Above all, always negotiate speed bumps with the tyres on one side of your car. Straddling speed bumps is a major cause of both wheel misalignment and tyre carcass damage. You have been warned!
Article Resource
Merityre.co.uk are one of the leading UK independent suppliers of car tyres. Why not visit their website for an online tyre quote or contact your nearest fitting centre.
So, how do you fix poor wheel alignment, thus making your car steer and brake better, as well as achieving maximum car tyre life? The good news is that car manufacturers provide a means of adjusting wheel alignment. The not so bad news is that you can't correct poor alignment yourself.
Cue a visit to your local friendly tyre man. Good tyre bays (and garages) have the equipment to check and adjust wheel alignment. All you have to do is watch (or not, depending on your preference) and pay for the work. Then, drive away secure in the knowledge that your car is shipshape in the wheel alignment department.
What happens in a wheel alignment session? Generally, three things are checked, and adjusted as necessary. The first check establishes that the car tyres are vertical, as viewed from the front or rear. Sometimes, the tyres may not be truly vertical. Some cars' tyres sit at a slight angle from the perpendicular. This is the camber angle, which can be adjusted to meet the car maker's specification.
The second check involves another angle, the castor angle. Does your car run on castors? Technically, yes, the castor angle permits the wheels and tyres to return to straight ahead when the car is rolling with no steering input. As you know, your front wheels turn from side to side in response to your turning the steering wheel. No matter how the wheels and tyres pivot, a line drawn through the centre of the axis on which they pivot won't be vertical. The line has to lean backwards slightly and if it doesn't, the steering will feel very odd. Again, this can be cured by adjustment.
The last check is on a figure called the 'toe'. All car suspension has a small degree of flexibility built into it. So, if the car tyres are parallel at rest, the drag between them and the road as the car moves would cause this flexibility to allow the wheels to splay very slightly. You wouldn't see this but your tyres would soon tell you all about it, by wearing out the inner edges of their treads. So, the wheels are usually set to 'toe-in', so they run parallel. If the tyres toe out, if the toe-in is too much or if the toe angle varies from side to side, the car tyres will wear out prematurely. Curing this is again a matter of adjustment.
Wheel alignment used to be checked with a special gauge that used a mirror and lens system. Nowadays, it's common for car tyre bays and garages to measure the angles involved using laser equipment. Yes, accurate measurement is necessary. In some instances, worn suspension or steering components mean that a problem can't be adjusted away. Then, the tyre man in question will tell you what needs repairing or replacing for accurate alignment to be achieved. It's also the case, especially on a car with independent rear suspension, for the rear wheels and tyres to be misaligned. Once again, adjustment is usually possible.
Is it possible to stop your car's wheels becoming misaligned and making the tyres suffer? In a word, yes. Don't kerb your car tyres. Avoid potholes and traverse speed pads carefully. Above all, always negotiate speed bumps with the tyres on one side of your car. Straddling speed bumps is a major cause of both wheel misalignment and tyre carcass damage. You have been warned!
Article Resource
Merityre.co.uk are one of the leading UK independent suppliers of car tyres. Why not visit their website for an online tyre quote or contact your nearest fitting centre.
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