Tyres - the unsung heroes on your car
Much discussed, often kicked, and frequently neglected for far too long, tyres are of course vital to the safe enjoyment of your car.
So here's a few thoughts on getting the best from your tyres…
The law says there must be at least 1.6mm of tread round the whole circumference and across at least 3/4 of the central width of the tyre. In reality, the performance of a tyre in wet conditions is compromised when worn to the legal limits and it’s worth thinking about earlier replacement.
Age of the tyres is also important as the rubber hardens with age and loses its ‘grippiness’. This could be of concern when cornering, but also it will affect how quickly you can do an emergency stop. Rubber can also crack with age and compromise the strength of the tyre. There’s a school of thought which says tyres should be replaced after 5 years regardless of the amount of tread left. Definitely though, don’t run a car with tyres older than 10 years.
Unless your tyres are incredibly ancient(!) they will have a code stamped on the sidewall. This will start with ‘DOT’ and the last 4 digits are the ones of interest. Of these, the first 2 are the week, and the last 2 the year, in which the tyre was made. So 2704 means manufactured in the 27th week of 2004.
Do inspect your tyres on a regular basis – tread depth, signs of damage, aged related cracking. And very importantly, check the pressures! The pressures stated in your car’s handbook will be for when the tyres are cold.
The wrong pressures will cause premature and uneven wear and can increase fuel consumption. Far more importantly, an incorrectly inflated tyre won’t provide the right levels of grip.
Which tyre to choose
There’s a confusing number of makes and models of tyres to choose from, and an equally confusing number of opinions (many of them subjective!) on what’s best.
It’s usually best to stick with the car manufacturer’s recommended tyre size. Sometimes it's assumed wider tyres automatically mean better handling, but it's not necessarily so. As an example, the tyres on the original Lotus Elan are unfashionably skinny, but fit modern wide wheels and tyres and you’ll spoil the feel and handling of a wonderfully balanced sports car.
Think about the sort of driving you do. Are you looking for maximum grip, good fuel consumption, best longevity or low road noise? Also consider the characteristics of your car. For example, a harder tyre lasts longer than a softer one but gives less grip. But when you have a car like a Morgan or Lotus or Caterham, you can run a soft tyre for improved grip as the car's light weight means tyre life won't be unacceptably compromised.
A recognised brand is often worth paying a slight premium for. There are quite a number of attractively priced but little known tyre makes out there. No doubt some will be fine, but others are noticeably worse when it comes to grip.
Tyres will have both a speed and a load rating and it is best practice when replacing tyres to go with the same ratings as originally fitted to the car (although you are allowed in the UK to fit tyres with a lower speed rating).
Some car manufacturers work in conjunction with a tyre company to develop tyres specifically designed and recommended for a particular car. Lotus have worked with Yokohama to produce tyres for some of their models.
Punctures and tyre repairs
Not all punctures can be repaired. Only punctures in the centre section of tyres can be repaired – see area T in the diagram below:
Also tyres which are speed rated V or above, are only allowed one puncture repair.
Even if a puncture can be repaired, a tyre should be carefully inspected before repair to ensure the structure hasn’t been damaged, e.g. by driving on it when flat.
Many modern cars do not have a spare wheel and aerosols of tyre sealant are supplied instead. These can do an adequate job of repairing a puncture and inflating a tyre at the side of the road, but the repair's not permanent. The car should be driven at reduced speed and the tyre inspected and repaired/replaced as soon as possible.
The grip from normal tyres decreases in cold weather and it’s well proven that a proper winter tyre which has a different rubber compound and tread pattern will give significantly more grip in wet or indeed snowy conditions.
In the UK, it’s relatively uncommon for someone to have two sets of tyres – i.e. summer and winter – whereas in many parts of Europe where winters are colder, it is common or indeed a legal requirement.
For many people, the problem with owning a set of winter tyres is the cost and the logistics of storage and swapping wheels/tyres. So if these are issues, the simplest solution is to drive more cautiously in winter time and ensure the tyres are in top condition with plenty of tread.
Do carefully check the condition of your tyres before doing a track day – you’ll be putting a lot more stress on the tyres and you don’t want any nasty surprises.
Tyre pressures need to be kept an eye on during a track day. If you’re a regular attendee, you’ll know what works for you and your car and the ideal pressures to get the right grip, turn in and performance.
If you’re new to track days, be aware that your tyres will get hotter than normal which in turn causes higher tyre pressures. As a rule of thumb, you should aim to keep the tyres pressures at their normal hot running pressure (as measured after a spell of road driving). So check tyre pressures between track sessions and adjust, i.e. reduce if necessary.
If you drive a classic Morgan, the tyre pressures recommended for road use are quite soft so as to give a good compromise between ride comfort and handling. You’ll probably find for a track day that road pressures are too low which mean the sidewalls flex too much under hard cornering and the handling isn’t as sharp as it can be. Another 3 – 5lb pressure may make a useful difference.
At the end of the track day, check the condition of your tyres before driving home to make sure you’re still safe and legal and ensure the pressures are returned to the correct pressures for road driving.
If you’re after more detail about specific areas or issues relating to tyres, the website for the British Tyre Manufacturer’s Association has a number of good articles. Click on - BTMA Tyre Articles