17 March 2006: Tyres

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he Accord will be needing at least two new tyres before the summer and so I’ve started looking at tyres again. By default the UK-specification Accord takes 195/60/R15 V-rated tyres but some tyre websites quote 185/65s and H-rated on the same steel rims. With both sizes being compatible there are a large number of potential choices.

Some people are more than happy to take their car along to a tyre and exhaust “specialist” and either see what is available or opt for the cheapest tyre on sale, occasionally talked up into another tyre model, new brakes, new shockers and maybe for good measure a new exhaust too. Getting back to tyres, if one has been driving around on worn out booties then new ‘uns are almost certainly going to feel just fine.

There is a certain logic to getting the cheapest possible tyre after all... but it isn’t something I subscribe to. You see, the opposite side of this coin happens late on a wet night when somebody pulls in front of you. Or after a year when your budget special tyres have worn out and you’re back again for more tyres, plus the hard sell for brakes, shockers and tyres.

Instead, I try to find a tyre that is of a good enough quality and has the right characteristics for what I would like. This means spending more on the individual tyres but if you want a harder wearing option, the running costs can be similar if not lower since you’ll get many more miles from the bootie.

Tyre design has come a long way in the last twenty five years. Many tyres claim to have good grip in the wet and the dry, good braking, low rolling resistance, good longevity and low noise levels. As a rule of thumb this is all very true but as with all things car related, there is a degree of element. Going back twenty five years, higher performance, lower profile tyres tended to be noisy in use, didn’t last long and had a high rolling resistance. Tyre manufacturers have developed new technologies both in the tread design and the construction of the tyre itself. There are several influences on current tyre design but rolling resistance and noise appear to be making the most significant changes.

In the dry it is the rubber compound that makes an important difference to available grip. All things being equal, the softer the rubber compound used the more grip. In the wet the same is true but to a lesser extent, since the design of the tyre and how effective it is at expelling water from between the rubber and the road is critical. Certain compounds can be added to the rubber to improve grip, typically silica but there are others.

Many modern tyres have areas of open space, or grooves, in the tread, which are designed to drain water. Circumferential grooves provide the shortest distance from the front to the rear edges of the contact patch.

The rolling resistance of a tyre is becoming increasingly more important as manufacturers look to reduce vehicle fuel consumption figures. Depending on what research you place more emphasis on the difference between an ordinary tyre and a low rolling resistance may amount to five or six percent on the official fuel consumption and emissions test. How this translates into road use varies, but in the United Kingdom the Carbon Dioxide emissions dictates the vehicle duty paid. There is a wider issue associated with carbon credits, whereby a manufacturer has to ensure the “fleet” of vehicles available for sale have an average carbon dioxide emission below a certain level - those few percent can make a material difference.

Of course, the improvement (or reduction) in fuel consumption is all but irrelevant if the tyres offer mediocre grip. Low rolling resistance tyres have a reputation for being slippery but from my research, this theory is not true any more. A good quality tyre will perform on wet and dry roads regardless of its rolling resistance. A tyre can offer poor levels of grip and a high rolling resistance. It’s all in the design, construction and materials used in the tyre. There really are advantages to picking a good quality tyre!

I should also touch on tyre (and road) noise. Just a few years ago, a high performance tyre meant high rolling resistance and lots of noise. Modern higher performance tyres are not like this (or they certainly don’t need to be). Not only can tread patterns be designed to improve grip but also to reduce noise.

Phew. A lot of rambling. So what do I want from my tyres? Okay I need good grip and braking on wet and dry roads but as specific requirements I’d like a quiet tyre with good life and low rolling resistance. Oh and I don’t want to pay too much for it either. I’m not too bothered what it looks like, but a more aggressive-looking tyre is preferable. So doesn’t everybody?

Going back to the Accord, she’s sitting on H-rated Bridgestones on the front and V-rated Michelin Energies on the back. There’s some difference between the two: the Bridgestones feel less grippy and are noisier on the motorway. Of more importance, the speed rating of the front tyres is below what Honda specify. Although all four tyres have between 3 and 5mm of tread left, the fronts need replacing. The easy and logical choice is to replace the Bridgestones with Michelins, putting new tyres on the back and moving the current Michelin Energies to the front. Michelin Energy tyres are one of the more expensive choices but from my experience with them in the past, they are worth it. Providing I keep the tracking in check, Michelin Energy tyres last and last and last especially if I don’t try to get too gung-ho in the twisty material.

Meanwhile, I’m going to get the Accord’s SRS system fixed. I’ll have this sorted before the tyres reach 2mm. Then I can worry about getting them replaced.