Archive for February, 2008

Our Experts on: Tyre pressure, part 1

Given that tyre pressure is one of the few things about a tyre that you, the average driver, have direct control over, it’s no wonder that a lot of people take an interest in it. Tyre pressure can have a surprising influence on your car’s performance and fuel efficiency, so it’s worth understanding.

Originally, back in the days of bias tyres, your tyre pressure was highly important to the health of your tyre. If you over-inflated a tyre it wore heavily on the centre of the tread, and if you under-inflated it wore on the shoulders (edges) of the tyre. This was before those clever Frenchmen invented radial tyres and front wheel drive (traction-avant) motor-cars. The steel belts of a radial tyre are laid criss-cross under the tread, bracing it. The tread rubber, and the tread pattern particularly, are then held stable, and the pattern is able to perform its major function of providing drainage channels for water trapped under the tyre to escape

So what is the role of tyre pressure? First, and most obviously, it is the air that carries the load. The air pressure inside the tyre and rim creates tension, which allows the tyre to support the weight of the car. The quickest way of proving this is the rather extreme method of letting all the air out and seeing how far you get. Incidentally, a tyre has to be below about 17 p.s.i. for it to look “flat”.

We’ve established what not enough air can do, what about too much air? First off, it shortens the footprint (area of tyre in contact with the road), which lessens the time available for the tyre to drain water out from under it. In compensation, it increases the pressure under the contact patch, increasing grip. Whether it entirely compensates for the drop in drainage time is a matter entirely for the design of the tread pattern, the speed, depth of water, texture of road surface, and how much tread pattern depth remains on the tyre. Naturally, the less pattern depth, the more drainage is impaired- worn tyres don’t perform as well as new tyres in the wet.

With extra pressure in the tyre, a turning input from the steering will get to the road surface with more sensitivity as well. Things happen quicker and more predictably if the tyre is pumped up “hard”. The tyre distorts less in a sideways direction under extreme cornering forces too – sporting drivers say that the car “handles”. That’s something to notice – the steering response (ability to change direction quickly, as in negotiating a course of witches hats) gets better as tyre pressure increases.

High performance and premium quality tyres have complex bead and lower sidewall structures and low profiles, so that the message can get to the road quicker WITHOUT the necessity to run high pressures. A tyre with extra pressure can give a bone shaking ride, and transmit a lot of thumps and bumps from concrete road joins and the like to the cabin – not exactly ideal for the driver. There are more components in premium tyres to accomplish this feat, which is why they cost more.

Next on the CarbonBlack blog, we use our newfound knowledge of tyre pressures in some detective work.


February 26, 2008 at 1:06 am 2 comments

U.S. places import duties on Chinese Tyres

Reuters reports that the U.S. has placed large import duties on several brands of off-road tyres manufactured in China.

In an effort to protect domestic tyre manufacturers, on Wednesday the US Commerce Department placed preliminary tariffs of up to 210 percent on millions of Chinese-made off-road tyres. They argue that the tyres are being ‘dumped’ on the American market, i.e. sold for unfairly low prices.

The final duties will not go into effect until the U.S. International Trade Commission determines whether producers in the U.S. have been harmed or threatened with harm, which will probably not be until August. The off-road tyres may join more than 60 other Chinese products with anti-dumping restrictions.

Full article can be found here

February 20, 2008 at 4:02 am Leave a comment

Our Experts on: Aircraft Tyres

While we’re mainly focused on car and truck tyres on CarbonBlack, occasionally something comes along that piques our interest. In this case it was a question posted to our tyre expert David Matthews on aircraft tyres. Here’s David’s response:

The job that aircraft tyres have to do is very simple, but very specialised. They only have to track in a straight line, and operate within a narrow range of speeds. The epitome of this is, of course, a jet aircraft tyre. These have three layers of nylon built into the tread crown to hold the tread on at very high speeds (around 230 knots) – the nylon shrinks when hot, strengthening the hold.

The real issue is the amount of deflection they have to absorb on landing. Around 50% of the tyre section height (the distance between rim and ground) is lost on impact. The tyre flattens out, wears out after around 200-230 landings, (leaving furry bits of nylon protruding) and is retreaded, with the nylon replaced. While taxi-ing, the tyre deflection (percentage of section height lost) is around 30% on a jet, so some airports have limitations on plane weight when it has to taxi a long way in high temperatures.

The qualifying test for an aircraft tyre used to be (I have no recent knowledge, but it wouldn’t be any less today) that the tyre did 50 simulated landings without flaps at one hourly intervals – from memory around 180 knots. This is all done on a machine under controlled conditions.

The tyres operate at about 230 p.s.i on massively strong rims bolted together with massively strong bolts. This is possibly a bit removed from recreational aircraft tyres. What finally brings an aircraft tyre undone after six or seven retreads is fatigue in the lower sidewall, where the massively strong bead wire bundles (3 a side) are tapered into the flexible sidewall. So speed is not what it’s all about- reliability is. Comforting for recreational flyers!

February 20, 2008 at 4:00 am 2 comments

Michelin leads in online exposure from US study

A recent study done by Envisional and published in the USA’s Tyres & Accessories ranks tyre brands’ online presence in terms of both prominence and sentiment.

According to the study, Michelin was found to have the most “online prominence” of all tyre brands, a position it has held onto strongly since 2005 when the survey began. Bridgestone had the biggest gain from last year in prominence, jumping from fifth to second place.

The second, and perhaps more innovative survey, was Envisional’s “Sentiment Index”. Also won by Michelin, this survey looks at positive or negative references across the internet to the brand. It’s an interesting study as it does not measure how much the firms invested in online advertising, or even how much exposure they had – rather it looks at how ordinary people are talking about them. Blogs, reviews and public messageboards are all scanned, giving a perceptive look into the minds of consumers. It makes a big difference, as well – in 2005 public sentiment lifted Pirelli from fifth to first in the online rankings.

Of course, we’ve got our own report – the CarbonBlack Tyre scorecard we mentioned a few posts ago. The CarbonBlack Tyre Scorecard is full of valuable insights based on prominence in the Australian online market. Michelin is in the top 5 in terms of ratings, recommended tyres and higest online sales, but has a few rising contenders. We will be reporting more specifically on online exposure in our upcoming reports We are quite excited about our upcoming series.

More information about the Envisional report here:

February 13, 2008 at 3:47 am Leave a comment