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Monday, August 22, 2011

Tires - Dull or Dynamic? Part two

Following is the second part of an article I was asked to write for a tire industry trade publication in the UK. “Tyres International.” I thought you might find it a bit interesting.

“To the untrained eye it might seem like the tire industry has not done much to improve John Dunlop's original. But looks can be deceiving.

Part two
A cost/performance comparison on the improvements in wet and snow traction, ride comfort, low noise, blowout resistance and handling response is significantly more difficult, as the tire of 1920 was so poor in many of these areas as to be considered useless when compared to today's tire.

When one considers high-speed capability it is a little easier. In 1920 most cars were not capable of a sustained 85mph, yet today that is considered an absolute minimum high speed capability for a tire to be sold for use on the public highway.

Material World
Some would have us believe that today's tire engineer is not willing or even encouraged to look at new ideas or materials. Even the use of rubber, both natural and synthetic is used as an example of the perceived lack of advancement in tire technology.

I know from personal experience that alternate materials for both wheels and tires have been investigated but either lack of performance or poor reception in the market prevented those ideas from making it into production. I have seen non-metallic wheels that were too flexible to hold air at high temperatures and too stiff so they shattered at low temperatures. New tire sizes with improvements in safety and mobility were not accepted because non- standard wheels were required. Even well engineered items such as the mini-spare, still meet with resistance and ridicule despite the fact that they can deliver acceptable performance when needed. They even have an impact on vehicle fuel economy when not needed

Rubber band
The basic material in Mr. Dunlop's tire, natural rubber, comprises less than 10 per cent of today's modem passenger radial. Today's tire, with 25-30 different materials, made up of hundreds of different chemicals, is one of the more complex components in a modem automobile. This is especially surprising when you consider that some materials are considered contaminants and are incompatible with other materials in a tire yet we have managed to make these incompatible materials work together to deliver improved air retention and blow- out resistance.

It is likely the concept that tire materials have not changed is a concept only held by those with little training in the an of tire design. There are few materials that are capable of 300 per cent strain for tens of millions of cycles over an operating range of temperatures from -20°F to +200°F while at the same time having a coefficient of friction of 0.8 or higher. Today's steel belted radial could be improved upon and even have its weight lowered, with increased use of rayon, fiberglass or other materials as belt material. There are however, restrictions on pollution or customer resistance to materials other than steel which have so far proven insurmountable obstacles to broad appeal for the average consumer.

Some of our biggest challenges will come in the next decade as we are asked to change from making a product that will last indefinitely under extreme conditions as the tire industry has been asked to do for more than a hundred years. We are now being asked to design a product that will be almost indestructible until the user wants to change it, then the tire should, as if by magic, become easy and inexpensive to deconstruct into its chemical components. Some OEMs are even starting to suggest that old tires should be able to be recycled into new tires with no loss in any performance characteristic.

I have every confidence that the tire industry will rise to this new challenge and methods will be developed to address the disposal and reuse of materials in a tire. It is unlikely the recycled materials will be used 100 per cent in another tire just as the OEM will not be able to recycle the leather car seat into a good as new' leather car seat, but we will incorporate an ever increasing percentage of recycled materials in tires and we will find acceptable methods of recycling them into some usable material or product at the end of their useful life as a normal tire.

To the uninitiated it is easy to look at John Dunlop's tire of the late 1800s and say that since today's tire is still made of "rubber' it is not really any different. Thus some would consider this sufficient proof to postulate the tire industry is not capable of looking at history, learning from it and moving on.

It is my belief that this thinking ignores the advancements in both the materials and performance delivered at a very low cost to the often uncaring consumer.

Thursday, August 18, 2011

Tires - Dull or Dynamic? part one

Following is an article I was asked to write for a tire industry trade publication in the UK. “Tyres International.” I thought you might find it a bit interesting.

To the untrained eye it might seem like the tire industry has not done much to improve John Dunlop's original. But looks can be deceiving.

Many people think the tires on their car are just a necessary evil. Most seldom, if ever check their inflation while alignment is something few ever consider. Then after 40,000 miles, they complain about the fact they have to buy new tires. Even within the automotive industry, there are those who don't appreciate the dynamic nature of tire design, and the significant improvements and changes made since John Dunlop invented the forerunner of today's modem tire.

There are many challenges facing the tire engineer today, but one of the most challenging is to make continual improvements in rolling resistance. In North America, the Original Equipment Manufacturers, otherwise known as "Detroit", demand the improvement or lowering of the rolling resistance value of the tires they approve. The rolling resistance of tires has a direct impact on the fuel economy of the vehicle. Many would think the primary reason for an interest in rolling resistance would be to allow the manufacturer to advertise good gas mileage for their vehicles.

Stopping the gas guzzle
While good fuel economy is something that can be advertised, a more concrete example of why this is a major concern of the OEM is the avoidance of what is known as the "Fuel Guzzler Tax". This tax can amount to many tens of millions of dollars as the OEM must pay for each 0.10 mpg their vehicles are over a government mandated rating.

There is some data that shows that a one per cent reduction in rolling resistance could be worth US$60 million on certain car lines. Despite this major interest by Detroit, I have never been asked about the rolling resistance of a brand or line of tires by any individual considering the purchase of a set of tires.

Significant strides have been made in improving the rolling resistance of tires going to Detroit. Figure 1 shows the trend as well as the ultimate value possible with a steel wheel on steel rail. It is obvious to see the majority of improvements have already been made and while we may expect some level of continual improvement, we will not see the dramatic improvements of the past 20 years continue in the future.
RRC or Rolling Resistance Coefficient is one way of comparing a variety of sizes and adjusting for vehicle load as well.

Figure 1

Pricing opens the purse strings
At the same time as these improvements have been made and despite great strides in ride quality, crisper handling, improved snow and wet traction and other various measures of performance, Detroit also expects us to lower our price a few per cent each and every year. The fact that many people are willing to spend more for shoes, simply because some athlete wears the same brand, than they are willing to spend on a tire points out the level of disdain and disinterest most feel toward tires. Seldom does a driver consider that it is the tires that must deliver strong performance in emergencies to help protect them and their family from harm.

History in the making
A quick look at the advancements in tires during just the last 80 years can be very instructive. In 1920. your normal auto-mobile tires cost between US$25 and US$60 each. This tire was advertised as being capable of delivering 6,000 miles. This translates to about US$0.007 per mile. With normal inflation considered, these sale prices translate to US$200 to US$500 per tire in today's dollars. When we consider that today's normal tire is capable of delivering 40,000 miles, yet can be purchased for about US$70, we can see that the cost per mile is now only US$0.0018 per mile.”

We will conclude this article in the next post.

Tuesday, August 2, 2011

Special considerations for duals

Highways March 2011 had a post titled "Tire Snafu" on pg 40

A person mentioned that both rear duals tires got hot due to air loss and subsequent overload. One tire was identified with a leaking valve and was replaced but there was no suggestion that its mate might have also suffered internal structural damage from running hundreds to thousand miles in an overload condition.

Few tire dealer salespeople or even tire technicians have the training to see the tell tale signs of overload.

Here is a picture I call "Shades of Black".

We know the tire in the picture was run overloaded as it had an improper repair (plug) and had continued to slowly leak air for many hundreds of miles. By "reading" a tire when doing a true forensic level examination the experienced tire engineer will notice the darker inner sidewall portion of the tire. This darker shading comes from increased level of flexing that can occur when run in overload or under inflated condition. The darker black is physical proof that the subject tire had been operated for many miles while under significant overload.

This operation resulted in degradation and weakening of the tire's structure which meant that in all probability, it could fail catastrophically with little or no warning hundreds or thousands of miles later.

This type of structural weakening is not visible from the outside and is difficult to see even with a proper inspection of the inside of the tire which takes more than the few seconds most tire techs are given to do an inspection.

I don't expect the magazine writer to know this but when responding to complaints about tires I strongly suggested that they touch base with tire technical resources and to provide a little education to readers.

When one tire in a set of duals is run "flat" i.e. more than 20% under inflated, it means the mate was also operated in an overload condition. Unless there are some special circumstances, the operator seldom knows how many miles, at what speed, at what % overloaded the tire was operated. Only the most experienced tire engineer and not tire store personnel, have the training necessary to pass judgment of the probable condition of the tire. Many times the mate to the "failed" tire should also be replaced or retained as a spare for temporary use.

Failing to warn readers of this potential safety issue is not a good policy.