How are RV tires developed?

 By Roger Marble

If a tire is being designed for a specific vehicle manufacturer such as Ford, Chevy, Toyota, or BMW, there will be a number of tires submitted by competing tire companies all trying to deliver the best overall compromise in performance characteristics. Please note that all original equipment ("OE") vehicle manufacturers have slightly different requirements but all make similar requests for performance improvements in many areas. In the future I will use the term "OE" to include these car and pickup manufacturers.

Compromise: Now is a good time to talk about some of the various trade-offs the engineer is faced with when trying to meet conflicting goals and customer wants. I am sure we would all like an RV that has all the interior space and amenities of a 40’ diesel pusher but gets 25 mpg and can be driven down crowded city streets without knocking off our mirrors. Oh yes, it should also cost under $30k. Well, Bunkie, that just ain’t gonna happen in real life.

The same goes for a tire that handles like an Indy tire, is as quiet as the proverbial mouse, has great off-road traction, is good for 100k miles, and costs $25. One thing few people realize is that most if not all performance characteristics are a compromise. For example, if you improve wet traction you probably hurt fuel economy unless you use a special type of rubber that costs double per pound and is more difficult to process. If you improve handling you might hurt ride and noise. When you improve noise you can significantly increase the cost of making the molds used in manufacturing. The cost of a tire mold can be as low as $10,000 and can approach $100,000 each. Depending on the production volume needs, a tire manufacturer could need 30 or more molds. The list of trade-offs goes on and on.

The competition for a tire application might start three or more years before scheduled start of delivery with two to five tire manufacturers competing for the contract, knowing that only one or two will end up being selected to actually provide tires. The costs associated with building and testing special prototype tires can run in the hundreds of thousands of dollars and are absorbed by the tire company. The only way a tire company can afford this type of activity is by landing a contract for a few hundred thousand tires so the costs can be spread out.

Unlike “OE,” an RV manufacturer may only need a couple thousand tires, so a custom tire designed for a specific RV would be cost prohibitive. Since the RV manufacturer won’t be trying to get custom tires, it doesn’t have staff engineers working on developing specifications for such tires. The RV company will in all likelihood either take what comes already on the cut-away chassis or the bare chassis for Class-C or A vehicles, and in the case of trailers, may buy the tire with the lowest cost that can meet tire size requirements and expected delivery schedule.

For RV applications the one thing that is in the control of the manufacturer is “Reserve Load.” This is the difference between the load placed on each tire with the RV normally loaded and the load capability of the tires at specified inflation.

##RVT802

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.

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.

How RV tires are developed and why some are a compromise

If a tire is being designed for a specific vehicle manufacturer such as Ford, Chevy, Toyota, or BMW, there will be a number of tires submitted by competing tire companies all trying to deliver the best overall compromise in performance characteristics. Please note than all original equipment vehicle manufacturers have slightly different requirements but all make similar requests for performance improvements in many areas. In the future I will use the term "OE" to include these car and pickup manufacturers.

Compromise: Now is a good time to talk about some of the various trade-offs the engineer is faced with when trying to meet conflicting goals and customer wants. I am sure we would all like an RV that has all the interior space and amenities of a 40’ diesel pusher but gets 25 mpg and can be driven down crowded city streets without knocking off our mirrors. Oh yes, it should also cost under $30k. Well Bunkie, that just ain’t gonna happen in real life.

The same goes for a tire that handles like an Indy tire, is as quiet as the proverbial mouse, has great off-road traction, is good for 100k miles, and costs $25. One thing few people realize is that most if not all performance characteristics are a compromise. For example: if you improve wet traction you probably hurt fuel economy unless you use a special type of rubber that costs double per pound and is more difficult to process. If you improve handling you might hurt ride and noise. When you improve noise you can significantly increase the cost of making the molds used in manufacturing. The cost of a tire mold can be as low as $10,000 and can approach $100,000 each. Depending on the production volume needs, a tire manufacturer could need 30 or more molds. The list of trade-offs goes on and on.

The competition for a tire application might start three or more years before scheduled start of delivery with two to five tire manufacturers competing for the contract, knowing that only one or two will end up being selected to actually provide tires. The costs associated with building and testing special prototype tires can run in the hundreds of thousands of dollars and are absorbed by the tire company. The only way a tire company can afford this type of activity is by landing a contract for a few hundred thousand tires so the costs can be spread out.

Unlike “OE”, an RV manufacturer may only need a couple thousand tires so a custom tire, designed for a specific RV would be cost prohibitive. Since the RV manufacturer won’t be trying to get custom tires, it doesn’t have staff engineers working on developing specifications for such tires. The RV company will in all likelihood either take what comes already on the cut-away chassis or the bare chassis for Class-C or A vehicles and in the case of trailers, may buy the tire with the lowest cost that can meet tire size requirements and expected delivery schedule.

For RV applications the one thing that is in the control of the manufacturer is “Reserve Load”. This is the difference between the load placed on each tire with the RV normally loaded and the load capability of the tires at specified inflation.

Next time:
.
Before we cover tire manufacturing -- perhaps dull to you but interesting to me -- we will do our first post on tire loading. I say first, as this topic is the single most important performance characteristic for we RV owners. But few of us truly appreciate the potential safety issues involved.

Updated/reposted for RVT 802