Tires for Automotive Vehicles which are Soft-Riding

This invention is a fairly simple improvement to automotive tires that will provide a much softer ride for the passengers and cargo. Even a GEO could ride as smoothly as a Cadillac!

The sidewalls of the tires are greatly "bulged out" so they are more flexible than the current stiff vertical sidewalls. Since ride quality is a great selling point for suspension and tires, this would seem an extremely desirable improvement.

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Modern tires tend to keep getting wider contours, which means lower height sidewalls. This necessarily requires more straight, vertical sidewalls, which means less cushioning of road irregularities. This improvement would involve very little additional cost, either in R&D, production costs, or product cost differentials.

History

Early tires were not much more than doughnut shaped balloons wrapped around a wheel. The cross-sectional area of the tire was rather round, and the function of the rubber of the tire was primarily to protect the inner tube and the compressed air within it.

The tire sidewalls were extremely convex. This allowed them to flex rather easily when road irregularities were encountered. This configuration had some problems, but it represented a soft ride.
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Later designs tended to get wider and lower (a lower aspect ratio) because of customer preferences regarding appearance. This tended to make the sidewalls less (vertically) wide and also with less convex curvature. This was necessary for engineering reasons, to support the various loads on the tires, from the vehicle's weight, side forces due to cornering, and from the internal pressure of the contained air. This situation causes harsher ride, because the sidewalls lower height and less convex shape was less "giving" for flex in response to bumps in the roadway.

Compounding this situation was the rapid growth of popularity of radial bias tires, and particularly steel-belted radial tires. The sidewalls on such tires were even MORE stiff, and made for even harsher ride. But they lasted a very long time, which made them very popular. I happened to buy a set of some of the very first steel belted radials imported to America. The tires lasted over 130,000 miles (and four vehicles!), but they rode so roughly that I was glad I did not have false teeth! EVERY pebble on the road vibrated through the car(s).

Improvement

The foregoing discussion emphasizes the central nature of the rigidity and minimal convexity of the sidewalls in causing the harshness of ride. This can easily be improved.

Now, consider pushing the middle of the sidewall OUTWARD halfway between the road and rim. Push hard enough to move the center of the sidewall one inch outward on each side, while the tread width and the rim width remained as before. Instead of rigid vertical sidewalls, the tire now has extremely convex shaped sidewalls that can easily flex when road irregularities are encountered, giving a MUCH smoother ride! Air pressure within the tire supports the bulk of the weight of the vehicle, as it initially did with early tires. (In modern steel-belted radial tires, the sidewalls are so stiff they actually support a significant portion of the weight of the vehicle).

How could this be done? Internal cross bars between the two sidewalls would do it, but it turns out that there would then be no way that such a tire could be mounted on a wheel!

Imagine a ladder-shaped air bladder, of very heavy construction, with rungs two inches in diameter with two inches between them, and with side rails also two inches in diameter. This ladder would be about six feet in total height and seven inches in total width. Place this (minimally inflated) bladder INSIDE a (tubeless) tire, curving the ladder all the way around the inside of the tire. The now curved side rails of the ladder now press gently against the inner sidewalls of the tire, with the rungs spanning across the width of the tire.

The tire would then be mounted on a rim in a normal way.

A second, special air filler valve nozzle (similar to the normal tire filler valve nozzle) would allow filling this bladder to very high pressure (say 100 psi). This pressure would push the middle of the sidewalls outward a substantial amount, say an inch. Then the tire is inflated normally. This change in contour of the sidewall would allow very easy flexing of the sidewalls in response to road surface variations, which would tremendously add to the cushioning effect of the tire. Harshness of ride would all but disappear!

As contour ratios of tires keep reducing, with sidewalls getting narrower and narrower, this improvement could possibly offer added new range. It may be possible to make commercial 30 or even 20 aspect ratio tires, with acceptable ride quality.

An additional benefit might be that higher tire pressures may be usable. The elbowed sidewalls would be able to flex easily, while nearly all the job of supporting the vehicle is done by the compressed air contained within it. Higher pressures would not adversely affect ride quality, and might improve other tire characteristics.

Complications

The heavy bladder will add rotating mass to the tire. This might be counteracted by lighter construction in the sidewalls, but that would remain for research to establish. Balancing the tire might become problematical. The bladder should never be able to shift position within the tire, but if it did during severe driving, re-balancing would probably be necessary. If the owner ever released the bladder's pressure, it would certainly move, again requiring re-balancing.

Construction and production of the tires themselves could be extremely similar to present procedures. The one major change would probably be a change in the orientation of the bead of the tire, especially in low aspect ratio tires. That bead may need to be tilted to provide for the immediate outward direction of the sidewall (similar to tires of 60 years ago!)

The public may be reticent to buy tires that look so unusual. Instead of a smooth rounded profile, they would tend to have an elbow shape, with a distinctive (curved) corner halfway between the rim and road.

This configuration should offer far softer ride, and with increased tire pressure should also offer precise and clean vehicle handling. There wouldn't be the mushiness common in (often heavy) cars that have smooth rides. This technology should be able to combine performance handling and extremely smooth ride, even on vehicles with low GVW.

Whether the bladder would excessively heat is unknown. The results of that are unknown.

The bladder is designed to press against the inner sidewalls of the tire. It may be desirable to surround the rungs with chicken wire type stainless steel restraint cages, so the bladder's pressure doesn't excessively inflate the bladder laterally.

I have been attempting to create some prototypes to test them. I don't really have access to the equipment with which to make the unusual shaped bladders, and have therefore been slowed. If there is someone who has access to the necessary equipment, I welcome the possibility of pursuing a combined effort.

This presentation was first placed on the Internet in April 1998.

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C Johnson, Theoretical Physicist, Physics Degree from Univ of Chicago