The Wastefullness of Automobile Tires

Dear BlackWater:

Here in the land where it "never" snows, we grind the tires up, mix them with asphalt (and other goodies) and coat our roads with them. It makes things a lot quieter.

Now if I can figure out why I pay a fee for disposal of the used tire, and taxes pay for the fellow to coat the road... ;>)

As to your assumption that any amount of mass can be added to the "unsprung weight", to help absorb shocks, better guess again.

As to your assumption that heat transfer would be improved, better guess again. Same area, same load, same distortion, same heating.

If you are talking about a solid rim with rubber bonded to it, I would think you've never ridden a bicycle with a bent rim. We drive on real roads, with real objects on them. You'll not get cheaper than a "standard" pneumatic tire. Quite forgiving of hitting a pipe or lawn chair at 80 kph. NO solid rim would be.

David A. Smith

Another great thread. What's going on here?

Anyway the thing that bothers me is a $7.00 27" bicycle tire from K-Mart only weighs 400 grams and won't even go 4,000 km. Motor vehicle tires are much cheaper on either a distance basis or weight basis.

It's cheaper to drive.

Bret Cahill

snipped-for-privacy@barrk.net (BlackWater) wrote in news:425597a0.35334678 @news.east.earthlink.net:

Won't work very well for motorcycle tires. IIRC the motorcycle tire takes advantage of the deflection of the contact patch due to load to help the motorcycle turn. Same applies to auto tires. The deflection of the tire creates the patch of rubber on the road, if you had steel backing, that would become more or less a line contact instead, greatly reducing available traction.

Maybe not so easy, but Michelin is all over it with their Tweel. Check it out:

I suggested that the strip of rubber tread be crimped into a thin metal retaining/mounting ring. Just curl the edge of the metal over at the edge into a shallow 'C' that grips the edge of the rubber. In practice, you'd probably want some adhesion between the back-surface of the tread and the metal ring so the center of the tread wouldn't tend to pooch out at high speeds.

Now as for 'constant load-bearing surface', I don't think this is a problem. Automobiles really aren't supposed to lean onto the sidewalls of their tires anyway - the suspension is supposed to keep 100% of the tread in flat contact with the roadway at all times while the passenger compartment sways a bit.

If you've seen some of those ultra-low profile tires that are popular with the 'low rider' set, you'd see they were

A good use for old tires - but most communities don't DO that, plus the steel-belted tires don't recycle well.

It's a scheme to make MORE MONEY of course ...

If they quit doing that, they'd just have to raise fees or taxes elsewhere.

What I'm proposing would have LESS mass than a traditional tire - ten, maybe twenty percent less. The less unsprung mass, the easier for the suspension system. The 'metal retaining ring' for the rubber tread would be quite THIN sheet metal, just something you clamp to when attaching the thing to the wheel rim. Envision little slotted tabs every couple of inches. You place a ring or cover with L-shaped catches along the edge over it, twist to lock, and then apply a retaining bolt or something so the thing can't unscrew.

BUT - since the back surface of the tread is in direct contact with a metal 'heat-sink' instead of a pocket of insulating air ...

Also, a lot of the 'distortion' you're talking about in a traditional tire is SIDEWALL flex. This design eliminates the sidewalls.

I think I addressed that issue in two ways.

First, modern automobile suspension systems are a lot better than on your old bicycle. Existing suspensions could be 'tuned' better for the hard tires and new cars could be optimized from the drawing-board up. Electronic-assisted suspension seems a coming thing anyway - and that would be even easier to tune to accomodate hard tires.

The second option I offered was to substitute flexible tires with more flexible wheel rims. The olde tyme spoked rims offered a certain amount of flex. Using curved sections for solid rims would achieve a similar effect. Think of two slightly hemispherical discs of springy sheet steel - hitting a bump causes them to pooch outwards slightly. These are undamped of course, so your suspension system has to be able to deal with the rebound.

In any event, given the economy of this approach plus the benifits of eliminating accidents due to blow-outs plus the fact that no NEW technology has to be developed plus that older vehicles can be retrofitted at comparatively low cost ... I think the idea's a winner.

Priced gasoline lately ... ?

Still, $7, 400 grams, 4000km ... not bad. That's 517 km per dollar. An el-cheapo automobile tire might go for 15-25,000 km, but it costs $50 - and you need FOUR of them.

It'll turn anyway. Makers might want to adjust the rake & trail equation just a bit to take best advantage of this 'hard' tire.

You're assuming the rubber is attached to an inflexible rim. Doesn't have to be. Indeed you may WANT somewhat flexible rims to make up for the loss of 'bounciness' the air pocket used to provide.

Oh ... and the (sort-of) 'line contact' puts more weight on a smaller area. By using the correct type and hardness of rubber, this extra loading can be translated into more friction. It's easier to slide a pencil eraser along a desk if you don't press hard. If you do press hard, it 'digs in' and the friction increases greatly.

Bastards (kinda) stole my great idea !!! :-)

UGLY-looking wheel though ... I suppose it could be dressed-up ...

I've also heard of foam-filled tires (tend to run hot and the foam breaks-down). There's some other guy who wants to make solid tires out of urethane 'rubber' too.

The cops would be mightily peeved about unpuncturable tires though ... they've all invested a lot of money in those 'stop sticks'. Of course a 30-06 bullet fired down through the hood from a helicopter will bring the car to a rapid halt too .....

Anyway, *my* idea works best with metal-spoked wheel rims, where the rim comes all the way down to within an inch of the pavement. You see almost the same thing now on 'low rider' cars ...

Dear BlackWater:

They are recycling ALL tires for this use.

Agreed.

With geomtery this thin, then you have no hope of supporting a car. A pneumatic tire is not as heavy as you think, and supports thousands of pounds.

Terminal temperature is all that you are affecting. The losses are the same.

AND any method of supporting a vehicle, or restoring the "rim" to its original shape after a deflection.

No. They are tuned to the range of frequencies that are passed through by pneumatic tires. Running on "rims only" even padded ones, makes the suspension system transparent. The whole car rattles.

Not without increasing upsprung weight.

Already here. And damned expensive to maintain.

No. You end up with air shocks of some sort, so there is your pneumatic barrier again.

Lunar rover wheels. You'll drive my taxes up, paying for the damage you'd cause to the roads?

They have low air sensors in/for wheels now. You get warned before the tire is low enough to blowout from overheating. Quite a lifesaver.

Room for improvement? Yes. But you have offered no answer. Your rims don't restore to shape once deflected.

David A. Smith

Tires are recycled. Good tires today can also last 30,000-60,000 miles. Silical and various plastic compounds added to tires will make them longer lasting, easier rolling, with longer life.

In the future, cars might not have tires at all- they might have wheels like small lawnmowers. But that's a ways away yet.