h a l f b a k e r y
This would work fine, except in terms of success.
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Low rolling friction requires small contact patches among other things. High breaking efficiency requires large contact patches. This is a way we can get more of each when needed.
This tire would have a kind of hinge built into the tire, a very stiff bit of rubber. Under normal weight for the car
it would not flex. But a braking car puts far more weight on the front wheels. Under this condition the hinge, which would go all the way around the tire in the middle, would be forced to stretch. The tire would expand horizontally. Thereby the contact patch would be significantly expanded but only on the front wheels during braking. So the wheels with the most opportunity for grip would have more grip right when it's needed but otherwise rolling friction would not be increased.
[xaviergisz, Nov 17 2020]
Stretching widthways seems to be strongly fought against. [wjt, Nov 21 2020]
||Perhaps we could work it the other way. With some added
mass in the middle of the tread, "centrifugal force" could
more severely render the tire contact patch smaller by
stretching out the diameter of the center beads. Then as the
car slowed down for a curve or somesuch, the rolling
diameter of the tire could shrink down again to allow more
||Wait a minute, I thought this was strictly a forum for unhinged
||It's possible (but expensive and heavy) to have a self
inflating tire system. What if such a system overinflates
the tires when it senses good conditions (normal highway
travel). It could be equipped with a large valve to
quickly reduce the tire pressure in the event of
maneuvering or braking that would benefit from softer
tires. Maybe the increased fuel efficiency could pay back
the cost of the system. I would worry about such a
system malfunctioning and would also worry about
handling while the air is being let out, but I think the
normally recommended tire pressure is a compromise
considering handling, tire wear, and tire heating, so
reducing the pressure below what is currently considered
normal during emergency braking may actually increase
safety as well.
||Since a softer tyre has higher rolling resistance, you could
(almost) not need brakes at all; just gradually (faster or
slower, depending on need) reduce the tyre pressure and let
the rolling resistance be the brake. Obviously it would need
a tyre designed to handle it (maybe foam-filled or partially
"air-less", but with an airtight outer layer?).
||Might be an idea for those complete airless tyres, which rely on material flex and has spaces for hinging and extra material placement. It's seems a couple of orders higher in force vectoring calculations, though.