Airless Tires - Lower Rolling Resistance & Lower Maintenance?
 

As I took a moment to take a second look at this picture of the MIT ' Hiriko' folding urban EV:

http://i146.photobucket.com/albums/r.../bubblecar.jpg

I did a double take on the wheels. They look to be earth-going versions of the Lunar Rover wheels? And they are similar to the ERW (Energy Return Wheel).

If their aerodynamic openness would need a solution, but they have two things that would be very good for a high efficiency car: lower rolling resistance than conventional wheels (the ERW claims 50% improvement) and they would not require inflation checks; which are more difficult when they are enclosed in low drag body work. And they can't blowout.

first thing I thought when I saw those is that they might get full of debris and need to be cleaned out constantly to stay balanced :confused: a rock in one of those openings would make for a really wobbly ride!

...no worse than current "snow" tires I'd guess.

How often do you get big rocks in an urban enviornment, though?

I could see some jokers stuffing garbage between the spokes, though.

Well, if the spaces were filled in with a strong fabric, that would solve both the aerodynamic drag and the sand/gravel/schmeg problems at the same time?

Normal pneumatic tyres can be run at higher pressure to compensate for increased load, even between the front and rear of the car.

Can these compensate for increased load?
If not, how are these practical for everyday use where you might drive alone, or with four passengers, on the same day.

In the same vein, would each model car only use a tyre made for that car?
What happens if I want to run wider or taller tyres, or maybe I'd want to run fancy mags.

I think these are a great concept, but like many concept cars, maybe it's just not practical.

... or am I missing something? :confused:

probably work great and cost the same , guessing not good for heavy vehicles .

Let me add another important possibility - and that is tunable suspension. It is likely (though possibly not) true that low rolling resistance means a stiff tire, with the only large scale flexing being for the purpose of keeping a good contact patch on the road - but the tire ideally would probably not act like conventional pneumatic ones.

So, already the requirements on the suspension are different: a pneumatic tire absorbs about half of all the bumps - all the small ones - while an über-low rolling resistance tire *probably* would not. The suspension would then have to be much more compliant in the first small part of the motion, and then it would have to be progressively less compliant and higher compression dampening and spring rates.

So, these together would be roughly the same with heavier loads - the über-low rolling resistance tire already would be similar to a higher pressure pneumatic tire. And since the suspension would be the area that would be most affected by heavier loads with either kind of tire, I don't think this is something we need to particularly worry about.

The suspension *does* need to be considered for both ride height and level attitude, when the vehicle is a low aerodynamic drag. If a heavy load is put in the vehicle, the ride height and/or the normal angle of the body will be affected - so the suspension on a low aerodynamic drag vehicle would ideally be able to level itself and compensate for load changes. And this would have the ability to work correctly with very low rolling resistance tires, along with a low aero drag bodies.

Thanks Neil.
You're right of course, I feel silly now. :o

I remember, now, when our locally produced GMH vehicles went from cross ply tyres to radial tyres.
Their marketing people made a big deal about their new "Radial Tuned Suspension".

High end performance cars already feature suspension that's adjustable on the move, something similar could certainly be used in conjunction with these tyres.

They look like Michelin's Tweel :

Michelin Tweel - The Airless Tire

Urban EV.

Why would you need a big(ish) EV to do what you can do (and has been done for ages !) on foot, by bike, heck, even public transport whenever they're not on strike ?

Greenwashing, like the electric bikes that no-one really needs.
Making self-propelled, power-hungry vehicles out of what already were perfectie good, human powered vehicles ...

To bump an old thread, it looks like the tweel is getting closer to a releasable product.

https://interestingengineering.com/p...m-and-michelin

Now known as "Uptis"

2024, that sucks.
Global warming will have killed us all by then.

We don't if the airless tires will have any specific advantages, but it is interesting to have this come up.

At least earlier in development they were touting reduced rolling resistance and increased lateral stiffness.

I wonder if you brake hard, if there's a weird snap-back from all those ribs allowing the wheel to twist an inch or two?

https://smartech.gatech.edu/handle/1853/37202

Probably no worse than the spring rebound on a regular car. One would think the rebound would be engineered out

This part is hilarious:

In other words: $$$!Kaching!$$$

https://newatlas.com/automotive/mich...ess-tire-demo/

Finally they have something ready enough to drive passenger cars on.

After 4 punctures in 5 years I'm ready for airless tires.

Michelin claims

"Michelin says it will withstand much greater impacts than a regular tire and wheel, and will have a "dramatically" longer lifespan, while adding no extra rolling resistance, not feeling any different to the driver and adding only around seven percent to the weight of the wheel – less than existing run-flat tires do."

I can't see why an airless tire would last longer. Tires normal wear out due to tread wear. Given the same tread depth and rubber compound I can't see why an airless tire would wear slower than a conventional tire. Maybe they are counting longer life due to tires not failing early due to punctures?

First, I would be very careful about what Michelin claims. Don't forget, they are responsible for the TRX which left many people high and dry for tire replacements.

Second, because of the difference in the way an airless tire COULD be manufactured, the rubber COULD be quite different and not have some of the processibility issues some rubber compounds have.

For example, some retread rubber is processed using a high pressure press, so the rubber can be made stiffer, and therefore wears longer.

Instead of airless how about foam filled? Been the latest rage in forklifts since 1980 and the foam people can taylor densities for any load.

The reason they are supposed to last longer: the contact point is more flat

They have foam inserts for motorcycle tires used off-road. The problem is they don't last long at high speed. The flexing builds up heat and kills them.

Michelin says 6 months max life, 80 mph max, and keep them under 40C.

https://www.michelin.com.au/motorbik...ssure/off-road

I want the ability to fine tune the pressure, and therefore characteristics of the tire.

I've got tire puncture repair down to about a 5min process from stopping, to going again.