You'll also find industrial equipment examples like https://www.sourceproequipment.com.au/crocodile-skid-steer-b...

As the person you're replying to said, though, the problem for passenger cars is NVH. They aren't quiet.

Even with that downside, though, they are still used in consumer-facing applications like some bike sharing programs: https://medium.com/@fredchang/by-now-youve-probably-heard-of...

Where a smoother ride is less significant than unlocking a bike & finding a flat tire.

Don't care about weight, noise, ride quality, just need unbreakable tires because riding through neighborhoods where people break glass bottles on the bike paths will make me smash someone's head with one someday.

https://www.panaracerusa.com/collections/commuter-city/produ...

Might give these Panaracers a try when the tread of the GP are gone (or if I start getting punctures but so far they are as impervious as the Gatorskins for me).

https://www.continental-tires.com/bicycle/tires/race-tires/g...

However, in my experience they are really sketchy in wet conditions. I've wiped out or almost did multiple times on gatorskins. Deflating them in wet conditions works but the rolling resistance is then quite high.

I've found that the Schwalbe Marathons in wider sizes (I think I got 38s?) are much more confidence inspiring and comfortable, and makes up for the fact that I have to change a flat twice a year instead of once a year.

You can't really win, the stiffer the tire the better it is at protecting the tube but the rolling resistance is higher and the tire flexes less which makes it less grippy.

[0] https://www.bicyclerollingresistance.com/tour-reviews/schwal...

I have never read these two words in the same sentence. I've put thousands upon thousands of miles on my Schwalbe Marathons with nary a flat. Granted, nothing is 100%, but I find Schwalbe's a solid urban/touring choice.

I switched to Continental Grand Prix 4 Season and haven't had a flat in 2 years in Portland, OR (though my frequency is down with the pandemic).

...added weight is for better traction. Almost all 2WD tractors will have their back tires filled with a water/radiator fluid mixture (ice doesn't work well if you want to keep the tire on the rim).

My guess would be one or more of: the above; greater heat capacity; or, something to do with surface area vs. volume meaning that at a large enough size water in a tire is far lower-pressure and easier to contain than air at a high enough pressure to keep it inflated, and/or, relatedly, something to do with heat dissipation from compressing gasses being really hard to deal with once you hit a certain surface-to-volume ratio.

[EDIT] LOL, guess all these were wrong and it's just for the extra weight.

https://en.m.wikipedia.org/wiki/Sphere_(1998_film)

that is confusingly similar to The Abyss,

https://en.m.wikipedia.org/wiki/The_Abyss

I always get the two confused.

Beet juice is interesting! lol

That isn't strictly true, but in general such equipment spends most of it time moving very slowly it it moves at all. Transports speeds do become a problem, but that is only done for a short time (or you have it on a trailer so you can go faster) so nobody worries about the issue.

IMPORTANT: Never fill any tire to more than 90% full. More solution could damage tire.

Why do you assume this?

Many of the reasons you don't are the same reasons airless tires have not escaped niches.

You don't actually have any reason to assume it will happen other than blind optimism.

"There's no reason to assume this is a solvable problem"

What's "nitro oxygen", then?

First, permeation decreases with pressure, at different rates for the two gases. If you consider only this fact you will find that the partial pressures of O2 and N2 asymptotically approach homeostasis, rather than simply all the O2 leaving and all the N2 remaining.

Second, permeability changes with temperature, so the ratio of O2 and N2 exfiltration rate changes seasonally, as each gas has a different permeability-vs-temperature curve. Third, the ideal gas law causes pressure changes seasonally which will also decrease exfiltration in winter, and once again, each gas will have its own permeability-vs-pressure curve, so these become very confounding factors.

All in all, the reality of the situation is that filling up your tires with atmospheric air will probably settle on partial pressure ratios of, say, 85/15 rather than 100/0. The deflation that you get comes from only about 5% of the O2 leaving the tire; and of course you get another big deflation when the weather first turns cold.

I don't know the exact numbers because I've frankly never thought to look into this before. So like I said, it was a clever thought! But it needed to be taken a few steps further.

That at least helps with some of the logic. However, doesn't directly answer what "nitro oxygen" is. Guessing some sort of slang. It's definitely not a scientific phrase. Nitrogen oxide or something maybe too much for grease monkies so they call it nitro oxygen??? just guessing.

Also worth pointing out: NVH is not just Noise --- it includes Vibration and Harshness that are only felt by the people inside the vehicle.

1. https://en.wikipedia.org/wiki/Electric_vehicle_warning_sound...

Airless is really close to working for bikes. If I were commuting on a bike now I'd be comfortable going for it. The downsides - painfully hard installation, uphill resistance, ...etc. - will be worth it.

One easy way to picture this is: recall your last long road trip, or airplane flight, anything more than 3 hours or so. You get so tired after those, especially considering that you've only just sat still for a few hours. But in actuality your body is making hundreds of tiny corrections to posture each minute, in response to the vibrations of the vehicle, and that literally exhausts your muscles and nervous system. Now imagine that you make that car "5% more harsh" and redo the road trip; you will feel the compound effects of that additional harshness. Auto manufacturers take NVH very seriously, because it turns out to be a pretty big deal.

My point is that even if NVH comes back OK in the lab, they still will need a good deal of real world data with test subjects representative of the 'average driver' before they can make a determination.

Edit to add: I know of at least one case where the entire drivetrain of a vehicle was redesigned due to NVH.

Edit to add: Thanks for your input on this, it's insightful and interesting!

I imagine this will sound naive, but I wonder why this sort of vibration can't be addressed with shock absorbers in the seats?

Not at all naive, because it is addressed with shock absorbers in the seats; that is one of the very many tools NVH engineers use. :) But they're not 'shock absorbers' in the way you're thinking; the actual foams used in the car seats are specifically designed and selected to dampen certain frequencies. But, kind of like a speaker or headphones or even ear plugs, the dampening happens over a spectrum, and in general our organs resonate at lower frequencies, which are harder for foamlike materials to dampen.

NVH engineers view the entire road-vehicle-driver system as a huge, complex, spring-mass-damper system, and do a whole ton of partial differential equations to solve for the outputs.

Edit to add: so why not use traditional 'shock absorbers', the spring-damper kind that you're used to seeing? For passenger vehicles the answer is weight and complexity. But many trucks and tractors and so on do in fact have these.

Works for me. Feels comfortable and fast. Is economic.

YMMV.

edit: Thinking about it, one could even omit the spray can because in cities there's almost always a gas station near, which is stocking that stuff. So only the small adapter would be necessary, if your valves aren't like the ones for cars anyways. I didn't do that so far because I'm often bicycling out of the city, instead of into it.

But it's probably just a matter of time before an exotically shaped piece of glass gets through :D

Gas cars don't have big heavy batteries but they do have big heavy engine blocks and more complicated (heavier) drivetrains.

1. https://en.wikipedia.org/wiki/Tesla_Model_3

2. https://www.caranddriver.com/bmw/3-series/specs

Size up to the Accord which is 8 inches longer and a half inch wider than a Model 3 (and 9ft^3 more interior space), and it still only weighs 3131-3362 lbs.

Really though, the Civic and Accord aren't competing with the Model 3. They're front wheel drive. They have less power and torque. They use struts for the front suspension. All of these measures save significant weight (and cost). That's why I picked the BMW 3 series. It's similar size, performance, and cost. If we look at other competitors to the Model 3 we get similar weights:

- Volvo S60: 3,724-4,468lbs. (The low number is front wheel drive. The high number is a plug-in hybrid.)

- Audi A4: 3,682-3,726lbs.

- Mercedes C-Class: 3,472-3,605lbs.

- Cadillac CT4: 3,422-3,616lbs.

- Volkswagen Passat: 3,014–3,794lbs. (The lighter versions are front wheel drive only. The heavier versions are hybrids.)

In general, fancier cars are heavier. Also safer cars tend to be heavier. Yes batteries are heavy, but so are engines, drivetrains, starter motors, turbochargers, exhaust systems, fuel tanks, and so on. Early electric cars were significantly heavier because they were based on combustion platforms. When EVs are designed from the ground up, the weight penalty is less than 10%. Vehicle models in the same market segment vary more than that, and some combustion vehicles are already heavier than their electric competitors. This will likely get better with time as battery technology improves.

The statement "EVs are heavier" is approximately as true as "AWD vehicles are heavier". All else equal it's more likely than not, but the difference is rarely enough to matter for any practical purpose.

1. https://www.caranddriver.com/honda/accord/specs/2021/honda_a...

The RAV4, CR-V, and Rogue are the top 3 best selling SUVs in the US so far this year. They're about half the price of a Yukon. The rest of the top 25 are almost all sedans, similarly sized midsize SUVs and pickups.

Regardless, the Accord dwarfs it and supports the above point that the Model 3 is a heavy car, and the BMW 3 series is heavy because it was built to have a premium feel as a design priority, not because it is ICE.

The BMW comparison is interesting as the performance numbers are similar. The 3 series heft vs a civic is largely due to the engine and drivetrain choices. Its much easier to optimize weight on a low powered FWD car.

I saw a documentary on this once where they interviewed some psych guy who was advising the car industry. He said that it took him some time to convince them to make everything ridiculously big. Not just the car, but the lights etc. It was based on his theory that when we first see something we evaluate it using the bit of our brain that has been there since we were lizards. And that bit is impressed by size. His theory was that it overrides everything. Most people will pick the bigger thing. He was right.

Wouldn't that mean that most people---regardless of culture, education, etc.---would pick SUV over sedans? Is that true?

Granted there are plenty of SUVs in the US, but as far as I can see on the road and parking lots, sedans are still quite popular. I even see a lot of Minis and Beetles, which are even smaller than a regular sedan.

https://yourstory.com/2014/08/torches-of-freedom/

[0]: https://www.irs.gov/publications/p946

In my huge group of friends, I know one person who does this with his truck, and he readily admits that it involves lying to the IRS and it fraud. Everyone else with a big SUV just prefers them to minivans.

Contrast that with an SUV. No need to lean or hunch. You can see everything without trouble. You can move without trouble. It's actually possible to use the backseat.

I'm of a similar height, but oppositely proportioned, and the driver's seat in most cars doesn't go back far enough that my lower thighs rest on the seat, which makes for a lot of butt discomfort on long trips.

If the seat does go back far enough for my legs to be comfortable, it's almost unavoidable that the steering wheel is uncomfortably far away, and I put the seat pretty close to bolt upright to put my shoulders closer and reduce the impression that I'm hanging on to the wheel for dear life as it's trying to pull away from me.

Bicycles are similarly problematic: I want a shorter top tube than is common for my nominal frame size, so I ride a 59cm road bike frame with a short stem and a lot of seatpost showing. You'd be more likely to find somebody with my inseam (34" [0]) on a 61cm or 63cm frame.

[0] Sorry for the mixed units. I'm giving them in the trade sizes. Road bikes are sized in metric, and pants are sized in inches, at least in the US.

Clearly this is a situation where, quite literally, YMMV.

Considering the sales numbers of MPVs, it would seem that the argument you make is not what is pushing the disproportionate commercial success of SUVs.

On the one side you've got the tragedy of the commons that is big vehicles are less safe for other people to be around unless they two are in a big vehicle.

On the other side, Tesla, Toyota, Honda, and Nissan still all have relatively strong sales of sedans in the US. The US market decided that sedans were best from "imports" decades ago and GM/Ford just gave up trying to compete. Then there's of course Tesla telling GM/Ford exactly where the hockey puck was going if they wanted to compete with "imports".

99% of the "SUVs" you see today are CUVs, which in turn are barely more than a lifted sedan.

So the difference is gas milage is miniscule, to the point gas prices will no longer affect the sales of the most successful SUVs

One thing I really like about the van (Honda Odyssey) is that you step slightly up to enter and step down to exit. Very comfortable. And this is on a car that's so low to the ground (good for little kids and old dogs) that it's like a snow plow if there's more than a few inches of snow.

I want something lifted more than a sedan so I step up to enter and also has more ground clearance for snow, potholes, rough roads, etc. But that doesn't mean 44" tires with a lift kit.

Now, it's true that someone dropping all of the extra cash for one is less price sensitive but we're still talking a pretty big difference going from mileage in the teens to the 40+mpg a decent car gets. High gas prices would get at least some people to reconsider, especially since you have to pay a fair premium as well.

None of those physics issues are specific to SUVs. Even full size SUVs end up on shared platforms with full size sedans, with "reasonably close" weights (essentially take a well optioned sedan and it weighs around what the base SUV version does)

With the focus on all of these automakers on modular platforms, we've reached the point where even the largest SUVs could meet the exact same standards their sedan counterparts do and not really change at all.

?? Cars are available for sale in the US.

https://www.statista.com/statistics/199981/us-car-and-truck-...

https://www.rockymountainatvmc.com/tires-and-wheels/michelin...

An "equivalent psi" of 13, which is basically what I run my dirtbike at anyway in the New Hampshire forest trails. Although this is slightly different since it replaces the tube not the whole tire.

The above assumes the spokes(?) become stretched over time it would increase displacement of the center of rotation from the center of mass which if recall is what creates rolling friction.

That said, tweels are typically designed to be much thinner and have much less interior volume than air-filled, in order to close the gap in rolling resistance. So you'd really need to compare a specific model tire against another specific model tweel in tests to know. But my intuition tells me that the rolling resistance will still be worse almost no-matter-what with today's tech.

So that's partly the reason they target lighter vehicles, and that's partly the reason they seem to be marketing around EVs specifically. That extra rolling resistance may be worth a few $s in gas each month vs only a few cents in electricity for the same driving conditions.

For anyone wanting to do this to their electric scooters, dont... until Michelin makes a scooter form-factor wheel I suppose.

And I should have been a little clearer in my parent post: I'm mentally comparing something like the BMW i3 to something like the BMW X3; the i3 is about 1000 pounds lighter.

https://tweel.michelinman.com/michelin-tweel-family-of-produ...

The real thing here would be high speed (65+) with good ride / noise.

Maybe launch on local fleet delivery vehicles first (ie, neighborhood driving etc) if there were some lighter options there? Service pickup trucks (light?).

These have been available for years - look at Tannus for a good example.