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Dust from car brakes more harmful than exhaust, study finds

e360.yale.edu

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Re: Dust from car brakes more harmful than exhaust, study finds

#311

Post by kstrauser »

lukevp wrote: post #215
kstrauser wrote: post #207

Earlier quoted context omitted.

Not significantly. Otherwise they’d get hot and work less well. Pads ride very closely to the disc so that road stuff can’t get wedged between the surfaces, and so that you don’t waste break pedal travel just getting the pads close to the surface. Well adjusted drum brakes should be arranged almost exactly the same way. From https://mechanicswizard.com/how-close-should-brake-pads-be-t... : > Typically, the optimal ga…

Are you familiar with how disk brakes on a car operate? They’re essentially a hydraulic piston clamping the brake pads against the rotor. When you let off the brake pedal, the pressure is removed, but there’s not a “retraction” of any kind. So there’s no pressure but nothing is actually making that gap. That article was articulating basically that the piston, when not compressing the brake pads, should not be too far…

I'm very familiar, having changed many sets over the years. If there's no air in the system, pulling fluid away from a hydraulic piston must retract it. It can't just sit there unless there's an air bubble to expand or so much negative pressure that it forms a vacuum somewhere. Even then, pressure on the atmosphere-facing side would push the piston back toward wherever the vacuum or air bubble is.

Re: Dust from car brakes more harmful than exhaust, study finds

#312

Post by jeffbee »

MengerSponge wrote: post #259
jeffbee wrote: post #107

Earlier quoted context omitted.

They aren't inherently torquier. That's a design point.

It's Lenz's Law, friend. It's as much a design point as a=F/m. Because of it, induction motors and magnet synchronous motors generate more torque at 0RPM than any combustion engine I've heard of. You could have software limiters, but you'd need regulatory mandates for that. Actually, I support that. 3+ ton trucks with a sub 4s 0-60 shouldn't be street legal. Or they should at least require a special license and liabi…

All EVs already use limiters because, as you correctly noted, just shorting the battery across the motor will rip the axles off and set the battery on fire. The question of whether an EV should put down grip-limited amounts of torque, or should limit itself to .5g at most, is a question of tuning.

Re: Dust from car brakes more harmful than exhaust, study finds

#313

Post by akoboldfrying »

orev wrote: post #88

The Yale article and the paper both highlight the fact that EVs use regenerative braking and produce less dust. I was worried that this was a rehash of the astroturf campaign from a few years ago focusing on EV weight and how that was so bad for the environment because of tire and road wear. Unfortunately you need to read through the whole thing (instead of the headline and a few paragraphs) to see that information.

>astroturf

Is the much greater weight of EVs not worse for tire and road wear?

Re: Dust from car brakes more harmful than exhaust, study finds

#314

Post by crazygringo »

> For the study, published in Particle and Fibre Toxicology, researchers grew human lung cells in a lab and exposed them to dust from car brakes and from diesel tailpipes, finding that brake dust caused greater injury to the cells.

That seems like an overly narrow way of defining harm.

E.g. what if brake dust is bad for your lungs but your lungs can repair the damage, but diesel fumes are harmful to your brain and the damage is permanent?

I'm not saying that's the case (I have no idea), just that studying lung cells in a lab doesn't tell you anything about the full-body harmful effects.

Re: Dust from car brakes more harmful than exhaust, study finds

#315

Post by Gibbon1 »

ghaff wrote: post #310
Gibbon1 wrote: post #299

Earlier quoted context omitted.

Just a note. If the manufacturers can get solid state batteries to the point where they are economic then EV's will be as heavy or perhaps lighter than gas cars. Actually a 50% increase in energy density is enough. And solid state batteries have twice the energy density. So likely lighter. Jevons paradox says cheap EV's are maybe not so great. Consider if a cheap car cost a $100k most people wouldn't own cars. They'd…

Many people live in locations where walking, the bus, or subway are never going to be practical and/or do regular activities that need personal transportation. If a car cost $100K I'd almost certainly still own one.

Interesting historia I saw. A bus schedule for Geary st from 1924. Buses came every few minutes and took less time than it takes by car today.

Just saying electric cars not a panacea for everything.

Re: Dust from car brakes more harmful than exhaust, study finds

#316

Post by AngryData »

melling wrote: post #217
hypercube33 wrote: post #206

Earlier quoted context omitted.

Rubber still wears off tires though so that may be worse or not for heavier vehicles

Worried about heavy vehicles? The best selling vehicle is the Ford F-series.

It is actually the RAV4 now, just barely. The f-150 is still in a close second and spent many years at the top though.

Re: Dust from car brakes more harmful than exhaust, study finds

#317

Post by ghaff »

Gibbon1 wrote: post #315
ghaff wrote: post #310

Earlier quoted context omitted.

Many people live in locations where walking, the bus, or subway are never going to be practical and/or do regular activities that need personal transportation. If a car cost $100K I'd almost certainly still own one.

Interesting historia I saw. A bus schedule for Geary st from 1924. Buses came every few minutes and took less time than it takes by car today. Just saying electric cars not a panacea for everything.

Yeah, but Geary St. is close to downtown in a fairly large city. At that point, you can argue about whether you'd still want to own a car for casual trips outside the city. But you could survive without one.

But I can't walk anywhere from where I live (well, except down to the river in the woods) and there's no real transit system at all. If I couldn't drive, I'd have to relocate.

Re: Dust from car brakes more harmful than exhaust, study finds

#318

Post by AngryData »

m463 wrote: post #181
Fronzie wrote: post #170

Earlier quoted context omitted.

There are EV's which have drum-brakes. That's only possible because the regenerative braking takes most of the load. Also, there are stories of brake-discs rusting out on EV's. Both point to less (friction)-brake use on an EV compared to an ICE.

I suspect drum brakes were chosen by the electron pinching EV engineers. They're the only brakes that are friction-free when not applied. Disc brakes rub (and slow the car) even when not applied.

They use drum brakes because drum brakes are protected better from the environment while brake discs are not and will quickly get covered in rust and dirt when not used for awhile and then be less effective when they are actually needed for an emergency braking situation.

We only ever really went to disc brakes because they were slightly cheaper and easier to manufacture and since racing vehicles used disc brakes (because they benefit from the extra cooling capacity that commuters don't need) it was easy to convince customers that they were "better" and they became standard.

There was also a time when they didn't figure out traction control very well using brake drums while they did manage it with brake discs, but part of that could be just because brake drums were out of fashion in racing where traction and stability control were invented and implemented first and nobody bothered improving drum brakes to take advantage of that tech until decades later.

Now that EV drivers can go weeks without touching their actual brakes and just rely on regen braking, disc brakes have become a liability since they aren't worn down smooth and cleaned whenever someone stops at the end of their driveway.

Re: Dust from car brakes more harmful than exhaust, study finds

#319

Post by AngryData »

lukevp wrote: post #215
kstrauser wrote: post #207

Earlier quoted context omitted.

Not significantly. Otherwise they’d get hot and work less well. Pads ride very closely to the disc so that road stuff can’t get wedged between the surfaces, and so that you don’t waste break pedal travel just getting the pads close to the surface. Well adjusted drum brakes should be arranged almost exactly the same way. From https://mechanicswizard.com/how-close-should-brake-pads-be-t... : > Typically, the optimal ga…

Are you familiar with how disk brakes on a car operate? They’re essentially a hydraulic piston clamping the brake pads against the rotor. When you let off the brake pedal, the pressure is removed, but there’s not a “retraction” of any kind. So there’s no pressure but nothing is actually making that gap. That article was articulating basically that the piston, when not compressing the brake pads, should not be too far…

Technically there is a slight amount of rubber spring back for a fraction of a millimeter and the air traveling with the rotor surface puts a small amount of pressure back on the pad and pushes it imperceptibly backwards. Of course that is only really effective if your rotors are perfectly flat and warp free, which most peoples are not because rotors never get resurfaced any more and 95% of them are super cheaply casted and turned which leads to warpage extremely quickly.

Re: Dust from car brakes more harmful than exhaust, study finds

#320

Post by AngryData »

YZF wrote: post #202
rafaelmn wrote: post #190

Earlier quoted context omitted.

Teslas eat tires for breakfast. Instant torque and high weight - any benefit you get from regen breaking is not scratching that.

My model 3 is 5 years old and I'm still on my original set of tires (though in recent years I do put on winter tires for a few months a year). I don't usually drive like crazy (and it's an SR+ which is the least powerful model).

I could be wrong and be using outdated information, but aren't Tesla's stock tires also low rolling resistance tires? Which does mean less road friction and less wear, but also means lower maximum traction which is a tradeoff most anybody could make if they wanted.
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