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Switching to electric vehicles would reduce brake dust even more, because they use regenerative breaking to avoid using the break pads when possible.
by mrob 7y ago
Switching to electric vehicles would reduce brake dust even more, because they use regenerative breaking to avoid using the break pads when possible.
- murkt 7y agoAdditionally, roads can be designed in a way that calms vehicle movement instead of accelerate-brake cycle. For example, narrower roads with curves instead of wide straight roads with speed bumps near pedestrian crossings.
- sandworm101 7y agoCurves are just accelleration in a different direction. Tires would degrade just as quickly.
- thrwaway69 7y agoWouldn't that cause friction too? I feel like it might even increase braking more if it's a busy road and people want to move faster.
- Scoundreller 7y agoAt least newer automatics finally do engine braking as well.
- Jamwinner 7y agoAs well as all cars with manual transmissions.
- sandworm101 7y ago"Engine braking" isn't just letting the engine spin down at 0 throttle. Propper engine braking, aka "Jake brake", is letting the engine spin at 100% throttle but zero fuel input (and some valve trickery). This lets air in to be compressed, releasing it before the down stroke of the piston. No car does that. It is a separate installed system on trucks. It can be almost as powerful as the engine. In a car, it could handle all but emergency braking. https://en.m.wikipedia.org/wiki/Compression_release_engine_brake https://en.m.wikipedia.org/wiki/Compression_release_engine_b... When you hear a truck making popping noises like a machine gun, that's the Jake brake in action.
- hamandcheese 7y ago> Engine braking occurs when the retarding forces within an engine are used to slow down a motor vehicle, as opposed to using additional external braking mechanisms such as friction brakes or magnetic brakes. > The term is often confused with several other types of braking, most notably compression-release braking or "jake braking" which uses a different mechanism. https://en.m.wikipedia.org/wiki/Engine_braking https://en.m.wikipedia.org/wiki/Engine_braking
- sandworm101 7y agoBut when you see a sign saying "no engine braking" it refers to the jake brake, not down-shifting in a car. (It's a long trademark story over the use of "jake")
- saiya-jin 7y agoI have on my manual 15-year old diesel bmw very much an engine brake. It breaks quite well compared to neutral which seems to like to go on forever, and actually indicates proper consumption. On highways and motorways, I rarely need to use brake at all. Of course, being a sensible driver helps (in contrary to what many people expect from me when they see the car and expect yet another immature aggressive driver)
- ironmagma 7y agoIs this (jake brake) what the parent comment was referring to that newer automatics finally do?
- sandworm101 7y agoNope. That was reference to automatic transmissions not up shifting immediately every time you decrease throttle.
- ironmagma 7y agoWhy do they upshift when throttle is decreased? Wouldn’t it make more sense to downshift since the driver is probably about to brake?
- eyegor 7y agoI mean, you can still shift gears in an automatic car. I used to do it all the time when I lived in a snowy, hilly city. I've never in my life seen an automatic where the only options were drive, reverse, neutral, and park. There's always some amount of control, even if it's only 1/2/3. Edit: Upon reflection, I assume your comment meant that newer cars will somehow use engine braking themselves. Since electric brake systems are rare in ice cars, would this be referring to cruise control features?
- woodpanel 7y agowhile switching to electric vehicles likely reduces break dust, such switch would simultaneously increase dust from tires, since increased acceleration. The latter being already 80% of urban "particulate matter" pollution.
- iguy 7y agoAnd weight, presumably heavy vehicles wear through more rubber, and batteries are heavy.
- brownbat 7y agoWeight. This is so much about vehicle weight. I think the heavier EVs hit a crossover point because of regenerative braking, but weight does set them back, that's one of the whole points of this study: https://www.sciencedirect.com/science/article/abs/pii/S135223101630187X https://www.sciencedirect.com/science/article/abs/pii/S13522... This is a curve though. We could almost simplify the problem and only look at what heavy trucks generate and ignore all the cars completely, it'd be a non-crazy approximation.
- DenisM 7y agoI don’t think Nissan Leaf is particularly good at neck-breaking acceleration, and it probably outnumbers the drag-racing Teslas. Even then, a Tesla isn’t particularly speedy in traffic.
- Geeflow 7y agoI often drive a Renault Zoe which also isn't a sports car. I frequently leave sports cars behind at the traffic light. From 0-30 kph even the small/cheap electric cars are sport cars. And it is terribly tempting to develop a pedal-to-the-metal habit. So I assume tire dust will increase significantly in the cities.
- sandworm101 7y agoRate of acceleration isnt the issue. You may make more dust per second but so long as you are getting to the same end speed, and not spinning tires, the total amount of acceleration is the same. In my experience, over braking is the greater problem. Front tires degrade more quickly than rears. The average driver brakes far harder than they accelerate.
- dsfyu404ed 7y agoA set of pads typically lasts about as long as a set of tires (at the very least they're within a factor of two of each other). Compare relative volumes of materials. Brake dust is always going to be a much smaller source of particulate matter in the air than tire dust. FWIW if the fumes/particulate from burning them are any indication tires are probably way nastier than brakes.
- samatman 7y agoFirst paragraph is perfectly reasonable. Second paragraph, though: I've never been around a brake pad fire, but I'd rather breathe vulcanized rubber than "metal shavings of copper, steel, graphite, and brass bonded with resin": https://www.yourmechanic.com/article/what-are-brake-pads-made-of https://www.yourmechanic.com/article/what-are-brake-pads-mad...
- dsfyu404ed 7y agoIn my non-chemist, non-doctor opinion the circumstantial evidence points to brake dust being way less bad than tire dust. Being inert in the presence of most common substances tends to correlate well with low toxicity. It's the stuff that chemically reacts to all sorts of things that tends to be the most poisonous. Tires break down over time under "normal earthly conditions" which includes a lot of the same temperatures and molecules that are found inside the human body. To me this is a massive red flag for toxicity. High temperature tends to make things react more readily. Most of the stuff in brakes has to be really stable at high temperatures and being stable at high temperatures tends to correlate well with being chemically inert. The most reactive stuff in brakes are the long complex molecules used to bind it all together. These sorts of molecules are similiar to the molecules used in tires and all sorts of other plastic like things. So all else being equal tires probably have more of the chemically interesting things that cause problems in the human body. Burning brakes smells way better than burning tires which seems to confirm this (remember, your nose has millions of years of incremental improvement when it comes to indicating what is and isn't suitable to ingest). And before anyone thinks they're gonna get some easy internet points by saying "but asbestos", the amount of asbestos in brake pads is nonzero (to account for the sketchy unbranded stuff that may or may not use it) but still tiny enough that people working in proximity to it have mostly stopped dropping dead at 60 thanks to lung cancer so I think that however much asbestos is in brake pads it's low enough to not be an issue from a public health POV. TL;DR I'll take my chances with brakes over tires.