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Comment by daft_pink | Hacker News Reader

Just want to point out that most electric and hybrid vehicles use regenerative braking most of the time and only use real brakes at very slow speeds or in emergencies. So it might be totally misleading to say that electric vehicles are the problem, when they are probably the solution.

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Not only does regenerative braking itself reduce PM emissions, the reduced demand on friction brakes is enabling some EVs, such as the Volkswagen ID3 and ID4, to switch to drum brakes.

Due to their enclosed nature, drum brakes greatly reduce PM emissions compared to disc brakes.

That seems like the ID.4 has drum brakes on the rear only and disc brakes on the front (which is not unique to it; some lower end gasoline cars still have rear drums as well).

Yeah it's juste because it's cheaper, twingos also have drum breaks for the rear, as well as smarts and probably a boatload of other vehicles

And the brakes are only employed if needed. So even if you had disc brakes and has a good Regen design, you'd only use them in aggressive /emergency situations.

The other benefit of EVs is that the feedback on regeneration and efficiency tends to make you less aggressive and a better driver. Which also leads to less brake use.

Yes, although worth remembering that many EVs are rear-wheel drive only.

An all-wheel drive or front-wheel drive EV can regen more effectively than one which can regen on the rear wheels only.

I understand the theory of that but wonder how much difference there actually is.

The article has weird reasoning. If we remove tailpipe emissions, which are by far the largest, then brake/tire wear emissions become visible and are next in the list to deal with. But we won't deal with the latter before the former is dealt with.

They're just orthogonal concerns. There is no ordering between them.

> If we remove tailpipe emissions, which are by far the largest

im gonna need a source on your claim. heres a source that claims the opposite

https://www.washingtonpost.com/climate-environment/2023/07/0...

> our brakes and tires isn’t benign, either. Tests by Emissions Analytics, an engineering consulting company based in England, found tires produce about 2,000 times more particle pollution by mass than tailpipes.

> tires produce about 2,000 times more particle pollution by mass than tailpipes.

(emphasis mine)

The fact that the majority of tailpipe pollution is not particulate means that tailpipe pollution can be the biggest problem we need to fix, even if it isn't the biggest particle pollution problem.

The majority of modern tailpipe "pollution" is CO2.

the article was about brake emissions. Yet you're pointing to an article about tires.

comment I was responding to:

> If we remove tailpipe emissions, which are by far the largest, then brake/tire wear emissions become visible and are next in the list to deal with.

(clearly claiming that tailpipe emissions are by far larger than both brake and tire emissions)

This is by mass, which is a weasel metric that discounts all gaseous emissions, and the smallest particulates that stay in the air.

Impact on health is not linearly proportional to the mass.

It's almost the opposite - the smallest particles can linger in the air and get absorbed. You could eat a chunk of a tire without a significant health effect, but breathing the same mass of almost any gas would kill you.

Gas has mass, but regardless the word 'particulate' already discounts all gaseous emissions. Particulate emissions are liquid or solid by definition.

CO2 is bad for other environmental reasons, but it doesn't get stuck in our lungs.

Absolutely right. I had to change brake pads on my electric car at about 120 k miles. My previous gasoline cars usually had their brake pads last about the advertised 30K miles. Some people are complaining that the rear brake rotors of their teslas are rusting and looking bad. That is how little they are used.

Furthermore, it is entirely possible and probably desirable that some electric cars actually remove the brakes altogether (with the exception of an emergency brake that is only used in case of total system failure). Theoretically, electric motors should completely capable of doing all necessary braking. Of course there would have to be more emphasis on the reliability of the power electronics but it is doable.

Regen has limitations in how quickly the power can be stored which limits the braking rate. Also, when the battery is fully charged there is no place to put the electricity which also limits regen braking.

Most EVs blend regen into the brakes so that when you press on the brake pedal it uses regen for normal braking down to about 10mph at which point the friction brakes take over. At low speeds regen is ineffective. That low speed use of friction brakes produces very little wear and very little particulate output.

Those EVs doing blending will also switch entirely to friction braking if you really stomp on the brake pedal in an emergency stop as you can stop more quickly than any regen system. In those cases the priority is stopping quickly regardless of energy efficiency or particulates.

I don’t see a likely hood that EVs will completely get rid of friction brakes using current/near term technology.

I didn't really see them picking on EVs terribly in the article but maybe I missed it? Agree that a lot of EVs have regenerative braking so they should in theory produce less charged particles from the brake and caliper interaction, which they mentioned.

Inspection station in my state made comment to me that EVs are failing inspection for rusted brake components because of their heavy use of regen. Add to cost of ownership.

> Inspection station in my state made comment to me that EVs are failing inspection for rusted brake components because of their heavy use of regen.

Are you suggesting some metal brake components have unusual rust because of disuse, where they aren't being used regularly enough for friction to "clean" their surfaces?

Otherwise I don't see how regenerative breaking could cause rust, since the braking force is supplied by electrical fields.

its pretty obvious he's saying its because the main brakes dont get used because regenerative breaking is enough to stop the car.

>>Are you suggesting some metal brake components have unusual rust because of disuse

Yes, the brake disks, especially if you drive some place where they salt the roads during the winter. I had to change the rear disks on my hybrid after two years because they started to fall apart from rust, now I have learned to do some heavy braking at the end of trips to clean and dry the disks

My 2021 EV simply favors mechanical braking over regen for a short period at the start of each trip, specifically to avoid this. (Seems a trivial software feature once you have hybrid braking at all...)

I own a 2010 Prius and I've had to replace the brake pads more often than a regular car because of this, around every two years or 20k miles. I've had to replace the brake rotors twice over 80k miles, as the pads rusted and then wore it down unevenly.

Below 5mph the brakes are used, but it doesn't seem to be enough. Compared to my ICE car they always look a lot worse, and after parked for a day when it's damp have surface rust.

As another comment says, it seems like a software change could fix it by using the physical brakes more. I believe the issue is they get wet, and then don't get hot enough to dry out before parking.

they still emit tire particulate emissions. moreso than ICE vehicles due to the increased weight

There's a whole load of anti-EV FUD going out right now.

And pro ev fud too. Hopefully they balance out.

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