Why car wheels are so flat these days

Re:Why car wheels are so flat these days by ben_w on Wednesday September 14, 2022 @07:30AM (#32835702)

I don't claim any physical engineering skills, but don't you need a mechanical (non electrical) system for parking breaks?

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Re:Why car wheels are so flat these days by jasode on Wednesday September 14, 2022 @08:24AM (#32836147)

>, but don't you need a mechanical (non electrical) system for parking breaks?

To some of the replies... I think some clarification needed because the wording caused folks to think of something else such as electronically _controlled_ physical brake pads: https://en.wikipedia.org/wiki/Electronic_parking_brake

I think the gp was trying to ask about feasibility of electric _powered_ magnetic field resistance braking ... similar to an exercise bike ... which would require constant electrical power source. (Similar to : https://www.google.com/search?q=magnetic+resistant+braking+o...)

Magnetic field resistance brakes is practical for regenerative braking but not safe for parking brakes on an incline if the batteries run out of juice. The context is the gp's premise of no physical friction brake components via "(ie. no hydraulics, drums, rotors, or pads)."

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Re:Why car wheels are so flat these days by londons_explore on Wednesday September 14, 2022 @07:44AM (#32835814)

You do, yes. But that can be a metal pin the size of your pinky finger. It's a super easy engineering challenge compared to the regular brakes that slow down the car, which, when emergency braking a 2 ton car from 100 mph, needs to briefly absorb nearly 1 megawatt. Thats the power used by 1000 houses, which is a lot to absorb in a lightweight system that needs to still work if part of the system fails.

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Re:Why car wheels are so flat these days by thatcat on Wednesday September 14, 2022 @08:09AM (#32836029)

The parking brake is the emergency brake, cant be a pin

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Re:Why car wheels are so flat these days by 2III7 on Wednesday September 14, 2022 @08:11AM (#32836039)

You don't, many modern cars have electronic parking brakes with small electric motors mounted on the rear calipers which push the brake pads against the discs when activated.

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Re:Why car wheels are so flat these days by forgetfreeman on Wednesday September 14, 2022 @10:36AM (#32837853)

I am very glad you commented here as my initial skepticism of your claim lead me to do a spot of research that answered several unresolved questions I'd had about one of the most obnoxious features I've ever seen in a new car. My mother in law has a car with (apparently) electronic parking brake and I have loathed everything about it from the moment I first sat down in the car. This at least explains why an utterly unintuitive double toggle button replaced the "standard" mechanical lever on the center console and what notional benefits (hill holding) come with this system. I'd hate this a lot less if the manufacturer had included a tell-tale of some kind to visually indicate if/when the ECM thinks the P-brake is engaged.

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Re:Why car wheels are so flat these days by nicoburns on Wednesday September 14, 2022 @12:20PM (#32839382)

If it's using brake pads, then it's still a partially mechanical suggestion. The comment at the top of the thread was suggesting doing away with brake pads entirely!

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Re:Why car wheels are so flat these days by KingJulian on Wednesday September 14, 2022 @07:35AM (#32835737)

I would think so too. Any parking brake has to be a fail-safe type brake which has to function in the absence of electricity. Hence, as you mentioned, purely mechanical.

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Re:Why car wheels are so flat these days by Sohcahtoa82 on Wednesday September 14, 2022 @11:30AM (#32838594)

They need to be able to remain applied without power, but the application can require power.

In my Tesla, I push a button and I can hear an electric motor engaging the brake.

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Re:Why car wheels are so flat these days by kwhitefoot on Wednesday September 14, 2022 @08:54AM (#32836472)

It only has to remain engaged, engaging it in cars with push button parking brakes requires electricity to drive a small electric motor at each wheel.

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Re:Why car wheels are so flat these days by hollywood_court on Wednesday September 14, 2022 @08:15AM (#32836072)

Nope. Many modern vehicles have push button electric parking brakes.

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