2 ms·

Drum brakes can capture this dust for safe disposal, but are seen as old fashioned and for poor people.

by ZeroGravitas 2y ago

more_corn 2y ago
This is not true. Drum brakes are not sealed.
- sokoloff 2y ago
  They are not sealed perfectly, but every drum that I’ve removed had a pile of shoe dust that was a very significant fraction of the original mass of the shoe friction material worn. I’d estimate that 50% or more of the material ends up at the workshop instead of along the roadside.
toast0 2y ago
The interwebs say that disc brakes are better able to dissipate heat, provide more consistent braking performance, and generally reduce stopping distance. Drum brakes are old fashioned, most US vehicles switched to at least disc brakes in the front in the late 1970s and early 80s. Drums in the rear make the parking brake simple, and rear brake performance is less important as more braking force comes from the front. I don't know about being "for poor people", except that poor people may be more likely to have older vehicles, but I don't know that that extends to using vehicles that old, most vehicles with drums are 40+ years old at this point, and keeping something that old alive starts to get spendy because parts are trickier to find, and it costs time or money or both to adapt parts from other vehicles (like upgrading to disc brakes from a newer car)
- ZeroGravitas 2y ago
  Some modern EVs already use drum brakes on the rear. Since they have regenerative breaking you don't get brake fade on long downhills. New EU regulations are coming in to limit brake dust and so people are looking at them again. And other ideas, like mercedes has a prototype that puts the brake inside the motor.
- sokoloff 2y ago
  Note that some cars have parking/emergency brakes as drum brakes in the center of a rotor that provides disc brakes for the service (“normal”) brakes, so you can still get disc braking performance with the parking brake cable mechanism. Drum brakes are also slightly more efficient, with the shoes exhibiting less drag when not applied, which is important on small battery EVs. (They are worse for high-energy or repeated braking, but better in cruise.)

Drum brakes can capture this dust for safe disposal, but are seen as old fashioned and for poor people.

more_corn 2y ago

This is not true. Drum brakes are not sealed.

sokoloff 2y ago
They are not sealed perfectly, but every drum that I’ve removed had a pile of shoe dust that was a very significant fraction of the original mass of the shoe friction material worn. I’d estimate that 50% or more of the material ends up at the workshop instead of along the roadside.

toast0 2y ago

The interwebs say that disc brakes are better able to dissipate heat, provide more consistent braking performance, and generally reduce stopping distance. Drum brakes are old fashioned, most US vehicles switched to at least disc brakes in the front in the late 1970s and early 80s. Drums in the rear make the parking brake simple, and rear brake performance is less important as more braking force comes from the front. I don't know about being "for poor people", except that poor people may be more likely to have older vehicles, but I don't know that that extends to using vehicles that old, most vehicles with drums are 40+ years old at this point, and keeping something that old alive starts to get spendy because parts are trickier to find, and it costs time or money or both to adapt parts from other vehicles (like upgrading to disc brakes from a newer car)

ZeroGravitas 2y ago
Some modern EVs already use drum brakes on the rear. Since they have regenerative breaking you don't get brake fade on long downhills. New EU regulations are coming in to limit brake dust and so people are looking at them again. And other ideas, like mercedes has a prototype that puts the brake inside the motor.
sokoloff 2y ago
Note that some cars have parking/emergency brakes as drum brakes in the center of a rotor that provides disc brakes for the service (“normal”) brakes, so you can still get disc braking performance with the parking brake cable mechanism. Drum brakes are also slightly more efficient, with the shoes exhibiting less drag when not applied, which is important on small battery EVs. (They are worse for high-energy or repeated braking, but better in cruise.)