Rusty Brakes

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Paul K

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In most of Canada and parts of the U.S. road salt is used extensively during the winter. The resulting briny spray as you drive gets all over the underside of vehicles including the brakes. The problem with EVs is that the brakes don't get hot enough to dry out after driving on wet salty roads. With my Leaf every late spring change back to summer tires had my mechanic muttering about partially seized calipers and rusty disks.

I just discovered this nifty trick on a VW id.4 sub forum on another site. The id.4 agressively regenerates off the brake pedal even when in D mode using the brakes only for the final stop. But if you shift into N there is no regen at all. This gives one the opportunity to do the last few stops on the way home shifting in N and using the friction brakes to a full stop. This not only heats up the components but scrapes the rusty crud that may be building up on the rotors and rear brake drums.

This is a little cumbersome and potentially a little dangerous if a sudden evasive maneuver is required. A better solution would be for EVs to have an "off" option for regen so this trick could be implemented safely. It may be that in salt country brakes will rust out before they wear out. I posted here instead of the VW sub forum as this is a concern to all EV owners.
 
We had a gal from New York complaining about it with her Tesla. Tesla's service departments recommend she take the car out and slam on the brakes to clean the rust off on a regular basis.

I take it that running the vehicle once a week through a car wash isn't good enough.
 
Paul K said:
A better solution would be for EVs to have an "off" option for regen so this trick could be implemented safely.
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I remember reading a blurb in the manual on my new Kona and will try it out and report back once the roads are dry.
Brake Disc Cleaning (If equipped)
Use the Brake Disc Cleaning function if noise is generated when depressing the brake while driving or if the brake disc gets rusty. It helps reduce noise and rust. Regenerative braking is restrained while Brake Disc Cleaning is operated, which may lower the electric energy efficiency.

Press and hold the AUTO HOLD button for over 3 seconds.

  • Brake Disc Cleaning starts operating when the message ‘Brake disc cleaning’ is displayed on the instrument cluster.
  • Regenerative braking is restrained while the brake is depressed approximately 10 times while driving (it may differ depending on driving conditions). It helps reduce noise and rust.
  • The Brake Disc Cleaning function will turn off automatically when the operation is completed. It can also be turned off before the operation is completed by turning off the vehicle or pressing the AUTO HOLD button for over 3 seconds.
 
Don't know if my cars have this feature or not. But I doubt I have much rust on my rotors. First the cars are driven pretty well every day, and quite aggressively. When you own a nimble EV, you inevitably end up using some physical braking. And my wife is no different. In fact when I drive with her, she sometimes scares me with how aggressive she is. She does not like poky drivers that hold up traffic.
 
R P said:
Don't know if my cars have this feature or not. But I doubt I have much rust on my rotors. First the cars are driven pretty well every day, and quite aggressively. When you own a nimble EV, you inevitably end up using some physical braking. And my wife is no different. In fact when I drive with her, she sometimes scares me with how aggressive she is. She does not like poky drivers that hold up traffic.
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I tried it and made a report here, it works quite well as designed;)
 
My MINI SE uses friction brakes when I press the brake pedal, isn't this normal for EVs? I do rely almost exclusively on regenerative braking, and my brakes have rusted some but they still work. In fact, I'm still on the car's original brake pads after nearly 100,000 miles. And yes, the pad thickness gets checked at least twice a year.
 
The Prius had no regeneration going backwards so the pads would rub off the rust. Both the Tesla and BMW have slightly warm brake pads after a drive. I have thought about anti-friction, brake pad springs.

Bob Wilson
 
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