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Electric emergency brake

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632 views 23 replies 12 participants last post by  talespin  
#1 ·
New guy. Getting ready to pull the trigger on 2025 Crosstrek.
Big question on electric emergency brake. No mechanical release.
Feeling uncomfortable about this. Should I be? Thanks!
 
#9 · (Edited)
Electric parking brakes are not emergency brakes and not meant to be used that way. With all wheel disc brakes, the rear discs use a motor to move the caliper pistons, locking the rotor disc. I haven't read my owner's manual for this info but guessing electronics will not allow emergency braking - engaging parking brakes. If this info is incorrect and one can engage parking brakes while at speed, rear brake lockup may result, leading to skidding, possible loss of steering control and damage to the rear brakes.

In one way, I don't know if anyone has tried drifting, using electronic parking brakes. There's always one person willing to try it and see if it works..........

When used correctly, most of us already using auto vehicle hold will come to a stop with AVH (enabled) automatically engaging the parking brake to allow releasing the brake pedal wuth engine/xmission engaged at idle rpm. AVH will flash to indicate parking brakes are holding the vehicle until the accelerator pedal is pressed, automatically telling the brake control module to release the parking brake to allow normal acceleration. Hill hold is another way of describing AVH (when enabled). I can't find mechanical drawings for our Subarus' electronic parking brake system so I'm at a loss as to whether this is an improvement over the older cable system or brings a new set of future issues when electronic park brake systems age, corrode, and fall behind maintenance. In theory, at least in my mind, if failure occurs, it would be inability of parking brake use. Worse case scenario might be a stuck parking brake unable to release. This would suggest severe corrosion, poor/non existent periodic brake service, mods that interfere with operation, etc.

Suffice it to say that buying a new vehicle gives three years of warranty protection against failures or faults if parking brakes fail. During and after new vehicle warranty, it's up to owners to maintain brakes for safe and reliable operation, including inspecting parking brake operation for trouble free service.
 
#10 ·
On my Tesla, the EPB is there if needed for emergency stop.

From the manual:

Emergency Braking
In an emergency, fully press the brake pedal and maintain firm pressure, even on low traction surfaces. The ABS varies the braking pressure to each wheel according to the amount of traction available. This prevents wheels from locking and ensures that you stop as safely as possible.

If an alternative method is needed to bring the vehicle to a stop, press and hold the Park button on the drive stalk to apply the brakes and remove drive torque while the button is held.
 
#12 · (Edited)
As someone who rarely uses the e-brake on automatic vehicles (only), I was taught many years ago by me FIL (truck mechanic) that if you are to use the e-brake in an automatic vehicle, then ALWAYS use it or do not use it AT ALL. Reason being, at least for the mechanical versions, is the e-brake cable. This cable, once stretched and used often, needs to 'keep' being used to prevent sticking or binding. Occasional use is ok, but more use is better. Now, on the other end of the spectrum is the person who normally never uses it, but then decides that one time to use it, and the cable has a tendency to snap/seize from the 'lack of use'.
Again, this is what I was taught regarding the mechanical versions. I have always used the e-brake on manual trannys, and larger trucks with automatics. However, I have never used it yet on our 24 CTW. Not saying my way of thinking or practice is correct, just what I do.
Not sure how the lack-of use or the over-use on the electronic e-brake differs from the mechanical? Both still have a cable to engage the brake, but the electronic version just uses a servo to do it vs. a manual lever of some sort??
 
#13 ·
As someone who rarely uses the e-brake on automatic vehicles (only), I was taught many years ago by me FIL (truck mechanic) that if you are to use the e-brake in an automatic vehicle, then ALWAYS use it or do not use it AT ALL. Reason being, at least for the mechanical versions, is the e-brake cable. This cable, once stretched and used often, needs to 'keep' being used to prevent sticking or binding. Occasional use is ok, but more use is better. Now, on the other end of the spectrum is the person who normally never uses it, but then decides that one time to use it, and the cable has a tendency to snap from the 'lack of use'.
Again, this is what I was taught regarding the mechanical versions. I have always used the e-brake on manual trannys, and larger trucks with automatics. However, I have never used it yet on our 24 CTW. Not saying my way of thinking or practice is correct, just what I do.
Not sure how the lack-of use or the over-use on the electronic e-brake differs from the mechanical? Both still have a cable to engage the brake, but the electronic version just uses a servo to do it vs. a manual lever of some sort.
With little info from service manuals, very little drawings (photo illustrations, cutaway drawings, mechanical engineering diagrams, etc), I think rear disc brakes (without the top hat brake drum) electromechanically close brake pads against the rotors for electronically controlled parking brakes. No cables. Either a cam or screw drive acts on brake pads to lock or release them for parking or AVH/hill hold. If anyone has better info to correct me, please do enlighten me/us.
 
#14 ·
In the FSM is a way to release a STUCK rear parking brake. There is an actuator on each rear caliper with a motor that CLOSES the rear pads. It's a RATCHETING assembly which is why you must ROTATE the piston on the rear compressing it when replacing the rear pads. This is the same as the cable/lever assembly MY78, MY82 and MY85 Subaru's had but on the Front disk calipers. Also on my wife's front 80 Saab Turbo and her current rear Fiat 500. Needless to say I own for a long time a tool that rotates and compresses the piston on these.

In any case, attached is 4 pages from the FSM which have you jackup, remove the rear tire, the motorized actuator and twist the center spindle to release the pads.
 

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#17 · (Edited)
I'm familiar with the rotating/compression tool used for pad changes. Purchased a kit off amzn a few years back. Seems this is the way they are going :rolleyes:
Interesting on how that actuator works. Seems much simpler than what I remember trying to adjust the parking brake thru drums back in the day. Similar ratcheting gizmo, only inside the drum (from the rear) and you needed to use a small screwdriver to ratchet the tension. Appreciate the FSM PDF (y):cool:
 
#19 ·
What does this have to do with anything here?
Apologies, it was for demonstrating a counterexample of nutjob1's post which I took to mean the EPB doesn't work for emergencies, and sure enough a few posts later, an actual Crosstrek reference showed what I was trying to show with the Tesla example. I don't have 2020 Crosstrek Hybrid any more and had no emergencies to try the EPB that way.

I'm glad it functions like other cars.

ref:
Electric parking brakes are not emergency brakes and not meant to be used that way.