Leftwood
Member
Disengage spontaneously.
Nodge68
Well-Known Member
Potentially any electromechanical device can fail spontaneously.
Our VW Tiguan rolled away 3 times in 3 years, due to the EPB releasing itself.
Hippo
Lord Hippo
I'm curious to know why it released? Did something fail or did it just release due to losing grip as if it weren't on tight enough at the start with?
GrumpyGel
Well-Known Member
Yeh. Surely it doesn't hold the brake with force applied by electric. It would apply the brake with the force of and electric 'actuator' but hold it on a ratchet like a normal hand brake. Think the actuator needs an extra shredded wheat for its breakfast to pull it another notch!
Colthebrummie
Well-Known Member
I would be seriously pist off if my handbrake kept failing allowing the vehicle to roll away. Oh hang on, my handbrake doesn't work, I park it gear.
Col
Col
Nodge68
Well-Known Member
Apparently it was a software bug that allows the EPB to release itself randomly. The dealer did 5 software updates in the 3 years we had it, but the car still rolled away 2 days before we swapped it for the GTC.
The GTC also had an EPB, but thankfully that never gave any bother.
blue beasty
Leaks an prone to bits dropping off
There's been 3 cars with EHB fails go wondering off on their own here in town over the last year that I know of. Nearly got t boned by one as it headed out a carpark and into the shop opposite.
Someone obviously skipped the failsafe lecture at uni
Someone obviously skipped the failsafe lecture at uni
Nodge68
Well-Known Member
Most EPB actuators I've seen use a small RC type motor, about 45mm in diameter and about 75mm long, which is suitably geared for the task. This drives a worm gear that pulls on the cables, or caliper directly. The motor can't slip and theoretically doesn't need power to hold the cables, due to the worm gear.
The control systems are always active while the EPB is applied. This enables the EPB to be applied harder, after a brake cooling down period.
From my experience, the active control system is the main cause for them releasing by themselves. The EPB drive motor has to be driven on and off. So when a random release occurs, it has to be a software glitch that caused it.
Hippo
Lord Hippo
I think electric park brakes are funny. I can't wait until peeps start fixing them themselves in future and come on ere. Some of the newer ones will perform an emergency stop, well sort of. I tried it in a new RR at LR and it stopped the vehicle from 30mph. Some sort of brake assist strategy thing and automatically does other things at the same time, but don't count on that being correct as I'm not taking the blame if yours don't. I can't help thinking they should all be fitted with an auto box yer put in park as a backup in case it releases.
Nodge68
Well-Known Member
When using the EPB in an emergency situation. The ABS ECU activates the Emergency Brake Assist routine, which applies the main foot brakes at full capacity, to assist the EPB.
To bed in new EPB shoes, a service routine is used, as the main brakes need to be disabled. This ensures that only the EPB is functional. If you then try to stop something like a D3 or RRS on the EPB shoes alone. You'll very quickly realise why the ECU enters the EBA routine to help stop the vehicle in an actual emergency. If just the EPB shoes alone were used to stop the vehicle, the vehicle would take an age to stop.
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