Retracting parking brake with scan tool?

[Tev42]

Since I don't want to drive with the rear track pads for street use, I will be doing this twice for each track day. Not really happy about the idea of removing the brake actuator motor twice a day for at least 10 days per year. The electronic way is likely much better for me and much less likely to lead to some sort of mechanical issue

Sounds good, just letting people know the manual method doesn’t require any special tools or software

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[Dave B]

I started thinking about another potential issue and hope folks here have an answer.

I will be changing out rear pads repeatedly when changing from street pads to track pads and back again. I know that when putting in new pads, I need to retract the rear caliper either by the manual method or using the EPB electronic retraction method. I know that when using the EPB retraction I will also be required to push in the piston manually so that I will be able to mount full thickness new pads.

Question is, what do I do if I am replacing full thickness street pads with slightly used brake pads? Without the electronic brake on other cars, I would just pump the brake pedal a few times to get the pads close to the rotor surface. If the electronic part is fully retracted, but the replacement pads are a bit thinner than the pads previously on the car, should I do the same i.e push the pedal a couple of times before taking the EPB out of maintenance mode or should I take it out of maintenance /pad replacement mode first and then push on the pedal? I would assume I should not engage the parking brake at all.

Happy for all advice.

 

[hobby-man]

I started thinking about another potential issue and hope folks here have an answer.

I will be changing out rear pads repeatedly when changing from street pads to track pads and back again. I know that when putting in new pads, I need to retract the rear caliper either by the manual method or using the EPB electronic retraction method. I know that when using the EPB retraction I will also be required to push in the piston manually so that I will be able to mount full thickness new pads.

Question is, what do I do if I am replacing full thickness street pads with slightly used brake pads? Without the electronic brake on other cars, I would just pump the brake pedal a few times to get the pads close to the rotor surface. If the electronic part is fully retracted, but the replacement pads are a bit thinner than the pads previously on the car, should I do the same i.e push the pedal a couple of times before taking the EPB out of maintenance mode or should I take it out of maintenance /pad replacement mode first and then push on the pedal? I would assume I should not engage the parking brake at all.

Happy for all advice.

Wouldn't just activating then de-activating the EPB accomplish that?

 

[Dave B]

My concern is that I don't know the travel of the electronic part of the rear brake. Does it go out of kilter if it all of a sudden finds that the pad is much further from the rotor than expected? Normally that distance is taken up by the hydraulic piston and the EPB doesn't move the pads that much. If the travel of the EPB is just a few millimeters then it may not be calibrated to go as much further as needed with the thinner pads. I would have thought that the ideal thing to do would be to depress the brake pedal before re activating the EPB but that could lead to a significant brake drag when it is re activated. Obviously going from thin pads to thick pads, there would be no issue as you actually need to compress the hydraulic part to fit the pads in place. Just not sure about the reverse where the hydraulic piston needs to be extended.

 

[hobby-man]

My concern is that I don't know the travel of the electronic part of the rear brake. Does it go out of kilter if it all of a sudden finds that the pad is much further from the rotor than expected? Normally that distance is taken up by the hydraulic piston and the EPB doesn't move the pads that much. If the travel of the EPB is just a few millimeters then it may not be calibrated to go as much further as needed with the thinner pads. I would have thought that the ideal thing to do would be to depress the brake pedal before re activating the EPB but that could lead to a significant brake drag when it is re activated. Obviously going from thin pads to thick pads, there would be no issue as you actually need to compress the hydraulic part to fit the pads in place. Just not sure about the reverse where the hydraulic piston needs to be extended.

The step before that is to pump the brakes to reestablish pedal feel, I would think doing that then the EPB on/off setup would take care of everything by taking up the slack. It is a good question though. I'm just trying to not overthink it...

 

[whytfwontthiswork]

Im pretty sure when you first activate the epb the actuator pushes the piston to the pad regardless of distance. Its not some calibrated or memorized distance

 

[Dave B]

Im pretty sure when you first activate the epb the actuator pushes the piston to the pad regardless of distance. Its not some calibrated or memorized distance

That would have been my thought but the main distance is covered by the hydraulics not the electronics. (Hence the reason you have to push the piston back in manually even when in the EPB service mode when going from used to new pads). If would be really nice to know what sort of distance the EPB can cover and what parameters it uses for hill assist etc.

If the hydraulic piston is no where near putting pressure on the pad, the electronic brake may keep pushing beyond its regular limits and go out of range. I suppose it would correct itself the next time you put on the bigger pads but not sure.

I thought the EPB has a pressure sensor in it which allows it to put just enough pressure over a short distance to actually engage the parking brake or hill assist

 

[Blazinqwickly]

So I see where Autel has one now saying 2021 updated, anyone tried & see if that fixes it or not for the newer models? I saw where it worked for some 2019 users but didn't work for one user with a 2019 was this user error or does it really not work for late 2019?

 

[XxTeexX]

When using the Autel do you need to leave your vehicle in the on position the whole time its in maintenance mode?

 

[MadMage]

When using the Autel do you need to leave your vehicle in the on position the whole time its in maintenance mode?

The Autel will tell you. From memory, you leave the car on, but the engine off.

 

[Code Monkey]

When using the Autel do you need to leave your vehicle in the on position the whole time its in maintenance mode?

No, after you retract the calipers you can turn the car completely off and remove the Autel.

 

[XxTeexX]

No, after you retract the calipers you can turn the car completely off and remove the Autel.

Thank you very much! Then when I’m complete I plug it back in and it’s still in maintenance mode? And I can return back to normal? Thanks

 

[Code Monkey]

Thank you very much! Then when I’m complete I plug it back in and it’s still in maintenance mode? And I can return back to normal? Thanks

Yes, plug it back in and get out of the maintenance mode.

 

[Dave B]

I answered my own question recently when replacing some rear race pads that were hardly worn with the more worn street pads. The Foxwell tool worked like a charm and I actually kept the ignition on for the duration. Changing pads like this is virtually as easy if not easier than doing the fronts. Only issue is that the passenger side upper bolt has to be removed with a 7mm Allen key. On the left side, all I have to do is loosen it and then flip the key so that it can be spun easily but on the right side, I run out of room. A slightly shorter key would work but all in all it is only about 4 turns that need to be done 180 degrees at a time.

As for the part about getting the hydraulic slack taken up, yes, I stepped on the brake pedal after installing the new thinner pads to get the pads back in close proximity to the rotors before getting out of the EPB maintenance mode. Worked great.

 

[M16]

I started thinking about another potential issue and hope folks here have an answer.

I will be changing out rear pads repeatedly when changing from street pads to track pads and back again. I know that when putting in new pads, I need to retract the rear caliper either by the manual method or using the EPB electronic retraction method. I know that when using the EPB retraction I will also be required to push in the piston manually so that I will be able to mount full thickness new pads.

Question is, what do I do if I am replacing full thickness street pads with slightly used brake pads? Without the electronic brake on other cars, I would just pump the brake pedal a few times to get the pads close to the rotor surface. If the electronic part is fully retracted, but the replacement pads are a bit thinner than the pads previously on the car, should I do the same i.e push the pedal a couple of times before taking the EPB out of maintenance mode or should I take it out of maintenance /pad replacement mode first and then push on the pedal? I would assume I should not engage the parking brake at all.

Happy for all advice.

Yeah the preferable way is to pump the pedal till firm, then you take the epb out of maintenance mode. The way the epb stops is by sensing the current delivered to the motor(the motor only has +ve-ve leads, so the only feedback is electric current. No signal wires). When its pressing at the pads, the current starts shooting up and the ecu shuts off power. If you were to take it out of maintenance mode first, then pump the pedal, then you have to cycle the epb off, firm up the pedal, the re engage the epb and it will calibrate right back up, therefore theres really no wrong way to go about it. Just like when your pads wear down, when you engage the epb, it will go till it hits the pads and reaches it's electric current threshold then stop.

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