====== Disc rear brakes ======

I needed to change the rear brakes on Renault Megane IV. The car has rear disc breaks which I never had before, so I want you to spare some troubles. Apparently it is the same with many modern cars, like the ones from VAG, PSA, Ford, BMW, etc. with rear calipers. \\
I was told that for cars with electronic parking brakes (EPB), you may need to activate a service mode to retract the piston safely (either by some menu or via OBD service cable). \\

Translate if needed, e.g. to [[https://translate.google.com/translate?hl=en&sl=auto&tl=de&u=https://super-se.de/dokuwiki/projects:megane_brakes|German via Google Translate]] 
===== Short Info, not a guide =====

The piston cannot just be pushed back with Megane 4 (and other cars with rear disc breaks), the piston has to be screwed back in. There are two ways to get to the breaking cylinder. 

==== remove breakshoe ====
To me, the most logical thing is to remove the brakeshoe. For that, fist unhinge the hand brake cable. Be careful when unscrewing the brake line - it is advisable to loosen the bolt, then rotate the brakeshoe instead of the bolt to avoid stress on the brake line. \\
**⚠️ WARNING: YOU NEED TO BLEED THE BRAKES AFTER YOU ARE DONE!** \\ \\

Here is a picture of (half) the brakeshoe with the piston already screwed in: \\ {{:projects:megane-brakes:megane-brakeshoe.jpg?direct&200|}}

==== remove half of the break ====

There is a screw with special screw glue (see photo). If you remove that, you can take off half of the break. Renault said that it needs replacement once removed and one screw is ~30€, IIRC. I have seen breaking pads online with screw included for less. \\

==== pushing piston back in ====

After having removed the brakeshoe, it is necessary to screw in the piston **__clockwise with significant pressure__**. \\
(Buy a special tool) or use a hook spanner wrench with two pins, something like this: 
{{:projects:megane-brakes:zweilochschluessel.png?nolink&100|}}

Apply pressure on the piston/wrench while screwing it in. This way the piston is moved back again to make enough clearance for the new brake pads (as they are thicker and it is impossible to push back the piston). \\

Why is it this way? I was told, it is because the parking brake is part of the mechanism. I have unscrewed the piston to understand but I still don't fully. (Unfortunately, I have not taken any pictures :/ ) - **do not unscrew the piston if you have no special oil for the sealant!** The hand brake pushes the lead screw mechanically. The piston is screwed on the studbolt which has a steep thread. I can only guess how the bolt is screwed out on the steep thread by the hydraulics to automatically readjust the clearance. \\

==== exploded-view drawing and torque ====

I have grabbed a screenshot of some yt-video sometime (I have forgotten where it was from, sorry). See the  exploded-view drawing and torque for Megane IV rear break: \\
{{:projects:megane-brakes:megane4_rear-diagram.jpg?800|}} \\


==== IMO ====
I hate that there is no servicing manual available, I hope that this changes some time with future cars again (doubt it though, prove me wrong). Who ever designed this without documenting it publically should be fired immediately. \\