I can assume it's gone back to the "pre set position" of the worn brake pads and the new brake pads being thicker require it to go back further.

You can take the actual parking brake mechanism off of the back and rewind it manually so it goes right in....requires a spline/XYZ socket or a torx to whine it back... But the boot doesn't look how it should and is kinked/folded in on itself...which could be making it bind and not go back in

 

This would work, however, the bolt ended up stripping.

 

That's a beautiful coupe.

 

Wind the piston back using the scanner tool, then push piston back the rest of the way.
Note: the piston will give quite a lot of resistance so I use a ratchet pad/piston tool to push it back.

Like this

https://www.amazon.co.uk/Silverline-Tools-708247-Piston-Spreader/dp/B075KLLQW6/ref=asc_df_B075KLLQW6?mcid=b238cec4d1d03a8b8591da43c8e02c03&th=1&psc=1&hvocijid=2944728476623968675-B075KLLQW6-&hvexpln=74&tag=googshopuk-21&linkCode=df0&hvadid=696285193871&hvpos=&hvnetw=g&hvrand=2944728476623968675&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1006672&hvtargid=pla-2281435177378&psc=1&gad_source=1

The dust boot has creased as it may need some lube under the boot to help the piston spin and the boot slip around the piston whilst it's turning.

 

Wind the piston back using the scanner tool, then push piston back the rest of the way.
Note: the piston will give quite a lot of resistance so I use a ratchet pad/piston tool to push it back.

Like this

https://www.amazon.co.uk/Silverline-Tools-708247-Piston-Spreader/dp/B075KLLQW6/ref=asc_df_B075KLLQW6?mcid=b238cec4d1d03a8b8591da43c8e02c03&th=1&psc=1&hvocijid=2944728476623968675-B075KLLQW6-&hvexpln=74&tag=googshopuk-21&linkCode=df0&hvadid=696285193871&hvpos=&hvnetw=g&hvrand=2944728476623968675&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1006672&hvtargid=pla-2281435177378&psc=1&gad_source=1

The dust boot has creased as it may need some lube under the boot to help the piston spin and the boot slip around the piston whilst it's turning.

This spreader will do. Good lookin out with the link. Cheers!

 

Spray some wd40 around the seal so it doesn't twist as per pic & wind it back with a pair of long nose pliers if it's not too stiff or buy the wind back tool, generally turning of epb with car on & block the wheels so it doesn't move, disconnect battery so they don't auto wind back, then fit new pads refit all & battery then turn on epb via button, never failed for me.

 

This was the issue that happened no doubt. After using the scanner and hearing the piston set to service it possibly auto wound back after I left to do other chores🤷🏽.

 

thats a good point Dave, these caliper are wound back with the diagnostic computer and then piston itself can be pushed straight in, no need to twist them while pushing in.

Hopefully that rubber boot didnt get damaged. +1 for lubricating to get it aligned away but i would no use WD40, i had a few rubber pieces literally dissolve between my fingers after putting WD40 on them. all depends on what type of rubber it is.

 

I've used WD on various rubber caliper seals bud, it's fine as the heat & brake dust dissipates the WD quickly & afterwards just clean it with some brake cleaner or a cloth, simplessss

 

+1 for not using WD40 on brake components or rubber. some of my old cars when I used WD40, the boot looked like and old sock

 

the only kind of grease you should be using is the one that's meant for the slide pins. That one doesn't cause the boots to swell. WD40 will turn the boots to mush.

 

i recommend TRW PFG110 for any kind of brake jobs. Works really well

 

Piston may be hard to push back at the begining, but you can take a dental pick (found in most local hardware shops) and lift up rubber protector seal a bit then spray a lot silicone (or rubber protector) grease spray that has thermal rating -50 to +200 C (found in most local hardware shops) on the piston. Then use regular brake piston tool (also found in most hardware shops) to push back piston.

Also remember to clean slide pins and use new silicon (or rubber protector) grease to lubricate those.

Always use rubber protective greases in brakeparts that are in contact with rubber. With this habbit i've never had any problems with original brake parts in my 2008 A5 that has 300k with it!