Brake Caliper Retraction Tool for Audi A3 & VW Golf 4 Rear

Hello everyone!

Does anyone happen to know the dimensions of the brake caliper retraction tool for the rear axle (with integrated parking brake adjustment mechanism)?

I'm currently in the process of building a suitable tool myself and therefore need the dimensions.

What is the diameter of the brake piston on the rear axle?
What is the width and depth of the groove in the brake piston?

I read somewhere that the thread pitch of the follow-up mechanism is 2mm. Can anyone confirm or deny this? Accordingly, an M16 thread should work very well (pitch 2mm) to push and rotate.

Once my tool is finished, I'll be able to post some pictures here.

What is the width of the recess in the brake caliper where the tool would need to rest?

Of course, I could also take off my wheels and the brake calipers right now and measure everything, but I don't feel like doing that with the current temperatures .
Therefore, I would like to draw upon existing knowledge.
Perhaps someone could measure the VAG3272 and post the most important dimensions here.

Thank you for your support.

Regards,
Alex.

Oh, that's a great idea!
I've always wanted to do this myself. I've been stuck on the question of how to attach the end piece with the grooves to the threaded rod without using a welding machine. How are you planning to do it?

Regarding the thread pitch: I previously thought that the pitch didn't matter, as long as it wasn't too steep. So, you can rotate it as much as you want, but you shouldn't push without rotating (Is that clear )?
Or is this assumption incorrect? I can't imagine that there would be a fixed angle of inclination specified there, because if there were, you could simply rotate it – without pressing – to retract the piston as well.

Perhaps someone knows more about the internal structure.

Quote:

Perhaps someone knows the internal structure in more detail.

At least, that's what it says about mine.
A threaded rod extends from the lever to which the brake cable is attached, into the caliper. This rod rotates when the handbrake is pulled. In addition, there are three balls located between the brake caliper and the threaded rod on an inclined track, so that the rotation of the rod pushes it towards the brake pad. (When the handbrake lever is released, the threaded rod returns to its original position).
The thread is a trapezoidal thread, with either a double or possibly even a triple start, meaning it has a relatively large pitch.
On this threaded rod, there is a threaded bushing that is rotatably connected to the brake piston.
Apparently, the friction between the threaded rod and the threaded bushing, and between the threaded bushing and the brake piston, is designed in such a way that the adjustment functions, but I still don't fully understand it to this day.

However, I also think that the slope doesn't matter because the piston and the threaded bushing are not rigidly connected. Even if you only rotate it, the piston won't retract on its own.

Since I didn't want to constantly be fiddling with the rear brake, I built a very simple tool. It's a piece of square steel with a hole drilled in the middle and an M8 thread cut into it. I simply screwed a long M8 screw into that hole. With the screw, I applied some pressure to the cylinder. Then, I turned the cylinder using a wrench from a flexible shaft drill (which fits perfectly). It's not a professional tool, but it worked great and was cheap to make.
You can actually buy those reset tools quite cheaply, so it's questionable whether building them yourself is still worth it (considering all the effort involved).

That's exactly what I wanted to do today: replace the brake pads. Since I hadn't checked my 'manual' beforehand, I simply tried to retract the piston with a C-clamp (which has always worked without problems on every car I've worked on). But lo and behold, no chance. Then I completely removed it and looked in the manual again, but it offered a 'misleading,' or rather, insufficient description. After several attempts, I discovered that the piston can be screwed back in by simply turning it clockwise (without pressure) using a pipe wrench or something similar. Pressure is not necessary. It's a strange system; I've never seen anything like it.

For the reasons mentioned above, I believe that homemade tools or specialized equipment are not necessary for the average consumer. However, some caution is advised. When tightening the piston with pliers, one could inadvertently grab the cuff.

Greetings, E.

That's exactly what I wanted to do today: replace the brake pads. Since I hadn't checked my 'smart book' beforehand, I simply tried to retract the piston with a C-clamp (which has always worked without problems on every car so far). But lo and behold, no chance. Then I completely removed it and looked in the book again, but this offered a 'how should I put it' incorrect or insufficient description. After several attempts, I discovered that the piston can be screwed back in by simply turning it clockwise (without pressure) using a pipe wrench or something similar. Pressure is not necessary. A strange system, I've never seen anything like it.

For the reasons mentioned above, I believe that homemade tools or specialized equipment are not necessary for the average consumer. However, some caution is advised. When tightening the piston with pliers, one could inadvertently grab the cuff.

Greetings, E.

Okay, I always use clamps and pipe wrenches on my IVer, because, as mentioned above, you need pressure and rotation at the rear axle. Building a tool for this isn't really that difficult in principle, but the thread pitch should be correct, and the application should be very simple, since using clamps and a pipe wrench only takes about 20 seconds per piston. So, it wouldn't make much sense to construct a tool that would take longer .

Regards,
Best regards,
Sincerely,
(or simply)
Cheers,

I always use an adjustable wrench for that, but not the large one, just the regular size.
It fits on almost all calipers with 38mm pistons in the rear; you just have to press and turn it at the same time.