Brake piston retraction

[fixitflav]

I have an Hyundai i30 with rear brake below.

Looks like it needs a tool to retract the piston, and found this on eBay for about £10. But I'm curious, as it says it's good for "calipers fitted to most cars with right hand thread". As the brakes are mirror images, I don't see how it can be right hand for both sides of the car. The handbrake lever on the caliper is above the axis, so on the LH side when applied it turns CW looking from the inside, so the mechanism must have a LH thread. So to retract the piston it must be turned ACW (and CW on the RH side). As it's got the important bit, to engage the slots in the piston, I'm pretty sure it could be used either way, but interested in any comments.

 

[Burnerman]

Normally these pistons aren’t handed ( Mondeo being an exception, depending on the age) so they screw in clockwise on either side.
I’m sorry I can’t see your pics, but most Kia / Hyundai systems have a disc/ drum system on the back. If yours has this, the pistons just push in.
John

 

[Burnerman]

I’ve managed to see the pics on another device, and yours has the handbrake on the caliper, so keep the retractor tool nice and square and gently turn the pistons in.
If you attempt to turn the wrong way, the pistons won’t have it, and indeed try to expand out a little.
John

 

[jj4091]

Normally these pistons aren’t handed ( Mondeo being an exception, depending on the age) so they screw in clockwise on either side.
I’m sorry I can’t see your pics, but most Kia / Hyundai systems have a disc/ drum system on the back. If yours has this, the pistons just push in.
John

Hello John, sorry nothing to do with the post but wanted to ask if you are having problems not seeing pics. in all posts & avatars also. My Mac book has had this problem for a while now & someone suggested it was it was because it was an old level of software, but it only happens on this site so I'm really puzzled.

 

[fixitflav]

Normally these pistons aren’t handed ( Mondeo being an exception, depending on the age) so they screw in clockwise on either side.
I’m sorry I can’t see your pics, but most Kia / Hyundai systems have a disc/ drum system on the back. If yours has this, the pistons just push in.
John

Thanks John, interesting that they go clockwise on either side. The online manual only shows clockwise. I can't see how that works, unless the calipers are different (not just mirror image) but I must be missing something. I'll have a good look next time I get it over a pit. I can confirm on the (2004) Mondeo they were handed, I had one for years. Still miss it!

 

[Burnerman]

I have a truly ancient iPad which I use away from home, and recently it’s been occasionally difficult to see pics - I’m too tight to update it though! It doesn’t do emojis either.
I did fit some rear pads to a Hyundai late last year, and I don’t recall any issues with the piston rotation.....in fact my left hand retractor hasn’t been used for years.
Anyhow, carefully does it and all will be well.
John

 

[fixitflav]

I did fit some rear pads to a Hyundai late last year, and I don’t recall any issues with the piston rotation.....in fact my left hand retractor hasn’t been used for years.
Anyhow, carefully does it and all will be well.

OK John, thanks again

 

[Bodgedbuild]

I believe you may be misleading yourself on how an integrated parking brake caliper actually works vs why the piston requires rotating to get to to go back in but essentially the rotation of the parking brake lever does not rotate the piston, rather there is an adjuster behind the piston that is designed to hold the piston in a fixed position close to the brake disc even when there is no fluid pressure.
What there is is basically a ratcheting system that requires the piston to be rotated to push it back in but this system uses linear (straight push) motion when either the parking brake or fluid pressure pushes it out. A "cam" actually converts the rotational motion from the parking brake arm to straight linear motion which then pushes the piston and its adjuster straight out. That lot sounds confusing but this video, although slightly rubbish, might help.....

 

[fixitflav]

I believe you may be misleading yourself on how an integrated parking brake caliper actually works vs why the piston requires rotating to get to to go back in but essentially the rotation of the parking brake lever does not rotate the piston, rather there is an adjuster behind the piston that is designed to hold the piston in a fixed position close to the brake disc even when there is no fluid pressure.
What there is is basically a ratcheting system that requires the piston to be rotated to push it back in but this system uses linear (straight push) motion when either the parking brake or fluid pressure pushes it out. A "cam" actually converts the rotational motion from the parking brake arm to straight linear motion which then pushes the piston and its adjuster straight out. That lot sounds confusing but this video, although slightly rubbish, might help.....

Thanks for that, interesting.

I realise the piston does not rotate, and there are pips on the pad backing plate to engage with the notches in the piston to prevent it.

If I’m reading the video right, the arm appears to rotate about an axis perpendicular to the piston axis, but I think that must be for illustration purposes. On the Hyundai (and the Mondeo) it’s inline, as in the pic above.

My logic was that as the arm turns CW on one side and ACW on the other, the mechanism must be handed. So retraction would be CW one side, ACW the other (as on the Mondeo). If it’s CW to retract on both sides of the car, I assume there is a clever mechanism (as you’ve described) which moves the piston to apply the brake, separate from the adjustment part, which has a CW thread both sides.

I’ve only worked on this type of caliper on the Mondeo, before that I had company cars for 25 years, and before that had drums on the back, and sometimes the front as well.