Caliper pin backed out

[dms-01]

Does anyone have any idea what would cause this?

I installed OEM Red calipers and pads like 30k and 3+ years ago. Over the past week I was feeling a shudder when braking and when I got my oil, brake and diff fluid changed I asked them to check that area and they sent this picture.

You can see the retaining clip is still there but the pin has backed out far enough that the top section of the inner pad was floating.

[gunsmoker]

The clip needs to be positioned between the indentations of the pin otherwise I am affraid it can come out.

[dms-01]

For sure it was but who knows at this point.

[TractionControlDelete]

Originally Posted by dms-01

For sure it was but who knows at this point.

This has been an issue before:

https://f80.bimmerpost.com/forums/sh....php?t=1810412

So one thing that stands out to me is that it's pretty common on the F8X platform for owners to re-use the guide pins. I can completely understand why it's tempting to reuse them frequently in light of the fact that pad changes are so convenient (I'm guilty of it too). However, in past generations of BMWs the service manual instructed the user to replace the used guide pins with new ones. I can attest to BMWs as old as 1986 using this practice. I'd have to look to see how they recommend dealing with the F chassis pins but I wouldn't be surprised at all if they are single use.

[dms-01]

I can't remember if I reused them because when I bought the brakes they came with new everything. Either way my wife's car has the same setup and no issues there after replacing her pads and reusing the pins.

[JAI///M3]

Tha caliper pin and spring clip are designed to prevent this from happening when fully seated. I would suspect this pin was either not fully seated or the pin and/or spring have worn to a point where they will not lock and need to be replaced.

[dms-01]

Originally Posted by JAI///M3

Tha caliper pin and spring clip are designed to prevent this from happening when fully seated. I would suspect this pin was either not fully seated or the pin and/or spring have worn to a point where they will not lock and need to be replaced.

Yeah like I said it's a pretty simple mechanism. Why it backed out after so many miles I don't know.

[JAI///M3]

Just a guess but from the picture it looks like the spring clip isn't centered within the caliper opening. It's possible that when the upper pin was tapped into place, the spring was interfering with the pin and slid outboard with the pin. If this happens and the spring clip isn't re-centered, it seems like it might be possible that the pin will not lock into the clip and eventually work it's way out after repeated use of the brakes.

Again, just a guess but also something I observed as possible after changing pads recently. I went back and made sure the clips were centered top to bottom and left to right in the caliper ensuring the pins were fully engaged.

[melanthius]

Could be simple metal aging stuff like metal stress relaxation and fatigue - it's literally held in by spring force + friction - that can wane over time.

It's relatively cheap and easy to get new pins.

As an engineer I really hated the F8X caliper pin design for exactly this reason. I much prefer cotter pin style where the pin cannot physically back out. And from BMW perspective, yeah all their engineers have to do is enforce replacement in the service manual, then this problem won't happen. What do they care if customers have to spend a few extra $ during a service visit.

[dms-01]

Keep in mind that pic is from when the problem was discovered and an unknown number of miles since it broke loose. I only noticed it when it backed out far enough to cause a wobble/vibration when braking at speed so that clip without doubt was moving around along with the inside pad.