Suspension noise

[Ian21401]

I think that we are discussing the “guide pins” for the calliper which locate into the calliper bracket, and
the bolts which secure the calliper bracket to the hub carrier.
That’s the second time recently that I have come across the term “patch bolts” and yes, many of the OE bolts which I have bought from my dealer have been patch bolts.

[capt jack]

Yes, it’s the sliding guide pins, the ones that move within the calliper bracket , and then the two bolts which hold the bracket to the hub. There are of course two more bolts involved. These are the smaller ones which bolt through the floating calliper body and into the guide pins. These are the only ones removed to change the pads. They don’t do any more than locate the guide pins.

Took the car out yesterday and the noise has stopped, so I’m now certain that the low speed knock is definitely the floating calliper body moving slightly because the upper guide pin has a little bit of play as it sits within its bore. The additional brake grease is enough to cushion that bit of movement.

And of course Ian is right. The only permanent fix is a new carrier bracket.

I wonder if perhaps at some stage before my ownership that pin had seized, and then been freed and replaced. The bore would have been cleaned out but left a little oversized. With new pads and grease this wouldn’t have presented a immediate problem, but over time the fact that there was a tiny bit of movement in turn accelerated wear in the bore. The guide pin is a hardened steel I’d guess, but the calliper bracket is a casting. Either that, or it’s just the accumulated effect of almost 25 years of use that has eventually highlighted a tiny discrepancy in the dimensions of two components that articulate one within the other.

Again, thanks for the input and discussion.

Cheers

Jack