Stones in Brakes - how often?

[Pritchard]

in all my years of driving, i think once i had a stone get somehow stuck in my caliper (between the pads and disc) causing the most awful screech.

 

had my LC for a month.... happened 3 times now. its a real fingernail + chalkboard, except it seems to happen around 20-30mph so the noise is defening.

stopping and putting into reverse for half a meter and you hear a nice 'chink-dink' from the stone falling back onto the alloy and then you can drive off.

 

how is this possible? getting something in that gap while driving must surely be near impossible. unless the discs get very sticky and are sticky enough to hold debris / stones while they speed towards the pads.

[NemesisUK]

In all my driving memory it's only ever happened to me the once, in my 2016 RC300h ...

I also had to stop and reverse a couple of feet to free it.

[Barry14UK]

Not sure if the same applies with Lexus but well known on BMW - at least on my 5 series that small stones get caught up in the backplates with more chance of lodging against rotors.  Had this a couple of times and reversed quite quickly in empty car park and then braked hard.  Stones were ejected.  This is quickest and easiest method although some people use compressed air.

[malcolmw]

I have never had this happen to me in the LC and I live in a rural area with a lot of rubbish on the roads.

I had one instance in my Aston DB9 where there was an intermittent screech from the front brakes which cleared when moved in reverse. It was found not to be a stone but the disc shield just touching the disc after getting bent slightly. An easy fix.

I can't really see how a stone can get between the wear face of the disc and the pad as they almost touch. A stone could lodge between the pad base and the caliper but this must be a pretty remote possibility. The fact that it has happened to you 3 times makes this very unlikely. I should have a look at the disc shields.  

[Pritchard]

cheers guys. not just me then.
its with lexus tomorrow for something else, i might mention it

[Pritchard]

just thought i would add - 3 more in the last few weeks.
It seems whenever i drive over gravel (slowly, mind you! nothing over 10mph), something gets sucked into my caliper. how this is even possible, mathematically i dont know.

When i made this post, it was my nearside front, and reversing would get it straight out.
Now its my nearside rear, and reversing gets it out (by sound), but it doesnt 'drop' out, as soon as i go forward again its being screeched back between the disk and pad.

about to jack the car and take the wheel off to get out this stone thats currently in there. people can hear me driving from 100miles away! its like a banshee

[rich1068]

Bizarre that it's happening so often!

I've had it twice. Once back in around 1989 when I pinched my dad's Mercedes 190E and obviously thought I'd broken it and then the other week in the GS. I can live with once every 30 odd years.

[Pritchard]

3 minutes ago, rich1068 said:

Bizarre that it's happening so often!

I've had it twice. Once back in around 1989 when I pinched my dad's Mercedes 190E and obviously thought I'd broken it and then the other week in the GS. I can live with once every 30 odd years.

agreed. think ive only had it twice in my lifetime before this car.
i just dont get it. the space it has to fit into, the shield guard, the vertical impossible drop from a tyre to a caliper, how is it even happeneing?!

 

[NemesisUK]

Perhaps not related, as there was no sound/screeching whatever but I had this in January

Which has now gone to this after ~1k miles

Dealership advised just to monitor the wear as they checked it over (in January) and found nothing amiss

 

 

[Pritchard]

@NemesisUK that looks like a deep grove!

I found the problem on mine, i'll upload the pics when my telephone is no longer charging, but i had a stone stuck not in the branes, but inside the brake disck shield (around the back). so when i was driving this stone that magically got inside was gouging out a nice grove on the inner disk.
once the wheel was off it was easy to spot, i only needed a little gentle leverages pressure with a screwdriver on the bottom of the cover and it fell out.

But, for a laugh, i tried, and i couldnt get it back in! no idea how a stone of that size got in there to begin with.
Now i know where its getting stuck, i wont need the wheel off again. should be accessible by laying on the floor.

[NemesisUK]

The groove isn't really that deep, I can feel it with my fingernail but it hasn't got deeper, it just looks more concentrated, if that makes sense?