Rock in Disk Brake, Sounds Horrible

Question

Short Back story: I bought a Honda Ridgeline Second generation (2016 - current), 11,000 miles from the dealer, with a state inspection performed on the purchase date. The next day and a maybe 35 miles later...

Suddenly there is a loud noise coming from the back, it sounds like I am dragging a tin can. There is nothing visibly wrong, extensive safety check completed on road side. I am with in 2 miles of the dealers, so I return. (slightly stressed and anxious)

I just traded in a Second generation (2009–2015), with 100,000 miles that I put on myself, without ever hearing anything like this

The dealer identified the sound immediately as rock in the rear disk. He took it in the shop and in 5 minutes the sound was gone, and he had a tiny pebble that they removed without tools. Apparently it gets into a hollow on the disk brake like rocks used to do on hubcaps.

I googled around and found a couple of similar events to other Ridgelines in the same generation. I also found that it happens on other cars as well, some being more prone to it then others.

Questions:

1. Is there any danger from driving with this rock in there, or is just noise? I assume like a rock in your hubcap or tire tread, annoying but not life threatening.
2. If I leave it in there, how long before it comes out on it's own?
3. Is there any physical reasonable vehicle modifications that can lower the probability of this occurring? (i.e. a special shield)

This is distinicatly different then the related quesion rock groove on brake rotor OK? where the rock is between the pad and the disk.

Answer 1

1.Is there any danger from driving with this rock in there, or is just noise? I assume like a rock in your hubcap or tire tread, annoying but not life threatening.

The noise level would probably stop you leaving it there for long enough to do much damage. Most rocks are softer than steel.

Actually rocks in tire treads can be life threatening, if they gradually cut through the rubber and eventually cause a blow-out, and you don't usually get any warning about rocks in tire treads, unless you look for them regularly.

2.If I leave it in there, how long before it comes out on it's own?

Who knows? It depends on the shape of the rock, how fast it gets worn down, how many potholes you drive over to shake it loose, etc, etc.

3.Is there any physical reasonable vehicle modifications that can lower the probability of this occurring? (i.e. a special shield)

Not really. Having had one, you probably won't get another one in your driving lifetime anyway. Half a dozen events posted on the web, compared with the millions of vehicles on the roads every day, should tell you how common (not!) it is.

FWIW I've had one in a car (in 40 years of driving) and I sympathize with the level of panic it induces when a loud noise starts up with no prior warning that anything might be wrong!

Answer 2

Any possibility of a picture of the brake with where the rock got stuck circled? A small pebble will not lock up the wheel of a car but i suppose it would be possible for a rock to be lodged in a way that it doesn't allow the caliper to compress(you would still have the braking power of the other 3 wheels). Unbelievably unlikely and even more so for all 4 wheels to do this simultaneously. You could certainly fab up a little shield but that is more complications every brake job to mitigate something astronomically unlikely.