Brakes creep-groan

[adurer]

Definition: brakes creep-groan (BCG from now on) is that low frequency noise coming from brakes when your car is on a slope and you're lightening your foot on the brake to let the car roll very slowly with the brakes still engaged.

 

BCG is present on many cars, even on expensive ones. The noise is quite annoying giving the impression you're not driving a car but a rusty old wheelbarrow.

 

So my question is this: did anyone find a cure to this problem?

[@Lee]

Take your foot off the brake or apply the handbrake I know the sound you mean, it's present in the same situation on my 2003 Fabia and SWMBO's 2013 Yeti. It's a mechanical/ friction/ suspension kind of BCG.

[adurer]

Yeah, BCG is definitely coming from brake pads - rotor friction / vibration that resonates through caliper, wheel hub and struts. Some car manufacturers state it's normal (aka we don't bother finding a solution, the car owner has stress issues).

[@Lee]

Yeah, BCG is definitely coming from brake pads - rotor friction / vibration that resonates through caliper, wheel hub and struts. Some car manufacturers state it's normal (aka we don't bother finding a solution, the car owner has stress issues).

I think we need to find a Bentley/ RR owner and see if it's present on their lesser cars

[adurer]

I think we need to find a Bentley/ RR owner and see if it's present on their lesser cars

I know deep inside they envy us, Skoda owners, but they're doomed to stick to their fancy cars with seats massaging gently their royal balls while driving.

 

Now seriously, there are tons of forum topics for BMW, Toyota, Audi, etc that show people's concern over this low comfort issue. I have just read an article that explains in a rather rigorous scientific language how the BCG noise is created. In short it is called the Stick Slip excitation mechanism and I quote:

 

 

As suggested by the name, stick-slip consists of two phases, stick and slip. During the stick phase, the brake lining and cast iron move together, with no slippage at the interface. Eventually, the windup of the brake assembly causes a momentary slip phase. The stick time period is variable, depending on speed, load, and system stiffness. When slip begins, a noise burst occurs. The sudden energy burst often produces a more sustained audible oscillation. Most stick slip oscillations are of the rigid body form, so have low frequencies. Stick-slip in brakes generally is confined to creep-groan and similar low speed rigid body vibrations. Vehicle speeds are normally under 2 mph for brake stick slip.

 

 

Coming back to Earth, I wonder if:

 

1) Changing pads brand does make a difference ?

2) Changing rims helps dampening the noise?

[fordfan]

I noticed it on my car the other day, so we can establish that it's present on superior cars, maybe you could borrow SWMBOs car Lee to check out the lesser car theory .

 

Seriously it may have something to do with the pad/pad carrier clearance, I'd rather have the noise and unrestricted movement of the pads, than the silence and sticking pads.

[@Lee]

I know deep inside they envy us, Skoda owners, but they're doomed to stick to their fancy cars with seats massaging gently their royal balls while driving.

 

Now seriously, there are tons of forum topics for BMW, Toyota, Audi, etc that show people's concern over this low comfort issue. I have just read an article that explains in a rather rigorous scientific language how the BCG noise is created. In short it is called the Stick Slip excitation mechanism and I quote:

 

 

 

 

Coming back to Earth, I wonder if:

 

1) Changing pads brand does make a difference ?

2) Changing rims helps dampening the noise?

I dunno. You're weirder than I am :( Have a search for friction

[Red Studio]

It's always the front brake when I hear it. Is it something that affects disc brakes but not drums? I suupose it's a similar effect that makes the noise when you run your finger down a wet window. Come to think of it, maybe even that awful noise old windscreen wipers make is related. It certainly fits the description as they appear to stick then slip rather than moving smoothly.

 

I never even considered it would have a name but every car I've owned has had it. At the risk of joining the weirdness top ten - that noise can entertain me for quite some time when stuck in traffic on a downhill.

[adurer]

At the risk of joining the weirdness top ten - that noise can entertain me for quite some time when stuck in traffic on a downhill. 

That is exactly the situation when the groan is most annoying. The only thing that makes me live with it is there are more expensive cars that have it too. New Toyota Prius owners yelled in vain for a solution because they got BS answers like 'it's the brakes recuperative system' (aka we will not issue another comeback after throttle pedal disaster), American car owners are told it's good to have BCG because it's a reassuring sound meaning 'you still have brakes'   and so on.

 

I am curious if Felicia original buyers had BCG with factory discs/pads...

[KenONeill]

The basic problem is resonance between pad, disc, and sometimes dust shield. You can sometimes cure it by any of:-

1. Fitting adhesive-backed pads that actively stick to the pistons.
2. Fitting new "anti-squeal shims" (but only if the specific calipers had them originally).
3. Throughily cleaning the calipers.
4. Applying copper grease to the pad backplates.
5. Changing the make of friction material you use.
6. Removing the dust shields.

It's also been observed on drum brakes (most usually on FX4 "London Taxis", by which I mean the original 1960s and 70s vehicles, or on heavy trucks with drum brakes).

[adurer]

Thank you for reply, Ken. All solutions make sense in general. Let's discuss which one is more probable to cure BCG.

 

1. Fitting adhesive-backed pads that actively stick to the pistons.

A very good solution in theory, but not applicable to Felicia without changing caliper design. Furthermore there are no such pads, not to mention that if they stick to piston, it will be very hard to remove them when they are worn.

2. Fitting new "anti-squeal shims" (but only if the specific calipers had them originally).

Felicia doesn't have such shims, but has steel wires attached to pads. Problem is they only cure high pitch vibrations, not BCG.

3.Throughily cleaning the calipers.

Now this is a good one. We all know what rust does to pistons and from what I have read, BCG is not present in new shiny cars, but as soon as they rust a bit.

4. Applying copper grease to the pad backplates.

I already did that, but didn't help for BCG. Again it's only good to cure high pitch noises.

5. Changing the make of friction material you use.

I was expecting that to be a solution. I will surely investigate more before buying my next brake pads. Meaning I will address BCG problem to manufacturers and I will ask about it on foreign Felicia forums (Czech, Polish, Romanian, Russian).

6. Removing the dust shields.

I presume we're talking about the anti-splash shield. Well... I wouldn't go that far because that shield protects not only against dirt and/or water, but also against rocks on unpaved roads. Yes, the shield can resonate, but we have to cure the initial source of BCG.

 

Bottom line, I will polish the pistons of calipers just to see if that makes a difference till they start to rust again. I will also check for better pads.