Thunk thunk on braking

[marcusus]

I've noticed that when I'm going slowly on the brakes, I can hear a repetitive thunking/creaking. It happens periodically and proportional to the speed I'm doing ie if I'm slowing down, the thunks slowly decrease in frequency until I come to a stop. There's no thunking when I'm off the brakes ie if I'm on a downhill and don't apply brakes, I don't get anything, but if I apply the brakes, the thunking kicks in.

Any suggestions? I won't have a chance to have a look at anything until the weekend, so I thought I might get some preliminary info first.

For those that don't know, it's a NB8A without any modifications to my brakes/pads/rims, but I do have coilovers, a front strut brace and a FM butterfly brace. The pads are wearing a bit thin too, but I would think that having thin/no pads would result in a squeal, not a thunk.

[AJ]

bushes??.......sway bar bushes maybe?

[manga_blue]

1. Flat spotted tyre(s)
2. Loose wheel nuts
3. Damaged brake rotor - warped or cracked
4. Collapsing wheel bearing

[marcusus]

bushes??.......sway bar bushes maybe?

Would these cause a repetitive sound only when on brakes? Doesn't seem intuitive for them to do so. If they did anything, it'd clunk once and that'd be it until you came to a stop.

1. Flat spotted tyre(s)
2. Loose wheel nuts
3. Damaged brake rotor - warped or cracked
4. Collapsing wheel bearing

Shouldn't be 1 or 2 because there's no sound if I'm not on the brakes. Although if it's possible that it can be these causing the noise only on brakes, what's the explanation behind it?
I'm guessing 3 and 4 won't be easy for me to check by just getting under the car...

[Sasso]

The track day probably wrecked your brakes. Get them machined and new pads. I'd do it before putting the brake bias valve on too.

[sliq]

i had a problem similar to that marcus. turns out there was a loose wheel nut.

[marcusus]

The track day probably wrecked your brakes. Get them machined and new pads. I'd do it before putting the brake bias valve on too.

It never did it before, and I didn't drive any differently than before. Didn't use the handbrake either. Might be worth getting looked at along with the other suggestions.

i had a problem similar to that marcus. turns out there was a loose wheel nut.

Hmmm... I'll definitely check the nuts. I swapped my rims over on the weekend. I'm just surprised that it only makes a noise when braking rather than all the time. I might go tighten them up now since that one's quite easy to do.

Any other suggestions?

[manga_blue]

1. Flat spotted tyre(s)
2. Loose wheel nuts
3. Damaged brake rotor - warped or cracked
4. Collapsing wheel bearing

Shouldn't be 1 or 2 because there's no sound if I'm not on the brakes. Although if it's possible that it can be these causing the noise only on brakes, what's the explanation behind it?
I'm guessing 3 and 4 won't be easy for me to check by just getting under the car...

I've had flat spotted tyres. Track day is the easiest way to get them. They were only obvious at low speed and on the brakes. Don't ask me why.

[marcusus]

^^^
Interesting. The good thing is these are my spare set of tyres which are going to be replaced by something a bit grippier for the track. However, I didn't take these tyres to the track recently (although they've been on the track before). Can you be a bit more descriptive with the noise you were experiencing so I can compare? Mine's more of a creak/groan combined with a thunk. It kinda sounds like something is flexing.

I tried tightening all the wheel nuts. None of them were loose, but they're all now extra tight. It didn't make a difference, but it was worth a shot.

[Sasso]

flat spots go thunk thunk, well if you have a busted axle anyway. But the whole car would be vibrating if you had a flatspot.

[marcusus]

flat spots go thunk thunk, well if you have a busted axle anyway. But the whole car would be vibrating if you had a flatspot.

I should probably take you for a quick drive and see what you reckon it could be...

Meanwhile, could this be a likely cause?

[Sasso]

prolly saturday or wednesday night, come pick up the brake valve too.

[marcusus]

prolly saturday or wednesday night, come pick up the brake valve too.

Well tonight's no good. And I might be rather hungover on Saturday, but I'll see. If I'm intact enough to go for a drive, I'll let you know.

Any other suggestions from anyone?

[philz]

From the brake pads thread, so we don't interfere with the thread topic.

Hmmm... mine's more half half. It groans a bit when it does it on mine. Does yours do it proportional to the speed you're going?

Well while driving it's less evident, because you have much more road,tyre,wind and outside noise.
But if you listen closely you can just hear it when it goes over uneven road, with the "thunk"

It's much more noticeable if you are going really slowly- say a car park for example, doing speed of less than 10km/h, and if the concrete slabs aren't joined together properly, you'll hear a thunk thunk, or clunk clunk, once you go over the uneven bump,oOr over a speed hump.

So I would say its proportional to the speed, because if I'm going 60km/h then thunk will be faster.

[Sasso]

From the brake pads thread, so we don't interfere with the thread topic.

Hmmm... mine's more half half. It groans a bit when it does it on mine. Does yours do it proportional to the speed you're going?

Well while driving it's less evident, because you have much more road,tyre,wind and outside noise.
But if you listen closely you can just hear it when it goes over uneven road, with the "thunk"

It's much more noticeable if you are going really slowly- say a car park for example, doing speed of less than 10km/h, and if the concrete slabs aren't joined together properly, you'll hear a thunk thunk, or clunk clunk, once you go over the uneven bump,oOr over a speed hump.

So I would say its proportional to the speed, because if I'm going 60km/h then thunk will be faster.

Sounds like wheel bearing or that area, I have similar sound, it clunks, check if the wheel has any amount of play in the camber plane. I changed the bearing but didnt fix it.