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[skidado]

'98 2.0L CDX manual with 138k on the clock.

Some years back I drove (quickly!) over Breknock Pass in Cumbria and started getting a knocking noise like warped front discs.  I could feel it through the pedal.

Replaced the discs and all was fine for a while, until it started to come back slightly.  Then I drove over the St Gotthard pass in the Alps, and coming down the Italian side the brakes sounded like they were about to part company with the car!!

Replaced them again, but all the time now, with moderate braking at low to moderate speed, I can feel something knocking in a cyclic manner.

I know that the drop links from the front anti-roll bar need replacing (these make a different sound! ), and I'm not convinced that the new discs are warped again already.

What else could be causing this?  Any ideas?

Thanks

David

[rustym95]

have u checkd the berrings, or spining the wheel of the ground, see what sounds u get.

[skidado]

Bearings are ok.  I've jacked the car up and spun the wheels and there is no noise - wheels spin freely.  I've also tried to move every joint in the front suspension, and the only ones that knock are the anti-roll bar drop links.

David

[Ironingboard]

I've got a similar sound, everything suspension wise is fine, but I need to change my caliper carriers since my powdercoating guy went nuts with the sandblaster and took off too much metal, now my pads clunk everytime I reverse, could be a place to look.

I also think my front shock top mounts need to be replaced as well, that could be source of clunkyness

[feeutfo]

so is this noise/knock in time with wheel speed, or random as if over bumps.
If road speed related, and the noise goes when new discs are fitted then comes back, then first question is what discs are you fitting?

[skidado]

Sorry for the slow response.

Yes, the clunk noise is in time with the wheel revolutions.  I'm fitting good quality (but not Vauxhall) discs, and they seem fine to begin with but gradually get worse.

I am very gentle on brakes generally, so it's not due to overheating them.

I wonder if the hubs are running true.  I'll take the discs off and make sure the mating surfaces are clean.  I also have a dial gauge somewhere in my shed - I'll have a go at setting this up to measure the runout of the disc.

David

[skidado]

Update (at long last).

Replaced the anti-roll bar drop links and this quietened the general rumbling sound, but not the main knocking under braking.

Had a mate replace the lower control arms, and hey-presto, all noises gone.  I haven't done any hard braking with warm brakes yet, so I'm not 100% sure that the discs aren't warped, but certainly much better than it was.

I wonder if normal manufacturing tolerances on run-out are enough to excite a knock with very worn LCA bushes...?

Anyway - thanks for your input.  On to the next problem now...

David

[feeutfo]

i've had wobble on the brakes due to wishbone bushes failed but it was a random thing. Ie you could brake hard and all would be well sometimes not, or brake gently and at slow speed and it would feel like the wheels where off a clown car.

Seems to depend if you hit a bump as you brake,  it sets the whole assembly flapping.

[TaxiManDan]

i seem to suffer from this to its doing my ed in