Clonk on braking

[Iain]

Recently my Nova has been making a loud clonk from the front when braking quite hard. You can feel it through the cabin/through the brake pedal

Doesn't seem to do it all the time, and I have a theory it may only do it after sharp acceleration (where I've felt a slight clonk once or twice as well) then stamping on the brakes but haven't proved this yet.

Setup on the front to help diagnosis:

ATE calipers with new pads (did it with the old pads too though)
Poly bushed lower arms
Standard lower balljoints
Lowered tiebar brackets with spherical bearings
Gaz coilovers with eccentric bearing topmounts

All new 4000 miles ago.

Any suggestions would be most welcome, I've inspected it in the air and can't see anything obviously wrong (like the tiebar nut loose or anything daft like that)

Cheers

[Andy]

My escort van does exactly the same,only at low speeds though,i reckon its either the pad moving and or the caliper on the holder

[Iain]

This will need a fair amount of braking force to do it but when it does it sounds horrible

Had both calipers off recently for the new pads so they're definitely torqued up correctly.

[Steve0011]

i suppose the only thing you might not have checked is loose anti-roll bar and/or tie bar

[Riggy]

i had something like this , it turned out to be the bottom arm to ball joint bolts , they stretch and after been undun a few times dont quite go tight enough , even though they felt tight , changed them and the noise went

[marc69]

I had this before after rebuilding calipers, although I had tightened the up when putting them back on, they both seemed to slack slghtly after a few weeks, perhaps worth checking. A loud clonk only on hard braking.

[Iain]

Cheers guys will get my spanners and torque wrench out tonight and double check everything. Will grease up the bushes/bearings and see if it helps also

[Lee H]

I had this with front tie bar polybushes before. The sleeve in the centre of the bush was too long meaning the nut was fully tightened without the washer sandwiching the bush properly and allowing it to slide back and forward in the bracket under acceleration and braking.

Edit - just noticed you are on Rose joints. Just check these aren't sliding in the bracket slightly though.

[Iain]

Will do Lee cheers.

[Steve0011]

my moneys on the tie bar :) any takers :d

[Iain]

OK had it up on axle stands, one of the four lower arm/tiebar/balljoint bolts felt a bit looser than the rest but nothing else out of the ordinary - maybe that was it.

Have cleaned and lubricated the tiebar brackets and lower arms now so will take it for a spin later and see if it's gone.

[craig green]

I've had this with caliper bolts & tiebar bolts..........

[Iain]

Think the above has solved it! So it was either the loose(ish) lower arm bolt or things needing lubricating.

Thanks guys.

[Riggy]

Iain , i found that it would keep coming loose as the threads have stretched abit and the knock came back , i bought new bolts in the end , not done it since ,

[Iain]

Cheers riggy ill keep an eye on them. They are loctited and ft but can put some new ones in if needed

[Will F]

I have the same issue - I am interested in Lee's suggestion re the tie bar bushes - How did you sort it Lee?
(sorry to hi-jack)

I have changed everything!!! lol

[Lee H]

I just trimmed a bit off the sleeve that goes through the centre of the bush so it was a little bit shorter than the bush.

This allowed the washers to clamp up on the bush before they bottomed out on the sleeve.

I was using the yellow Rally Design bushes when I was having this problem.

[Will F]

Cheers Lee - replied to your PM, I did notice that the bush looked a bit odd and tried the nut which was tight - that would explain it!

[Iain]

Will I might have some bushes not currently fitted if you want me to check the insert measurement for you

[Will F]

That would be awesome mate - cheers

[Iain]

Sorry for the delay Will it's 35.5-35.6mm long for the tiebar insert.