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Front Wheel Knock

ALC 68A

Donation Time
One of my front disc brakes has developed a regular knock/tap noise with each revolution of the wheel. I've had it looked at by a Sunbeam specialist workshop here in the UK, and they tried copper grease on the backs of the pads, but were unable to fix it. It is definitely linked with the brakes, because a light application of the pedal stops it for a short while. The workshop's opinion is that it is caused by the disc pad being knocked back slightly against the caliper, due to wear in the caliper (which are rebuilt original ones, rather than new) and a slight eccentricity of the wheel or disc as it rotates. Does this seem feasible? I had the front wheel bearings changed recently, so I'm wondering if that has anything to do with it. I don't think its a serious problem, but it is annoying. Any suggestions please? The car is an S3, but as the calipers are rebuilds, I don't know what series they were from originally. Regards and thanks. Steve
 

sunalp

Diamond Level Sponsor
Can't tell for sure, but your avatar photo looks like you have wire wheels. Is this correct?
If so, you may have a worn hub/wheel combo that is giving you the knock. I know if your
lug nuts on bolt on wheels are loose, they'll knock while driving and applying the brakes
too. If you haven't check that, you should to at least rule that out.

Hope this help,

Steve
 

alpine_64

Donation Time
Id say its missing the reatining pins for the pads.

You would get a clunk sound under braking and occasionally feel it in the pedal as the movement takes up.

There will also be a squeak with rotation of the wheels especially when you first drive and the pads are cold.. If you apply the brakes lightly the squeak will go away.

Id guess thats the issue
 

Jimjordan2

Donation Time
It appears to me that Steve meant that it's a constant, with every rotation of the wheel. Not necessarily while braking. Is that right? If it started after the wheel bearing change, something there would be suspect to me. Gotta think about this.
Possibly a nick in the rotor? Just a far out idea.
 

alpine_64

Donation Time
It appears to me that Steve meant that it's a constant, with every rotation of the wheel. Not necessarily while braking. Is that right? If it started after the wheel bearing change, something there would be suspect to me. Gotta think about this.
Possibly a nick in the rotor? Just a far out idea.
He does say knock and tap....

I know if the pins are missing the offending side will have a squeak or tick with each revolution of the wheel that inceases with speed.. If you lightly touch the brake while driving it will go.

The pad will then "knock" or clunk on applying the brakes to stop as the movement takes up.

Couod be rlthe wheelsl bearing but he also had the calipers rebuilt and often people dont have access to or fit the pins
 

ChrisR

Donation Time
I have a very similar issue. Very light tapping/tick sound (not a clunk) that goes away when I just touch the brakes. Cannot feel anything through the steering. Jacked up the front and spun the wheels. Nothing, but that was not straight after a drive. The sound does not start right away, I can hear it after a couple of miles of driving which would mean a few applications of the brakes, which suggest it is maybe brakes rather than bearings. I checked the calipers. Pins and pad backing shims are all there and greased. Nothing appears stuck or seized. Brakes work well. (no trouble locking the wheels when I brake hard). Going to try and isolate if it is one side or both. Probably need to get somebody to drive while I hang out the passenger side and listen. Likely going to be my 1st winter project. Will check the discs for flatness. Rebuild the calipers (No idea when or if they were last done by the PO). Maybe as a last resort, renew the front bearings as they are fairly straight forward and available.
 

ChrisR

Donation Time
This weekends investigation revealed that the disc is causing the pad to knock against the retaining pins once per rev. I have a pretty good video with the sound but have not worked how to load. The holes in the pads are slots so clearance between the pin and pads cannot be the issue. Pads have lots of material left. Have not checked flatness of discs yet. (No dial indicator handy). It is puzzling because if the disc moves the pad tangentially in the directzion of rotation, what causes the pas to move back again?
 

Gordon Holsinger

Diamond Level Sponsor
This weekends investigation revealed that the disc is causing the pad to knock against the retaining pins once per rev. I have a pretty good video with the sound but have not worked how to load. The holes in the pads are slots so clearance between the pin and pads cannot be the issue. Pads have lots of material left. Have not checked flatness of discs yet. (No dial indicator handy). It is puzzling because if the disc moves the pad tangentially in the directzion of rotation, what causes the pas to move back again?
It sounds like a warped brake rotor
 
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