j.kenzie@sbcglobal.net

Hi,
I recently finished replacement of front brakes, rotors and repacked front bearings. I now have very smooth brake action, but I have a "thap, thap, thap, thap" sound that begins about 10 miles per hour, is speed dependent, and blends in with other sounds by 40 MPH. It feels like brake rotor/pad sourced.
The pads are new Pagid, the rotors are Zimmerman slotted. I put a dial indicator on the rotors and they are true to .001". I really super cleaned the rotors and pads with brake cleaner and I tried different bearing tightness, all with no improvement.
Could this be a pad dragging on the rotor? Will it go away as the pads are bedded in?
Any ideas?
Thanks,
Dave

Jim M.

If the rotors are new and you have a dragging bake then you should see some minor polishing or wear on both the pad and the rotor. Is it coming from one side or both? Could it be a stone caught in one of the rotor slots?

Dave928S

In case it is something that has caught in the slots, as Jim suggests, you don't want to leave it there or it'll possibly damage your nice new pads and rotors.

If it were me I'd jack up the front and try and isolate the offending side, by spinning the wheels. If you can determine it's just one side then unbolt the caliper, slide it off, and take a look. If not sure check both sides.

To be speed dependent it has to be something catching on a rotor, if that's the only work you've done prior to this issue.

928mac

Sometimes if a pad is loose it will wiggle in the caliper which can cause a tapping noise.
Some guys use silicone on the back which attaches the pad to the cal/piston and reduces tapping.
If the clips/spring is in place this should not be required

j.kenzie@sbcglobal.net

Thanks guys. I have pulled the calipers and looked at the rotors plenty. Both sides turn smoothly with no sounds, just constant, low friction. These are single cylinder, floating calipers. I used caliper grease on the slide pins, and after compressing the cylinder, I was able to get pads over the rotor easily. I can't really localize the sound very well, left to right or even front to back. How do you get a dragging, floating caliper. Is it just the thicker pad? Will it wear in?
Thanks,
Dave

j.kenzie@sbcglobal.net

Also the tapping sound happens without applying the brakes.

LT Texan

I have a rock stuck between the tire treads that made a tapping sound. Varied with speed too!

longleader

I had that kind of sound. After changing the rotors, pads and wheel bearing I found out it was the o2 counter on the passenger side under the cover if it is an early car try pulling the connector off and take it for a drive. Fixed my problem and I'll bet that could be yours as well

Dave928S

If the noise wasn't audible before the brake job, as I'm interpreting from your original post, then the odds would have to lean towards it being something done in that repair process ... and less likely to be something else that you haven't touched ... but stranger things have happened.

I'm at a loss on providing any more suggestions, other than getting the car up in the air and checking everything. If you can get it on a hoist and safely have the motor running and in gear, you could at least eliminate driveline issues and narrow it down to the front wheels. If driveline is OK then you need to find a way to spin the front wheels up.

Just had a lightbulb moment .... you haven't got a balance weight on the inside of a wheel brushing a caliper have you?

longleader

https://rennlist.com/forums/928-foru...use-panel.html

Melo928

Hi,

I had same problem after changing brake pads and disk in front with same brake model that OP has. Problem was on driver side and even though rotors had same manufacture and right P/N there was difference on groove design. Driver side had longer groove with sharper edge.

My conclusion was that pads where bit loose after brushing all rust out of calibers and when I brake caliber and pads moved forward. Grooved slots from disks hitted internal pad and gave sound especially since groove direction was "leaning forward".

I changed rotors from side to side and that cured problem (Groove now leaning backwards). Not recommending this but it was a quick fix. Just rebuild my calibers and going to test is new rubber parts will do any difference..

-mikko

j.kenzie@sbcglobal.net

Thanks to everyone. I will get the car up on jack stands again soon. I will go around and check all wheels and see if I can isolate sound. I will also look for an o2 sensor counter although I'm not sure my 84 has one.
Thanks again, will report back
Dave

j.kenzie@sbcglobal.net

OK, I finally got back to my noisy brake problem. It was the rear brakes!! After replacing front pads and rotors, the pulsation was gone and the car felt much smoother. I did notice the periodic noise that I described, I could not localize it, and I assumed it was related to the front brake job I had just finished. Well I raised the rear wheels and particularly on the rear DS I had a lot of brake grab due to totally rusted out rotors and worn pads. I ordered new pads and rotors, and when installed, everything is quiet. Really quiet, better than it ever sounded. Thanks for all the suggestions, I'm sure if I had given better information, the problem would have been spotted sooner.
Dave