Thought I'd write a little article on this as its not been covered for a while. I remember 3-4 years ago someone would be complaining of this all the time.. lol
First of all I want to refer back to a couple of weeks ago when I had some calipers in for servicing that had ALL 8 pistons completely seized....in order to get the pistons moving I had to undo my brake line, attach them up, and use my servo to get some movement in the pistons..... a bit of a nightmare, but hey, that's another topic
After re-attaching my hose and spraying down my calipers with brake cleaner, I noticed as soon as I went out in the car, within a few miles the dreaded (and really annoying) brake hum appeared!...
Ggrrr I thought!.... my conclusion of this was that maybe somehow the brake cleaner had spoilt the lubrication of the pistons over the seals or, perhaps it had caused some copper grease to go in the seal area??? very strange as i didn't even remove any pads...all i did literally was fire brake cleaner around the visable piston area....
The story continues....couple of days later, decided to strip down the calliper in question, re-polish the pistons, clean the seals and clean up the pads etc etc....all was looking good and 'so far so good' on the new stainless pistons too!... no pittng!...
Took the car out and drove up to Wizards Of Nos the next day...and STILL droning on and off like the clappers!......driving me crazy!...
Here are my conclusions to the problem!
1. Condition of the disc and pad shims seem to be the main trigger for this problem!... ..... fitting new pads onto lipped discs may trigger this problem, and also fitting non oem pads without a good shim may also trigger this even worse!...
2. It has NOTHING to do with the condition of the pistons! Or the quality of the movement across the seal....when i had this problem a few years ago new seals and pistons (which was what EVERYONE seemed to recommend at the time) did not solve the problem!.... buying new discs instantly cured the problem
3. Personally, I have only ever experienced this problem AFTER a full caliper service..
4. Out of all the poor condition calipers ive seen and worked on, the owners of such calipers have seldom reported this problem
5. It would appear to me that cleaning the calipers and re-fitting the cleaned sliders etc creates more room in the caliper for the pads to move around! this, coupled with older and slightly lipped discs seems to aggravate the issue even more..
6. Again, poor working and seized caliper pistons generally seem to cause excessive Squeal, not this droning problem!
7. If the noise occurs after a full service, it will probably settle down as the pads find their place again and become more settled on the discs surface. If it doesn't go, skimming the disc may cure it, but new discs may be the only long term fix!
A final tip!.... after a caliper clean, try to keep on the brakes regularly (town driving)... As this will usually get them settled in quicke!. A few country road bedding in sessions is usually a good thing!...
All of this is just my opinion of course. Others may have different views or experiences on the matter.... owners like myself that have had the car for 5+ years now will have almost certainly come across this noise more than once. I would say owners that have the calipers cleaned regularly are far more likely to come across it too
Have fun out there!
Chris
Frp453
This post has been edited by eldoodarino: 16 September 2008 - 07:30 PM