Post Number: 72
|Posted on Friday, 09 June, 2017 - 08:38 pm: |
Went to Ipoh last weekend, rolling along nicely at 120-150kmh...on the way back i got a speed related vibration. Once back at home I could see a thin strip of metal hanging down from the right rear caliper assembly rubbing on the tire...started to think of catastrophic wheel bearing failure as the only thing that might spit out lumps of metal.
Tonight I had a chance to look & found two unrelated and relatively trivial problems!
The wobble was caused by a left rear failed tyre...large bulge on the inside...only a few years old & with correct speed/load ratings..just bad luck.
On removing the right rear wheel I found the metal piece was the remains of the metal band that is secured around the periphery of the rear brake disc. This band has somehow dislodged/snapped & fallen down but remained trapped in the brake caliper & just dangling.
The brake disc looks in good condition otherwise, thickness measured at 0.489 inch, i understand original is 0.5 & wear limit 0.4inch.
So my question: Whats that band in the edge of the disc for?? some anti-shudder invention?? Will driving without it cause distinctly un-RR behaviour? Should I remove the band from the left rear disc to preserve symmetry? I know changing these discs is a rather significant job...if possible I would like to spend my time elsewhere on the upkeep of the car...
dave SRH4452 '68 Shadow
Post Number: 63
|Posted on Saturday, 10 June, 2017 - 01:51 am: |
It's a sort of damper. The friction between the band and the disc helps absorb the vibration energy generated when the brakes squeal. If the brake squeals you need it, if not, not.
Post Number: 74
|Posted on Saturday, 10 June, 2017 - 08:57 am: |
Thanks Alan, I will test drive it today and see if I can make it 'sing'..I put new discs on the back of a Jag a few years back and they would resonate quite tunefully when new...now its all quiet after some bed-in & wear.
gordon le feuvre
Post Number: 193
|Posted on Saturday, 10 June, 2017 - 05:54 pm: |
I AM SURE THAT IF YOU LOOK CLOSELY, BEHIND THE METAL BAND IS A WIRE CORE WOUND AROUND GROOVE IN EDGE OF DISC WHICH IS COVERED BY METAL BAND. THIS WAS TO STOP BRAKE SQUEAK. LATER? CARS DID NOT HAVE THIS AS IT WAS FOUND SOLD DISCS WORKED.
Post Number: 64
|Posted on Saturday, 10 June, 2017 - 06:07 pm: |
Interesting, Gordon. The catalogue shows the disk as an "assembly" so RR says that the band can't be replaced, but it may be possible to replicate the effect with a welded strip of metal. David, is the inner wire component still there? That may be the bit that does the business, or it may be too fragile to endure without the protective outer band???
Post Number: 75
|Posted on Sunday, 11 June, 2017 - 12:49 am: |
I couldnt see a wire band. The edge of the disc is quite badly corroded,the rust doesnt extend into the swept area, but I could see no sign of a wire. I did wonder about grinding the outer perimeter of the disc to clean it up...but felt since it is working fine as-is it is best left alone. Thanks Gordon for the insight into the construction...looks like another piece of over-engineering. I work for a german company making components for the automotive industry so i recognise over-engineering....
Post Number: 75
|Posted on Sunday, 11 June, 2017 - 04:27 am: |
My bands separated from both rear discs and wrapped around the half shafts. I removed them and drove on and don't notice any adverse effects without the bands. When I had been working on the hydraulics I removed the rear wheels for easy access to the bleed screws and rested the car with the brake discs on timber blocks, I suspect that this is what caused the metal bands to separate,
Robert Noel Reddington
Post Number: 1453
|Posted on Sunday, 11 June, 2017 - 06:18 am: |
When disks were first introduced they had loads of problems with squeal. Dunlop spent ages getting them right.
Because of this Crewe carried on with drums until 1965 and even then Crewe wrapped the egde in wire with a band to hold in place.
Modern materials and the design of the pad shape has largely cured the squeal problem.
So not to worry if the wrappings fall off.