Dutchman said:
Thanks Clive.........
Are they black in colour or copper.........?
OE are copper backing plates, the ones I've just purchased have the same part # you've just quoted and are black painted steel.
The 1200 OE ones are supposedly made of copper to stop the squealing (and avaoid the use of creeping grease............?
Same shape, different material................?
We need to be told................
(I'll post some pix when I sober up...............late Jan/Early Feb)
Cheers
Dutch
Just applying basic engineering and bike experience, perhaps the colour change is not so drastic. Anyhow each generation of engineers at BMW or wherever has to relearn what their fathers forgot 30 years earlier. For sure they will not read or follow the company engineering good practice standards unless held at gun, or salary, point.
So, copper or just copper coloured as with lots of Jap bikes etc???
It makes neither engineering nor commercial sense to make backing plates of elemental copper. The damn things would expand at a rate so different to the other metals in proximity that buckling would be quite likely, and the cost would be probibitive. And that would deter any manufacturer.
Copper or nickel are used in anti sieze compounds, such as grease for brakes, because they handle the temperature but do not gall(attack and bond to)the steel components with which they are in intimate contact at elevated temperature. in our world it is a surface phenomena so we do not need, or want, solid parts made of expensive materials which do not exhibit the surface or structural qualities we require. This is a super gain on our part due to the molecular qualities of these materials working together at low cost.
One example of how not to do it is titanium, in almost any stress bearing joint, as a nut or bolt etc with a steel(or other metallic)mating component, especially at temperatures above ambient.
Titanium has a strong affinity for other metals and galls while you are tightening the thing, especially without anti sieze lube. At temperature it turns to oxide(Moo3) faster than any otherwise stable metal. That is why corrosion with Ti is usually no problem as it forms an oxide skin instantaneously so preventing further reaction with chlorides(salt)etc. This is the reason that welding must be done with a shielding gas to exclude oxygen as molten titanium will not be able to bond with titanium oxide so no welding takes place. Same for all metals but we have developed different methodology.
The two daftest applications I can think of, off hand, are exhaust fasteners and brake line banjo bolts. But no doubt the aftermarket gannets will think up a few more to make a crust on. Sadly, having little or no engineering knowledge, ability or conscience, they usually have no idea of, and no care for, the potential problems they create.
Anyhow we should not be concerned if BMW or others use black paint or copper looking coating on the disc pad backing plates, they are all mild steel and will work fine. And a little copper lube just may stop the squeal. But we should not bet too heavily on it as the cause can be in the metallurgy of the disc material.
