Rear Discs on E220(124) - Bands of rust around face

[Jim Gallagher]

During a full tyre change today I noticed that the rear discs, on my '94 E220 had a 5mm band of rust around the inner and outer most diameter of the disc face. The front discs were "shiny" on the full disc surface. How long will these discs last before they need replacing, assuming the rust will spread. How much to replace a pair of discs ?

 

[pmac1]

Rear Discs on E220(124)

hi jim,
just replaced rear discs and pads on
my 190e,total cost was £70 for genuine parts
from merc dealer.diy fitting only took 1 hour for
both sides.makes a world of differance.

 

[Arnie]

Rear Discs on E220(124)

The "bands of Rust" are there because the pads work only on the central part of the disc leaving this inner and outer 5mm margin that is not covered. This is normal. However, because the rear discs tend to do less work than the front ones, they can get replaced less frequently and over time salt spray etc will cause the edges to corrode. This rusting should not spread to the pad swept area of the disc, but after a while, it will eventually cause the edges of the disc to errode away as rusty flakes. Ususually, if vented, the inner vanes will also be rusty and flaky.

It is better to change the discs regularly before it gets too bad.

You might notice that after you wash your car, even the shiny area of the discs will form a very light rust covering which then is wiped off next time you use the brakes.