54.1 vs 55.0 mm
After fitting the ST205 rear brakes on my car, I heard a high pitched squeak coming from the left hand side brake. At first I thought 'oh that'll go away after a while', but it didn't. When I pulled the handbrake slightly while driving, the squeak stopped only to come back again after a few seconds. Therefore I thought it was set too tight and thus touching the disc, hence I adjusted the handbrake. The squeak however, still appeared after a minute or two.. I decided to put the car on a lift and drive it with the wheels off the floor to see and hear where it came from. To my surprise I clearly saw the disc show radial movement!
246 kB, 3gp format, play with Quicktime
As you can hear in the video above, the squeak/tick is clearly noticeable. After removing the wheel and brake and spinning the hub only, the squeak was gone. My previous thought of the handbrake shoes rubbing against the dust shield was ruled out.. The only thing I could think of which could cause the disc to move around was the different center bore ST185's and ST205's use.
The ST185 uses 54.1 mm OD hubs all around. The ST205 however uses 55.0 mm ID center bore discs. The 0.9 mm difference in diameter had to be the cause of my squeak! So I had to find a solution to properly centre the disc on the hub. I figured out a thin strip should be able to fill the gap between the disc and hub:
Although the right hand side brake disc didn't move around, I decided to properly centre it just to be safe. Some maths (circumference = π • diameter) showed I needed strips with a length of 170 mm and a thickness of 0.45 mm to fill the gap. The company I got my strips from only had 0.5 mm stainless steel sheet metal in stock so I went for that assuming it would fit without problems (which it did). I had them cut two strips with a width of 10 mm:
10 mm turned out to be too wide though - 7 mm is what I needed. So here's what the gap looked like before:
And this is the new situation with the strip in place, a nice and tight fit:
Since fitting the strips I no longer hear the squeak so I assume/hope I solved the problem successfully. If you fit ST205 brakes on your ST185, I recommend to install strips like these at the same time. The size you'll need is 170x7x0.5 mm for each side.
How to install ST205 rear brakes
Modifications - Brakes