In between coats I thought I would see if I could resolve my brake hanger clearance issue. The more I thought about it and drew it out I could not understand why the disc was not sitting central to the calliper. I was really sure that I had measured it right and made it so that there should not be a problem.
It turns out the problem was a mismeasurement on my part not on the lateral positioning of the disc but rather on the distance of the calliper from the centre of the wheel spindle. I had made my brake hanger and drilled the mounting holes for the calliper 0.5mm too small a radius. This was compounded by the cheapo Chinese disc which had a radiussed outer edge. The edge of the Brembo disc is right angular. So the new disc was c 0.25mm larger than OEM although the machined (wearing) face was the same size.
The bridge of the calliper was fouling the outer edge of the disc and would not permit the hanger when the spindle was inserted to sit square. The spacering of the disc outwards was correct but the calliper could not straddle the disc at right angles.
I had 3 options at this point
1. remake the hanger bracket – I really could not face a Mk 5
2. relieve the inside of the bridge of the calliper by 0.5mm – not easy to do and I do not want any swarf or filings anywhere near the seals (which are OK)
3. reduce the OD of the disc – I checked the pads run inside the OD so no loss of braking swept area and no risk of the pads getting a wear lip on the outer edge.
I came up with this contraption
which put it in the pillar drill and applied a 115mm angle grinder with a floppy abrasive wheel in and the disc is now 1mm smaller on OD (and about 20g lighter).
Lo and behold the brake hanger now fits – result.
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