This time, all eight pistons were extremely difficult to pull out, despite using a proper piston-extractor tool. I invested in a Powerhouse kit to include eight stainless pistons in hope that the problem would be solved once and for all. When I did get the old pistons out, they were immaculate, so the seizure was due to the seals gripping them far too tightly. Here things get a little tricky, because the seals had some sort of residue on them. At one time, I was using a red grease on hydraulic assembly that I subsequently found was mineral-based and not compatible with rubber, so I suspect I was responsible for the seals expanding and sticking the pistons. Well, you live and learn, even if it takes several lessons!
So I cleaned the otherwise immaculate calipers and proceeded to fit the Powerhouse kit. Fine with the larger pistons, but the smaller ones were almost impossible to get to go in, despite using proper Brembo lubricant. There was no option for it but to refer to Powerhouse, who were extremely responsive and offered to have the complete calipers in their workshop and even contributed to the postage. However, they found the small pistons were indeed very difficult to fit, despite their seals having been successfully used in very many Brembo calipers of this spec. They rebuilt the calipers twice, and even fitted new stainless clamping screws to the two halves, returning them free of charge, but felt that there might be inconsistencies in the original machining of the seal grooves. Seems unlikely to me, and I'd question the spec of their 30mm seals.
Whatever, after a protracted bleeding session which never got the proper feel at the lever, presumably because because the pistons were not yet moving freely, I went out on the bike. I thought if I put light pressure on the front brake, I'd get some heat into the system and get the pistons to advance more closely to the discs. Maybe they did all of a sudden, because the next moment the front wheel locked! The road was not clean so I should have been more wary, but the bike stayed upright. Scary though: I've never locked a front wheel before.
And stayed upright anyway.In the course of the subsequent ride, the brakes improved a lot. It may well be that the very recent pads need to bed back in properly, but the bike won't go out again this year because the roads are so slimy around here and the road-tax expires in a couple of weeks anyway.
Aside from all the other complications in this saga, please do ensure that any lubricants you use with hydraulics are compatible, and don't trust them just because they are the traditional colour!
Nick
