To recap a bit... my brake lever travel was slowly getting less and less and the brakes started dragging some. I'm guessing the original pre-problem travel was about 1 1/2". It was now at 1" and no longer acceptable.
A local bike shop suggested the silicone fluid I ran had swelled the piston seals and with the pistons no longer retracting correctly, they dragged and created my "hard lever". The shop was correct as I replaced the seals and thoroughly disassembled/flushed the silicone out and the problem was gone. The pistons could now be pushed back with finger force, where before they were stuck solid. After re-assembly, I could feel the small amount of play that both caliper assemblies should have when the lever is released. There was zero play before at both calipers. I'm positive the new seals had fixed things. I bled the brakes by hand and with a pump and ALL air was positively removed.
However, now I had the opposite problem. There is excessive lever travel now. 1 3/4". This actually is close to many new bikes I tested at the local dealer but I knew it wasn't right. I re-bled/flushed and couldn't figure out what was going on (as some of you have read)...until now.
Sometimes fixing something can expose a second problem. In my case, it seemed the only problem was swelled seals. Wrong.
After all the bleeding, etc, I noticed the play at the left caliper had lessened as compared to the right caliper. There was no doubt the left caliper was now a little tighter against the rotor. When released, you could see a gap between pad and rotor on the right, but not at the left. Wiggling the caliper body by hand also made it obvious that the left had lost some play and was no longer equal to the right. Hmmm. Now the earlier signs during disassembly made it obvious. There was a small leak from the seal that couldn't be seen until the caliper was upside down in my hand. It also required 100 PSI to blow out that piston (only 35 for the right side). There was also a very small "shiny spot" in the bore where the piston, barely changing position, rubbed. I could not feel this spot with my finger, I could only see it so I thought it was OK.
It now seems obvious that I also have a cocked/semi-sticking piston. The piston isn't moving straight in and out as it should, thus the shiny mark in the bore. The cocked piston would tend to make the seal leak prematurely too. With the left piston now sticking out a little more than the right side, I have less play at the left pad and rotor. This is why the excessive travel I believe.
Since I have two calipers, as the lever is pulled in, the left side contacts before the right side now. With the right side "lagging" behind the left side now, there's no way you're going to get a solid feel at the lever until both calipers are contacting reasonably hard. They MUST operate equally. After the left contacts well, the right still needs more fluid/lever pull to contact solidly. Thus the extra travel/pull needed. Makes sense to me.
Now my problem is I need a replacement caliper body. I have no faith in trying to sand/polish, etc, the bore in an attempt to make the piston move correctly. The factory manual says the service/wear limit of the piston or bore is only .001" from new. Any attempt at re-surfacing the bore would surely take me out of spec. So now I have to try to find an NOS caliper if I can, or play the used part game. The caliper is no longer available at the dealer.
Thanks for reading this and let me know of any thoughts you have.
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