I've just recently replaced the brakes on my MTB with a pair of Shimano XT hydraulics. The rear brake line was extremely long for my frame's routing, so I had to cut it and subsequently bleed the system. For the most part, everything seems to have gone well; the rear brake lever is now very firm and responsive, slightly more so than the front (which I did not shorten or bleed). However, I've noticed that the rear brake lever no longer returns instantaneously. If I had to guess, I'd say it takes around 0.2 seconds to return from the fully depressed position. By contrast, the front lever returns so quickly that it makes a slight "snap" sound when it hits its limit.
I replaced both the olive and needle insert when reinstalling the brake line. I noticed that both of these parts had a thick grease generously applied to them from the factory. I'm unsure if this is typical for Shimano brakes, though I've never seen pre-applied grease on the spares for Avid or Tektro brakes. I have a sneaking suspicion that this may be the culprit, but I'm not sure how to validate that without disassembling the brakes again and swapping in new connector spares.
This doesn't seem to affect the brake's function right now, since the pads don't noticeably drag against the rotor during the return interval. But it does concern me that I may have done something wrong while reinstalling the brake line, and that this might be a precursor to more serious problems in the future. Any ideas what I might have done wrong, or how to further troubleshoot this issue?
Some more details:
- The instructions I followed for shortening my brake line are these: http://www.epicbleedsolutions.com/blog/shorten-shimano-hoses-without-bleeding/
- Shortening the line introduced some air, so I followed the official Shimano bleed instructions here [PDF]: http://techdocs.shimano.com/media/techdocs/content/cycle/SI/Bleeding_SI/SI_0037A/SI_0037A_002_EN_v1_m56577569830648123.PDF