July 17, 2026

Goal for today: bleed the rear hydraulic brake on my commuter before a longer ride Saturday. The lever pull had gone soft over six months of wet-weather use — not alarming, just tired.

I run Shimano MT200 levers with matching calipers. Bleed kit is a Shimano TL-BT03-S. I've done this enough times to trust the procedure, but apparently not enough to trust my own pace.

1. Clamp the bike level in the stand, wheel in.
2. Attach the syringe to the caliper bleed port — M6 fitting, snug but not over-torqued.
3. Remove the reservoir lid at the lever. Mineral oil only: I keep a labeled bottle in a sealed bag so I never grab DOT by mistake.
4. Push fluid slowly up from the caliper; tap the hose occasionally to move bubbles toward the lever.
5. Close the caliper port, then draw back slightly from the lever syringe to pull out any remaining air.
6. Reinstall the reservoir lid and wipe every surface clean before releasing anything.

The failure was step 5. I closed the caliper port while the syringe still had pressure on it. The olive didn't seat cleanly and I lost about 2 ml of mineral oil straight onto one brake pad. Mineral oil in resin pads isn't recoverable by wiping. Swapped in a spare set of Shimano B05S pads — I keep two pairs for exactly this kind of mistake. Lever feel is now firm and consistent. The half-hour job became ninety minutes.

What got me unstuck, once I stopped being annoyed, was remembering the rule: release syringe pressure before closing any port. Fluid under pressure finds gaps. Next time I'd release first, pause, then close — and not rush that pause just because I think the job is nearly done.

#workshop #bikemechanic #brakes #maintenance