![]() ![]() I may not lube after cleaning unless I notice an issue although I have never done a piston cleaning myself yet. I hadn’t heard of this but it makes sense. I appreciate the comment above, warning about over lubing pistons and needing some friction. And definitely a very light coat so as to not get everywhere and contaminate the pads. Brake nerds there recommend a grease that is compatible with mineral oil or dot accordingly, but not brake fluid because it washes away too quickly. I have been diving deep on the Frankenbrake discussion on ride monkey. You can also use this technique with pads installed as a way to narrow the gap while maintaining alignment, and then make minor adjustments by hand once you fit the rotor in. Haven't cracked any pistons as of yet, but ymmv. I've used the same allen key by rotating it 90 degrees then pressing on both ends. Only tricky part is pushing the pistons back in since a tire lever usually won't fit. I find this trick works to get all the pistons out relatively quick, even if they don't move at first, because the other ones will stop once they hit the allen key and the only thing that's left to move is the sticky piston. The size of that gap depends on brand, but it's usually somewhere around 3-4mm. See 3rd, 4th, and 5th pictures from bottom: If you look at the caliper front to back, the top half is narrower than the bottom half. If you wanted to do a really fast cleaning, you could stick the largest allen key you can fit in the smaller slot of the caliper, and it should be enough that none of the pistons will pop out. *I use a Pedros long tire lever or a nylon tire lever for this step ![]() Reverse the process and repeat this step for the other piston(s). A quick clean with a shop towel here to make sure no fluid will contaminate your fresh pads is a good precaution. After quenching and cleaning, I dip the Q-Tip in a little Mineral Oil (for Shimano or Magura) or Dot 5.1 (for SRAM or Hayes), and coat the exposed portion of the piston. Once you are there, use your Q-Tip and alcohol again, remembering to have a swig of beer at regular intervals. Be careful not to push the piston out of the seal, because at best you're going to have to re-do the bleed and at worst you'll create a large mess. This allows the other piston to push out further than normal exposing even more glorious black contamination. To do this use a blunt tool* carefully, or a finger even more carefully, to prevent one piston from extending, while gently pulling the brake lever. Once the first wipe is done it's time to allow the pistons to extend further for a better clean. Doing this will push those contaminants into your brake system. It's wise to do this every time you replace your brake pads because by the time they are worn out they will have pushed more deeply out of the seals since you'll need to make room for the thickness of the new pads. Without these results I wouldn't be so keen the task. In my experience however, the action of my brakes always feels noticeably lighter and more positive after a good clean. Which means theoretically we don't clean pistons to make them move more freely, we do it to prevent contaminants from entering the system and I suppose to extend the life of the seals. The seals also act as a supplemental return spring so your brakes reset more positively and quickly. This nifty design allows the pistons to gradually self-adjust as the pads wear, at least in a perfect world. The seals, which are square rings rather than o-rings, actually flex and move with the piston. It turns out only part of that is partly true. I always assumed that brake pistons slide through their seals and retracted thanks to negative pressure in the hydraulic system. I also worked at Robson Cycles, Bicycles Plus and Boulevard Bikes/West Point, all in the city of Vancouver. I didn't manage my 10,000 hours but there was a time during my year-long stint at Cap's* when most days felt at least that long. Unfortunately my shop time, in the primordial mid-to-late 80s, pre-dated disc brakes, and was even before suspension, so I have some gaps in my expertise, and there's no quick way to reproduce the endless task repetition you get working in a shop. Cantilever brakes, V-brakes, side-pull, and even U-brakes all the rim brakes were in my wheelhouse. Overall I probably spent more time on the tools than doing sales by a 70:30 margin, and I learned some stuff about fixing bikes. Most of it was part time or during summers while going to school but one year I worked six days a week mostly wrenching. I worked in 4 different Vancouver bike shops over a span of about six years. ![]() Before we dive too deeply into this mildly technical task, I need to come clean about my experience as a mechanic. ![]()
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