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DIY! How to Maintain the Brake Caliper!


Speaking of motorcycle braking systems, there are wholly no worry even OEM parts because its performance has been evolved and stabilized remarkably since the ’90s. However, speaking of the brake system of the ’70s and ’80s, which is the early days of the brake revolution, it is already vintage parts, so regular maintenance is essential to maintain its performance.

There is a great effect on maintaining its performance even just washing parts with neutral kitchen detergent. Here, I will explain the points to note when maintaining the brake caliper.

1. For long-time abandoned motorcycle, “rust” brake caliper piston is common


This is the brake caliper piston removed from the motorcycle that had been left under the eaves (an environment that is not indoor but not exposed to rain) for more than 10 years. As shown in the photo above, it is rusty and cannot be reused as it is.

The brake caliper piston on the right was finished with “recycled hard chrome plating” in the rusted situation of the left side in the photo when it was disassembled. The finishing touches by the special professional shop who is undertaking reproduction are wonderful.

If parts are not available for vintage motorcycles, there is no other way than finishing with such a reproduction method. But if it is possible to get OEM parts from the manufacturer or reliable reproduction parts,, it is cheaper to buy reproduction parts. For popular vintage models such as the KAWASAKI Z1 / Z2 and HONDA CB750K series, there are many cases that reproduction parts have been sold from part constructors.

However, in the case of other models, even the brake piston of the important safety-related part is difficult to obtain, so the work may get stuck. Whether parts are OEM or duplicated, timely maintenance is easy if parts are available, but, in the case of a model that cannot be diverted a brake caliper piston, there is no other way but to recycle the disassembled and extracted defective piston.

Not only for brake pistons, but also for the reproduction of the front fork inner tube and the rear suspension damper rod is common at present.However, since it takes days to complete and deliver from the order of recycled hard chrome plating, when servicing a vintage motorcycle, it is better to start to restore from these hard-to-find parts.



・If the brake caliper piston is the rust-proof anodized aluminum, it may be reused by polishing.
・Hard chromium plated iron pistons often have pinhole of rust..
・A single pinhole will cause oil leakage.


2. Special tool for “extracting” brake caliper piston seal groove!!


In case that the condition of the piston seal which is the key to the brake touch feeling is bad even if there is no problem with the brake caliper pistons, the disc brake system will not be able to exhibit the maximum performance.

3. The key point in “cleaning” on the inner wall of the caliper cylinder


If you have a small sharpening stone for a hand drill, the inner wall of the caliper cylinder can be cleaned quickly and comfortably. Work can be more efficiently advanced than hand polishing.

Click here to purchase a honing stone

Sometimes the brake caliper piston is too rusty and will not come off. In such a case, consult a professional mechanic or go to a motorcycle shop for maintenance. Because if attempting to pull out the piston by force can cause irreparable damage to surrounding parts.. Be sure to keep this in mind.

Even if a new brake caliper piston is installed, if the condition of the caliper-side seal groove is poor, the operability of the piston will be significantly deteriorated. Since the glycol-based brake fluid of DOT3 and DOT4 has a “strong hygroscopicity”, the moisture is absorbed from the brake piston seal and the dust seal groove, and the moisture reacts with the fluid and becomes impure deposits.

Calipers are often disassembled during brake maintenance, and many veteran mechanics always check the condition of these grooves. As for the cylinder of the caliper body also, it may have been scratched by the sediments.

“I want to polish the burrs that appear on the edges of the scratches, but if you brush it by hand with waterproof sandpaper, strictly speaking, the roundness will be warp.” In such a case, it is best to lightly polish with a hand bore honing tool of a special tool on the market.

Just spray with an anti-corrosion a lot, attach the bore honing tool to the hand drill, insert the grindstone into the cylinder, turn it and polish it lightly.



・If you don’t have a groove cleaning tool, you can use the tip of the pickup tool to extract.
・Work carefully so as not to scratch the seal groove.


4. Insert only a piston into the caliper. Check the operation properly!!


Let’s insert the piston alone into the caliper alone and check that it works smoothly. It is important that both the front and rear directions and the rotation direction move smoothly. After finishing the seal groove cleanup and polishing the inner wall of the cylinder with a hand bore honing tool, degrease and clean the caliper body.

Next, insert the degreased piston into the cylinder and check if it works smoothly. In fact, this operation is important. This is really effective in the sense of recognizing in advance the quality of the brake touch feeling.

Instead of inserting the piston seal into the cleaned caliper and inserting the brake caliper piston forcibly, first try to check “operability between individual parts and between parts”.



・ If the piston seal is interposed, the operability of the piston will not be known, so let’s check in advance between single parts.
・・In final assembling, apply a thin layer of rubber grease to the piston seal and brake caliper piston circumference to improved lubricity.


Webike staff

Webike staff

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Webike Moto News Editor

Our mission is to look for unique and valuable news that are from Japan and Asia related to motorcycles and publish to the world. "Webike staff" is name of a team who edit, translate and draft the articles we publish that are brought from all our branches around the world. Not all of our employees ride motorcycle, but find worth living to bring reader say "wow".

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