Summary: the first rampart of your pump

The bellows (or protective cap) is located at the back of the piston, where the thrust rod enters the body of the pump. Its role is often underestimated:

• Physical barrier: It prevents track dust, gum residues and moisture to enter the cylinder.

• Piston protection: Once the dust enters, it mixes with grease and creates an abrasive paste that shines the surface of the piston and the body of the pump.

• Sustainability: A bellows in good condition multiplies two the life of your internal cups.

- Technical specifications

- Mounting tuto: the accuracy of the "clipping"

The assembly seems trivial, but it must be done properly not to create a suction or crushing effect.

1. Cleaning the seal plan: The throat on the body of the pump must be perfectly clean. Use a plastic tip to remove old rubber residues or dried grease.

2. Inspection of the stem: Before putting on the bellows, check that the thrust rod (the "Pushrod") is perfectly smooth. A small scratch on the stem could tear the nine bellows from the inside.

3. Internal lubrication: Apply a very fine silicone grease layer or rubber compatible grease inside the bellows. Do not use heavy mineral fat that could attack the material.

4. Setting up: Enter the large diameter of the bellows in the pump body groove while riding with your thumb. Check that it is well lodged on 360 ° to seal.

💡 Michel's trick

"The bellows is often the witness of an invisible internal leak. The trick: If you remove the bellows and find brake fluid (wet) inside, it's not an external leak. This is the sign that the internal seal of your piston (the primary cup) is making the soul. My Pro Council: Do not just give a new bellows if you find liquid below; It's time to open the pump to change the internal joints before the brakes do not go on the track. "

❓ FAQ SEO (Frequently Asked Questions)

Q: Is it serious to ride without bellows if the circuit is closed ?

A: Yes, very serious. The piston will accumulate dust. At each braking, this dust is sucked into the inside of the cylinder. In a few sessions, your piston will be scratched, and your pump will be good for the trash.

Q: Is the bellows compatible with all Birelart pumps ?

A: No, the piston diameters and the hold grooves vary between old pumps and 22SR / 22SRR models. Use the specific reference to the EVO / 22SR model to avoid sealing problems.

Q: Can we put glue to make it stand ?

A: Especially not. The rubber must be able to deform during the movement of the piston. The glue would rigidify the bellows, which would tear him immediately.

✅ Ready for your maintenance ?

You have now inspected the outside of your pump. To finish your revision:

• [Graisse silicone] (Indispensable for preserving rubber).

• [Liquide de frein (DOT 4/5.1)] (Check if you need to purge).