I cannot reset my calliper pistons. What now?
I cannot reset my calliper pistons. What now?
If you're having difficulty resetting the position of your calliper pistons it is probably because your brake has been filled with too much brake fluid.
The brake system can become over-filled if a brake bleed is performed without resetting the pistons. The most obvious example of this is when a bleed is carried out with part worn brake pads in situ.
Shortcuts can be taken when it comes to brake bleeding. Not removing the wheel and brake pads prior to carrying out the work is one such shortcut. It only becomes a problem when fitting new brake pads and you are unable to create enough space between the pistons to accommodate the new pads.
Here's how to fix it
The problem is easily fixed by removing the excess brake fluid from the brake system.
Always remove excess brake fluid from the highest point. If your bike is the correct way up this will be your brake lever's bleed port or reservoir top cap. Removing the calliper bleed port screw will result in air entering the system.
1. Remove the brake lever bleed port screw or reservoir top cap and rubber diaphragm.
2. Now try to push back the calliper pistons with your flat blade screwdriver if your pads are in place or, if your pads have been removed, use a plastic tyre lever.
3. Be sure to catch the excess brake fluid with some paper towel. Then refit the master cylinder bleed port screw or rubber diaphragm and reservoir top cap.
4. Wipe away any brake fluid from your lever assembly with a wet rag.
Now you've successfully reset the position of the calliper pistons you can go ahead and insert your new brake pads or bleed block.
