Mountain Bike Brake Bubble Bleednate collins
How to Bubble Bleed Your MTB Brake For Great Lever Feel
What You Need
Appropriate Brake Fluid. Don’t mix and match, ever! It will destroy seals and fail your brake system.
Bleed container. We use a variety of these.Whether craft bottles, Shimano bleed cups or a syringe the key is to be able to gently top off and “burp” the lever.
Window cleaner and a rag to clean up.
What It Is
A bubble bleed will help produce a crisp as well as consistent lever feel.
Inconsistent lever or need to pump for power are symptoms of a bubble in the system. Bubbles may form from heat saturation or aging fluid. As pads wear down topping off the lever will help the feel remain constant.
A way to check if your brakes could use a bubble bleed is to bounce the bike on the rear wheel while pumping the brakes. If you feel the lever suddenly pull through without pressure it’s a sign you have a bubble in the system.
This trick is good for bubbles in the lever. If you follow these instructions and still have symptoms of a bubble it maybe hiding elsewhere in the system. A full bleed may help if the bubble is in the caliper. Ensuring the lever is the highest point while manipulating the brake line to move any bubbles towards the lever may help as well. Front brakes seldom have bubbles anywhere but the lever, which is the consistent high point. Rear brakes can be more tricky.
As always – if you have questions get an expert’s opinion. Bike service costs much less than medical bills!
What To Do
Level your brakes if needed. A quick pencil mark on your bars at the clamp split is an easy way to reset your positioning.
Open the bleed port.
If you are working with a bottle or syringe carefully push some fluid into the lever. You are not trying to fill or pressurize the bladder, simply coaxing the bubbles out. Over pressurizing the bladder will cause failure.
Repeat while applying the lever a couple times and shaking the brake line if required.
Typically if you feel the symptoms and see a bubble come out that’s that.
Replace the bleed port and clean any fluid on the brake.
Test the lever feel for consistency and power.
Check Your Work
Ride the bike in a safe area ensuring appropriate power, lever predictability and bite. Above all if you have any questions stop and find a competent resource. After all malfunctioning brakes are extremely dangerous.
Not comfortable working on critical systems on your bike? You’re not alone, which is why we have an unmatched service department in order to help you with any maintenance you require.
*BikeCo.com takes no responsibility for your mechanical aptitude. If you have ANY doubts about your mechanical ability we suggest using a competent resource for bike service. These tips are posted to help riders with specific issues. In the event you are unable to competently diagnose your issue use a qualified resource. All systems should be tested and confirmed safe prior to resuming normal riding.