I like to do a full bleed on my brakes. On most brakes I like to use syringes to push clean fluid both up and down. The funnel method is suitable, I think, because you can still use the lever to push fluid through the system and out the caliper.
I'll explain why I do what I do, but first go pour yourselves a beer. I know it's a lot to ask from you bunch of thirsty mountain bikers, but let your beer sit there in the glass for a couple minutes. Watch the beer. Specifically, watch one of the bubbles that clings to the inside of your beer glass. Some of those little bubbles will stay there a LONG time. Brake fluid is more viscous than beer, and brake hoses are considerably smaller than your beer glass. Expecting gravity to dislodge a bubble that's jammed up inside your brake system is unrealistic thinking.
The next experiment is more for the lever-bleeders. Shake up your bottle of beer and pour all that foam into your glass. Now pour a new beer on into the glass, so the level reaches the top of the rim. Did all the foam and bubbles go away? No? That's why I do a full bleed.
Lastly, look closely at Rod's pictures, specifically the last one. See those little specks of black scrunge in the caliper? A lever bleed lets all that filth stay in the caliper. When you bleed brakes that have been ridden hard and have many hundreds of miles on them, the brake fluid comes out somewhat opaque. This is caused by microscopic particles of black scrunge. The scrunge decreases performance and longevity. A full bleed gets out most of it.
I'll explain why I do what I do, but first go pour yourselves a beer. I know it's a lot to ask from you bunch of thirsty mountain bikers, but let your beer sit there in the glass for a couple minutes. Watch the beer. Specifically, watch one of the bubbles that clings to the inside of your beer glass. Some of those little bubbles will stay there a LONG time. Brake fluid is more viscous than beer, and brake hoses are considerably smaller than your beer glass. Expecting gravity to dislodge a bubble that's jammed up inside your brake system is unrealistic thinking.
The next experiment is more for the lever-bleeders. Shake up your bottle of beer and pour all that foam into your glass. Now pour a new beer on into the glass, so the level reaches the top of the rim. Did all the foam and bubbles go away? No? That's why I do a full bleed.
Lastly, look closely at Rod's pictures, specifically the last one. See those little specks of black scrunge in the caliper? A lever bleed lets all that filth stay in the caliper. When you bleed brakes that have been ridden hard and have many hundreds of miles on them, the brake fluid comes out somewhat opaque. This is caused by microscopic particles of black scrunge. The scrunge decreases performance and longevity. A full bleed gets out most of it.
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