Categories: Ask MO Anything
1 year ago | Updated 1 year ago

Why Are My Brakes Still Mushy?

Dear MOby,

I’ve bled my ’08 Sportster’s front brake caliper rePEATedly as per instructions after putting on a new braided steel brake line, but there’s still a little more sponginess in there than feels right. I get pretty good braking power at first squeeze, but the power immediately seems to fade and I wind up pulling the lever onto my outer two fingers. Do I need to research gnarlier brake pads? What’s the deal? Help! I love my Sporty.

Brake Down
Springfield, Illinois

Dear BD,

Let’s not panic, Brake. All you have to be is smarter than air, which will always rise to the top of any closed hydraulic system. The highest point on your Sportster’s brakes, and most bikes, is the hydraulic line where it attaches to the master cylinder. Plenty of motorcycles have placed bleed valves up there like the ones atop each caliper, but not lately. Which is a shame, because it’s easy for a little bubble of air to get trapped up there at that master cylinder banjo fitting. It only takes a tiny bit of air to create a world of sponginess.

Do this before you do anything else: Cover the tank and anything else where brake fluid might drip with shop rags or towels or whatever, then loosen that 12mm brake bolt that holds the brake line onto the master cylinder with a box-end wrench just a smidge while applying pressure to the brake lever. A little fluid will ooze out; tighten the nut again while still applying pressure to the brake lever, which you will feel grow firm as you do so. Nine times out of ten, the air bubble that was trapped up there will excuse itself along with that tiny bit of fluid. If not, give a tap tap tap on the upper part of the hose with your wrench and try it again. After you’re done, make sure to top up the reservoir, not that this old trick should cost you more than a soupcon of brake fluid, which you should sop up immediately as it is a known destroyer of finishes of all kinds.

If that doesn’t result in a super-firm brake lever, write back and we will give you a free lifetime subscription to MO.

Send your moto-related questions to If we can’t answer them, well, ahhh, hey, nobody’s perfect.

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Tags: ask mo anythingbleedingbrakesHarley-Davidsonjohn burnssoftsportster