Air brakes?
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Intermediate
Joined: Dec 2009
Posts: 29
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From: Kremmling Co.
Air brakes?
Ok, heres the problem. I've got an 01 ultrta. The rear disc brake is giving me fits. It stops fine here in town, but when I go up to high altitude the petal goes to the floor and on the second pump the brake is fine. Come back to lower elevation and the brake works fine. I have rebuilt the master cylinder, rear caliper, new pads, and use the recomrnded DOT 5 fluid. What am I missing? I am beginning to think the fluid "outgasses" at elevation. Oh I live at 7400 ft of elevation in the Rockies and ride up to the 11-12000 foot elevation. Jetsam
Tourer
Joined: Jan 2011
Posts: 300
Likes: 10
From: Black Hills
I have to go with the obvious: air in the system. There is no gas in the fluid to come out of solution. Fluid is not compressable, air is; and it expands as altitude increases, so even a little air will become a lot at high altitude. Try bleeding extra carefully. There are good stickies on here about it.
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Intermediate
Joined: Dec 2009
Posts: 29
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From: Kremmling Co.
Thats the best Idea. I'll get the wife in the garage with me tonight and we'll try again. This will be the fourth time I've bled the brakes. Where could that darn air bubble hide? Jetsam
Club Member
Joined: Jun 2007
Posts: 45,429
Likes: 2,898
From: Bedford UK
In a small nook such as a change of pipe, or any dip in the pipe, between cylinder and caliper. Harley brake pipes are not known for being simple or straight! I replaced the pipe on my Glide with an HEL hose kit, which is much simpler in shape and makes life easier.
My first Harley was also my first bike with hydraulic brakes and I had a devil of a problem bleeding the rear brake. I resorted to disconnecting the caliper and lying it on the ground, so it was the lowest point in the system. That worked, by allowing any air to find its way back to the reservoir.
You need to burp this darned thing, just like a baby! Best of luck.
My first Harley was also my first bike with hydraulic brakes and I had a devil of a problem bleeding the rear brake. I resorted to disconnecting the caliper and lying it on the ground, so it was the lowest point in the system. That worked, by allowing any air to find its way back to the reservoir.
You need to burp this darned thing, just like a baby! Best of luck.
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