Lost rear brake coming down mountain
Ultimate HDF Member
Joined: Aug 2008
Posts: 5,413
Likes: 17
From: eastern oklahoma
the people who designed the brake system were probably pretty good with brakes. they specify dot 4 or dot 5 for a reason and it's covered in your owners manual as well as labelled on the top of each master cylinder cover. i really prefer the older stuff that doesn't eat paint, but i also really prefer much more, growing to a ripe old age. obey the reservoir cap and use what is specified. i'm glad you got it figured out and swapped back to the right stuff after flushing. ride safe.
Tourer
Joined: Jul 2006
Posts: 447
Likes: 2
From: Sooner Central
30 posts into this thread and none of the Keyboard Kowboys paid attention to the OP's description of brake fade on a mountain road.
Basic physics that most of us flatlanders ignore: high elevation = lower atmospheric pressure = lower boiling point for liquids, including brake fluid.
Minor issues with braking systems or braking techniques that aren't noticed at sea level can cause fade (boiling of the fluid) at elevation with even mildly heated brakes. Best practice is to take it easy and gear down on mountain roads to avoid brake fade.
Basic physics that most of us flatlanders ignore: high elevation = lower atmospheric pressure = lower boiling point for liquids, including brake fluid.
Minor issues with braking systems or braking techniques that aren't noticed at sea level can cause fade (boiling of the fluid) at elevation with even mildly heated brakes. Best practice is to take it easy and gear down on mountain roads to avoid brake fade.
Thread Starter
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Grand HDF Member
Joined: Nov 2007
Posts: 4,067
Likes: 60
From: Chesterfield, VA
Guys like you, got nothing to add except asshat replies.
Road Warrior
Joined: Nov 2008
Posts: 1,296
Likes: 3
From: Cheltenham, UK
30 posts into this thread and none of the Keyboard Kowboys paid attention to the OP's description of brake fade on a mountain road.
Basic physics that most of us flatlanders ignore: high elevation = lower atmospheric pressure = lower boiling point for liquids, including brake fluid.
Minor issues with braking systems or braking techniques that aren't noticed at sea level can cause fade (boiling of the fluid) at elevation with even mildly heated brakes. Best practice is to take it easy and gear down on mountain roads to avoid brake fade.
Basic physics that most of us flatlanders ignore: high elevation = lower atmospheric pressure = lower boiling point for liquids, including brake fluid.
Minor issues with braking systems or braking techniques that aren't noticed at sea level can cause fade (boiling of the fluid) at elevation with even mildly heated brakes. Best practice is to take it easy and gear down on mountain roads to avoid brake fade.
I took the liberty of checking first and can confirm as follows:
Highest point on BRP is just over 6000 ft. Whilst I could not find the specific altitude vs boiling temp relationship for brake fluid it was, naturally, readily available for water. The boiling point drops from 100 degrees (Celsius) to 93.5 - so I am going to have to beg to differ with you on this.
I have also ridden through much higher altitudes on the Rockies and was blessed enough to drive the Grossglockner pass in Austria. On both occasions I did not see any signs warning motorists that they were about to plunge to their deaths due to premature boiling of their brake fluid!
Cruiser
Joined: Jul 2011
Posts: 172
Likes: 0
From: Tennessee
Good day gents, thought I'd chime in. I still have a race bike and try to do 1 or 2 trackdays a month, money permitting. Most of my days are in the summer months at little talladega, road atlnta, barber and nashville. Obviously all are in the south and I dont have to tell you how hot it is on the pavement somedays. With that being said I have never boiled the brake fluid(dot 4) and of course if Im not on the gas im on the brakes. Yes, I have experienced some fade at times when doing long sessions with old fluid and mostly prior to running steel braided lines. I know this is apples and oranges comparing sport bike to harley, but at the end of the day the brake systems operate the same. In my expereince my problems with the brakes have been mechanical in nature or low fluid level. Just my 2cents.
Thread Starter
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Grand HDF Member
Joined: Nov 2007
Posts: 4,067
Likes: 60
From: Chesterfield, VA
A lot of techno mumbo jumbo on this thread so far.
Bottom line: the fluid was low. It did not boil or foam. When I flushed it out existing fluid was nice and clean.
Looks like, when I did the pads and bled the brake, I should have pumped it one more time to add more fluid.
So 2 lessons learned: Make sure reservoir is filled and don't use DOT 5.
One more thing ... The touring series bikes have outstanding front brakes. I was never in any danger coming down that mountain road. Front brake and gearing brought the machine to a stop nicely.
Bottom line: the fluid was low. It did not boil or foam. When I flushed it out existing fluid was nice and clean.
Looks like, when I did the pads and bled the brake, I should have pumped it one more time to add more fluid.
So 2 lessons learned: Make sure reservoir is filled and don't use DOT 5.
One more thing ... The touring series bikes have outstanding front brakes. I was never in any danger coming down that mountain road. Front brake and gearing brought the machine to a stop nicely.
Cruiser
Joined: Nov 2011
Posts: 188
Likes: 4
From: Arizona
A lot of techno mumbo jumbo on this thread so far.
Bottom line: the fluid was low. It did not boil or foam. When I flushed it out existing fluid was nice and clean.
Looks like, when I did the pads and bled the brake, I should have pumped it one more time to add more fluid.
So 2 lessons learned: Make sure reservoir is filled and don't use DOT 5.
One more thing ... The touring series bikes have outstanding front brakes. I was never in any danger coming down that mountain road. Front brake and gearing brought the machine to a stop nicely.
Bottom line: the fluid was low. It did not boil or foam. When I flushed it out existing fluid was nice and clean.
Looks like, when I did the pads and bled the brake, I should have pumped it one more time to add more fluid.
So 2 lessons learned: Make sure reservoir is filled and don't use DOT 5.
One more thing ... The touring series bikes have outstanding front brakes. I was never in any danger coming down that mountain road. Front brake and gearing brought the machine to a stop nicely.
Ya I know I`m a smart A$$ can`t help it, no harm intented
I`ve followed guy like you that check there brake fluid after they have no brakes also, bottom line,,, at the bottom of the hill, they have no brakes
Elite HDF Member
Joined: Apr 2007
Posts: 3,766
Likes: 16
From: Roseville, CA
Using the rear brakes too much (and fluid too low).
All that weight going downhill, why even bother using the rears?
All that weight going downhill, why even bother using the rears?
Last edited by Deuuuce; Nov 16, 2011 at 08:16 PM.
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Road Master
Joined: Sep 2011
Posts: 1,075
Likes: 21
From: Florida / Colorado
For the altitude statement/question, I have lived for many years an hour or so away from both Loveland Pass and Independence Pass here in Colorado. Both passes are approximately 12,000 feet. I've ridden and driven over both numerous times every year. I've never heard of nor experienced any brake fade due to the change in atmospheric pressure. Interestingly, I have found my muffler bearings seem to wear out much sooner when riding at high altitudes.
Road Warrior
Joined: Nov 2008
Posts: 1,296
Likes: 3
From: Cheltenham, UK
I have to say I am somewhat confused by this whole thread. Maybe it is a case of 2 countries separated by a common language, but my understanding of "mumbo jumbo" is a polite term for BS.
As I stated above, I see a case of listening to what you want to hear! Why not do independent research - it takes 5 minutes on Google and the information is overwhelmingly clear and evident
The OP has a potentially serious and dangerous situation on his hands that can only be correctly rectified by doing a thorough inspection and service.
That is not going to happen, so I have moved on