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Brake Fluid and Fade

 
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JayBoy



Joined: 26 Jan 2005
Posts: 234
Location: Lexington, KY

PostPosted: Thu Feb 04, 2010 3:13 pm    Post subject: Brake Fluid and Fade Reply with quote

I started thinking about the last couple of hard runs at Maggie Valley last year where at the end of the run when I slowed way down or came to a stop, I lost all braking capability. Ralph has always said we need to get more air on the calipers but that's easier said than done. But my research enlightened me to the fact that all brake fluids collect moisture over time, some more than others. This moisture content lowers the boiling point significantly. There are numerous articles comparing the characteristics of particular brake fluids and how often one should flush and change to fresh fluid.

It's likely You racers and ex-racers already know this, but on the track many racers change their fluid after every run or at least before each race day, this includes cars as well as motorcycles.

So here is the question, has anyone else experienced this?
How often do you change the fluid and what type of fluid have you found to be the best all around for street and track?

Also, Talking with my brother in law who works on a Nascar race team he says that the harder the brake pad the hotter it runs. Any thoughts on this?

Can't wait to go fast again and stop safely! Big Grin
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Paul



Joined: 27 Jan 2005
Posts: 182
Location: Utah

PostPosted: Thu Feb 04, 2010 3:49 pm    Post subject: Reply with quote

Doesn't everyone get brake fade? If you don't you aren't going fast enough!

It sounds like you may have brake fluid boiling - when you slow down after a high speed run, you have no more cooling effect (no more air flowing over the brakes) but they're still hot. So, the fluid gets even hotter than it was on the track, and can boil - once it does, you have zero brakes.

Things to do are (a) cooling scoops, like you mentioned; (b) higher boiling point fluid (like DOT 5.1 instead of DOT 4) and fresh fluid every year; and (c) better brakes, especially stainless steel lines.

The harder pads running hotter doesn't make sense to me - to stop you need to dissipate a certain amount of energy. The amount of heat generated is the same, no matter what pads you run. A soft pad may generate a lot of heat quickly, a hard pad will generate lower heat but for a longer period of time - ends up to be about the same total heat.

But I wouldn't worry about hard pads anyway - I'd get some good soft aftermarket pads, and just be prepared to replace them once a year or so.
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docmike



Joined: 27 Jan 2005
Posts: 630
Location: Eastern NC

PostPosted: Thu Feb 04, 2010 5:23 pm    Post subject: Reply with quote

I've been fighting brake problems on the K1100 for a while. Because of that I've probably changed fluid about twice a year.

I finally got them much better, turns out the front hub wasn't straight and caused a lot of runout on the disk, pushing the pads back in the calipers. So somethimes there would be nothing on the first pull of the brake lever, but the next would give solid brake feel.

Now that that's fixed I'll probably go back to a once a year (right before MV) flush and replace. As near as I can remember I've been using Valvoline 5.1, its the one rated for abs so is supposed to have a higher boiling point.

Mike
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93 BMW K1100RS / EML Speed 2000
89 Honda GB 500 (6,700 miles, all original except tires)
67 Triumph 650 chopper
92 Suzuki GS500 (eldest son)
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David



Joined: 18 May 2006
Posts: 104
Location: Chelsea Michigan

PostPosted: Fri Feb 05, 2010 3:46 am    Post subject: Reply with quote

Yep Jay,
That's what happens to people who run fast and close. Can't get enough air. I've never had that problem. Very Happy

I have always used Valvoline Full Synthetic from Auto Parts Store. I change brake fluid when I lose the clear clean look. The trick is in bleeding the brakes properly. After bleeding brakes, pull front brake lever in as far as you can. Use electrical tie from handle bar to lever to hold in that position. For the rear brake, use some kind of weight to hold it on. Let set overnight. This supposedly works any little air left in back to the filler cup. I was always under the impression that harder pads were for racing, meant to work better with high temperatures. That is why they are not good for the street. That's why I wear shoes with soft soles, just in case. Big Grin

Anxiously waiting Maggie Valley.

Dave
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zentime



Joined: 22 Jan 2005
Posts: 823
Location: Massachusetts USA

PostPosted: Fri Feb 05, 2010 12:03 pm    Post subject: Reply with quote

As you mentioned, brake fluid can absorb water. I've been told that once you open a bottle of brake fluid, it immediately begins to absorb water. Some fanatics only use a bottle one time regardless of how much is left. I wonder if Dot 5.1 is Hydroscopic as well?

http://en.wikipedia.org/wiki/Hydroscopic

What everyone else said but in addition, I would be sure the insulating shims are on the back of the pads. They are supposed to help block some of the heat transfer from the pads to the calipers.

FWIW, My Blackbird and Roger's Blackbird have identical front brakes.............. So we all make a quick trip down the mountain and when we get to the bottom the brakes on my blackbird will all but be gone and Roger's will be completely fine. Roger has ridden my Blackbird a number of times and has never had the problem. Clearly he goes much faster than I can so technique is a factor. I tend to over use my brakes whereas Roger seems to always be in the right gear and uses the motor more than his brakes to control things. More effectively I might add.Smile

That said, with the larger vented rotor, the radial calipers and whatever else, I've never had the problem with my zx14. It's also worth noting that the problem of brake fade seems to be some how related to Maggie Valley! Laughing
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will August ever come............


Last edited by zentime on Fri Feb 05, 2010 9:14 pm; edited 1 time in total
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zentime



Joined: 22 Jan 2005
Posts: 823
Location: Massachusetts USA

PostPosted: Fri Feb 05, 2010 6:17 pm    Post subject: Reply with quote

Just got this information from a friend.

"DoT 5 is silcone based brake fluid...does not absorb water...a very big plus. Does not remove paint either (I think). I put it in my KZ1000 and in my ATV.... Just be sure you get all prior fluid out...remove calipers...turn upside down....compress pistons....limit piston travel use commpressed air to push piston out....turn upside down and compress piston to get remaining fluid out. Reassemble and give a good bleeding."
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will August ever come............
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Ralph



Joined: 27 Jan 2005
Posts: 572
Location: Lexington, Ky

PostPosted: Fri Feb 05, 2010 6:24 pm    Post subject: Reply with quote

It's also worth noting that the problem of brake fade seems to be some how related to Maggie Valley! You think!! Big Grin

Roger is smoother than anybody that has showed up there so far.

More motor less brakes Laughing
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zentime



Joined: 22 Jan 2005
Posts: 823
Location: Massachusetts USA

PostPosted: Fri Feb 05, 2010 9:33 pm    Post subject: Reply with quote

Ralph wrote:
It's also worth noting that the problem of brake fade seems to be some how related to Maggie Valley! You think!! Big Grin

Roger is smoother than anybody that has showed up there so far.

More motor less brakes Laughing


+1
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will August ever come............
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zentime



Joined: 22 Jan 2005
Posts: 823
Location: Massachusetts USA

PostPosted: Fri Feb 05, 2010 9:41 pm    Post subject: Reply with quote

Here's more information on brake fluids.

DOT 5.1, like DOT 3 and DOT 4, is a polyethylene glycol-based fluid (contrasted with DOT 5 which is silicone-based). Polyethylene glycol fluids are hygroscopic and will absorb water from the atmosphere, which is necessary to prevent sheer and undiluted water in the braking system, which is very corrosive.
As of 2006, most cars produced in the U.S. use DOT 3 brake fluid.
Boiling points
Minimal boiling points for these specifications are as follows:

Boiling point ranges
Dry boiling point Wet boiling point
DOT 3 205C (401F) 140C (284F)
DOT 4 230C (446F) 155C (311F)
DOT 5 260C (500F) 180C (356F)
DOT 5.1 270C (518F) 191C (375F)

Most automotive professionals agree that glycol based brake fluid, (DOT 3, DOT 4, DOT 5.1) should be flushed, or changed, every 1-2 years.[1] Many manufacturers also require periodic fluid changes to ensure reliability and safety. Once installed, moisture diffuses into the fluid through brake hoses and rubber seals and eventually the fluid will have to be replaced when the water content becomes too high. Electronic testers and test strips are commercially available to measure moisture content. The corrosion inhibitors also degrade over time. New fluid should always be stored in a sealed container to avoid moisture intrusion.
DOT 5 is silicone fluid and the above does not apply. Ideally, silicone fluid should be used only to fill non-ABS systems that have not been previously filled with glycol based fluid. Any system that has used glycol based fluid will contain moisture, glycol fluid disperses the moisture throughout the system and contains corrosion inhibitors. Silicone fluid does not allow moisture to enter the system, but does not disperse any that is already there either. A system filled from dry with silicone fluid, does not require the fluid to be changed at intervals, only when the system has been disturbed for a component repair or renewal. The United States armed forces have standardised on silicone brake fluid since the 1990s.


And here's way more information on brake fluid than one can imagine!!

Federal Motor Vehicle Safety Standards Sec. 571.116 Standard No. 116; Motor vehicle brake fluids. See:

http://frwebgate.access.gpo.gov/cgi-bin/get-cfr.cgi?TITLE=49&PART=571&SECTION=116&YEAR=2001&TYPE=TEXT
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will August ever come............
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JayBoy



Joined: 26 Jan 2005
Posts: 234
Location: Lexington, KY

PostPosted: Sat Feb 06, 2010 7:32 pm    Post subject: Reply with quote

The deal with the hard pads vs the soft is the hard pads apparantly retain the heat longer. Has anyone ever used ceramic pads?


Even more information you might not need. Although it is interesting his comments on each of these.

DRY WET
Castrol LMA DOT 3/4 446 311
Ford Heavy Duty DOT 3 550 290
ATE Super Blue Racing 536 392
ATE TYP 200 536 392
Motul Racing 600 585 421
Castrol SRF 590 518
Performance Friction 550 284

Castrol LMA is very good at rejecting moisture and may be kept in your brake system for a couple years. The LMA stands for "Low Moisture Absorption". This is the minimum quality stuff that I would use in my Impala. It comes in plastic containers which do not have a long shelf life. Don't buy lots of this stuff at a time because moisture can make its way through the plastic containers.

Ford Heavy Duty DOT 3 is VERY inexpensive and is popular among racers because of its excellent dry boiling point. It absorbs moisture quickly, but the racers don't care since they change their fluid frequently. Comes in metal cans so it may be stored. I would not use this in my Impala for the street.

ATE Super Blue Racing and ATE TYP 200 are the same brake fluid in two different colors (blue and amber, respectively). BMW recommends this brake fluid for their street cars because it, like Castrol LMA, absorbs moisture very slowly. The advantage over LMA is that ATE has a much better wet boiling point. You can put this stuff in your car and forget about it for a long time. An excellent choice for a weekend track car which also sees regular street duty. Comes in metal cans. This is what I use in all my street cars.

Motul Racing 600 is a very exotic and expensive synthetic fluid with high wet and dry boiling points. I use this exclusively in my race cars. Too expensive for the street and requires frequent changing due to its hydroscopic nature. Sold in plastic bottles.

Castrol SRF is a hyper-exotic and hyper-expensive brake fluid that is generally used by wealthy Porsche owners at track events. I've seen prices of $78 per liter for this stuff. It is not suitable for the street because it absorbs moisture quickly. Sold in metal cans. I can't afford this stuff!

Performance Friction High Performance DOT 3 has a good dry boiling point but a crummy wet boiling point. It comes in metal cans which is good for shelf life and sells for $7.87 per 16 ounce container. If you are even considering this fluid, I would go with the cheaper Ford Heavy Duty DOT 3. In either case, change this fluid frequently due to the poor wet boiling point.
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Paul



Joined: 27 Jan 2005
Posts: 182
Location: Utah

PostPosted: Sun Feb 07, 2010 5:54 pm    Post subject: Reply with quote

JayBoy wrote:
The deal with the hard pads vs the soft is the hard pads apparantly retain the heat longer. Has anyone ever used ceramic pads?


I just put ceramic pads on my car (with huge assistance from Bill). They took a long time to break in, and my impression is that they have slightly less performance than stock. The advantage is they don't deposit nasty black brake dust everywhere.


JayBoy wrote:
Ford Heavy Duty DOT 3 is VERY inexpensive and is popular among racers because of its excellent dry boiling point.


I heard somewhere that Ford fluid got reformulated, and now has a more normal boiling point.

Is there any difference between DOT 3/4/5.1 on paint? On a motorcycle the master cylinders are perched above the gas tank, so even the slightest leak will destroy your paint. Go ahead, ask me how I know this Evil or Very Mad
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