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Discussion Starter · #1 ·
Hi all
has anyone used dot 5 silicone brake fluid in any post 2000 Brembo brake system? I have been told it is incompatible. I have used dot 5 in my older brembos (The old dual piston calipers) and it has been fine. In fact I rarely change it (like 10 years) and there is never any rust, the seals are perfect (some are now 30 years old) and the brake works fine. I also use it in other braking systems with no probs. In addition it doesn't damage any surfaces. I just wonder if it is not used cause of some rumours that dot 5 is slightly compressible. If it is then I haven't noticed it. My Streetfighter is almost out of warranty and i would prefer to use dot 5 in it unless there is any real reason not too.
Thanks
 

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From what I have heard, stay away from Silicone brake fluid. It will corrode the seals and once you've used Silicone based fluid, you must replace the complete system when using normal fluid. Just do a search on google...
 

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Discussion Starter · #3 ·
Hi yes I have been doing a little googling. However the problem is always the same, there are rumours that it causes problems but no facts from people who have used it. Like I said I have used it for many years in older Brembos and other bikes (Harley and japs) with no problems. I keep my bikes for many years and the problems with dot 4 and 5.1 is that they attract moisture and corrode systems and must be changed frequently, which is a pain when you have a few. And if you get the stuff on paint or chrome it starts eating it. I wonder if there is a way to contact Brembo directly?
 

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Old Wizard
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This is what Brembo has to say:

BREMBO TECHNICAL NOTES

All Brembo braking products use natural-rubber base seals, and therefore are incompatible with DOT 5 silicone-based brake fluids. DOT 5 silicone-based fluids react with natural-rubber seals to swell them which can cause severe piston retraction problems.

There is no cure for problems caused by DOT 5 use other than complete seal replacement. Use only DOT 3 or 4 non-silicone type fluids … in your Brembo components.

(Yes, we know the cap on the Ducati rectangular master cylinders says “DOT 3—5 Fluids”, but please note: silicone-based DOT 5 fluids are not generally in use in Europe, but glycol-based DOT 5.1 fluids are. Hence, the DOT 5 cap designation.)

For best braking performance, we recommend changing brake fluid twice a year. If the machine is to be stored in a damp environment (over the winter, say) , we recommend installing fresh fluid before and after the storage period. At minimum service levels, glycol brake fluids must be completely changed at intervals not to exceed a period of 18 months.
 

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Discussion Starter · #5 ·
Cool this is the info I need. Have you got a link for this quote? I would like to know when Brembo changed their seals so that I can use the dot5 only on their systems that won't cause problems. Obviously dot5 was compatible up to some point. I have contacted Brembo directly but am still waiting for a reply.
 

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The other thing you mentioned above is that dot 5 wont absorb moisture like dot 3-4..... so where do you think that moisture goes? thats right there will be moisture in the brake system and in dot 5 systems it will be at the bottom of the system. Thank you Brembo for having piston's that are not suspect to corrosion like the Nissan or other brands that pistons will corrode badly from moisture. I cant tell you how many brake systems I have rebuilt that I have seen moisture damage at or near the very bottom of the brake system even with dot 5....
 

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Discussion Starter · #9 ·
From my experience and the blurb provided about dot5 the moisture is NOT absorbed. This is why i try to use it. As stated I have systems that have had dot5 in them since 1980. I rarely change the fluid. These brakes have never needed rebuilding and have NO corrosion in them whatsoever. If they have moisture in them then it is well hidden. One set is Brembo dual piston calipers made from Magnesium alloy in the early 80's. The dot 5 seems to keep them in as new condition. This is not an argument just a statement of fact from my experience. I have also had systems that within a few years, running dot4, have corrosion in them. I must admin that I do not change the fluid @ 2 year intervals as recommended, so I must accept some of the blame for this. However I don't want to have to change the fluid all the time which is why I am searching for info on Dot5 and modern systems.
I do know of people who changed to dot5 and had heaps of dramas. They failed to RTFM and didn't fully flush and clean all the dot4 out before adding dot5...the 2 fluids really don't like each other.
Interestingly I have motorcars with dot4 that I have never changed....my ute is 1988 model. Maybe this is why its brakes are pretty crap...might need some fresh fluid!
Thanks for all the feedback.
 

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Old Wizard
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Brembo sells their own brand of DOT 3–4 hydraulic fluid, and in their catalog specifically warn against using it in brake systems containing magnesium parts—obviously because water absorption by the fluid will readily cause corrosion.

So given crasher's experience, I'm thinking that it's possible that Brembo uses a different seal material in their mag brakes that is compatible with silicone-based fluid.

http://www.brembo.com/en/car/Racing/Street-products/Documents/USA CATALOGO.pdf
 

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Discussion Starter · #11 ·
I am not sure if the glycol based fluids are a problem for magnesium products in general as my brakes could use dot4....but I never did so I cannot say with certainty. Upon reading the brembo catalog I certainly wouldn't try the LCF600 in mine. Magnesium can be a tricky material that has specific requirements. Thanks for providing the link.
Motodave, silicone based products DO reject moisture. Next time you wax your vehicle (they are silicone based) check what the rain does....it will bead off. The same thing happens in the master cylinder, moisture may well condense but it will not be absorbed into the liquid but the microscopic fluid will bounce on the top untill the air above is drier at which point it will be reabsorbed into the air. Thiis is why you should never find water in a silicone based braking system. Just basic high school science.
 

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Know this is an old post, but many of you probably know the new Brembo M/C states use DOT 3-5. Brembo has a disclaimer on their site saying that this is all crazy and a mistake and whatever. I have been using Silicone brake fluid in my Brembo system, elements of which are both pre and post 2000, w/o issue. But it's really pretty moot. Silicone is chemically inert. Thus incapable of reacting with anything. The US Military went over to Silicone years ago because it DOES NOT attack rubber parts and in every other way is far superior to glycol fluids. They're saving -- in the army alone -- 10 million dollars a year because of the switch. (There is one exception, air-over hydraulic brakes; jury still out).

The one issue is, it is not hygroscopic. It does not absorb water. It's always been unclear to me, why that's considered an issue. Glycol absorbs water and will impart it's boiling/freezing points to that water. Thus it's necessary to "flush" your system every couple years or so (which you could do with a silicone based system as well, so..?) But because Silicone can't absorb moisture that moisture retains its normal freezing/boiling points. Conventional wisdom -- those people -- believe this means water will "lodge" somewhere in the system. Which makes no sense as the first time your braking exceeds H20 boiling point that water will enter a gaseous state and be ejected through the master cylinder cap. My 750 GT sat for 12 + years and I just put it back on the road. While my Lockheed master was history as it sat w/o fluid for 12 years, rest of the system is in perfect shape. If I had been using glycol I would have had to rebuild everything. Bled it, fluid was clear. Drove.
 

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I've replaced dot 3 in cars with dot 5 and had spongy brakes no matter what bleeding method I used. I just go with the recommended grade now.
 

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I've replaced dot 3 in cars with dot 5 and had spongy brakes no matter what bleeding method I used. I just go with the recommended grade now.
ABS? Correctly purged? Honestly never tried it in a car. Seems to work in tanks though. The army was having issues with "air-over" brakes where air assist was used to activate the hydraulics. Read a "paper" designed to determine if Silicone fluid absorbed more air than glycol (because of complaints of spongey brakes in air-over applications). The paper concluded that silicone did "absorb" more air than glycol, but the difference was really small. Paper did NOT conclude this was the issue.
 

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Come up again?

Dot 5 silicone is not recommended in any high performance application. It may be fine for a mail truck or tank but all seals leak, albeit minutely, so air with a water vapor content enters every brake system. In non-silicone fluids, it is absorbed into the fluid, which is discarded periodically. In silicone, the water is not absorbed and hangs around in the calipers where it lowers the boiling point significantly. This will cause vapor lock when the brakes are worked hard, hence brake failure. That is why companies such as Wilwood highly recommend avoiding Dot 5. They make a super high temperature Dot 4 style fluid that starts out dryer than pedestrian products. Many other manufacturers make DOT4 style fluids that are drier. Eventually they degrade to a lower quality water level but you will hopefully change the fluid before that.

If you never actually get your brakes hot, you won't get the water past the boiling point and experience vapor lock failure. Even slower track day riders don't use the brakes aggressively but in all the years since silicone became available, virtually everyone I have personally seen try to use it ended up with a mushy pedal right after aggressive braking after the fluid had been installed for a couple months.
 

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If you never actually get your brakes hot, you won't get the water past the boiling point and experience vapor lock failure. Even slower track day riders don't use the brakes aggressively but in all the years since silicone became available, virtually everyone I have personally seen try to use it ended up with a mushy pedal right after aggressive braking after the fluid had been installed for a couple months.
Have heard this mantra repeatedly and would really like to see links (citations) proving this. Not just repeating this. Proper installation of Silicone really requires a completely new system, not a purged one, supposedly. As I said a test was made for the US Gov to see how much air was absorbed by Silicone fluid. Here it is (conclusions, fluids behave as expected and problems likely driver induced or due to an unknown factor):

BTW, over years and years of service have got my brakes plenty hot enough to induce the theoretical "vapor lock". I lived in Vermont for years driving my bike literally until snowfall stopped me. In that climate there would have been plenty of opportunity for moisture to enter my system. Never an issue.

Again, looking for any sort of real citation backing this vapor-lock theory up.

http://www.dtic.mil/dtic/tr/fulltext/u2/a251835.pdf

and...

MIL-PRF-46176B MILITARY SYMBOL: BFS RADCOLUBE SBR-1 | RADCO
 

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Do Not Use DOT 5 Fluid in Brembo Brake Components

Know this is an old post, but many of you probably know the new Brembo M/C states use DOT 3-5. Brembo has a disclaimer on their site saying that this is all crazy and a mistake and whatever. .

This is what Brembo has to say:

BREMBO TECHNICAL NOTES

All Brembo braking products use natural-rubber base seals, and therefore are incompatible with DOT 5 silicone-based brake fluids. DOT 5 silicone-based fluids react with natural-rubber seals to swell them which can cause severe piston retraction problems.

There is no cure for problems caused by DOT 5 use other than complete seal replacement. Use only DOT 3 or 4 non-silicone type fluids … in your Brembo components.

(Yes, we know the cap on the Ducati rectangular master cylinders specifies “DOT 3–5 Fluids”, but please note: silicone-based DOT 5 fluids are not generally in use in Europe, but glycol-based DOT 5.1 fluids are. Hence, the DOT 5 cap designation.)

For best braking performance, we recommend changing brake fluid twice a year. If the machine is to be stored in a damp environment (over the winter, say) , we recommend installing fresh fluid before and after the storage period. At minimum service levels, glycol brake fluids must be completely changed at intervals not to exceed a period of 18 months.
 
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