Am not looking for this thread to become a fluid recommendation debate. Would like to know your experience using the sylicone brake fluid DOT5. It can be used in DOT3 & DOT4 vehicles after first flushing the lines w/ the DOT5 sylicone fluid. The sylicon doesn't absorb moisture, so it's wet boiling point (actually dry) is above 512*F; where as DOT3 &DOT4 are 300 something *F.

 

hmm sounds interesting. i havent used it but im interested in knowing more for sure

 

from everything ive read, you should NOT use DOT 5 ever. its for heavy trucks, and non-ABS only.

 

Dot 5 will eat away at the rubber seals inside the MC and bake calipers found on typical road cars.

DOT 5.1, on the other hand is 100% compatible with our brake systems.

 

From what I understand the peddle feel with a DOT 5.1 is very mushy (even more so than what we all already have).

 

Good info. guys, keep it coming.

 

That hasn't been my experience.

Fluid doesn't compress unless there is air present. Unless there is a 5.1 fluid that is carbonated, my guess would be an inadequate bleed.

 

That's an interesting statement. I am currently re-building my front C4 brake calipers & found that the seals kind of mixed w/the aluminum caliper material which basically stuck to the metal pistons & froze them to where they would drag on the rotor. My guess is that they were due for a re-build, but also thought that perhaps heat combined w/ fluid & aluminum may have caused the issue. Was using DOT 3 fluid.

Do you see any reason for this while using DOT 3?

In reference to your DOT 5 statement. What is it about sylicone that causes it to "eat" the rubber seals ,or is it one or more of the other ingredients in the sylicone mix that causes the problem?

 

I'm no expert ... just a graduate of Hard Knocks High.

My guess is it's not the silicone rather than the cocktail that makes up the fluid blend that prevents it from absorbing moisture.

When choosing a brake fluid for my use, I look at wet boiling point first. That's why I use Castrol SRF. But, at $90 a liter, it's not for every one. But, for whatever reason, it doesn't attack rubber.

 

Here are some handy links:

http://www.performancefrictionbrakes...?pageId=47#dot
http://www.federal-mogul.com/en/Afte...+Brake+Fluids/
http://www.apracing.com/info/index.a...Brake+Fluid_33
http://www.apracing.com/info/index.a...rake+Fluid_978
http://www.stoptech.com/tech_info/faqs.shtml#9 (the question should be "what kind of brake fluid should I use?")

I can explain chemically why it isn't a good idea to use DOT 5 in systems, however for the purpose of this post I will grossly oversimplify as state that propylene glycol or similar diol alcohols is hygroscopic and generally miscible (mixes in all proportions). Silicone (not to be confused with elemental silicon) has distinct chemical properties such as the ability to repel water and/or form watertight seals (though not completely hydrophobic) and it's highly flexible (analyse on the molecular level and NOT so much on the macro-visual level). My estimation would be that one or more of the chemicals in Silicone based brake fluids probably contain methyl chloride or something similar, which is a major enemy to rubber (especially small membrane like rubber seals present in several hydraulic systems, e.g. many automotive brake systems).

FWIW, DOT 5.1 has very similar dry and wet boiling points as DOT 5, yet it's easily available and can mix easily with DOT 3 and DOT 4 (though there will be an obvious compromise dependant on mixture ratios). As stated earlier by other posters and through the links I've provided above, DOT 5 CANNOT be mixed with the others.

My take on this: Unless a new system has been properly engineered to use DOT 5, it's highly suggested to choose the others recommended and leave DOT 5 alone.

 

My head hurtz ...

 

Yeah,

my hijack question in relation to this is...

is it from the mere discussion of how brake fluid works, or just from simply working the brake fluid?

 

I used DOT5 brake fluid in a racecar for 8 seasons of racing. I used it based on the dry boiling temperature, but bled the system periodically to help keep any moisture out. If any water gets into the brake system with DOT5 it does not get absorbed in a way such as DOT3/DOT4, making the wet boiling temp lower then the other two. During this time, I never had any problems with seals in the master clyinder or brake caliper at all. Fwiw, I've also heard of DOT5 being used in motorcycles and show cars. One major benefit of DOT5 is that it will not eat away paint if it leaks or is spilled.

 

Thank-you to everyone whom posted. This thread contains excellent information. Have decided that DOT5 is not for me.

Found some 417*F wet boiling point, reasonably priced DOT 3,4 fluid @ Summit & have decided to go w/it. Although there are higher wet boiling point DOT 3,4 fluids, I figure thie product found @ Summit is a reasonable compromise between price & wet boiling point.

 

Any motorcycle shop will have a great selection of quality brake fluid. A liter of fluid should be plenty for a brake fluid flush. Motul and ATE are good brands.

Tip: Buy a cheap turkey baster and suck all the fluid that you can out of the master cylinder. Many will just bleed the fluid level down, but this is kind of dangerous. You run the risk of running the MC dry and getting air in the MC. Once all the fluid is removed, then pour in the new fluid and begin bleeding. This significantly reduces contaminating the new fluid with the old in the MC.

 

Are you talking about Wilwood EXP600 brake fluid? You really can't go wrong with that or the Wilwood 570. If you get your rotors glowing red, you're eventually going to have brake fade after a period of time. Are you racing this car, or just driving it on the street?

 

A few road course days. I have brake duct coolers as well. With the coolers, fronts are always cooler than the non-cooled & less applied clamp force rears.

 

[QUOTE=ss1;10738152]Are you talking about Wilwood EXP600 brake fluid? [QUOTE]


Yes, got the EXP-600 & (4) Earl's Performance solo brake bleeders. Should be here tomorrow. Finished re-building the brakes today, fronts were jammed stuck prior to re-build. Anyway, am looking forward to bleeding w/ the solo bleeders. It should be a much less pain in the a$$ than even w/ a self bleeding bottle.