Thunder240 Posted December 9, 2011 Share Posted December 9, 2011 I need a lesson in brake fluid. I've read in several places on the forum that our cars use a DOT 3/4 braking system, and that DOT 5 should be avoided like the plague. But in at least one thread on this forum I also read that folks were using DOT 5.1 without problems. My car is a 2011 Legacy 2.5i with all-stock brakes at the moment. I'm getting read to replace the OEM pads, and am thinking that I'll upgrade to SS brake lines at the same time in order to reduce the slop in the pedal. When I do this, I'll probably flush the fluid. When I do the pad/SS line upgrade, what are the advantages and disadvantages to flushing with DOT 4 versus DOT 5.1 brake fluid? Does it make a difference which pads I go with? I'm still reading reviews of various pads. The lines will be Techna-Fit stainless steel. I plan to keep my stock rotors and calipers. Regarding driving style, I am a "spirited" city driver. (Some might call it "aggressive".) However I don't have any intention of taking the car to the track. Thanks for explanations regarding fluid type. Link to comment Share on other sites More sharing options...
AZP Installs Posted December 9, 2011 Share Posted December 9, 2011 Brake fluid levels (ie DOT 3/4/5.1) are based on the amount of heat they can take before boiling and possible chemical differences in the fluid. So DOT 3 fluid has the lowest boiling point and DOT 5.1 being the highest. However the higher the rating the faster the fluid will absorb moisture and need to be flushed. Since your car is street driven DOT 4 is the highest I would put in as you simply have no need for anything more. Really DOT 4 is over kill but its still a good fluid. We recommend ATE Super Blue as it is a good fluid and not expensive. We keep in stock and can ship it if you like. -Jake http://www.pbase.com/paisan/image/91072632.jpg http://www.pbase.com/paisan/image/133406601.jpg http://upload.pbase.com/image/137566671.jpg Call directly for your best Whiteline Price! | We also carry almost every manufacturer now, so before you buy parts call us. AIM: AZP Installs | E-mail: sales@azpinstalls.com | 725 Fairfield Ave | Kenilworth, NJ 07033 | 908.248.AZP1 (2971) | T-1 Certified Amsoil Direct Jobber "Race Tested, Enthusiast Approved!" Link to comment Share on other sites More sharing options...
BAC5.2 Posted December 9, 2011 Share Posted December 9, 2011 Remember, you can go up but not down. You can replace DOT 3 with DOT 4 (DOT 4 is DOT 3 with boron ether included). You CAN go back to DOT 3, but it's not recommended. You can go from DOT3/4 to DOT 5/5.1, but you CANNOT go back. You'll never get all of the silicone out, and you'll ruin the brake systems ability to mitigate water (potentially trapping water in the caliper, and causing it to boil and lock the caliper). DOT 5.1 is for race-use-only. Even then, it's recommended to keep the bleeders cracked before a lap session to purge the calipers of any water that might have contaminated the system. DOT 4 is suitable for all enthusiast drivers. There's no real difference in absorption rate between DOT 3 and DOT 4, as long as you change your brake fluid at appropriate intervals. [URL="http://legacygt.com/forums/showthread.php/proper-flip-key-interesti-159894.html"]Flip Key Development Thread[/URL] "Genius may have its limitations, but stupidity is not thus handicapped." - E. Hubbard Link to comment Share on other sites More sharing options...
Thunder240 Posted December 9, 2011 Author Share Posted December 9, 2011 Okay, what you both have said regarding DOT 3/4/5.1 makes sense, but since BAC5.2 mentioned DOT 5, I'm gonna probe a little further. You indicated that DOT 5 is silicone based (so presumably it doesn't absorb water the way DOT 3/4 does). Why doesn't everyone ditch DOT 3/4/5.1 and go to DOT 5? I assume that cost is one reason, but if it doesn't absorb water, presumably you don't have to flush it as often, so for the moment lets pretend that cost is a wash. How would water get trapped in my calipers? Is this an issue with caliper design (meaning can some calipers accommodate DOT 5 and others not)? AZP, thanks for the offer. I'll email when I'm ready. Link to comment Share on other sites More sharing options...
BAC5.2 Posted December 9, 2011 Share Posted December 9, 2011 Water can get in the system for any number of reasons. Condensation, opening the reservoir cap, during vacuum bleeding, and it'll work it's way to the caliper. It'll boil at 212F, and lock up the caliper. Thus, it requires constant attention (hence the draining on race cars). In old cars, it'll desludge the brake system and clog the ABS unit. It's also expensive. 100% not worth it in street cars. [URL="http://legacygt.com/forums/showthread.php/proper-flip-key-interesti-159894.html"]Flip Key Development Thread[/URL] "Genius may have its limitations, but stupidity is not thus handicapped." - E. Hubbard Link to comment Share on other sites More sharing options...
Thunder240 Posted December 9, 2011 Author Share Posted December 9, 2011 Okay, thank you! Link to comment Share on other sites More sharing options...
BAC5.2 Posted December 9, 2011 Share Posted December 9, 2011 http://i267.photobucket.com/albums/ii287/bac52/wordwb7.png [URL="http://legacygt.com/forums/showthread.php/proper-flip-key-interesti-159894.html"]Flip Key Development Thread[/URL] "Genius may have its limitations, but stupidity is not thus handicapped." - E. Hubbard Link to comment Share on other sites More sharing options...
AZP Installs Posted December 11, 2011 Share Posted December 11, 2011 Just an FYI, DOT 5.1 is NOT silicone based and is fine for regular street driven cars, however it is not worth the exhorbinent cost. Mike Link to comment Share on other sites More sharing options...
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