{"id":16209,"date":"2015-06-25T17:15:03","date_gmt":"2015-06-26T00:15:03","guid":{"rendered":"http:\/\/www.racingjunk.com\/news\/?p=16209"},"modified":"2016-11-30T15:07:32","modified_gmt":"2016-11-30T23:07:32","slug":"brake-fluid-and-a-silicone-future","status":"publish","type":"post","link":"https:\/\/www.racingjunk.com\/news\/brake-fluid-and-a-silicone-future\/","title":{"rendered":"Brake Fluid and a Silicone Future"},"content":{"rendered":"

\"Fluid<\/p>\n

Drag Race 101:<\/strong> Silicone-Based Brake Fluids. Yay or Nay?<\/p>\n

Want to open a can of worms with racers?\u00a0 Engage in a debate on brake fluid.\u00a0 What?\u00a0 Brake fluid is brake fluid.\u00a0 Right?\u00a0 Not exactly.\u00a0 Over the past several years, there have been many advances made in brake fluid — not the least of which are the silicone-based fluids.\u00a0 Unfortunately the fluid situation isn’t as simple as swapping one type of fluid for another.<\/p>\n

Boiling Point<\/strong><\/p>\n

For some time, the Department of Transportation (DOT) has issued a set of stringent specifications for brake fluid types.\u00a0 The more common glycol-based or “conventional” fluids fall under DOT 3 and DOT 4 specifications.\u00a0 DOT 3 has a minimum dry boiling point of 401 degrees F while DOT 4 has a minimum dry boiling point of 446 degrees F.\u00a0 On the other hand, silicone fluids fall under DOT 5, which has a dry boiling point of 500 degrees F minimum.\u00a0 In a typical drag race car, the conventional fluid boiling point diminishes with time.\u00a0 How long does it take for this to happen?\u00a0 I can’t locate statistics for a drag race vehicle, but in most passenger cars that are operated under damp conditions there can be a rapid deterioration of the brake fluid boiling point in as little as six months.\u00a0 Obviously, drag cars aren’t used in the rain, but it does go to show that brake fluid definitely is effected by time and weather.\u00a0 That’s why some drag race brake manufacturers recommend you flush the system with fresh fluid on a regular basis (as an example, some road racers change fluid after each event!).<\/p>\n

So what’s the big deal in regard to brake fluid boiling points?\u00a0 In reality, one of the most critical factors in regard to a hydraulic brake system is the dry and wet boiling points.\u00a0 If the fluid boils, small gas bubbles occur.\u00a0 These bubbles don’t disappear.\u00a0 Instead, they’re trapped in the system.\u00a0 Since gas bubbles are compressible, then the brake pedal becomes spongy.<\/p>\n

Wet Versus Dry Boiling Points<\/strong><\/p>\n

Generally speaking, a street driven passenger car is further plagued by wet boiling points.\u00a0 Normally, the brake system will function with a percentage of moisture in the system.\u00a0 Over time, this moisture content increases and as a result, brake performance decreases.\u00a0 That’s why “wet boiling point” specifications are also provided by the Department of Transportation.\u00a0 These “wet boiling points” are outlined as follows (keep in mind all are minimums!).<\/p>\n

DOT 3:<\/strong>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 284 degrees F\u00a0 (Glycol Ether Based)<\/p>\n

DOT 4:<\/strong>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 311 degrees F\u00a0 (Glycol Ether Based\/Borate Ester Based)<\/p>\n

DOT 5:<\/strong>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 356 degrees F\u00a0 (Silicone Based)<\/p>\n

DOT 5.1:<\/strong>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 356 degrees F\u00a0 (Borate Ester\/Glycol Ether Based)<\/p>\n

As you can easily see, the wet boiling point of silicone brake fluid and DOT5.1 is significantly higher than it’s glycol-based counterparts.\u00a0 In the case of silicone fluid it\u2019s because it does not absorb moisture while standard glycol-based brake fluid does.\u00a0 When you take a look at a can of conventional glycol-based brake fluid, you’ll almost always find a warning with regard to using the fluid immediately.\u00a0 The reason, of course, is moisture absorption. Once the seal is broken, then moisture will attack the fluid in the can.<\/p>\n

DOT 5.1 is a wee bit confusing. While DOT 5 is synthetic based, DOT 5.1 is pretty much a lighter viscosity synthetic poly glycol fluid with DOT 4 performance parameters. It was developed for use in mechanical ABS systems that require a higher cyclic rate capability.<\/p>\n

Moisture + Brake Fluid Don’t Mix<\/strong><\/p>\n

Further to the decrease in brake efficiency when the fluid is intermixed with moisture, a number of internal brake components can be attacked by the water found in the system.\u00a0 Things like disc brake pistons can corrode beyond repair, which in turn can create both a dangerous situation and an expensive repair bill.\u00a0 On a similar note, it’s always a good idea to use the brand of brake fluid in the system (or the brand you’re planning to use) as a lubricant when assembling brake calipers and assorted brake components.<\/p>\n

So why don’t the OEM manufacturer’s make the big switch to silicone-based brake fluids?\u00a0 Silicone brake fluids have some admirable qualities:\u00a0 They don’t absorb moisture and they don’t harm paint finishes if spilled.\u00a0 Unfortunately they aren’t perfect.\u00a0 One problem is slight compressibility under high temperatures.\u00a0 If the brake system is exposed to very high temperatures, the silicone fluid can compress slightly with the end result being a spongy pedal.\u00a0 In addition, silicone fluid is affected by atmospheric pressure.\u00a0 When a silicone brake fluid-equipped vehicle is driven in high altitude conditions, the fluid can expand significantly — again contributing to a spongy pedal.\u00a0 Further to this, many of the rubber components used in brake systems are manufactured from “ethylene propylene rubber”.\u00a0 Some silicone fluids are not compatible with the “EPR” – causing them to expand.<\/p>\n

Basic Brake Fluid Rules<\/strong><\/p>\n

So what’s the answer?\u00a0 Always use a brake fluid that is recommended by the brake manufacturer (or if you use OEM parts on your race car, by the motor vehicle manufacturer).\u00a0 Never mix brake fluid brands or types and make every effort possible to keep contaminants out of the brake fluid (as well as the brake system).\u00a0 Once the protective seal is broken on a can of brake fluid, use it immediately.\u00a0 Never re-use brake fluid which has been bled from a system.\u00a0 It’s a disposable item.\u00a0 Silicone brake fluid can be used in cars that are driven very little (i.e.:\u00a0 collector cars, antiques, “stretcher queens”).\u00a0 Finally, to maintain the health of your system, try flushing out the old glycol fluid in your race car braking system on a regular basis — replacing it with fresh DOT 3 or DOT 4 fluid (or possibly DOT 5.1).\u00a0 By the way, the DOT specs are the bare minimum specifications.\u00a0 As a result, the DOT 5 fluids do not provide the highest boiling points available. There are no DOT 5.1 brake fluids that exceed the dry and wet boiling points of the best of currently available DOT 4 racing brake fluid formulas (some \u201csuper DOT 4\u201d racing brake fluids have wet boiling points well over 400-degrees F). They do meet the lower viscosity specifications, however. Use the good stuff and stay away from silicone.\u00a0 Your brake pedal will be much happier.<\/p>\n

\"The
The Department of Transportation (DOT) specifications for brake fluids include a varied mix of dry (and wet) boiling points.<\/figcaption><\/figure>\n
\"Once
Once the protective seal is broken on a can of brake fluid, use it immediately. Otherwise, the brake fluid will collect water, and for all intents and purposes, it’s junk.<\/figcaption><\/figure>\n
\"In
In order to maintain the health of the braking system, try flushing out the old glycol fluid in your race car braking system on a regular basis — replacing it with fresh DOT 3 or DOT 4 fluid. Further to this, every effort should be made to insure that the fluid (and the brake system hardware) is clean.<\/figcaption><\/figure>\n","protected":false},"excerpt":{"rendered":"

Drag Race 101: Silicone-Based Brake Fluids. Yay or Nay? Unfortunately the fluid situation isn’t as simple as swapping one type of fluid for another. <\/p>\n<\/div>","protected":false},"author":20,"featured_media":16215,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[5009,3448,11,9],"tags":[2983,318,2984],"class_list":["post-16209","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-brakes","category-drag-race-101","category-how-tos","category-tech-tips","tag-brake-fluid","tag-brakes","tag-silicone-based-fluid"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/www.racingjunk.com\/news\/wp-content\/uploads\/2015\/06\/Fluid-1Feature.jpg","jetpack_shortlink":"https:\/\/wp.me\/p42YSK-4dr","jetpack_sharing_enabled":true,"amp_enabled":true,"_links":{"self":[{"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/posts\/16209","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/users\/20"}],"replies":[{"embeddable":true,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/comments?post=16209"}],"version-history":[{"count":1,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/posts\/16209\/revisions"}],"predecessor-version":[{"id":16231,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/posts\/16209\/revisions\/16231"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/media\/16215"}],"wp:attachment":[{"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/media?parent=16209"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/categories?post=16209"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/tags?post=16209"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}