Understanding Brake Fluid: DOT 3, DOT 4, DOT 5.1

[TAG UR IT]

A large group of us went to a driving school this past weekend to "learn high performance driving skills."

During my 4th and final 20 - 24 min course run, my brakes hit the floor at about 80mph. Needless to say, I mumbled, "awe shit..." as we approached the corner. I pumped the brakes a few times and went into the corner with too much speed throwing me at the very edge of the track. Luckily, it was a corner that I could go into a bit faster...and not a corner that had a barrier, creek, trees, etc. It could have been bad.

So, with that happening and losing my brakes (so not cool), I figured my brake fluid began to boil. If that happens, condensation and air begin to build up in the lines. From here on out, I learned that my brake fluid will boil more quickly and my brakes won't work to the best of their "Brembo" ability. I can't ever let this happen again on ANY track or ANY street.

So, I bought Super Blue Racing DOT 4 brake fluid. Yes, the cap on the cylinder says DOT 3. This confused me and I wanted to make sure I was not about to screw something up. So, I began reading and reading.

In my search, I found this to be EXTREMELY helpful. I wanted to make SURE that everyone here go the same info I just had and was able to make a well informed decision on their own if they ever decide to head out to a "driving school," 1/4 mile track, road course, or plain flat out, RACE.

Check out the link here. It could SERIOUSLY help.

Understanding Brake Fluid


Automotive brake fluid has many responsibilities. Corrosion protection and lubrication of brake system components are only a portion of the role brake fluid must play.

All automobiles that have a hydraulic braking system must use brake fluid in order for the brake system to operate. The type of fluid used can depend on the type of vehicle and the demands of the vehicles brake system.

The two most common brake fluids used in the automotive industry are fluids that contain Polyalkylene Glycol Ether and fluid that contains Silicone or Silicium-based Polymer. Both Fluids are common but very different in regards to the manner in which they perform. Fluids containing Polyalklene Glycol Ether are more widely used and are the only fluids that should be used in racing brake systems.

Because brake systems may reach extreme temperatures brake fluid must have the ability to withstand these temperatures and not degrade rapidly.

SILICONE BASED FLUID
Fluids containing Silicone are generally used in military type vehicles and because Silicone based fluids will not damage painted surfaces they are also somewhat common in show cars.

Silicone-based fluids are regarded as DOT 5 fluids. They are highly compressible and can give the driver a feeling of a spongy pedal. The higher the brake system temperature the more the compressibility of the fluid and this increases the feeling of a spongy pedal.

Silicone based fluids are non-hydroscopic meaning that they will not absorb or mix with water. When water is present in the brake system it will create a water/fluid/water/fluid situation. Because water boils at approximately 212º F, the ability of the brake system to operate correctly decreases, and the steam created from boiling water adds air to the system. It is important to remember that water may be present in any brake system. Therefore silicone brake fluid lacks the ability to deal with moisture and will dramatically decrease a brake systems performance.

POLYGLYCOL ETHER BASED FLUIDS
Fluids containing Poly glycol ethers are regarded as DOT 3, 4, and DOT 5.1. These type fluids are hydroscopic meaning they have an ability to mix with water and still perform adequately. However, water will drastically reduce the boiling point of fluid. In a passenger car this is not an issue. In a racecar it is a major issue because as the boiling point decreases the performance ability of the fluid also decreases.

Poly glycol type fluids are 2 times less compressible than silicone type fluids, even when heated. Less compressibility of brake fluid will increase pedal feel. Changing fluid on a regular basis will greatly increase the performance of the brake system.

FLUID SPECIFICATIONS All brake fluids must meet federal standard #116. Under this standard is three Department of Transportation (DOT) minimal specifications for brake fluid. They are DOT 3, DOT 4, and DOT 5.1 (for fluids based with Polyalkylene Glycol Ether) and DOT 5 (for Silicone based fluids).

MINIMAL boiling points for these specifications are as follows:


Dry Boiling Point Wet Boiling Point
DOT 3 401ºF 284º F

DOT 4 446º F 311º F
DOT 5 500º F 356º F
DOT 5.1 518º F 375º F





Racing brake fluids always exceeds the DOT specifications for dry boiling points. Wet boiling points generally remain the same.

DOT 3 VS. DOT 4 and 5.1
AFCO's 570º brake fluid is a DOT 3 type fluid. However, it has a dry boiling point that is 52º higher than DOT 5.1 specifications, 124º higher than DOT 4 specifications and 169º higher than DOT 3 specifications. AFCO's 570º fluid meets or exceeds all DOT 3, 4, and 5.1 lubrication, corrosion protection and viscosity specifications.

AFCO's 570º racing fluid meets but does not exceed federal standards for wet boiling point specification; therefore, its classification is DOT 3. Because AFCO's 570º fluid is intended for use in racing type brake systems that undergo frequent fluid changes, exceeding federal standards for wet boiling points is of little concern. Racing brake fluids always exceeds the DOT specifications for dry boiling points. Wet boiling points generally remain the same.

WET VS. DRY BOILING POINT
The term boiling point when used regarding brake fluid means the temperatures that brake fluid will begin to boil.

WET BOILING POINT
The minimum temperatures that brake fluids will begin to boil when the brake system contains 3% water by volume of the system.

DRY BOILING POINT
The temperatures that brake fluid will boil with no water present in the system.

MOISTURE IN THE BRAKE SYSTEM
Water/moisture can be found in nearly all brake systems. Moisture enters the brake system in several ways. One of the more common ways is from using old or pre-opened fluid. Keep in mind, that brake fluid draws in moisture from the surrounding air. Tightly sealing brake fluid bottles and not storing them for long periods of time will help keep moisture out. When changing or bleeding brake fluid always replace master cylinder caps as soon as possible to prevent moisture from entering into the master cylinder. Condensation, (small moisture droplets) can form in lines and calipers. As caliper and line temperatures heat up and then cool repeatedly, condensation occurs, leaving behind an increase in moisture/water. Over time the moisture becomes trapped in the internal sections of calipers, lines, master cylinders, etc. When this water reaches 212º F the water turns to steam. Many times air in the brake system is a result of water that has turned to steam. The build up of steam will create air pressure in the system, sometimes to the point that enough pressure is created to push caliper pistons into the brake pad. This will create brake drag as the rotor and pads make contact and can also create more heat in the system. Diffusion is another way in that water/moisture may enter the system.

Diffusion occurs when over time moisture enters through rubber brake hoses. The use of hoses made from EPDM materials (Ethlene-Propylene-Diene-Materials) will reduce the amount of diffusion OR use steel braided brake hose with a non-rubber sleeve (usually Teflon) to greatly reduce the diffusion process.

THINGS TO REMEMBER
Brake fluids dry boiling point is more important then wet boiling point when used in a racing brake system.
Passenger cars very rarely will undergo a brake fluid change making the wet boiling point more important.
Racing brake system fluid is changed often and a system with fresh fluid will most likely not contain water.
Because of this, racers should be concerned with the dry boiling point.
Racing fluid exceeds DOT 3, 4, and 5.1 dry boiling point specifications.
Never use silicone based fluids in racing brake systems.
Using racing brake fluid will increase performance of the braking system.
Never reuse fluid. º Never mix types or brands of brake fluid.
Use smaller fluid containers that can be used quicker.
If fluid remains in container be sure to tightly seal and do not store for long periods of time.
Purge system (complete drain) and replace fluid often.
Immediately replace master cylinder reservoir cap following any maintenance.

$129.00

Not bad.


Here's some more info for those wanting to know how to bleed those brakes.

#1 Remove the top of the master cylinder reservoir.

#2 Using a turkey baster, suck out as much of the old dark inky fluid as you can.

#3 Clean any sediment out of the reservoir with a clean, lint-free rag. (Do not spill any brake fluid on any painted surfaces, it will remove the paint immediately.)

#4 Fill the master cylinder with clean brake fluid.

#5 Replace the top of the master cylinder reservoir.

#6 Pump the brake pedal several times (15 or more).

#7 Using a box wrench that fits the bleeder bolt, loosen the bleeder valves, but leave them closed. (A little penetrating oil drizzled on the bolts the day before will help to loosen them).

#8 Using a piece of clear plastic tubing (aquarium tubing works fine), push one end of the tube over the brake bleeder bolt.

#9 Put the other end of the tube into a small, clear bottle with an inch or two of clean brake fluid in it. (This will keep air from being sucked back into the brake cylinder.)

#10 Put a piece of 1 x 4 lumber or some other "spacer" under the brake pedal to prevent the pedal from traveling too close to the floor.

#11 Remove the top of the master cylinder reservoir.

#12 Top off the master cylinder reservoir with fresh fluid.

#13 Replace the top of the master cylinder reservoir.

#14 Have your helper sit in the driver's seat and slowly depresses the brake pedal with an even force and hold it down. The helper should shout "down" when the pedal is down as far as it will go.

#15 Starting with the rear passenger wheel (back right for righthand drive cars), turn the bleeder bolt to the left one quarter-turn. Old fluid and air will go down the tubing into the bottle. When the fluid stops, close the bleeder valve.

#16 Shout "up" to your helper, who at this point should remove his foot from the pedal allowing it to move up.

#17 Repeat this process until new, clear fluid comes from the bleeder tube. (After every five (5) times the brake pedal is depressed, top off the master cylinder reservoir with fresh fluid. Never let the reservoir get too low, or air will be sucked into the master cylinder.)

#18 Tighten the bleeder bolt.

#19 Repeat steps 14 to 17 on the left rear wheel.

#20 Repeat steps 14 to 17 on the right front wheel.

#21 Repeat steps 14 to 17 on the left front wheel.

[Atti2de]

Wow, great info so glad u shared this with us...

[speedster]

TAG -

Thanks for posting such a great article. Again, it's the little things that really add up to make a safe vehicle, especially in racing conditions. I use Wilwood EXP 600 fluid in my "HP" vehicles for that very reason. No one thinks of brake fluid, just brakes, but you found out first hand - it makes a BIG difference.

Thanks again for the Thread. Should help some others stay out of trouble.

[TAG UR IT]

Happy to help.

Now....I'm thinking of upgrading to stainless steel brake lines. (Honestly, losing my brakes like that kinda got me prettttttty damn nervous. I am NOT going to let that happen again!)

[speedster]

Originally Posted by TAG UR IT

Happy to help.

Now....I'm thinking of upgrading to stainless steel brake lines. (Honestly, losing my brakes like that kinda got me prettttttty damn nervous. I am NOT going to let that happen again!)

Absolutely upgrade to BSS brake lines. MTI on this site has a good set. Goodridge makes them, StopTech makes them. Hate to sound like a broken record, but all our HP vehicles have been equipped with BSS brake lines.

[TAG UR IT]

Doesn't sound like a broken record to me! This is EXACTLY the kind of information that I'm looking for. What type of stainless steel brake lines?..."BSS, carried by MTI." THIS helps!

THANK YOU!

[Doc]

In addition to allowing some heat dissipation through the BSS lines, they also give a better, more solid feel to braking since they don't expand like rubber lines do thus you won't feel your brakes getting spongy as they heat up.

If you want a nice upgrade, especially you guys who've boosted your power, try the Racing Brake 2-piece drilled/slotted rotors. Besides being 6 lbs lighter than the stock rotors, they do a great job of ventilating and dissipating heat. And they look seriously cool too.

Here's how they look on my car (these are the fronts):

[TAG UR IT]

I remember you getting those....talking about unsprung weight, etc. How are they treating you?

[KEEP RT]

Excellent info. I am wondering though it often says NOT to mix types of fluid. How do you ensure that you are getting all the DOT3 out? There is always a bit left coating in the lines, master and calipers. (may not seem like it but 1oz. or a shot glass full is a very large percentage) Are you running enough thru to "flush" out the old? I upgraded my 57Caddy to front disc, I replaced it with all new. now it stops on a dime. After all if you cant stop don't start. It's just a question, I'm not questioning your intelligence.

[TAG UR IT]

the old stuff is a black/gray/clear fluid. The fluid that I used is blue (super blue racing DOT 4). You remove (with a turkey baster, etc) from the master cylinder and then pour in the new beginning to bleed one line at a time until you get blue fluid that comes out. Sure, there's going to be a teeny tiny bit left over... But, the majority will be out.

If you want to, you can always take the car to a professional shop. They have machines to properly drain the fluid out of the cylinder.

[Doc]

Originally Posted by TAG UR IT

I remember you getting those....talking about unsprung weight, etc. How are they treating you?

The rotors and braided stainless steel lines are great. Braking is very solid and linear; no sudden grabbing. Soon as they get the rear rotors done I'll be adding those and enjoying the performance.

[michael's maro]

Great write up...Lots of great info

[TAG UR IT]

Originally Posted by Doc

The rotors and braided stainless steel lines are great. Braking is very solid and linear; no sudden grabbing. Soon as they get the rear rotors done I'll be adding those and enjoying the performance.

Originally Posted by michael's maro

Great write up...Lots of great info

I figured after my little incident, it might be helpful to others...and if could save one person from flying off the track (better understanding what could happen IF they stayed with DOT3 OR got on the brakes that hard that often), then it's definitely worth the time to write up. I hope some folks put this to good use!

I have DOT4 in my lines now and if someone makes me a good offer on some new stainless steel brake lines, I'll pick some up.

[Doc]

Originally Posted by TAG UR IT

I figured after my little incident, it might be helpful to others...and if could save one person from flying off the track (better understanding what could happen IF they stayed with DOT3 OR got on the brakes that hard that often), then it's definitely worth the time to write up. I hope some folks put this to good use!

I have DOT4 in my lines now and if someone makes me a good offer on some new stainless steel brake lines, I'll pick some up.

The main problem with the factory brake fluid is it's not rated for track use. The repeated hard use on the track causes the factory fluid to boil and then you have no brakes. Super Blue or something equivalent is in fact rated for racing with a much higher boiling point so anyone tracking their car should definitely make this change.

The braided lines aren't that expensive; I got mine from Racing Brake but I know Pedder's and other sells them and the price is around $120 I believe give or take a few bucks. It's an upgrade that is WELL worth it.

[TAG UR IT]

Yep.

$128 on their site. Going to keep on looking...see what I can come up with. Thanks!

[franknbeans]

thanks for this info Tag. . . I myself had the same scare.. . Last Lap the 4th time out. . . I was lucky enough the brakes went out on my cool down lap. . .

[13 ZL1]

I have one of these and it works pretty well. I am not sure if there are any issues using it with ABS systems though.


http://www.summitracing.com/parts/MVP-0250/

[TAG UR IT]

Originally Posted by franknbeans

thanks for this info Tag. . . I myself had the same scare.. . Last Lap the 4th time out. . . I was lucky enough the brakes went out on my cool down lap. . .

Crazy! Last lap, just like me. Well, I'm sure the DOT 4 would be a great way to go. It's compatible with DOT 3 and you might even be able to get the dealer to change it out for you. Tell them it's "just in case."



Really, there is no difference other than wet/dry boiling points. In other words, DOT 4 can withstand a little more braking and heat. It's good stuff. Super Blue

Originally Posted by Orange2SSRS

I have one of these and it works pretty well. I am not sure if there are any issues using it with ABS systems though.


http://www.summitracing.com/parts/MVP-0250/

I needed to get one of those. I just had the dealer do it and they used pretty much the exact same thing.

[Shardik2SS]

Originally Posted by TAG UR IT

Happy to help.

Now....I'm thinking of upgrading to stainless steel brake lines. (Honestly, losing my brakes like that kinda got me prettttttty damn nervous. I am NOT going to let that happen again!)

You won't regret it. I upgraded to Goodridge G Stop SS lines as well as having Motul Racing brake fluid put in. It's DOT 4 rated with a wet boiling point of 421 and dry boiling point of 594.

[TAG UR IT]

WWWWWOOOOOOOOOOOOOOOOOOOOOO

HOOOOOOOOOOOOOOOOOOOOOOOOOO



Got my MTI stainless steel brake lines in as a Christmas present from Mrs.Tag! Now...to replace and bleed those brakes once again...lol

[BowlingSS]

Originally Posted by Orange2SSRS

I have one of these and it works pretty well. I am not sure if there are any issues using it with ABS systems though.


http://www.summitracing.com/parts/MVP-0250/

I have one like this and I used it on my 4th gen which had ABS. I never had a problem.

I also used super blue.

Worked great.

Bill

[gotroost]

I'm sold. Going with Super Blue DOT 4 before C5Fest II. How much does it take to flush the old stuff out of the sytem? Owner's manual doesn't have anything about brake fluid capacity.

[TAG UR IT]

We used just one bottle ...$14 and we were good.

[Dr Jkel]

One other point for those who may not know ( I sure didn't and had to be told) If you are doing any type of track events and you are heating up your breaking system you need to be careful when you are finished and DO NOT APPLY THE EMERGENCY BRAKES it has a tendency to warp your rotors.

I do not know if this will actually warp your rotors but this is what I was told by a track instructor and didn't want to find out the hard way.

Great write up about the fluid, and brake line, glad I changed my lines, now need to change my fluid.

[Moriartii]

I recently used Super Blue in my bike, I liked it and highly recommend it as it makes flushing very easy. Plan on doing the camaro soon.

Cheers
K