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Boiling brake fluid questions

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I can easily boil the brake fluid front and rear after 5-6 semi-hard brakes from about 50 miles per hour. The front looses effectiveness pretty quickly. I'm surprised this happens so quickly. The rear rotor heats up pretty quickly too, after a couple of uses. I have a wave type rotor front and rear, standard size. Brake fluid is DOT 4 Valvoline nothing special), about two years old, but very clean in appearance. Front has a SS brale line w/ EBC green pads (which don't have much bite), rear has stock rubber line and maybe EBC black pads. I have since switched the front to the Suzuki pads as I have read these are pretty darn good.

The bike is a 400S, I can't imagine ridding aggressively on the road through the twisties, as it wouldn't take but a few hard turns and brakes for the lever to become spongy, and the rotors become hot very quickly.

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Replace the brake fluid. It will make a big difference in the boiling point. It really should be replaced every year.

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Replace the brake fluid. It will make a big difference in the boiling point. It really should be replaced every year.

correction, it should be replaced after boiling.

:thumbsup:

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If you have the cash, a Mighty Vac is amazing. Open up the break fluid reservoir and attach the mighty vac to the bleed nipple and create a vacuum. Only thing you have to worry about is low fluid. It makes it so easy.

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correction, it should be replaced after boiling.

:ride:

No correction needed.. it was accurate..

It should be replaced yearly as suggested :thumbsup:

Or more often.. Replacement after boiling is just doing so in reaction, as a symptom of why you should have already done so for the reasons stated already,, Moisture....

DOT3

DOT3 brake fluid is the "conventional" brake fluid used in most vehicles.

Advantages:

DOT3 fluid is inexpensive.

Disadvantages:

DOT3 fluid eats paint!

DOT3 fluid absorbs water very readily. (This is often referred to as being hydroscopic.) As such, once a

container of DOT3 has been opened, it should not be stored for periods much longer than a week before use.

Since DOT3 fluid absorbs water, any moisture absorbed by the fluid can encourage corrosion in the brake lines

and cylinders.

DOT4

DOT4 brake fluid is the brake fluid suggested for use in some late model cars.

Advantages:

DOT4 fluid is available at most auto parts stores, and at some (but not all) gas stations or department stores.

DOT4 fluid does not absorb water as readily as DOT3 fluid.

DOT4 fluid has a higher boiling point than DOT3 fluid, making it more suitable for high performance applications

where the brake systems are expected to get hot.

Disadvantages:

DOT4 fluid eats paint!

DOT4 fluid is generally about 50% more expensive than DOT3 fluid.

Since DOT4 fluid still absorbs some water, any moisture absorbed by the fluid can encourage corrosion in the

brake lines and cylinders.

DOT5

DOT5 brake fluid is also known as "silicone" brake fluid.

Advantages:

DOT5 doesn't eat paint.

DOT5 does not absorb water and may be useful where water absorption is a problem.

DOT5 is compatible with all rubber formulations. (See more on this under disadvantages, below.)

Disadvantages:

DOT5 does NOT mix with DOT3, DOT4 or DOT5.1. Most reported problems with DOT5 are probably due to some

degree of mixing with other fluid types. The best way to convert to DOT5 is to totally rebuild the hydraulic

system.

Reports of DOT5 causing premature failure of rubber brake parts were more common with early DOT5

formulations. This is thought to be due to improper addition of swelling agents and has been fixed in recent

formulations.

Since DOT5 does not absorb water, any moisture in the hydraulic system will "puddle" in one place. This can

cause localized corrosion in the hydraulics.

Careful bleeding is required to get all of the air out of the system. Small bubbles can form in the fluid that will form

large bubbles over time. It may be necessary to do a series of bleeds.

DOT5 is slightly compressible (giving a slightly soft feeling in the lever), and has a lower boiling point than DOT4.

DOT5 is about twice as expensive as DOT4 fluid. It is also difficult to find, generally only available at selected

auto parts stores.

DOT5.1

DOT5.1 is a relatively new brake fluid that is causing no end of confusion amongst mechanics. The DOT could avoid a

lot of confusion by giving this new fluid a different designation. The 5.1 designation could lead one to believe that it's a

modification of silicone-based DOT 5 brake fluid. Calling it 4.1 or 6 might have been more appropriate since it's a

glycol-based fluid like the DOT 3 and 4 types, not silicone-based like DOT 5 fluid.

As far as the basic behavior of 5.1 fluids, they are much like "high performance" DOT4 fluids, rather than traditional

DOT5 brake fluids.

Advantages:

DOT5.1 provides superior performance over the other brake fluids discussed here. It has a higher boiling point,

either dry or wet, than DOT 3 or 4. In fact, its dry boiling point (about 275 degrees C) is almost as high as racing

fluid (about 300 degrees C) and 5.1's wet boiling point (about 175 to 200 degrees C) is naturally much higher

than racing's (about 145 C).

DOT5.1 is said to be compatible with all rubber formulations.

Disadvantages:

DOT 5.1 fluids (and Spectro's Supreme DOT4) are non-silicone fluids and will absorb water.

DOT 5.1 fluids, like DOT3 & DOT4 will eat paint.

DOT 5.1 fluids are sometimes difficult to find for sale locally, typically at very few auto parts stores, mostly limited to "speed shops." So buy it on line, it's cheaper, easy to find that way, and delivered to your door.

DOT 5.1 will be more expensive than DOT3 or DOT4, and more difficult to find.

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Motul RBF600 Synthetic DOT 4 Brake Fluid Has a high boiling point (593f) and a very good wet boiling point (420f), is available where ever you find Motul products. Is a synthetic product (not silicone-based). And one of the best DOT4's.. MAKE sure you fully flush a system that had 3, 5.1 in it.. While mixing this DOT4 with DOT 3 or 5.1 fluids does not destroy a system like mixing DOT 5 Silicone stuff will (or having to replace all rubber components and flush the system like changing to DOT 5 does),,, it does lower performance of the Synthetic DOT 4 Brake Fluid.

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Never thought about replacing fluid after boiling. I'll have to do that soon. The rear fluid is of an unknown age. (2003 bike).

I'm really surprised how quickly the rotors heat up after s few applications of the brakes. I'm sure the brakes aren't sticking. How can these things halfway preform on the track in extreme conditions??

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The rotors heat quickly because that is where the energy of braking goes. Ideally the rotors take all the heat and the pads and calipers stay cool. Of course that does not happen but still most of the heat goes in to the disc. It works because the disc dissipates the heat into the surrounding air. When braking creates more heat than the disc can dissipate, the disc overheats and the brakes fade (fade=less friction between the disc and the pad). There are many variables that control fade - disc material, disc size, air flow, speed, weight of machine and rider, caliper design, brake sweep area, pad material are a few. Some brake designs will operate well into red heat.

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Two thoughts, the caliper is dragging, not releasing.

Or your dragging the brakes with hand. finger position….

The brakes on an S / E are NOT up to the task of paved track duty.

The OEM set up is not up to fast, laps on a fast dirt track either.

1st Year I ran laps at a 24 hours GP race in Oregon,, there were several FAST sections close together, with TIGHT 120 (or more) deg turns between.. I smoked the front brakes in two laps that year..

And yes, the wet boiling temp is a best case deal…. IMHO, brake fluid gets replaced before every race, and once a year otherwise… It’s hydroscopic, and can’t help be absorb moisture, meaning your at the wet boiling temp faster than most think, and lower then that with age.

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I'm with the brake fluid change too. I run ATE Superblue in my DRZ, my streetbikes and my racebikes and it's flawless. Looks cool in blue, too.

And I'm also with E. Marquez....a gummed up caliper can leave a pad dragging more than usual, keeping the fluid hotter than normal. Might be time to pull the caliper off and have a look see.

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calipers aren't dragging. I did notice the rear pads didn't have the metal backing plates so maybe that will help as a heat sink for the rear. I'll just change the front fluid and see how it works out. Maybe I'm expecting too much from it.

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It’s an S, Small single disk.

It has old brake fluid that certainly is wet.

It’s Old, what is the condition of the disk? The Pads?

It’s a dirt bike, with a brake system that really was designed around the traction of rubber tire to dirt.

Add all that up with a rubber line, on known condition of the caliper to bracket slides, type of pads used.. and the relatively great traction a street condition provides,, and YES, 5-6 full power stops could easily over power the current braking system..

Using it mostly on street or mild off road,,

Install an EBC 320mm rotor kit, remove, clean, inspect, rebuild caliper, remove, inspect, clean, rebuild as needed the Master Cylinder (you will be surprised the amount of “stuff” you find in the caliper bores behind the pistons, and inside the master cylinder.,all of which is compressible) add a stainless steel line and good brake fluid.

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Mild off road/on road use.

F/R rotors- very little wear, can feel a slight ridge along the outside edge.

Front- pads were EBC green , stainless line, fluid is less than one year old, good lever feel until 4-5 stops from 50 mph. Now have stock Suzuki pads.

Rear- pads, EBC black, no backer plates on pads, fluid unknown.

Now the front has new pads, but I need to evacuate the fluid. Rear master has been rebuilt, caliper cleaned inside, installed metal pad backing plates on low mile stock Suzuki pads.

I'll report back after front evac of fluid.

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Never thought about replacing fluid after boiling. I'll have to do that soon. The rear fluid is of an unknown age. (2003 bike).

I'm really surprised how quickly the rotors heat up after s few applications of the brakes. I'm sure the brakes aren't sticking. How can these things halfway preform on the track in extreme conditions??

over heating brakes is more often caused by light braking, rather than hard braking.

You should brake as hard, and as short amount of time as possible. Easing on your brakes, just generates heat, and will boil them way faster (although works well on wet or cold days if the pads are cold).

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No correction needed.. it was accurate..

It should be replaced yearly as suggested :thumbsup:

agreed. I meant to say that it should be done after boiling, in addition to regular annual replacement.

:ride:

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Never thought about replacing fluid after boiling. I'll have to do that soon. The rear fluid is of an unknown age. (2003 bike).

I'm really surprised how quickly the rotors heat up after s few applications of the brakes. I'm sure the brakes aren't sticking. How can these things halfway preform on the track in extreme conditions??

I read your RR on ADV rider...Great write up! Are you still running the same fluid from riding the TAT?

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I read your RR on ADV rider...Great write up! Are you still running the same fluid from riding the TAT?

yes same fluid, that reminds me the fluid is 5 months old, that's when the front SS line was put on along with the EBC pads. 8,000 miles on the front which were 3/4 gone at the end of the trip.

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yes same fluid, that reminds me the fluid is 5 months old, that's when the front SS line was put on along with the EBC pads. 8,000 miles on the front which were 3/4 gone at the end of the trip.

After an EPIC ride like that Id say your DRZ needs new fluid and pads. :thumbsup:

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yes same fluid, that reminds me the fluid is 5 months old, that's when the front SS line was put on along with the EBC pads. 8,000 miles on the front which were 3/4 gone at the end of the trip.

Conditions very, and how the fluid got to the condition, which allow it to boil when there is no mechanical fault is hard to point to in a specific time line.

It boiled, the brakes faded after hard use.. Time for some maintenance. I did not see where you disassembled the caliper and MC, cleaned, inspected, replaced wear parts as needed. If not, I would do that as part of this service now.

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