Whats The Best Brake Fluid You Can Buy?

[blackrb20silvia]

just a question what is the best brake fluid you can buy??

how much?

where from?

and what expierance have you had with it any info would be good

im looking at a really good fluid so i can compete next year at clubmen level motor sport once a month

cheers

matt

[Sydneykid]

We use Castrol SRF

cheers

[Duncan]

I gave up on castrol SRF and moved to Motul RBF6000. Had to bleed the SRF after every race.

But they are both pretty good. The other worthwhile option is the Caltex dot 5.1 stuff, it is about half the price and 95% as good

[Eug]

Motul RBF6000

<{POST_SNAPBACK}>

werd

[blackrb20silvia]

ive read a fair bit or should i say as much as i can bout the motul rbf600 it sounds good a few people have recommended it (bullant47)

just want to know if there are other brands out there that are better around the same price i dont mind spending more money on something that will make a differance

especially with brakes

like i dont mind if i have to spend 50 for half a litre as long as it lasts and is good shit

also off the topic

does anyone use those oneway bleeders i have seen a couple around they make sense and would make things a hell of alot easier when bleeding when you cant find a mate??

[blackrb20silvia]

just found this on the net after a good 5hrs of looking for info i struck gold

This is some Generic Brake info from an Engineer in the U.S

Michael worked for Ford on brake development.

and to

Steve Gavin

Production Engineer

Disc Brakes Australia

cheers guys

I wrote all this stuff at different times for different reasons and thought you guys might find it interesting and hopefully even useful. Find any mistakes or typos let me know.

THIS IS JUST GENERIC INFO, NOT FOR ANY SPECIFIC VEHICLE.

Pedal Feel Contributors:................

First some quick definitions: Brake Pedal ratio is the measurement of how much mechanical assistance you are getting from the pedal. Example: a ratio of 4.1 will give you 41 pounds at the booster input rod for a 10 pound load at the pedal itself.

Dead or lost travel is how much pedal stoke is required before you actually start stopping.

Dead Travel or Lost travel and overall poor pedal feel is made up of the following:

[(Travel as measured at the brake service pedal assembly pin (where the booster connects)]

(Imagine traveling from the pedal through the brake system to the rotor, all lost travel must be multiplied by whatever your brake pedal ratio is.)

1. Tolerance between brake pedal pin and booster input rod. This can be quite a bit for systems that use a pin mounted brake light switch. If you do have such a switch do not remove it or take up the slack as your brake lights will be on all the time. If you don't have a pin-mounted switch just get a tighter bushing. If you do, you're s**t out of luck.

* will be felt during first few mm of travel

2. Slack in the brake pedal assembly itself. To see how good or bad yours is, with the car off pump the brakes until hard (2-3 pumps) and then grab the pedal with your hands and see how much it moves around.

* will be felt through first few mm of travel (I hope)

3. Dash flex. This can range dramatically from vehicle model to vehicle model. Not much you can do about this.

*felt during medium and high decelerations stops on most cars, on Fords dashes flex with the breeze

4. Lost travel in booster. This is designed to be there to allow for booster expansion due to climate and use over time. Only adds half a mm (multiplied by the pedal ratio).

*felt only in the first few mm of travel

5. Flex of booster shell. Can be a real problem on some designs. All you can do is try and brace the booster or replace with a better product.

*felt on medium and high deceleration stops

6. Design tolerances in the Master Cylinder. Varies greatly from one to another. Simply, if you want less lost travel in the TMC (tandem master cylinder), you have to pay for a more expensive one. A minimum lost travel of about 1-1.5mm is required for proper and safe operation. However, I've seen some with double that. (Again multiplied by the pedal ratio)

*felt during first 10mm or so of pedal travel

7. The brake tubes and ABS unit. Maybe .0000001mm here. Don't worry about it.

8. Brake hoses. Get steel braided ones, there worth it. Rubber hoses flex quite a bit even under low pressure.

*felt almost all the time

9. Brake Caliper Piston Roll Back. This is usually the worst offender. Only way to get rid of this is to get better calipers. Roll back is how far the piston moves away from the rotor when pressure is released. The bigger the gap, the more you have to push on the pedal to get contact.

10. Caliper Deflection. The caliper actually flexing under pressure, like 9 you can only improve this with better calipers.

*felt during medium and high deceleration stops

11. Brake pad backing plate. If this is flimsy it will flex and not allow a good contact between the rotor and pad forcing you to apply more pressure and therefore more pedal travel. Fixed by replacing pads with higher quality ones.

*felt most of the time

12. Brake pad material itself. If the material is low density it will compress like a sponge. And if it's a low mu (friction) pad it will require more pressure and therefore more pedal travel.

*felt all the time

13. Rare, but a problem on really cheap brake pads: The bonding process used to bond the brake pad material to the backing plate. A poor process will cause the material to "squirm" around.

Well those are the biggies, but not the biggest. The biggest is AIR in the system. Before you do anything else do a really good and thorough brake bleed. And only use the fluid it says to use on the cap, DOT 3 or DOT 4 or whatever.

Also, changing the brake pedal assembly to one with a lower ratio. Remember all lost travel is multiplied by the pedal ratio, the lower the ratio the less dead travel at the pedal pad. This also firms up the pedal as you're getting less mechanical assistance. Just be careful, because if you're brake booster fails it will take more force on the pedal to come to a stop.

Pedal feel can also be "tuned" with a different booster.

Cut-in is what sets the initial point of boost (when it kicks in)

2-stage (knee height) is what sets how much initial force

Boost ratio is just as it sounds, it sets how much assist you get

Run-out is the maximum assist

By lowering the cut-in and increasing the 2-stage you get a better initial bite sooner. Just have to be careful you don't go overboard and have the driver eat the steering wheel at every stoplight (like an '80s Audi).

Difference between Feel and Performance:............................

I want to make it clear there is a difference between making a brake system feel better and actually perform better.

The stopping distance of a car is not necessarily directly related to the feel. A poor feeling brake system can have very good performance, i.e. Jaguar. While a great feeling system can have lousy performance, i.e. Ford Focus

The only way to decrease braking distances is to create more heat through friction and conduct that heat more efficiently.

Basically, you need a bigger contact area between the rotor and pad (bigger pads and rotors) with the best contact patch possible between the two. Also higher friction levels with higher mu brake pads.

And most importantly.........REALLY GOOD TIRES!

And you need a way to get rid of that heat at a faster rate. More rotor mass and/or better conduction (vented, etc.).

How a car stops is simple, it takes Kinetic Energy (energy created by motion) and transfers it to Heat (Thermal) Energy. It does this by the mechanism of friction.

KE=1/2 the mass of the vehicle multiplied by the square of it's velocity

Stopping distance is determined by the rate of KE to TE transfer, or also know as WORK.

Simply, to stop sooner you need to transfer Kinetic Energy into Heat Energy faster.

There are no other tricks; you need higher levels of friction and ways to dissipate the heat quicker.

The big things to do to get shorter stopping distance:

1. Best Tires for the conditions (use common sense here, no Pilots in Feb in Alaska)

2. Higher Friction Brake Pads and/or rotors

3. Bigger diameter rotors

4. Calipers with more piston area

The other things you can do that give you that extra advantage:

1. LOSE WEIGHT (the car I mean), less mass, less KE

2. Minimize rotational inertia of wheels/tires. Get lighter wheels and tires (all else being equal). Note: the farther away from the center of rotation the mass is the great the inertia, so a 17" wheel will have greater inertia than a 16" all else being equal.

3. Try and balance out the braking, if the rears can do more work it spreads out the work. Less weight transfer to the front BY MOVING THE BATTERY TO THE TRUNK, stuff like that.

4. Practice! Get to know how your system works so you can best utilize it.

5. Don't drive to fast, remember it the square of the velocity. The amount of KE increase from 40KPH to 80KPH is not 200%, but 400%

Also, venting built up gases under the pad was a big problem, but pad tech has come so far that it's not something I would worry about (assuming your using race pads for racing). Again it's one of those things that are there but only makes a very, very, very minor difference (if any) most of the time. Same thing with slotting, which was developed to vent gases and clean pads.

Things like 2-piece rotors, X-drilling, slotting, cryogenics, heat-treating are all "at limit" technologies. In other words they only make a noticeable difference (if any) at the very limits. If you drive on the street in a manner that actually utilizes these technologies regularly you're probably dead and not reading this!

Brakes are as much art as science, there are just so many different variables involving not only performance but also feel and consumer wants it becomes a real pain!

Again, you have to know what you want to get out of your system and where you're going to use it.

In the end if you got the cash it won't hurt, but you get to a point of diminishing returns and you have to wonder!

Brake Performance Vs. Brake Feel:......................

Brake feel: pedal effort and pedal travel for any given desired deceleration. Ease of brake pressure modulation, accuracy and precision of modulation. Feedback through the pedal "describing" pad rotor contact dynamics and pressure fluctuations.

Brake Performance: Level of brake torque produced and the resistance to brake torque loss, better known as fade.

For performance I do not use the term stopping distance because that involves more than just the brakes.

Benefits of "better" feel:

Brake feel is just like steering feel. The better the feel/feedback is the more of the inherent performance you will actually be able to use.

Imagine a car that has 1.0g of lateral grip, but has lousy steering. Too light, completely dead, nothing happens just off-center, poor linear response and too much or too little ratio. Like a Mercedes AMG

How much of that great 1.0g are you ever going to be actually using with poor steering?

Same with brakes. Improving feel will allow you to better use what you have.

However, it will not objectively increase brake performance. If you are already getting the max out of you system then better feel will not get you more.

The formula below is a decent way to estimate what, if any, increase you have in brake torque after an upgrade:........................................

Brake Torque Increase %=

[(caliper piston area new/old) * (effective radius new/old)* (brake pad friction coefficient new/old)]

*effective radius is the distance from the center of the hub to the center of the brake pad

*For sliding calipers multiply the areas by 2

Any answer equal to 1 means no increase. Any answer less than 1 means you've gone backwards. Any answer greater than 1 means a torque increase.

This will NOT give you the actual brake torque, just the difference.

Now things like steel lines, stiffer calipers affect feel, not performance. Only force applied, torque arm and friction do that. You can change things like lines, calipers, pedals and boosters to change the characteristics. Such as, initial bite point and initial deceleration level, pedal travel and effort, pedal force multiplication. However, these do not actually produce more brake torque.

Stopping Force (estimated):.........................................

Equations:

(for ease and consistency try and use meters and kg)

1.

stopping force = weight of car * longitudal coefficient of friction of tires

2.

Stopping Force = pedal force * brake pad coefficient of friction * mechanical force ratio * (1/radius of the tire) * brake rotor effective radius

.....solve for mechanical force ratio

3.

Front Force = weight front + total weight * tire friction * height of CG * (1/wheel base)

4.

Rear Force = weight rear - total weight * tire friction * height of CG * (1/wheel base)

5.

% front = Front Force/Stopping Force

6.

% Rear = Rear Force/Stopping Force

7.

mechanical force ratio front = mechanical force ratio * %front

mechanical force ratio rear = mechanical force ratio * %rear

8.

Take that ratio and divide it by the pedal ratio and booster boost ratio.

This is the ratio of master cylinder bore area and caliper piston bore area.

(MC-master cylinder)

A larger MC results in...

> less pedal travel

> a firmer pedal

> less hydraulic advantage

A smaller MC results in...

> more pedal travel

> a softer pedal

> more hydraulic advantage

Larger caliper piston area results in...

> more pedal travel

> a softer pedal

> more hydraulic advantage

Smaller caliper piston area results in...

> less pedal travel

> a firmer pedal

> less hydraulic advantage

2-Piece rotors:.....................

I have seen a lot on 2-piece rotors. Some of the information contained in them is correct some is mythical.

Some definitions.

2-Piece rotor: A brake disc rotor that has a separate hat (cap) usually made from a lightweight metal. There are two types of common 2-piece street rotors. One uses a bolted hat and the other a pinned hat (also known as a "floating rotor" design).

The bolted type is just what it sounds like. Usually an aluminum hat bolted to a cast iron rotor. The only real benefit of this design is weight savings.

The pinned type has usually stainless steel pins that attach the aluminum hat to the rotors. This allows the rotor to "float" on the pins. The great advantage of this design is that it allows the rotor to move freely. When the rotor expands and contracts there is much less chance of binding or distortion. As you can imagine this cuts down on warping and uneven wear (DTV). The disadvantage of this design is really high costs and increased NVH.

As far as better heat conduction, not really. It does help a bit, buts it's not enough to make it worth the extra cost. The nice think about the weight savings is you can get larger rotor with out taking a weight penalty.

- It may help keep your wheel bearings cooler.

Lug Nut Torque:........................

Over-torque of wheel lug nuts is one of the prime causes of brake rotor distortion. This can lead to permanent warping of the rotors, uneven wear of the rotors and pads and lots of brake chatter (NVH).

With today's very stiff alloy wheels, like from BBS, SSR, Volk, etc., when you torque down the lug nuts the wheel-mounting surface will force what ever it contacts to take its shape. Which means whatever that surface looks like will be what the rotor looks like.

Get a torque wrench and check the torques on every lug nut and make sure they are within the specs (which you should be able to find in your owner's manual). And make sure that every lug nut is torqued down exactly the same. Even if all 5 on a wheel are within specs, not having all 5 be equal will introduce distortion.

And if you think that your light alloy wheel can't possibly be that stiff, you wrong they are MUCH stiffer than the brake rotor or even the hub.

WORD OF CAUTION: Don't assume that torque the lugs to the lowest range in the spec is the best. Try and keep it nominal not at the extremes of the range.

Much of the problems with rotor warp, brake chatter, disk thickness variation can be traced back to over-torqued and uneven torqued lug nuts.

After coming back from the shop, get that torque wrench and check the lug nuts yourself.

Brake Air Ducts:.........................

This is only for auto-x and racing.

Getting all that extra air on the brakes going down a straight gets the brakes nice and cool for the next corner.

Cheap and effective way to keep rotor temperatures down and therefore reduce fade.

Rear Brakes:.......................

Just want to add a little warning about the rear brakes. Be VERY careful when it comes to making changes back there. Upgrading the rears to increase braking power, not just feel, can be a double-edged knife.

More braking power to the rears will only do you good if; 1. the balance is woefully off and the rears are under-utilized, if you can easily lock-up the rears your already at full potential or 2. you have increased the weight the rear tires carry, the grip of the rear tires and/or minimized the weight transfer to the front.

Putting more powerful brakes on the rear alone do nothing more than cause you to lock up or go into an ABS event sooner. You must increase the rear tires load to benefit from an increase in the rear brakes power. Otherwise, the rears should be looked at only from a "feel" standpoint.

"Mini brake test"................................

2 friends and me performed a little brake test this morning.

I have a friend that works at Teterboro Airport and was able to gain access to a nice flat and large area. Not a runway.

To make it interesting we brought my 2000 BMW 328i with sport package.

Atmosphere Conditions at the time (benefit of being at an airport):

Temp: 54 F, Humidity 55%, Barometer 30.28in and rising, Wind 6 MPH East, partly cloudy

Surface was perfectly dry and smooth. Surface was concrete.

The vehicles:

2002 Impreza WRX Sportwagon with manual transmission, SSR Competition wheels, 225/45ZR17 Bridgestone Potenza S-03 PP tires, Tein H-Tech springs, rear 20mm anti-roll bar. All else stock, including brakes.

2000 BMW 328i with manual transmission and the sport package, all stock. The tires: 225/45ZR17 Michelin Pilot Sports.

The WRX tires have 650 miles on them; the BMW tires have 7000 miles on them. All pressures where set at the recommended settings as posted on the driver's doorjamb.

WRX has 720 miles on the pads; the BMW has 7000 miles on the pads.

Test procedure:

10 consecutive stops from 60MPH (using the car's speedometer, so chances are it wasn't exactly 60MPH). That's all I had the time to do.

Consecutive means the time it took to turn around get back to the start and then 30 second wait.

3 drivers. Myself, worked as a brake engineer and have experience on well over 100 different vehicles. Driver 2, Ralph, is a "car guy" and knows how to drive. Driver 3, Carmine, good driver but not a "car guy."

All numbers are rounded to nearest whole number, so no 120.5 feet, that would be listed as 121 feet. I do this because of the nature of the test and the measuring equipment. Which consists of 10 cones spaced 15 feet apart and a tape measure.

The BMW's DSC (ESP system) was turned off, so both cars had ABS only working.

For time reasons I was the only driver to do all 10 runs. Ralph and Carmine just did one each in each vehicle 15 minutes after I was done to add subjective data.

The results (all in feet):

---------------------WRX-------------------BMW

Run 1.......................121............................117

Run 2.......................121............................116

Run 3.......................121............................116

Run 4.......................123............................117

Run 5.......................125............................117

Run 6.......................125............................119

Run 7.......................128............................121

Run 8.......................133............................121

Run 9.......................133............................121

Run 10......................133............................121

Take these numbers for what their worth. Please keep in mind the difference in tires and miles on them. And the "test equipment" used. Disclaimer: This is for entertainment purposes only.

Common Brake Fluid Boiling Points (from 8complex as posted on www.i-club.com)............................

|| Wet Boiling Point || Dry Boiling Point

Castrol SRF || 518°F || 590°F

Earl's HyperTemp 421 || 421°F || 585°F

Motul 600 || 420°F || 593°F

AP-600 || 410°F || 572°F

Neosynthetic 610 || 421°F || 610°F

ATE-Super Blue || 392°F || 536°F

Valvoline || 333°F || 513°F

Castrol LMA || 311°F || 446°F

Earl's HyperTemp 300 || 300°F || 568°F

Ford HD || 290°F || 550°F

Wilwood 570 || 284°F || 570°F

PFC-Z rated || 284°F || 550°F

AP-550 || 284°F || 550°F

All brake fluids absorb moisture, some faster than others (except silicone which is not recommended for anti-lock brake systems). Castrol SRF resists moisture contamination (non-hygroscopic) more than any other fluid we tested; therefore change intervals can be greatly extended. This reduces the effective cost over a season of racing. Many drivers say that they can run the same fluid all year long with only bleeding off the fluid in the calipers for each event. This way a can or two will last all year. Other fluids (hygroscopic type) require additional flushing of the system for each track event to maintain the lowest percentage of moisture and the highest boiling point.

FYI - The Castrol SRF is around $77/container versus $10-15/container for the rest.

Silicone Brake Fluids

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-hygroscopic 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.

MINIMAL boiling points for these specifications are as follows:

|| Dry Boiling Point || Wet Boiling Point

DOT 3 || 401ºF || 284ºF

DOT 4 || 446ºF || 311ºF

DOT 5 || 500ºF || 356ºF

DOT 5.1 || 518ºF || 375ºF

Poly Glycol Ether Based Brake Fluids

Fluids containing Poly glycol ethers are regarded as DOT 3, 4, and DOT 5.1. These type fluids are hygroscopic 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 are 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).

Wet vs. Dry Boiling Point

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.

How does water get in there?

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.

DOT what?

DOT: Acronym for "Department of Transportation" -- an American federal agency or "Department of Transport" -- a British agency

DOT 3: This brake fluid has a glycol base. It is clear or light amber in color. Its dry boiling point is 401° minimum and wet boiling point of 284° minimum. It will absorb 1 to 2 percent of water per year depending on climate and operating conditions. It is used in most domestic cars and light trucks in normal driving. It does not require cleaning the system and it can be mixed with DOT 4 and DOT 5.1 without damage to the system. The problem with it is that it absorbs moisture out of the air and thereby reduces its boiling point. It can also damage the paint on a vehicle.

DOT 4: This brake fluid has a borate ester base. It is clear or light amber in color. Its dry boiling point is 446° minimum and wet boiling point of 311° minimum. It is used in many European cars; also for vehicles in high-altitude, towing, or high-speed braking situations, or ABS systems. It does not require cleaning the system and it can be mixed with DOT 3 without damage to the system. The problem with it is that it absorbs moisture out of the air and thereby reduces its boiling point. It can also damage the paint on a vehicle.

DOT 5: This brake fluid generally has a silicone base. It is violet in color. Its dry boiling point is 500° minimum and has no wet boiling point in federal DOT 5 specifications. It is used in heavy brake applications, and good for weekend, antique, or collector cars that sit for long periods and are never driven far. It does not mix with DOT 3, DOT 4, or DOT 5.1. It will not absorb water and will not damage the paint on a vehicle. It is also compatible with most rubber formulations. The problem with it is that it may easily get air bubbles into the system that are nearly impossible to remove, giving poor pedal feel. It is unsuitable for racing due to compressibility under high temperatures. If as little as one drop of water enters the fluid, severe localized corrosion, freezing, or gassing may occur. This can happen because water is heavier and not mixable with silicone fluids. It is unsuitable for ABS.

DOT 5.1: This brake fluid has a borate ester base. It is clear or light amber in color. Its dry boiling point is 500° minimum and wet boiling point of 356° minimum. It is used in severe-duty vehicles such as fleets and delivery trucks; towing vehicles, and racecars. It can be mixed with DOT 3 or DOT 4 without damage to the system. It maintains higher boiling point than DOT 3 or DOT 4 fluids due to its higher borate ester content. It is excellent for severe duty applications. The problem with it is that it costs more than other fluids and there is limited availability. It also absorbs moisture out of the air and thereby reduces its boiling point. It can also damage the paint on a vehicle.

What causes a mushy pedal?

DOT 5 fluid is not hygroscopic, so as moisture enters the system, it is not absorbed by the fluid, and results in beads of moisture moving through the brake line, collecting in the calipers. It is not uncommon to have caliper temperatures exceed 200° F, and at 212° F, this collected moisture will boil causing vapor lock and system failure. Additionally, DOT 5 fluid is highly compressible due to aeration and foaming under normal braking conditions, providing a spongy brake feel.

Brake Fluid and Cold Temps:......................................

Kinematic viscosities: All brake fluids (DOT 3, DOT 4 and DOT 5) must meet a minimum viscosity test of not less than 1.5 centistokes at 100° C (212° F) and must not be more than the following to meet their various classifications (the larger numbers indicate higher kinematic viscosities just like with motor oils).

DOT 3 1500 Centistokes at minus 40° C

DOT 4 1800 Centistokes at minus 40° C

DOT 5 900 Centistokes at minus 40° C

*-40° C = -40° F*

A centistokes is is 1 mm^2/s

sorry for the long post thought it would be handy here

also a link to the site http://www.mrtrally.com.au/forums/topic.asp?TOPIC_ID=403

[Sydneykid]

Oh my, now even I am confused;

He says don't use Dot 3 or Dot 4 because they absorb water and that lowers the boiling point

He says don't use Dot 5 or Dot 5.1 because they don't absorb water, so it collects, boils and causes vapour lock

Yeh, thanks........a lot

So I read the Castrol Product Data Sheet;

http://www.castrol.com/liveassets/bp_inter.../s/SRF_B768.pdf

It says that Castrol know about the vapour lock in silicone brake fluids and have formulated SRF for vapour lock protection.

cheers

Edited October 16, 2005 by Sydneykid

[Bl4cK32]

Ive heard that DOT5 (the synthetic stuff?) can stuff up the seals if used in your clutch master. Ive seen it happen on a number of r32's now, and even the brake and clutch guys here in Adelaide recommend sticking to the DOT3/4 stuff. This is on a road going car, so frequent fluid changes dont happen.

I suppose if you are on the track, and do fluid changes every race it doesnt matter

[Beer Baron]

from my own experience.

My friends and i race a porsche GT3 cup car (well, we prepare it, my friend drives it). We used to use the Brembo dot 4 race fluid. it's quite expensive and we had to bleed the brakes after each session. We then switched to Caltex GP 600 which we found could go a couple of sessions without needing to be bled out.

In my own car I have used:

some dodgy fluid

Nismo GTR race fluid (Dot 4) = $100 per litre (600degree dry)

Motul RBF 600 (Dot 4) = ~$60 per litre (600degree dry)

Caltex GP 600 (Dot 4) = ~$60 per litre (600degree dry)

Trust Super Dot 4 = $100 per litre (though I have heard it's come down a lot in price since i used it) (600degree dry)

of all these so far i've preffered the trust, the motul and the GP 600. Having said that i've recently been able to cook the motul (though i only flushed through 2 bottles, should have done 3), the GP 600 and the Nismo. Last trackday the GP600 held up fine, and for the next SS round i'll be using the Motul again. I think they are all much of a muchness. They are all rated to 600 degree dry boiling point.

The most important thing really is to change it regularly and be carefull when bleeding to make sure you remove all the air and old fluid. I do mine before each trackday as there is nothing worse than getting out there only to have your fluid boil after 6 laps. If they have been cooked i suck the fluid out of the reservoir first, then top it up with fresh fluid and bleed away.

[Sydneykid]

Ive heard that DOT5 (the synthetic stuff?) can stuff up the seals if used in your clutch master. Ive seen it happen on a number of r32's now, and even the brake and clutch guys here in Adelaide recommend sticking to the DOT3/4 stuff. This is on a road going car, so frequent fluid changes dont happen.

I suppose if you are on the track, and do fluid changes every race it doesnt matter

<{POST_SNAPBACK}>

Yep, standard R32's have non tolerant seals. R33/34 and rebuilt R32's have been OK to date.

cheers

[predator]

I have used Castrol 5.1 stuff.. which has not experienced boiling problems in some small track work (and is only $8 a bottle)...but didn't know about the effect on the seals. Oh well switching to r33 master soon anyhow.

[GTRgeoff]

I've been very comfortable with Motul DOT 5.1 which is half the price of RBF600. If I start to race regularly on semis it may make enough difference to change to 600. I bleed just before and just after each event.

[blackrb20silvia]

yeah sorry sydneykid

i didntnt really get it either but i learnt a little so thats why i posted it

i also read the castroll info sheet last night

also if i can ask you and everyone a question

i bleed the brakes this arvo all was well and good flushed 3 bottles of motul 5.1 (i used this because on motuls web site they said specially designed for ABS units so wont ruin seals in the ABS)

any way as i bleed the ABS unit the front the ABS again the front again

then moved round the back did the passanger side all good so far but when i got to the drivers side i found a problem

when i bleed the brake calliper after the fluid ran out the line (you can see it) no matter how long i bleed them for it looks like its sucking air in some where in the system and ill be stuffed if i know where from and it only happens on this calliper

if it only happens on this side what can it be

and is this causing my previuos problem

http://www.skylinesaustralia.com/forums/in...showtopic=91322

Edited October 17, 2005 by blackrb20silvia

[Mumbo#5]

are you bleeding the correct way?

This is the way i use (may be incorrect but i have my reasons for doing so)

Start bleeding from the furthest brake caliper (left rear on R33). Loosen the bleeder, make sure the bleeder hose goes upwards (so you can see bubbles much easier), slowly depress the pedal, but not to the floor as you dont wanna ruin ur master, come up slowly, allow around 1-2 seconds for the new fluid. This is to make sure that the fluid is fully lubricating the seals. Keep depressing etc until u are happy with the new fluid coming out. Hold the pedal in the depressed position, lock the bleeder nipple, pump the pedal up (relatively quick short strokes) so you have a nice and firm pedal, then hold weight on the pedal, release the bleeder so it goes down about half way, lock bleeder then move onto the next one.

I think thats how I do it anyways

[Duncan]

BTW are the left calipers really furthest from the master cylinder, considering that the ABS unit is on the right?

[Duncan]

BTW are the left calipers really furthest from the master cylinder, considering that the ABS unit is on the right?

[Mumbo#5]

im not quite sure duncan as I dont have ABS

[blackrb20silvia]

well actually they arnt as there is only one line going to the rear and it splits down the rear near the diff the ABS is on passanger side but the line runs back to driver side chassis rail then splits in half to eacj calliper

and no i wasnt bleeding correctly as i found out this morn as i have been going to the floor with the peddle and possibly damaged the bore in the master cylinder ( i hope not as a replacemant is like $700)

unless a slightly scored bore can be re kitted and sealed

[Beer Baron]

in every car i've bled the brakes on we always go to the floor. never had a problem with any of their master cylinders being damaged by doing this.

[ecl]

sorry for such a newbie question

but do you guys use dot 3 or dot 4 or dot 5 (is there such a thing?)? or is there no significant difference?