Weng

What type of brake fluid are you guys using? The local dealer is putting "Porsche factory supplied Super DOT 4 fluid" in my car. No boiling fluid problems to date and I'm wondering who makes this stuff (ATE?) - its seems to be pretty good fluid.

Recently had an off track excursion caused by brake failue in my F360. Blame was placed on the Shell fluid (DOT4) used by Ferrari which is supposedly good only for street use. Will be trying out ATE Super Blue racing fluid next (Castrol SRF is not available locally).

Bob Rouleau

Porsche dealers normally supply Pentosin. I have found that ATE Super Blue/Amber is superior. Motul racing fluid and/or Castrol SRF are even better but more costly.

Sloth

What about for the PCCB brake system? Is Porsche using the standard fill or something special there?

macfly

I'm using Brembo High Temp Racing Fluid, seems very stable, and free from 'boil softness' so far.

gtdrei

What are the downsides (if any) to using racing fluids on the street in a semi-daily driver ?

Robin

Henry GT2

None that I can think of regarding the brake fluid but basically the more race track you have your brakes the less friendly they are on the street. Track pads make a lot of noise, squealing,squeeking and do not work as good as your street pads until they are warmed up. I use the brake fluid Porsche supplied with my GT2, I don`t know if it is different for the USA or Canada?? The fluid works well so I haven`t touched it.

I think you have to find the right balance to suit your particular need.

Henry.

Bob Rouleau

Robin - there are two downsides to using racing brake fluid, cost and longevity. Top grade racing fuids like Motul 600 and Castrol SRF cost a lot more than conventional brake fluid. They also outperform them on a track by a big margin. Racing fluids provide a much higher boiling point than a regular fluid. Most are more likley to absorb water which affects the boiling point. Racing fluids should be changed every six months. Conventional fluids go for two years before a flush is needed. If you track your car, a better brake fluid like ATE Super Blue/Amber might be a good idea. It is not as expensive as Castrol SRF and changing it every six months is not a big expense. On the other hand, I ran my GT2 using the factory fluids with no problems (not with the brake fluid anyway).

Regards,

gtdrei

Bob

Thanks

Robin

Weng

Bob, do you know what's the meaning of dry and wet boiling points? The fluid producers typically refer to 2 boiling points - dry and wet. Are they refering to before and after the fluid becomes saturated with water molecules?

KINGSRULE

Bob,

You're way off base on brake fluid.
First Porsche uses ATE fluid. Pentosin is used in the power steering of 993's and older models. I don't remember if it's used in 996 power steering.
Second, "racing" brake fluids actually last longer because they absorb water at a slower rate. That's the main reason the more costly fluids perform better as they get hotter at the track. The higher boiling points of the better fluids are also important to the performance at the track. The fact that these fluids absorb less water allows them to maintain their higher boiling points over a longer period.

Also, it's amusing to me when the topic of brake fluid comes up on cost is always mentioned! Who cares if it's $100 more for the best (Castrol SRF)? These are $100k + cars and their owners asses on the line.....

Bob Rouleau

GJ - Pentosin is the factory fill for brakes at my dealer at least. Like Castrol, Pentosin makes a variety of hydraulic fluids. The local dealer has provided ATE at my request for some time. This year they suggested Motul 5.1 based on input from Porsche Cars based on the fact that it works well with high cyclic applications (read ABS).

Castrol SRF like all racing fluids has a high boiling point wet or dry. SRF is hydroscopic but has a high wet boiling point. Nothwithstanding the high wet boiling point, it is recommended to change it prior to every race or event. Note that PCA requires that brake fluid be changed every six months. I have not used SRF but I have been told that the pedal feel degrades after six months in spite of the high boiling point. Perhaps your experience is different.

Weng - the wet boiling point is an indication of the boiling point after one year. Web sites describing the characteristics of brake fluids will usually provide information on the boiling point when new (dry) then at 3 and 6 months. As you can imagine the better fluids have a higher boiling point at those intervals with SRF being the best. Motul 600 specs out as second best but it reputed to have a better pedal feel after a few events.

As GJ points out the price of the best fluids should not be a big deal compared to the other costs of a DE.

FixedWing

Actually, this is supposed to be the difference between Castrol SRF and the other racing fluids. SRF's wet boiling point stays relatively high while the other racing fluids have worse wet boiling points than do the standard DOT4 fluids. This means that if SRF is left in longer it will still work relatively well. But if the fluid is changed very frequently then other cheaper racing fluids will provide comparable performance.

From what I've heard, GJ is wrong about racing fluid absorbing water more slowly. I believe the opposite is true. If you are only going to change your fluid every two years (i.e. street use) then you are better off with standard DOT4.

In general, I think you are best to use fluid commenserate with what you need. If it only street driving the standard DOT4. Track use with changes every year then Castrol SRF. Racing then a racing fluid changed very frequently.

I was using Castrol SRF with my PCCB's and I will probably continue to use it on my cast iron system. As GJ says, on such an expensive car, why care about a little extra cost of the fluid? Except for the cost, Castrol SRF doesn't seem to have a down-side.

Stephen

Bob Rouleau

Stephen - While my info is anecdotal, local racing mechanics insist on more frequent changes when using SRF than a non racing fluid. I admit that I am now intrigued after being slammed by GJ. Some things which I do know as facts are:

1) Except for silicone based (DOT 5) all brake fluids are hydroscopic, i.e. they have an affinity for water.

2) This is a good thing because you don't want water collecting in your brake system. Corrosion is one reason, ice is another in these parts!

3) The wet boiling point is an indication of how the brake fluid will behave after it collects water. Since water has a lower boiling point (100 Deg C) the wet boiling point is lower than the dry. Castrol makes a point of this with their LMA fluid - Low Moisture Activity if I recall correctly.

Now comes the part that piques my curiosity. Does SRF achieve a high "wet boiling point because:

A) it absorbs water and somehow encapsulates it chemically so as to minimize degradation of the boiling point?

OR,

B) Absorbs less water than lesser fluids to maintain a higher boiling point. In this case, mechanics are probably recommending changes to avoid corrosion problems. I have anecdotal reports about a loss of pedal feel if the SRF fluid is not changed frequently. This is not a problem for hard core racers since they change the fluid before every race anyway.

Rgds,

bob_dallas

One comment - don't assume from Bob's (correct) assertion in #1 above that DOT 5 fluid is superior because it is not hygroscopic (commonly mis-stated as hydroscopic). DOT 5 typically has a spongy pedal feel because it is more compressible. You can also still get water in your lines, it's just that the water doesn't mix with the fluid. Still causes problems, just different. About the only real benefit I've heard of for DOT 5 fluid is that it doesn't corrode the hell out of anything it comes in contact with...

For more info on SRFs unique characteristics see:

http://www.racerpartswholesale.com/srf1.htm

Here's a more concise summary:

<snip>
Castrol SRF Racing Brake Fluid is an ultra high performance product formulated specifically to satisfy the ever increasing stresses placed upon the braking systems used in international motorsport. Castrol SRF is less hygroscopic than conventional brake fluids - it absorbs less water in a given time. Secondly, unlike conventional glycol ether fluids, Castrol SRF reacts chemically with the absorbed water to reduce its adverse effects, thus preventing the fluid's high temperature performance and safety margins from deteriorating as rapidly as they would otherwise do.
It's ability to withstand temperatures in excess of 300 C, and its superior resistance to the effects of absorbed water, have established Castrol SRF as the world's premier fluid for the hydraulic brakes used in all forms of motorsport.
TECHNICAL NOTE: Mixing Castrol SRF and conventional brake fluids will reduce the benefits of Castrol SRF. It is strongly recommended that conventional brake fluid be drained from the system before flushing and re-filling with Castrol SRF.
<snip>

FWIW, I haven't encountered a mushy pedal with SRF in both cars.

KINGSRULE

Stephen - While my info is anecdotal, local racing mechanics insist on more frequent changes when using SRF than a non racing fluid. I admit that I am now intrigued after being slammed by GJ. Some things which I do know as facts are:

Slammed? You must be joking..


1) Except for silicone based (DOT 5) all brake fluids are hydroscopic, i.e. they have an affinity for water.

2) This is a good thing because you don't want water collecting in your brake system. Corrosion is one reason, ice is another in these parts!
3) The wet boiling point is an indication of how the brake fluid will behave after it collects water. Since water has a lower boiling point (100 Deg C) the wet boiling point is lower than the dry. Castrol makes a point of this with their LMA fluid - Low Moisture Activity if I recall correctly.

Now comes the part that piques my curiosity. Does SRF achieve a high "wet boiling point because:

A) it absorbs water and somehow encapsulates it chemically so as to minimize degradation of the boiling point?

NO

OR,

B) Absorbs less water than lesser fluids to maintain a higher boiling point. In this case, mechanics are probably recommending changes to avoid corrosion problems. I have anecdotal reports about a loss of pedal feel if the SRF fluid is not changed frequently. This is not a problem for hard core racers since they change the fluid before every race anyway.

What? If SRF absorbs LESS moisture it's avoiding the moisture problems..thus SRF last LONGER in your brake system before you'd notice the degradition and its use avoids moisture problems. "Anecdotal reports" about pedal feel are meaningless. The physical data on SRF speakes for itself.
As I point I use SRF in my all my cars including daily drivers. No loss of pedal feel between 12-24 month changes. SRF absolutely lasts longer and has a harder pedal than the ATE factory fill that was in my 97 C4S.

Regards,

GJ