Hi-Temp brake fluid
- Thread starter wepsbee
- Start date
Dan--Highly dependent on the car's weight, mechanical braking ability, speed, the track and the driver (as well as how fresh you keep the stuff).
You want the best fluids, but stuff that is a known quality.
You will get lots of opinions, but unless you have experienced fluid boil, I would say that you are OK with what you have.
I personally like a good DOT 4 and use Genuine Mercedes Benz Brake Fluid, but I am pretty sure its composition is ATE Gold.
You want the best fluids, but stuff that is a known quality.
You will get lots of opinions, but unless you have experienced fluid boil, I would say that you are OK with what you have.
I personally like a good DOT 4 and use Genuine Mercedes Benz Brake Fluid, but I am pretty sure its composition is ATE Gold.
JeffYoung
New member
I agree with Greg and Dan.
I've got a seriously brake challenged car, and run Castrol SRF just for the added small bit of protection. BUT, if you are boiling a "good" (550 plus dry boiling temp) fluid like ATE, Motul or Castrol, then you have a cooling issue you need to address.
Note also that the dry boiling point is less important than the wet, according to the "experts" anyway. Most brake fluid starts to absorb water the minute you crack it open and the dry boiling point isn't really that relevant.
I've got a seriously brake challenged car, and run Castrol SRF just for the added small bit of protection. BUT, if you are boiling a "good" (550 plus dry boiling temp) fluid like ATE, Motul or Castrol, then you have a cooling issue you need to address.
Note also that the dry boiling point is less important than the wet, according to the "experts" anyway. Most brake fluid starts to absorb water the minute you crack it open and the dry boiling point isn't really that relevant.
...and that coming from a guy with a Brit car...doesn't that thing have finned front brake drums...
(yes, yes, I know: the Brits invented the disc brake. Too bad they kept it secret for so long so the Yanks wouldn't steal it!)
Actually though, Jeff, I'd disagree with you on the wet v. dry; for race cars where we change the fluid often (one would assume), the "wet" rarely comes into significance. IIRC, the DOT ratings for "wet" are based on a test with the assumption that a car that lives for a decade without ever changing the fluid; I seem to recall the sample for testing "wet" is with the fluid humidified to something like 3.5% water!!!
Since I bleed the brakes every race weekend, I tend to personally ignore the wet rating. - GA
(yes, yes, I know: the Brits invented the disc brake. Too bad they kept it secret for so long so the Yanks wouldn't steal it!)Actually though, Jeff, I'd disagree with you on the wet v. dry; for race cars where we change the fluid often (one would assume), the "wet" rarely comes into significance. IIRC, the DOT ratings for "wet" are based on a test with the assumption that a car that lives for a decade without ever changing the fluid; I seem to recall the sample for testing "wet" is with the fluid humidified to something like 3.5% water!!!
Since I bleed the brakes every race weekend, I tend to personally ignore the wet rating. - GA
JeffYoung
New member
Greg, I've always wondered about the wet v. dry deal. I've had some people I trust tell me what you said above, and others say that basically once you open the bottle you start taking on water and unless you are flushing every weekend you really should pay more attention to the wet boiling point.
Not sure which is correct, although it certainly seems to me that even fluids like Motul that are notorious for soaking up the moisture can't get all that bad right way.
Here's a discussion on this from a motorcycle racing site:
http://www.sportbikesolutions.com/motorcycle_brake_fluid.php?ssparms=articles/brake-fluid
I'll do some more reading later. Note that the biggest advantage of SRF is that its wet boiling point is a LOT higher than the other top flight brands.
I've boiled Motul, finned drums and all! (actually my drums don't have fins, but those pesky Z cars do). I've never done so with Castrol, but the key point is the one you made above. Cooling is more important than 20 or 30 degree differences in boiling point on the fluids. Once I maximized my brake cooling efforts (nice hats with splitters on the solid rotors, moving the ducts as far in board as possible, and going to a less aggressive pad compound, I solved most of my problems. It certainly was not the fluid.
Not sure which is correct, although it certainly seems to me that even fluids like Motul that are notorious for soaking up the moisture can't get all that bad right way.
Here's a discussion on this from a motorcycle racing site:
http://www.sportbikesolutions.com/motorcycle_brake_fluid.php?ssparms=articles/brake-fluid
I'll do some more reading later. Note that the biggest advantage of SRF is that its wet boiling point is a LOT higher than the other top flight brands.
I've boiled Motul, finned drums and all! (actually my drums don't have fins, but those pesky Z cars do). I've never done so with Castrol, but the key point is the one you made above. Cooling is more important than 20 or 30 degree differences in boiling point on the fluids. Once I maximized my brake cooling efforts (nice hats with splitters on the solid rotors, moving the ducts as far in board as possible, and going to a less aggressive pad compound, I solved most of my problems. It certainly was not the fluid.
rsportvolvo
New member
I ran across a chap who worked for Prodrive for @ 15 years and based on their testing they use Motul RBF 600 for the brakes and Castrol SRF for clutches. Not to just play copy cat, but if Prodrive did the research for those selections I'll take heed.
For racing use the wet boiling point shouldn't be a huge factor (negating the need for the liquid gold Castrol SRF). Some of the cheaper hi-temp fluids are available from Wilwood (EXP 600) and Brembo (LCF 600). Motul RBF 600 is only slightly more expensive. All are cheaper by the case, which is a reasonable consumption amount for a full race season.
For racing use the wet boiling point shouldn't be a huge factor (negating the need for the liquid gold Castrol SRF). Some of the cheaper hi-temp fluids are available from Wilwood (EXP 600) and Brembo (LCF 600). Motul RBF 600 is only slightly more expensive. All are cheaper by the case, which is a reasonable consumption amount for a full race season.
JeffYoung
New member
Generally agree, but my guess is Prodrive is flushing the entire braking system every weekend.
I'm pretty religious about bleeding, and flushing every few weekends, but I'm not doing it every weekend......so I still am not sure that the SRF's wet boiling point doesn't have value.
For what it is worth, the NASCAR guys use SRF.
I'm pretty religious about bleeding, and flushing every few weekends, but I'm not doing it every weekend......so I still am not sure that the SRF's wet boiling point doesn't have value.
For what it is worth, the NASCAR guys use SRF.
Great, now how do I know if I am boiling the fluid. I assume using the brakes too much is only an issue if you are going fast enough to begin with.
When you boil brake fluid, the pedal usually goes right to the firewall -- THUNK! -- and you can pump it back up, though the pedal feels "spongy". Each time you hit the pedal after that it wants to go to the firewall again, and you'll have to pump it back up. It feels similar to when you're bleeding the brakes and someone opens the valve. And, when you subsequently bleed the brakes after boiling the fluid, you'll see air in the lines (air that boils out of the fluid is not re-absorbed.)
This is a distinctly different feeling from "brake pad fade", which is when you exceed the optimal temperature of the pad compound you're using. In that case you'll feel the brake pedal get longer and spongier, and the transition to the firewall is usually slower and longer. Unless you completely explode the pads, you'll rarely get a THUNK! moment with pad fade.
This should also not be confused with pad "kickback", where variations in rotor, bearing, or wheel "true-ness" - or even spirited hits over curbs - cause the caliper pistons to move back into the caliper a bit too far, forcing you to have to pump the brakes to get the piston back in position against the rotor (it's the reason you'll occasionally see a fast driver lightly tapping the brake lights a few times along the straights). The difference there is that when you do pump up the brakes after kickback the pedal feels nice and hard again, versus a still-soft pedal in the case of boiled fluid.
Finally, you could buy temperature-sensitive paints or labels and stick them to your calipers. These devices change colors when a specified temperature is reached, allowing you to note how hot the calipers got. If the caliper temp is exceeding 600 degrees (for example), then you can be pretty confident your fluid is getting that hot, too.
Bottom line, though, Dan? It's not something to worry about at this point; it takes a lot of performance to boil brake fluid, and long before that happens you're gonna start slagging pads, rotors, and possibly even piston seals. Instead, take the time to ensure your brake system is in good shape, bleed the brakes properly and regularly, and just "shut up and drive".
Greg
This is a distinctly different feeling from "brake pad fade", which is when you exceed the optimal temperature of the pad compound you're using. In that case you'll feel the brake pedal get longer and spongier, and the transition to the firewall is usually slower and longer. Unless you completely explode the pads, you'll rarely get a THUNK! moment with pad fade.
This should also not be confused with pad "kickback", where variations in rotor, bearing, or wheel "true-ness" - or even spirited hits over curbs - cause the caliper pistons to move back into the caliper a bit too far, forcing you to have to pump the brakes to get the piston back in position against the rotor (it's the reason you'll occasionally see a fast driver lightly tapping the brake lights a few times along the straights). The difference there is that when you do pump up the brakes after kickback the pedal feels nice and hard again, versus a still-soft pedal in the case of boiled fluid.
Finally, you could buy temperature-sensitive paints or labels and stick them to your calipers. These devices change colors when a specified temperature is reached, allowing you to note how hot the calipers got. If the caliper temp is exceeding 600 degrees (for example), then you can be pretty confident your fluid is getting that hot, too.
Bottom line, though, Dan? It's not something to worry about at this point; it takes a lot of performance to boil brake fluid, and long before that happens you're gonna start slagging pads, rotors, and possibly even piston seals. Instead, take the time to ensure your brake system is in good shape, bleed the brakes properly and regularly, and just "shut up and drive".
Greg
This is the kind of information newer drivers and rookie crew chiefs really need. This info is much appreciated, Thanks
Please let me know when and we will get together.
John Herman
New member
An old racing tip: For a good low-buck alternative to the "racing" fluid, just go and get the stuff from the local Ford dealership. It's dry boiling point is rated way up there (don't have a can in front of me to look) compared to the "normal" DOT3 fluids. Only fluid I ever used on a severly brake challenged FWD car. Just for preventative measures, I would usually bleed the system every race weekend.
thanks, bleeding every race will now be a definite maintanence item.
