High temp brake fluid?

[PranK]

In all the track days I've done over the past few months I've only had 1 issue with braking and thats with my current EBC pads (can't remember the colour, but they're not a track pad). I don't *think* I have had issues with brake fluid getting too hot, my understanding is that when that happens you will have quite noticeable brake loss - which I haven't had. 

I'm using just regular ol' Penrite Super DOT4 fluid. I use this fluid in everything and my cars always seem to stop so I see no reason to change, except ... for the 335i. I need to do a fluid flush and was thinking about my fluid of choice and wondering if I should consider using something more high temp? Its not a super fast car by any standards but I'd hate to do a flush and then find myself with no brakes when I get. to Wakefield. 

I guess, my question can be summed up as "How fast do you need to be driving to need higher temp brake fluid?" 

I remember high temp fluid was considered a must have back in the day when I had my GTR. 

[GTSBoy]

That really depends on how hot the brakes get and how much of any heat is transferred into the fluid. That really makes it at least a vehicle specific question, and more than like a specific vehicle specific question, depending on what brakes (ie stock, bigger rotors, different calipers) or even what pads are on it. And then there's the question of cooling air. Is there plenty stock? Is there no special cooling arrangements stock? Has some/more been added?

In other words, I think you have to do the experiment to obtain the data. And if you;re worried - tie on some ducting?

[Murray_Calavera]

I've always approached this as, price is comparable between low temp and high temp fluid. Just put in the high temp fluid.

I've not going to lose any sleep thinking about could I have saved $20 on brake fluid that is going to live in the car over the next 2 to 3 years. 

[PranK]

27 minutes ago, GTSBoy said:

That really depends on how hot the brakes get and how much of any heat is transferred into the fluid. That really makes it at least a vehicle specific question, and more than like a specific vehicle specific question, depending on what brakes (ie stock, bigger rotors, different calipers) or even what pads are on it. And then there's the question of cooling air. Is there plenty stock? Is there no special cooling arrangements stock? Has some/more been added?

In other words, I think you have to do the experiment to obtain the data. And if you;re worried - tie on some ducting?

The brakes are all stock bar some DBA slotted discs and the EBC pads and braided lines. The car has brake ducts as standard but they're kinda pointed in the general direction of the brakes rather than really getting at the heat source. I guess I should hit it with an infra red thermometer after a session and see what they're at. 

14 minutes ago, Murray_Calavera said:

I've always approached this as, price is comparable between low temp and high temp fluid. Just put in the high temp fluid.

I've not going to lose any sleep thinking about could I have saved $20 on brake fluid that is going to live in the car over the next 2 to 3 years. 

100%! Its just a curiosity more than anything. As I said, high temp brake fluid was such a track day rage back in the day. From people I speak to at the track and threads on here everybody has their own take on it but I'm not gonna scoff at spending a few more bucks. 

[PranK]

49 minutes ago, GTSBoy said:

That really depends on how hot the brakes get and how much of any heat is transferred into the fluid. That really makes it at least a vehicle specific question, and more than like a specific vehicle specific question, depending on what brakes (ie stock, bigger rotors, different calipers) or even what pads are on it. And then there's the question of cooling air. Is there plenty stock? Is there no special cooling arrangements stock? Has some/more been added?

In other words, I think you have to do the experiment to obtain the data. And if you;re worried - tie on some ducting?

The brakes are all stock bar some DBA slotted discs and the EBC pads and braided lines. The car has brake ducts as standard but they're kinda pointed in the general direction of the brakes rather than really getting at the heat source. I guess I should hit it with an infra red thermometer after a session and see what they're at. 

36 minutes ago, Murray_Calavera said:

I've always approached this as, price is comparable between low temp and high temp fluid. Just put in the high temp fluid.

I've not going to lose any sleep thinking about could I have saved $20 on brake fluid that is going to live in the car over the next 2 to 3 years. 

100%! Its just a curiosity more than anything. As I said, high temp brake fluid was such a track day rage back in the day. From people I speak to at the track and threads on here everybody has their own take on it but I'm not gonna scoff at spending a few more bucks. 

 

OH, a quick side question - would you use brake fluid from an opened container even if the lid has been on? Eg, if you have a bottle that you opened last time you flushed, it's been tightly closed, is it still good? 

[soviet_merlin]

51 minutes ago, Murray_Calavera said:

I've always approached this as, price is comparable between low temp and high temp fluid. Just put in the high temp fluid.

I've not going to lose any sleep thinking about could I have saved $20 on brake fluid that is going to live in the car over the next 2 to 3 years. 

Does the high temp fluid degrade any different over time compared to normal one? That's one thing I've always been wondering. Because a track car is going to get the fluid flushed probably way more often than every two years and will see less kilometers driven. I would think the requirements are different.

I'm running Motul RBF 600 in mine. Was recommended by my mechanic before a trackday and I've stuck with it since. Hasn't seen the track since but I've kept buying and using it for servicing anyway.

[GTSBoy]

Well, back in the day..... "race" fluids, which were essentially only really "high temp" fluids, used to absorb water more readily. So they really needed to be changed more often anyway. The coincidence of that being directly necessary along with it being what racers would do as a matter of course was just fine.

[Duncan]

Yeah that is still true AFAIK.....good brake fluid should be changed annually because it absorbs water faster which is more often than most mechanics would do it. There are cheap tools that check water% in brake fluid if you all scientific about it.

I for sure would (do) run good brake fluid in anything that even casually saw the track like Murray said; avoiding the risk of "exciting" fade is worth it

[Murray_Calavera]

21 minutes ago, soviet_merlin said:

Does the high temp fluid degrade any different over time compared to normal one? That's one thing I've always been wondering. Because a track car is going to get the fluid flushed probably way more often than every two years and will see less kilometers driven. I would think the requirements are different.

 

3 minutes ago, Duncan said:

Yeah that is still true AFAIK.....good brake fluid should be changed annually because it absorbs water faster which is more often than most mechanics would do it. There are cheap tools that check water% in brake fluid if you all scientific about it.

Just checking, when we are talking about high temp fluid, are we all referring to DOT 5.1?

I haven't had any issues with changing it every 2-3 years. 

[Duncan]

Interesting....can't say I've ever checked it, have always just changed it in the off season as practice

[joshuaho96]

1 hour ago, Murray_Calavera said:

 

Just checking, when we are talking about high temp fluid, are we all referring to DOT 5.1?

I haven't had any issues with changing it every 2-3 years. 

Not sure why but RBF660/700 or Castrol SRF is listed as DOT4, not 5.1. 

[Duncan]

yeah I've never understood that either....

And to answer an earlier question, I write the date on open bottles and throw them if more than 12 months old (which they almost always are, because I don't need to bleed them unless I'm changing lines/calipers etc in between)

[robbo_rb180]

I use the penrite 600f in my cars and have had no issues even at Townsville v8s when I drove that but I bled fluid end of day for just in case. Good value and a about 38-40 on sale.

Use castrol srf on the supercars and no need to Bleed brakes over a race weekend. Do the 1000km with no issues. Over 120 a bottle I seen at repco.

A quality brake pad is always a good starting point the ebc stuff I've seen let go after 2 sessions with heavier cars. I'd be going to a decent track pad and maybe those porsche air guides on the control arm to help with some air over the rotor. Helps on 86/brz with stock callipers.

 

[MBS206]

6 hours ago, joshuaho96 said:

Not sure why but RBF660/700 or Castrol SRF is listed as DOT4, not 5.1. 

RBF660 doesn't meet DOT5.1 as it is too thick. DOT5.1 has a very low viscosity requirement compared to DOT3 or 4. (Dot5.1 must be half as "thick" as DOT4)

 

It would also be a big indicator for anyone using that fluid in extremely cold weather to possibly look to swap for something in the DOT5.1 range.

[Komdotkom]

This has been covered a bazillion times but google wet boiling point vs dry.

Motul is only good when it's fresh, once it absorbs moisture it gets pretty average very quickly. So as above, make sure you change it if you're going racing.

I run the Endless brake fluid in mind, but only because a mate is a distributor and it's cheap. It's not quite as good as SRF but I'm running 380mm rotors on a Skyline so it's not like they get hot.

[Predator1]

22 hours ago, Komdotkom said:

This has been covered a bazillion times but google wet boiling point vs dry.

Motul is only good when it's fresh, once it absorbs moisture it gets pretty average very quickly. So as above, make sure you change it if you're going racing.

I run the Endless brake fluid in mind, but only because a mate is a distributor and it's cheap. It's not quite as good as SRF but I'm running 380mm rotors on a Skyline so it's not like they get hot.

How hard are you tracking it? I have 378 in front and 355 in the back with decent pads and my brakes were spongy after a decent session with lots of braking. It was a short track though but got up to around 190-200 max. be keen to hear.

Mind you, I havent flushed my fluid so thats probably part of reason.

[GTSBoy]

11 minutes ago, Predator1 said:

Mind you, I havent flushed my fluid so thats probably part of reason.

Yeah, unless you're doing it by the book, your data is probably not useful. Boiling point drops rapidly with only just a little water in it.

[MBS206]

1 hour ago, Predator1 said:

How hard are you tracking it? I have 378 in front and 355 in the back with decent pads and my brakes were spongy after a decent session with lots of braking. It was a short track though but got up to around 190-200 max. be keen to hear.

Mind you, I havent flushed my fluid so thats probably part of reason.

Give the fluid a really good flush, then go do the same track again. Report back too please

[Dose Pipe Sutututu]

The hardcore tracks1ut guys I know would flush their brake fluid every 6 to 12 months depending on the amount of track work they did.

Unlike most of us SAU guys, probably flush it once a decade 🥲

[robbo_rb180]

Best practice for any track day should be Bleed brake fluid, inspect rotors and pads maybe even flip pads if they are prone to tapering. 

Quality pad (project mu, endless, hawk, winmax, ap), Good high carbon content rotor (dba4000/5000, Ap, projectmu), Quality fluid, Good air supply over the rotor and caliper are all required for best performance at a track day no matter the car. 

Even the bedding in of the pad and rotor is key to longevity. I've seen so many rotors destroyed on their first track day due to it.