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Toyman01 MegaDork
8/24/18 7:45 p.m.

I dumped Motul in the Mustang and the P71 before the wife and 18yo son ran a track day in them. Zero problems other than the P71 eating a set of rear pads. 

I run Valvoline Dot 3 in the Lemons Civic. It has lots of cooling and a very good set of pads. We get two races out of a set of front pads, rotors and calipers. It has never experienced any brake related issues. 

bcp2011 New Reader
8/24/18 8:11 p.m.
MINIzguy said:

In reply to bcp2011 :

Water is heavier than oil so the water molecules go towards the bleeders due to gravity?

Not sure if that's exactly how it works, but it makes sense to my small brain.

It sounded good until I looked at specific gravity of brake fluids.  BF is denser, so water should float on top rather than the other way around.  Here's one source for SG.  Others show similar range (e.g., 1.06ish)



bcp2011 New Reader
8/24/18 8:16 p.m.
GameboyRMH said:

it does make some sense that moisture could spread throughout the brake fluid even if the brake fluid doesn't really mix throughout the system (diffusion effect?), especially since brake fluid is hygroscopic (new fluid sucks moisture out of old fluid where they meet). This should also prevent pooling at the calipers, at least until the brake fluid is saturated.

THis is an interesting thought.  I did more digging and it appears that you are right in the explanation of diffusion, but at least this person thinks the moisture enters the system all of the place, and not just the MC.  Learn something new every day!



danl318 New Reader
9/13/18 7:00 a.m.

After digesting all the advice and discussion in this discussion, I've decided what to do...

Motul RBF660, Yellowstuff pads, and stainless steel brake lines.

Will this do the trick? I'll let you know.

Ram50Ron GRM+ Memberand Reader
9/13/18 10:18 a.m.

Anyone run any of these fluids year round?  With these increased boiling points on performance brake fluids does that shift the freezing point up as well or at least increase the viscosity to a concerning level at winter temps?

I'm thinking of doing similar brake upgrades when I refresh the brakes on my FiST which is also my daily and I live in Wisconsin. 

Fitz New Reader
9/13/18 11:35 a.m.

660 is probably overkill, but I'm a miata driver so my speeds are a bit different.

Are you going year round on the pads, or changing for events?

NOHOME UltimaDork
9/13/18 1:09 p.m.

Been there done that and new fluid fixed the issue right at the track. Pedal went right to the floor. I was running silicone fluid and a quick change with new stuff did the trick. Funny enough the brakes went away right after a high speed corner while I was actually coasting down for a cool-down lap.


If I were to go back to doing track day, I would buy Motul since it seems to have the higher boiling temps required for this game. That said, brake fluid does absorb moisture right out of the air and it also needs to be changed on a regular basis in order to maintain the high boiling temp. Motul boils at like 617 F and any water in the mix is going to boil at 212 F and put steam bubbles in the fluid. Your brake fluid suddenly goes from being a solid fluid to something more akin to beer foam.


Buy a vacuum brake bleeder and changing fluid becomes a non-event; just crack the bleeder and pump the handle. Have a helper  to keep the MC topped-up. I put a bit of grease on the bleeder screws to help maintain the vacumm around the nipple threads.






devina Reader
9/14/18 9:16 a.m.

For track use, i would recommend Motul but the ATE or any higher temp fluid should be fine.  The DOT 3 & 4 fluids all attract moisture which typically enters through the master cylinder cover.  This is probably not quite as important for AX due to the less demanding braking events generally.  

When replacing it for the first time especially, you should see the color difference between the old fluid and new even if both are (were) clearish.   After the flush with the new fluid, depending on the car and track, it should not require a full flush to get the potentially boiled fluid out.  Before every second race I will bleed my brakes to keep fresh fluid closer to calipers.  

For pads, I have not heard much good about EBC for track use so watch how those work in your car and track.  If you are running Blackhawk, be very careful with EBCs there.  Blackhawk is notoriously hard on brakes...

Lugnut Dork
9/14/18 3:47 p.m.

It depends on the car. For the MS3, probably Motul 660 would be sufficient.

On my Camaro, it was not. Until I went up to Castrol SRF, I couldn't get more than 13 minutes into a session before the brake pedal went away. Now, my car is waaaaaay faster and waaaaaaaaaaaaaaaay heavier than a Mazdaspeed 3 and I am fairly aggressive, and with Blackhawk Farms as my home track (Blackhawk is one of the very hardest tracks on brakes and there's no time to cool them down), but I tried a huge number of fluids. It also depends on what pads you're using. I like a real high initial bite and good solid pedal feel, so my preferred brake pad is the Pagid RS14 Black. I recently moved up to the very similar but more endurance-oriented RSL2, and those pads generate so much heat they'll cook lesser brake fluids. I had to go to the SRF in order to make the car behave the way I want for as long as I want.

I know that the SRF is more expensive than the ATE, and more than the Motul... But let's say at $35/liter more for the SRF than the Motul, is that still cheaper than wasting expensive track time not being able to drive, or tamping down your track time worrying about how your brakes are going to perform?

What kind of pads are you running on the 3? If you're still having fun with stock/stock-ish pads, then cheap is probably still fine. If you are needing higher temp pads, then you'll need higher temp fluid. Edit: oops, missed the post a couple before mine! Castrol SRF looks like it's actually cheaper than Motul 660. EBC Yellow stuff won't get *that* hot. I would say this is a combo worth trying :) But, if you're really cooking out there, though, especially at Blackhawk, those pads won't be enough.

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