Lost brakes on the 'ring' - was it boiled fluid or overheated pads/rotors?

So, just gonna rewind a few days to before the ring. The car in question is a lightly modded MK1 Ford Focus (now NA, not turbo D: )

I decided to be cheap and figure, what the heck? These eBay Powerstop brakes seem to be fine on the street/daily driving from all of the reviews I've seen. My OLD brakes were fine on the street/daily driving and SEVERAL laps around the ring. These Powerstops should be just fine, I'll order them up.

Fast-forward to the day of the ring, I installed the pads/rotors from Powerstop and did the emergency brake thing that they wanted to break in the pads. Button up a couple other odds-n-ends on the car and drive an hour and a half to the ring. Go to the hut by the Devils Diner and buy a ticket. Now I'm ready to get on the track.
 

The first 5-7 min of the run were great! Car was stopping well and I could huck it into the corners without worry. The problems came about when I approached what i believe is 'wehrseifen' to 'rundweg der nordschleife.' Its the corner(s) that have a dog leg right into a sharp left U turn into another dog right, tight left.

At the first dog leg the brake pedal started to feel a little spongey, but still slowed me down plenty well. The next corner I was more cautious and thank god because when I hit the pedal it went to the floor like there was no resistance. After a moment of absolutely nothing the car slowed down just enough to safely huck it around the first left. After that I limped it around the track fast enough to not be a danger but slow enough to let some of the pedal feel comeback/re-go away.

Once parked the heat from the brakes could be felt significantly about 1-1.5ft away. We let them cool over the next 30 minutes until the track closed. On the way home, the brakes worked great without issue. Upon visual inspection of the rotors on the outside, I see no bluing of the metal nor do I feel the infamous hot spot pulsation.

Based on what I've said, do y'all think I boiled the brake fluid or that the Powerstop eBay brakes were the culprit?

I'm trying to decide if I want to spend 600+ on brakes or a 20-40 dollar bottle of liqui moly racing fluid.

Do the fluid, you'll need it either way and test.

Fluid

Yup.

Overheated pads still have a nice firm pedal, but there's just no friction. Bad smell, too. The rotors won't necessarily be blued and you won't necessarily have pulsation unless you parked the car with them overheated and the pads in contact with the rotors. It all depends on the pad compound. If you're running a good street/daily pad on the track, you can expect them to struggle.

Overheated fluid boils and creates air pockets, which lets your pedal move further. That's what you did. I'm guessing it's been a while since they were flushed?

ah, so if I smell brake (which I did a couple times) back off for a minute or two? how bad should overheated pads be? slightly noticeable, noticeable, pungent or unbearable?

It was probably just under a year ago that the fluid was changed, I typically wait longer than that without issue though. Oh well, I'll order up the liqui moly and do a complete flush.

Brake fluid absorbs water over time, and that water will decreate the boiling temperature by a surprising amount. For example, Wilwood 570* has a boiling point that is nearly 300F lower when it has absorbed 3.7% of its volume in water. Street driving may not show a problem, it's only an issue when you start putting a bunch of heat into the braking system. A turbo Focus on the Nordschliefe should have fresh fluid in it.

If you do start to smell brakes, back off. The smell will get stronger as the pads get hotter. 

Time for cooling ducts. Also racing brake fluid needs to be changed much more frequently than DOT4 street fluid. The trade off for extra high dry boiling point is greater hydroscopic tendency. Your odor may be a one time thing during first serious heat cycle. If the odor recurs next outing the pads are not strong enough for the use.

In reply to TurnerX19 : time to get out the temperature sensitive paint.  See what temps your rotors actually get to and that will tell you What your next move should be. 

Its too late to check temps in the pits because as you’ve already felt the brakes cool down quickly.  

Definitely bleed your brakes/change fluid. And check your caliper pistons to make sure they still move freely. The last thing you'll want is potential corrosion from the water affecting your pistons. 

Yep the fact that the pedal travel massively increased means the fluid boiled. A spongy pedal is a serious warning sign to turn your hot lap into a cooldown lap before it becomes a yellow-flag section for everyone else and a wrecker truck ordeal for you.

With overheated pads, you get a lot of stink and not much deceleration no matter how hard you push. It might feel like travel increased a bit but that's mostly a change in the relationship between pedal pressure and deceleration. If you can smell your own brakes from inside the car at speed, that's another warning sign.

Obviously a higher-temp fluid will help, cooling ducts are a good idea, another is some kind of insulating shim on the back of any pads that touch a piston. Even a regular anti-rattle shim is better than nothing for reducing heat from the pads being conducted into the hydraulic system.

I'm using "Motul RBF600" for brake fluid in the car I take to the track.  I'm near ya and have had trouble finding it on the local market so you might have to order it but it's good stuff (probably overkill).  IIRC, you wont be able to order fluids to your APO, but you can get some off of Ebay.co.uk at a pretty decent price.

Did not see new high temp fluid in the "to do" list. My money is on boiled fluid.

I got paranoid after what was just described happened to me on the track. Half an hour to flush in new fluid before trackday was cheaper than new underwear.

Pete

In reply to Hungary Bill :

where are ya at? hungary?

In reply to NOHOME :

whats life without a little adventure

In reply to TurboFocus :

I'm about halfway between Vienna and Budapest in a small town called "Papa".  I've got a liter and a half of brake fluid in the garage if you wanted to make the drive

google makes your town looks like a cute little place. almost like a mini Trier

i live in a jankey run down farm town lol

In reply to TurboFocus :

Married to a Redhead. Caught my limit.

GameboyRMH said:

Obviously a higher-temp fluid will help, cooling ducts are a good idea, another is some kind of insulating shim on the back of any pads that touch a piston. Even a regular anti-rattle shim is better than nothing for reducing heat from the pads being conducted into the hydraulic system.

And on this note, for cars that come with a choice of plastic or metal piston calipers for stock replacments (assuming stock brakes are still in use), use the plastic piston ones.  They'll put less heat into the fluid.  

Keith and Turner covered it.  I’m going back to bed. 

In reply to AngryCorvair :

that is high praise considering your occupation

rslifkin said:

GameboyRMH said:

Obviously a higher-temp fluid will help, cooling ducts are a good idea, another is some kind of insulating shim on the back of any pads that touch a piston. Even a regular anti-rattle shim is better than nothing for reducing heat from the pads being conducted into the hydraulic system.

And on this note, for cars that come with a choice of plastic or metal piston calipers for stock replacments (assuming stock brakes are still in use), use the plastic piston ones.  They'll put less heat into the fluid.  

Downside is that they don't last as long though, deformation or cracking tends to do them in. A metal piston with a ceramic coated face is a good compromise. BMW factory brake pistons are metal with the face coated in the same phenolic plastic.

Sounds like it is time to bring the rest of the brake system up to the level of the pads and the driver. 

Add cooling ducts and a fluid change. When adding ducts make sure to make up some sort of plug or cover to be installed for every day street use to keep water and junk out. Pull the covers before you go to the track and have fun!!!!

+1 for Motul AND ducting.

dean1484 said:

Sounds like it is time to bring the rest of the brake system up to the level of the pads and the driver. 

Add cooling ducts and a fluid change. When adding ducts make sure to make up some sort of plug or cover to be installed for every day street use to keep water and junk out. Pull the covers before you go to the track and have fun!!!!

You also need to have the ducts closed for break-in.

TurboFocus said:

google makes your town looks like a cute little place. almost like a mini Trier

i live in a jankey run down farm town lol

Yeah, google's giving you the highlights by the looks of it.  I mean, Papa's not terrible by any stretch of the imagination, but it is very much a farming community stuck in between two much larger cities with nothing but farms and villages all around.  And I love it!  Absolutely nothing happens here, aside from the seasonal festivals in the town square.  I can walk everywhere, ride my bicycle to work, and the beer is cheap.

If you find yourself at a trackday in Hungary or Slovakia, be sure to hit me up!