To my road course homeboys - brake discussion

B8 S4
#1

Them brakes. I am finding that I have a peculiar problem. They work fine on the track. Pedal is firm, pads work out etc. I usually give the car 2 warm up laps and 2 cool down laps at the start/end of my run. When I complete my cool down lap, my pedal is still there. Now, I pit for maybe 20 minutes or so and let everything cool off. Jump in my car again and touch the brakes - pedal goes to the floor.

What’s happening here is that my fluid is cooking when the car is in the paddock without any airflow going to the caliper. All the fluid in there is cooking. Give the brakes a few pumps to circulate the fluid, and the pedal firms up…but of course, by now, the pedal is no longer 100% and needs to be bled after the track day.

Should I simply accept this as the norm (read: required bleed before/after each event), or have u guys found a way around this? dafuq?

PS - i always had this problem with any car.

PPS - upon further research, I learned that WRC cars use water cooled calipers. Uh, I need dat.

#2

what brake fluid are you running?

#3

Water cooled calipers are very expensive. :stuck_out_tongue:

I’ve never had an issue with Stoptech 660 brake fluid (I stuck the 600 on the S4).

Something that you could use are the titanium alloy brake pad shims. It’ll help insulate the brake piston (and in turn, the fluid) from heat. However, it will also reflect more heat back into the pad. I used to run them on the S4, but currently do not run them in the RS5 (which also has some active cooling).

On the S4, airflow to the front brakes is a real issue (more accurately, a lack of airflow). Did you ever get around to doing the ducts?

#4

Yeah good points. I have the ti shims but havent used them last season due to pads being at full thickness… i use castrol srf or motul rbf600. Same thing happens regardless. Scott–no cooling but i do not run with the splash shields behind the rotor, so that helps a lot. I will be adding the macan brake scoops to my car also.

#5

Fwiw i had this issue on my boss302 even with active cooling and ti shims XD sooo i dont get it. Am i alone in this? : (

#6

Never had the problem that bad with AP or Brembo calipers on 380 discs. After parking I’d give the brakes a half pump 3x and they were back to super firm.

#7

So question - you did have to pump the brakes though–because if not, the pedal would be low after being in the pits for a while. Is that right?
At this point i sold my 355 stoptechs and am debating between the 370x36 ap option or the 380x32 stoptech option.

#8

You will regret that 370x36 AP option. The problem is the fasteners on the 2 piece disc. They don’t allow the disc to expand properly and it knocks against the pads. It only happens when you take it to the track and they get super hot. Eventually when 2-3mm wears off your pad it stops doing it.

Stoptech is better out of the box. Brembo GT is what you really want…

#9
#10

Fwiw the ap system has been revised. Early shudder issues uou describe were due to the caliper not being centered on the rotor. Previously, they provided shims to correct this. Stillen has simce redesigned the mounting bracket to remedy the issue completely. Whats holding me back from ap though is that the total piston area is 2500mm^2. Stock is also 2500mm^2. The problem then, is that the rotor is now 370mm vs 345 but with the same piston area–throwing the bias very forward. You probably liked ur brembo kit much more because the bias on the brembos was much better than ap–which explained why your rear rotor temps went up simce switching to the brembos.

I dont think ap is the way to go cause of this. But the reason i keep falling back on it is bc a 370x36 disc is going to have much better heat tollerance than a 380x32. Shrug. I do not even mind going back to stock size if i can make it work. Cost of consumables is much lower. It just desperately needs airflow

#11

The 370x36 disk is nearly 30 pounds. Not advisable. Brembo has far better metallurgy.

#12

Update.

Went a totally unexpected direction.
I stumbled upon a used set of RS5 brakes. Going that route.
RS5 8pots mated to 365x34 OE rotors. RS5 brakes will go well with my RS5 springs and shocks hahaha.
Looks like it’s still a weight savings over stock - most of that savings goes into the caliper.
In the future I will run the Girodisc 2 piece rotors that Scott runs. Much more thermal capacity here than 355x32 stoptech rings.

#13

Remember to rotate the pads within a caliper as well (using a cross pattern). There’s uneven wear with that caliper.

After two days at Laguna Seca:

https://lh3.googleusercontent.com/rvtp5w-fonkIiVKX-Bq32erK9fj6hxaDZG3s898TTazjcjcEctFSC4eeShzxL26h7NVVuJFAitViqI5GK1mvo0G6K5NLOL6_l6ISXqfz4iKJNPTqO0E5vQv67Iq9n2hUv-0PA5O0SbqiL1rTqpSOFycR5ERMFG0BoZsq5sBiywDAL5qfMdWNSlTnw1mRoHi1vQxRy6GyLu0zuT3pxJeCjFcaXaiO07eX-sBsiP6DA4lVhvvWQdmpfxXXIuAK8cIwAh2_COe9AWOqP1AByJMw3Fs0hFh84C8wJfRtPVOYCqnoqlNuNOxTwQ7CUV2Z7R57Kes7v6yUVmPkGex0PqI7zPM-lVQhvIKWcf1jPaM00IbasThurkqWB_pRBaGgvfba3DtkY68-T4GIZttaz_dAaMRTRgx4czdFm8UtVV0TFQXpNYivQQRiWWRDDkuleFXbj1kI6YCojefsNlhhthVIbERE1tXlHNzBLHVNrbLQJPXevlDdFN1OaZo9aoC0RPj6p0mZE2FQPAsvhle8rrr8pKsl0vXVUR88kmDCcZNegLeAqQLBfXAa5f9ZUNB7pPwIJXie=w1694-h1253-no

#14

ROFL yes I remember that.
Thanks for the tip, Scott!

Regarding the RS5 itself - the stability control is essentially undefeatable, yes? I wonder if that’s why you get the pad wear you get. I do not get anywhere near that pad wear - even on stock size brakes. I can go 4 maybe 5 track days on my stock pads if I could live with the freaking fade and fluid boiling.

I thought I read somewhere that the RS5 awd system and the crown gear blah blah, audi uses brake based torque vectoring on the nose of the car to increase agility. Even with all systems off, it does this. But the S4 does not (thank goodness). BTW what pads are you using? I’m planning on RS19 or RS29.

#15

It does, but I’ve adjusted my driving so that it doesn’t come on. I’m running Carbotech XP24 and with the abrasive/noisy nature of that pad, I can actually feel/hear when the front brake based torque vectoring is kicking in. So I’ve adjusted my driving to circumvent that (basically being more gentle when the car is rotating - can’t get on power as fast - annoyingly).

I probably get 4-5 track days per set of Carbotech XP24 (so that’s only like $100 bucks in front pads per track day LOL).

#16

I have the RS 5 system on my B8 S4 and I use the RS 29 in the front and RS 19 in the rear. Car feels great in braking. I got 6+ events out of the pads and 9 out of the rotors. Plus DD duties as well

#17

Not bad. Which tracks were these at?

#18

NJMP Thunderbolt
Pocono Long Course (IMSA Config)
Pocono North Course
VIR Full x 2 events
Daytona International Speedway (24h Config)

#19

This is the shop in SoCal that I source all of my brake gear from. Lots of good tidbits in here.

https://racetechnologies.wordpress.com/category/brembo-performance/