ACR E Brake Fade

[ViperGeorge]

^^^^ At the Viper Rendezvous in Hastings this past weekend a friend in a TA 2.0 9 Liter Extreme with steel brakes running Raybestos ST45/ST43 pads and fresh Motul 600 had brake fade. He bled the brakes and said the left front caliper's fluid was horrible looking. Once bled the brakes were fine again. His fluid was new right before the event. Fake Chinese fluid? Defective batch of Motul? I have never experienced a problem with Motul in the 20 years or so I've been using it.

[13COBRA]

^^^^ At the Viper Rendezvous in Hastings this past weekend a friend in a TA 2.0 9 Liter Extreme with steel brakes running Raybestos ST45/ST43 pads and fresh Motul 600 had brake fade. He bled the brakes and said the left front caliper's fluid was horrible looking. Once bled the brakes were fine again. His fluid was new right before the event. Fake Chinese fluid? Defective batch of Motul? I have never experienced a problem with Motul in the 20 years or so I've been using it.

What pads do you run?

I've been looking at the Raybestos because they're quite a bit cheaper than the Pagid, Endless and PFC pads.

[GTS Dean]

With only one caliper position showing problems, I would suggest 2 possible causes:
1) perhaps the pre-event flush may not have been thorough enough to clear all old fluid
2) any potential blockage in, or damage/disconnected air ducting to that wheel position?

[ViperGeorge]

What pads do you run?

I've been looking at the Raybestos because they're quite a bit cheaper than the Pagid, Endless and PFC pads.

ST45 in front and ST43 in rear. I like them. Pretty easy on rotors and not very dusty.

[TKO MOTORSPORTS TEAM]

I think I need to clarify. This was my first Time Attack event, not my first track day. I have been tracking my Viper for 2 years on many different tracks. Not saying I'm the fastest guy out there but I am certainly not the slowest This was the first time I experienced brake fade. The reson behind me discussing brake cooling is because my friend, who is a national Time Attack champion (in a ACR-E) told me that I needed it. I don't know if he's right or wrong though, hence me asking in this thread.

The only change (relevant to this issue) I did before this event was changing brake fluid to Motul RBF 700 and installing the TKO Brake Line Kit.

Anyway, I have now ordered PFC 665 as per TKOs suggestion. I'm hoping that this will help! I will also try to add some cooling tubes to my front brakes to direct the air flow better. Btw, Should it be directed to the disc or the caliper?


This is a film from the last track day last year. No problems what so ever with brake fade:
https://youtu.be/bX4r37dZICM


This is from the Time Attack event where I had brake fade (not recorded in the film):
https://youtu.be/SISPjWoqMT8

If your going to add brake cooling you will want to route brake ducts to the calipers. Smaller hoses 2-2.5" ( 50mm-60mm) work better for stock vipers. Not alot of real-estate in the wheel house and lots of pinch points. Run 2 small ducts rather then one big 75mm duct so the ducts dont get pinch or chewed up by the wheels.
I think I would first look at getting some cheap onboard data like a garmin catalyst before making changes. With data you can trace you brake usage and really see whats going on. It will also help you with evaluating your driving technique all around. Once you have some good data then decide what changes need to be made.

[blackbeast99]

Just adding that on my ACR-E, I've not had any fade with my CCB's or Girodisc. Other than fluid (RBF 600 or 660) my brake setup is stock (with the OEM cooling ducts).

- - - Updated - - -

ST45 in front and ST43 in rear. I like them. Pretty easy on rotors and not very dusty.

This is a solid combo. I'm not running this now per availability, but something close.

[ViperGeorge]

Has anyone tried Motul RBF 700? Seems to have higher dry and wet boiling points.

[eckeph]

Has anyone tried Motul RBF 700? Seems to have higher dry and wet boiling points.

I use RBF 700.

[ViperGeorge]

I use RBF 700.

And what do you think about it? Why did you go with RBF 700?

[eckeph]

And what do you think about it? Why did you go with RBF 700?

What I think is inconclusive. See my first post.

I bought it on recommendation from another Track Junkie Viper ACR owner.

[GTS Dean]

It may be an issue of proper definition of "fade." I have always considered it from the perspective of drum or disc/drum systems where the friction linings themselves were often overheated and started outgassing with no more effective friction with applied pressure, but the pedal stays hard. This can still be a problem if your pads are outside their design temperature window.

Fluid boiling, OTOH, is where the pedal goes spongy - but repeated rapid pumps tend to restore some speed control.

Modern ABS systems may blur the line from a more traditional view.

[Lawineer]

If you're overheating any of the race fluids, there's probably something else wrong.

[ViperGeorge]

What I think is inconclusive. See my first post.

I bought it on recommendation from another Track Junkie Viper ACR owner.

Sorry I missed that in your post. Grassroots Motorsports had a table in a recent edition of their magazine that showed the dry and wet boiling points for most racing fluids. RBF 700 seems like it has among the highest. I use RBF 600 and haven't had a problem but thought maybe I would try the 700. Problem is I can't find it anywhere in the USA.

Brake Fluid Boiling Points.pdf