quattrogirl

I just came from a day on the track at Thunderhill (Willows, CA) and here's the sitch:

Brakes heading on downhill excursions into turns 10 and 14 were "light"- they worked, no fade, but felt too light & soft for the car. I have a 99.5 A4 2.8 QMS with suspension upgrade, etc - oh, see the sig pic for the full list.....

I'm not the fastest driver by far on the track - I'm the slug at the back of the instructor pack, and I'm not THAT heavy on the brakes, but 2 others driving my car said "what the hell you have no brakes"...

I also cross-drove with another instructor with a 1.8T, same pads & rotors as me, but different lines (braided) and different fluid (Motul vs. Pentocin) and had 25% more braking power in his car vs. mine...

Here's the setup I have now (been on the car about 250 miles before the event, noticed a little weakness on street driving but nothing to make ya say EWWW YIKES):

Pentocin Dot 4 fluid (been told this is the same as stock Audi brake fluid BUT when I flushed the system, the thickness was different - new stuff thinner and the color of the new was lighter also);

Hawke HPS (high performance street) pads front & rear;

Brembo Slotted Rotors front only (stock rears have lots of wear left).

Hmmmm we bled the system- no air....
We checked the pads & rotors- seated (or is it seeded?) properly....
We checked rotors and I called the place I got em from- they are not veined ,they're straight, so direction does not matter....
Rotors came zinc-plated and I didn't need to turn them before installing.....
The pads are 1 month old, almost no wear showing....

Still I have weak brakes....any suggestions?

CP

Hmm...I was going to say bleed them again.

absolutcq20v

Interesting....you don't have any mechanical problems such as a frozen slide pin or anything like that right? Experiencing fade ONLY after they warm up sounds like a pad issue. Have you boiled the Pentosin fluid at all? I dont have any BTDT on the Hawks, but try a different pad...maybe. Good luck....finding better help, that is.

PS - cute sig pic

Audiboy

My switch to Mintex C-Techs took away my grabby but fade quickly on track stock brakes to something that resisted fade but you had to stomp on the pedal harder all the time. I think I gave up on them after this weekends AutoX after I boiled my Motul 5.1 after an AutoX - AutoX? boiled fluid? jeez, I had to clean up the mess it made around the reservoir. Anyway, my fluid probably needs to be flushed again. But, I am switching to Pagid Blues. I heard they feel like stock with less fade. In other words, I think it's your pads.

Audiboy

oops, this was supposed to be under Christine's post. Where's the cut and paste or move feature ;P

JA

I had similar experience with stock pads and fluid.

The Motul has a higher BP, thus resists boiling. Vaporized fluid is a lot more compressible than liquid and gives spongy pedal feel.

The Porterfields work very well on the track and on the street (including rain and snow), but they do squeal at certain temps and pedal pressures on the street.

Be sure to break them in thoroughly and pretty agressively. I was black-flagged off the track the first time I used them, because they out-gassed so much smoke -- apparently I was too gentle with them during break in and never got them up to temp. (Now they are very well broken in!)

This is a compromise as the R4S is not a full-on track pad (R4 is) so they might not tolerate the most extreme driving, and they do squeal a little on the street. It works well for me, however.

Some folks swap pads for street and track. It is more trouble, but provides optimum performance for both environments.

I have heard that Pagid makes a similar high perf street/track pad that may squeal less. Also braided brake lines should add a more solid pedal feel.

Good luck,
John A
1999.5 1.8Tqms, GIAC V1.5

quattrogirl

Where to find Pagid pads? TIA :-)

markbradford

I have the same DOT 4 fluid. I was out getting some soundbytes of my new APR exhaust, driving spiritedly. When I tried to pull in the reins from about 130 mph, my foot went right to the floor. I had to pump them to regain some clamping force.

I had not been driving anywhere near the level I had at the track, so I think the Pentosin fluid is crap, although my local tuner shop swears by it. I'm going to check for air this week.

stanj

As everyone knows, I am not just hard on the brakes, I am plain abusive. Over the past 2 years I worked my way from stock, to stock with Redbox, to Drilled Zimmermann with Redbox, to the same with Super Blue fluid and C-Tech pads, to 993TT brakes. Now THAT was a change.

I found the Zimmermann drilled with C-tech pads and superblue fluid to be pretty darn good. The only time I got this to its knees was in Laguna Seca, but then again that's Laguna. And one excursion on a long, hot day at THill #10. Note I didn't have steel lines which would have made things probably much better.

The 993TT kick ***, naturally. I still don't know what way I will go for my S4, either the 2Bennett Brembos or StopTech. I would just advise against the superblue because that fluid has killed three clutch master cylinders of mine - go with the M600.

Good luck!

WClark

My pad supplier (EBC) indicated that until the plating on rotors is worn off, braking friction will not be optimal.

Other symptom question. Does the brake pedal feel spongy compared to others? This would be a symptom of something related to loss of brake pressure. Could be air in the lines, water in the fluid, swelling flexible brake lines, leaky master cylinder, loose pad material.