wmond

Just finished 2 day NNJR DE at NJMP Lightning, had a great weekend, learned a lot. But having an issue with the stock brakes.

Pads and rotors are brand new, replaced in Feb/March. Worked great since then, street driving, maybe 1000 miles on them, tops. Started NJMP great, but by the end of the day Sunday, and even driving home, I am feeling some "background noise" like flutter in the brakes. not grinding, no audible noise, but a barely perceptible flutter is the best word. Like what grinding would feel like if it kept getting worse, but this is the very very start of it; like feeling white noise through the brake pedal. Plenty of pad and rotor left. Now what is also strange, is the same thing happened to the brakes before, after a 3-day Watkins event last year. I left with a much more pronounced flutter, was told that the hard driving and breaking probably left some deposits on the brakes and it would "wear off" over time. It did, a little, but never disappeared and I had to eventually replace the rotors and pads to get back to normal, however I assumed that with 20,000 miles on the car (and brakes) at that point, and 2 prior DE events, maybe it was time. And now it happening again, after only 2 days on track. This leads me to believe I am the cause of this. I run in Yellow group. I don't think i am doing anything especially egregious to the tires and brakes (Michelin PS4S) to cause this. Even if I was, would I be able to do this again to brand new stock pads and rotors?

Would love to hear from someone knowledgeable about what could result in this flutter (again, hardly noticeable, and if it didn't just happen last season after Watkins, I might not even notice it), and what I may be doing to cause it. I would have figured an average driver like me on stock tires wouldn't be able to abuse the brakes enough, even if I was trying to be abusive, to do this. Thanks in advance.

Mr. Turtles

This happened to me in my 2012 991s as soon as I started going faster with MPSC2s on the car. (The PS4's are not as sticky but still pretty good grip to allow for hard braking which is part of problem) The flutter as you call it is essentially brake judder that was caused by, as you mentioned some transfer of the brake material to the rotors. You are likely now going faster and braking harder (not necessarily in a bad way) so this creates a ton of heat that stock pads and eventually stock rotors cannot handle. I've seen stock 991 pads melt and fall apart in one track day on a friends car. You need to get higher performance brake pads...choices are limited. I used Pagid RS29 but I understand there are more options now. Call Clarke at Apexperformance.net he can help you out with choices. Don't change change your rotors unless cracked to the outside or from hole to hole. IF you put some good streetable track pads on you can clear up the judder with some very hard breaking several times in a row. A day or two at the track should clear it up completely. Next time you need rotors get some Girodiscs. While the cost of the aftermarket pads and rotors is high they also last a very long time.

wmond

oh, awesome. Thanks for the info. I thought it was me. Definitely getting better. So streetable track pads will clear this up for now? I'll call Clarke asap.

Inbyten

I've had the same thing happen to my stock brakes on my '14 C4S after 1.5 days at the track. I'm considering switching to Sebro rotors and Ferodo ds2500 pads when the time comes.

Mr. Turtles

I don't believe they make Sebro rotors for the 991 yet, unless something changed very recently. I've only found Giro available for the 991. The DS2500 are a pretty aggressive pad if mostly driving on the street. The DS1.11 is likely a better compromise and easier on the rotors. Even guys running GT3's (including my next set) are running the DS1.11. But hey they make a variety of styles to keep us all happy.

Inbyten

Pelican parts lists the Sebro as available for the 991.1. I haven't purchased yet. Maybe it's new?

I thought the ds2500 was the street/track pad and the ds1.11 was the more track oriented pad? I only do about 3 DE events a year, so I figured the ds2500 would work for me (without having to change pads before each event).

wmond

This was my understanding also, DS2500 is the street/track pad, DS1.11 is track focused. Clark at Apex was awesome, spoke to him today for a bit. Ferodo DS2500 front pads on the way to NJ. Clark, who appears to be supremely knowledgeable (and a nice guy) thinks the fronts only will solve my issue, and a day at the track will burn off any residue on the rotors. See y'all at The Glen.

erko1905

I was running in the yellow group with you, #34. It was a great event.

I had the same problem starting out last year at Thunderbolt. OEM pads broke down at high heat and covered the rotors w pad material. I ran Pagid RS29s on stock rotors after that for a while, and then switched to DS1.11s on Girodisc rotors later that year. Either Pagid yellows or Ferodo DS2500 or 1.11 should work, but I'd suggest switching to non-drilled rotors next time you change rotors - the drilled OEM ones crack fairly easily, especially if you're running a more aggressive brake pad.

Inbyten

What's the consensus on continuing to use the OEM pads and rotors at the track once they start exhibiting this behavior? My last instructor thought the behavior was just an annoyance and not a safety issue. I was hoping to get one
more track weekend out of mine before replacing them with aftermarket items, but safety is my primary concern.

Jabs1542

Jabs1542

NaroEscape

Street/OEM pads were never meant for the track. The extra heat generated and extended use when on the track not only wears out/degrades the pads quickly, but transfers too much heat to the rotor which could cause eventual warping or overheating of the brake fluids. 991 is a heavy car, so the stress on the brake system as you progress and go faster is compounded by the weight the pads are trying to stop.

We carry Pagid RS29 for your car.
Front p/n is Pagid U-4922 https://naroescapemotorsports.com/product/pagid-u-4922/
Rear is Pagid U-4909 https://naroescapemotorsports.com/product/pagid-u-4909/

I also recommend going with better brake fluid (if you haven't already) to make sure you don't end up with boiled fluid as you get faster. either Castrol SRF or Motul 660. We carry both.

bccars

I had a 991 carrera 2 (not an S) before that I took on track. Only thing I had to do is swap OEM brakepads for RS29. Fluid and rotors were fine in my case.

Mr. Turtles

Hey that's great to know and thanks for sharing your experience with them. When I was looking last spring I did not see them anywhere. This is good news for anyone looking for rotors. Will you buy them for the front next time? They seem a lot cheaper.

Inbyten

Fwiw, I had my car at the dealer for something else and they felt the brake judder. They felt it was due to the rotors being slightly warped instead of too much brake material being deposited.