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Thread: PFC08/rotors and pulsing

  1. #1
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    PFC08/rotors and pulsing

    Sup guys,

    Need some help figuring out why I’m having some pulsing issues under hard braking at the track. I have read some other related threads, good and bad, but I wanted to see what you guys have to say about this case.

    So it’s my first time out with the big boys on some dedicated track pads!
    I do drive to the track so I decided to install them the day before the track-day. So I installed them and I did some sort of “bedding in” I guess, might not be considered bedding, but I did a couple hard stops on them and maybe totaling 15 minutes of driving, if that. Drove up the track with no issues, about 140’ish mile drive up, and felt really good with a solid pressure feel.
    First and second lap came around and was pretty damn surprised on how they were (came from Z-rated pads), but the pulsing came in as the 3rd and on laps came around. It’s definitely not ABS kicking in, it was full on front-end and steering wheel shaking. I did keep driving throughout the day and eventually learned to brake LATER, which felt way better, but the pulsing was still there. Checked the pads and and rotors, little to no deposits, but could be wrong, even though others checked them out and said they're fine.

    Fresh pads, fresh blank rotors, sort of fresh brake fluid, running NT01 tires. Think the rack is going on its way out, too. So that may be a possibility.

    Leaning towards getting them resurfaced and running a fresh batch of Z-rated pad's for street, and getting a new set of blank or even slotted rotors to swap out at the track, and then bed them the "proper way" on the first lap at the track. Instead of using the same rotors.

    Any thoughts?

    Thanks!

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    I had the same issue but with my new rotor rings. They are fine for street but pulsing after 2 laps when the rotors get heated up. I got them checked for runout and resurfaced. The machinist said run out was very little but i think when the rotors heat up and expand, it makes the runout worse and the track was the only place i could get enough heat into them to experience the pulsing. After the resurface, no more problems.

    Hope a resurface fixes your issue. Trying to find someone to cut rotors was very difficult since replacement rotors cost about the same. Went to a machine shop with a grinding table.

  3. #3
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    Thanks for the response!

    That makes sense. I’ll check in on the resurfacing / cutting the rotors. Also thought I warped them, but I can’t see how I would’ve warped them.
    Blank rotors are 25-30 bucks and just a bit more for the slotted rotors. I think at this point slotted would be best to have along with the track pads so they work better together. Just figured I can be lucky like others running stock blanks with no issues. lol
    Last edited by z3m.casey; 05-11-2019 at 03:34 AM.

  4. #4
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    Warped rotors just don't happen. (Once upon a time, I received a new rotor that was well out of spec for run out, but that's obvious from the start.)

    99.9% odds that the pads/rotors weren't bedded correctly, and you have/had some uneven transfer deposits on the rotor. Usually, getting a lot of heat into the rotor/pad will remove the uneven deposits. I've had a rotor or 2 that didn't bed right, that I also couldn't clear up. They got replaced (another benefit of $40 rotors).

    PFC08s usually bed pretty easily. I don't do much special when I put a new set on. Just a timid 1st lap or 2 with firm braking into T1. Or such. I don't really think about it.
    Last edited by aeronaut; 05-11-2019 at 08:28 AM.

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    Buy dedicated front rotors for your track pads. Keep street rotors with you at events for a backup. Use cheap blanks (centrics) so when you have this issue it is easy to swap to new rotors. Ensure front control ARM bushings and bearings are in great shape.

    Aside from that, I never bed race pads until at the event (on track) and get heat in them quick and try to beat the as hard as possible because nothing else has given me any better luck....

  6. #6
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    That's definitely a plus for the centrics. Blanks that I've been using are like 30 bucks on amazon, shipped too. I'll be at the track next weekend so lets see what the new rotors and bedding at the track does. Hopefully have no issues and get some faster times.

    Thanks for the info fellas.

  7. #7
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    This is pretty normal for track pads where you don't intentionally try to bed them quick and hard at the track. Typically a track pad is abrasive on the street, so even if you do bed them in, the pads will scrape that adhesion layer of pad material off with street driving while cold.

    You want to get to the track, and get them bedded in a hurry, as long/lazy braking zones can tend to unevenly build that layer of pad material, which then tends to exacerbate and build up more runout as the day goes on.

    I know my Hawk DTC-60s didn't like lazy bedding in at track, and tended to have much smoother performance when I went out and hammered them pretty good.

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    I'm having the same problems with PFC-11s, even though I installed them with fresh rotors. It got REALLY bad due to several BTB track days in the rain. Now, on a dry track I can get them heated up and they vibe less for the rest of the session, but the next session it's the same deal, they vibe hard until I heat them up again. I am going to try a new set of rotors and a lower temp pad compound.
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    My PFC08's had some shuddering on first use. I think it's because of what some people have mentioned above about them more or less "debedding" from daily driving. Now I do ~6 60mph-5mph bed-ins on my way to the track. Haven't had the shuddering since doing this. Also, they screamed for the first two weeks or so (two track days and dailying) to the point I was about to remove them for dailying. However, they've significantly quieted down after some use. Don't know if that's specific to my case or not.

    Edit: Just re-read what Def mentioned, and I remembered a similar experience. The harder I worked the brakes the better they performed. First time the first lap had shuddering (did not bed them in), but after I hammered em they smoothed out perfectly (basically bedding them in). Now that I bed them in en-route to the track, no shuddering. Also, my cheapo temp gauge says I'm running them to about 750-800 degrees F which is in the low-middle range of their operating temperature. Make sure you're getting them hot enough.
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  10. #10
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    Interesting stuff! so you did “bed” them in, also drove to the track, and had the shudder. i think its you (or the driver) that gets used to the brakes, which then means your braking later, which you’re supposed too anyways and kept going.. but in my case, I even tried braking “earlier” again and it still did it. Braking later for me still did the shudder, but not as much because I limited the brake input to a minimum while stomping on them. lol (still beat my PB by over a second)

    Also drove around afterwards for a bit and took it out for a few canyon runs and nothing seemed to change. still have the shudder so I decided to throw the fresh batch of Z-rated PFC’s back on.

    I won’t be at track for a couple weeks (wish I could go this weekend) but I’ll throw the 08’s back on with the fresh rotors and I will...absolutely... stomp on them at the track.
    Last edited by z3m.casey; 05-21-2019 at 02:46 AM.

  11. #11
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    Some pads won't clean up over time... I know DTC-60s are right on the borderline of being abrasive enough to clean up rotors with some street driving. So minor pulsations would clean up over time, but if you really borked the rotors, they wouldn't clean up evenly like using Hawk Blues to just machine rotors when cold.

    Driving my car to the track, I'd always try to get a quick bedding in with ~2-5 mins left to get to the track. Depends on roads, but it always seemed to help to at least build up some friction material on the rotors before going out first time. Then definitely get things up to temp quickly your first lap out there using the brakes.

  12. #12
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    I had a similar problem on my E36.. 3 laps in and pulsating started... got worse every lap. I had the rotors on the wrong sides. They are vented and directional. Doh! Wrong side and they overheat.
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    Quote Originally Posted by Def View Post
    Some pads won't clean up over time... I know DTC-60s are right on the borderline of being abrasive enough to clean up rotors with some street driving. So minor pulsations would clean up over time, but if you really borked the rotors, they wouldn't clean up evenly like using Hawk Blues to just machine rotors when cold.

    Driving my car to the track, I'd always try to get a quick bedding in with ~2-5 mins left to get to the track. Depends on roads, but it always seemed to help to at least build up some friction material on the rotors before going out first time. Then definitely get things up to temp quickly your first lap out there using the brakes.
    Someone told me to try that on my current rotors. To put my 08 pads in at the track and bed them in again. But wouldn't that not work because I drove TO the track, which means the rotors will still have a good amount of heat, even if I car sat for a little while? I think I'd be better off purchasing another set of blank centrix rotors (or slotted) and do everything all over again, AT the track.


    Quote Originally Posted by Hallatauer View Post
    I had a similar problem on my E36.. 3 laps in and pulsating started... got worse every lap. I had the rotors on the wrong sides. They are vented and directional. Doh! Wrong side and they overheat.
    I thought I had that issue, too! I took the wheel off mid-day trackday and thought I installed them wrong. fins were pointing to the rear, but I was thinking that they were supposed to "scoop" air and point forward.... I hoped that was issue, but it wasn't. FACEPALM. Confused under pressure and frustration. haha
    Last edited by z3m.casey; 05-22-2019 at 07:56 PM.

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    uhm what....?

    There's different ways of getting your post count up...lol

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    To all of you who are experiencing warped rotors with PFC08 pads, what rotors are you using?

    I took my HPDE car out on its first track event to Road Atlanta and after about 4 laps braking into turns 1,6, and 10 I had way too much pulsing, and I could almost instantly smell the brake pads. My car is a 1994 E36 with a complete M3 swap. It has all new bushings, ball joints, tierod ends. Tires only have 1500 miles and balance is smooth up to 123mph on the track.
    My calipers have been rebuilt and the pads and Meyle rotors (they are on the proper side) where on a race car that changed classes and went to E36 325 pads and rotors. They only have a few(less than 5) practice-shake down laps on them and rotor surface looked new, no discolor or marks on them. I have put about 1000 street miles on them before the track event.
    It also has Hard brake duct backing plates, 3" hoses and air ducts in the driving lights locations.

    After the track event driving home and during short drives, there has been zero pulsations/vibrations.
    Last edited by AJLM34A; 03-30-2021 at 09:35 AM.
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    I would toss a set of new centric rotors on the front and go bed them in with the PFC08s.

    - - - Updated - - -

    Hard to tell what your rotor situation was based on your post, sure sounds like mixing pad compounds causing surface deposits but cant tell where/who ran those rotors before and what they were run with.

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    I haven't seen a warped rotor in 30 years. If they were warped they would pulsed at street speeds all the time. As they only pulse once warmed up it points to improperly bedded pads or mixing of pad compounds.

    I've found that PFC compounds do not play well with other non PFC pads.

    When switching pad brands the rotors need to be turned, ground, bead blasted, etc.
    I have had some success using very aggressive Scotch Brite on an angle grinder.
    It's important to get to the base metal to remove the old transfer layer then properly bed the new pads.

    Jeff Ritter in one of his Essex videos mentions using a pure metallic pad and driving around for 50 or so miles to clean the rotors when switching pad brands.

    Or you can have dedicated match rotors and pads. Only takes a few extra minutes to swap rotors while changing pads.

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    Quote Originally Posted by AJLM34A View Post
    To all of you who are experiencing warped rotors with PFC08 pads, what rotors are you using?

    I took my HPDE car out on its first track event to Road Atlanta and after about 4 laps braking into turns 1,6, and 10 I had way too much pulsing, and I could almost instantly smell the brake pads. My car is a 1994 E36 with a complete M3 swap. It has all new bushings, ball joints, tierod ends. Tires only have 1500 miles and balance is smooth up to 123mph on the track.
    My calipers have been rebuilt and the pads and Meyle rotors (they are on the proper side) where on a race car that changed classes and went to E36 325 pads and rotors. They only have a few(less than 5) practice-shake down laps on them and rotor surface looked new, no discolor or marks on them.
    It also has Hard brake duct backing plates, 3" hoses and air ducts in the driving lights locations.

    After the track event driving home and during short drives, there has been zero pulsations/vibrations.
    Did you fully bed them before the track event?

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    Quote Originally Posted by lmtfi View Post
    Did you fully bed them before the track event?
    They were used on a dedicated track car for about 5 laps and were bed in then. I have driven with on my car for about 1000 miles on the street with them before the track event.
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    So, to be clear, you did the following?
    - installed used race (PFC08) pads from another car onto yours.
    - drove 1000 miles on the street
    - after 4 laps at Road Atlanta, started getting pulsing

    If that's correct, it's not a surprise. And as stated above, it's not a warped rotor. It's uneven pad material build up. Sometimes it'll clear with hard on-track use, sometimes not.

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    Quote Originally Posted by AJLM34A View Post
    They were used on a dedicated track car for about 5 laps and were bed in then. I have driven with on my car for about 1000 miles on the street with them before the track event.
    My thinking is that use doesn't mean that they were bedded. I'd do the full bedding procedure without variation and then evaluate.

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    Quote Originally Posted by AJLM34A View Post
    They were used on a dedicated track car for about 5 laps and were bed in then. I have driven with on my car for about 1000 miles on the street with them before the track event.
    PFC's are abrasive when cold - driving 1000mi on the street more than likely wiped out any bedding layer you had built up. If you went straight back to the track and experienced pedal pulsing, that's 99% going to be pad deposits from improper (nay, zero) bedding procedure.

    I usually spend the first cold laps of session 1 bedding in pads regardless - the track's frozen, other idiots are spinning off the track, may as well make sure the brakes have no excuses to stop your fun later in the day.

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