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      06-22-2021, 10:08 AM   #1
smchuck
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Brakes pulsing

Hi friends,

I need some thoughts on my brakes. I have M Sport brakes with basic rotors and Hawk HP Plus pads, steel lines and high temp fluid. Iíve run a handful of track days with this setup and the brakes always worked perfectly. Yesterday, I took a step up in my driving speed and braking aggressiveness and after a few laps the brakes started to chatter/pulse/vibrate under hard braking. I took a cool down lap and they returned to normal. A handful of aggressive laps and problem returned. I inspected everything today and donít see any problems. Rotors look fine and plenty of pad left. I didnít take the pads out to inspect them. Thoughts?

Thanks,

Chuck
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      06-22-2021, 03:06 PM   #2
ScottSinger
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Any vibration in steering wheel ?

Iíd replace the pads. But first carefully disassemble inspect and reassemble and test.
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      06-22-2021, 04:28 PM   #3
smchuck
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Quote:
Originally Posted by ScottSinger View Post
Any vibration in steering wheel ?

Iíd replace the pads. But first carefully disassemble inspect and reassemble and test.
I talked to a buddy who is an engineer at Hawk's parent company. He said its called Judder. Thats a perfect description of what it felt like. Felt like the entire car was juddering. He said pads probabbly got hot and laid down some material on rotor. Once I cooled the braked down a bit the material came off and I was back to good. I had braking power the entire time so I think I'll try another track day and see what happens. If it happens again, I'll switch pads.
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      06-22-2021, 04:29 PM   #4
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Quote:
Originally Posted by smchuck View Post
Hi friends,

I need some thoughts on my brakes. I have M Sport brakes with basic rotors and Hawk HP Plus pads, steel lines and high temp fluid. I’ve run a handful of track days with this setup and the brakes always worked perfectly. Yesterday, I took a step up in my driving speed and braking aggressiveness and after a few laps the brakes started to chatter/pulse/vibrate under hard braking. I took a cool down lap and they returned to normal. A handful of aggressive laps and problem returned. I inspected everything today and don’t see any problems. Rotors look fine and plenty of pad left. I didn’t take the pads out to inspect them. Thoughts?

Thanks,

Chuck
The chart in the upper left-hand corner of this page showing Hawk Motorsports compounds indicates that the HP Plus is very much a street/track pad: https://www.hawkperformance.com/compounds/motorsports. The thing with street/track pads is that they're really street pads and not track pads at all unless you've got a light and lower-powered car like, say, a Miata.

If you've gotten after it on a race track with that pad, you could easily have exceeded its temperature capacity, and as a result you may have pad deposits on your rotors. If you do, they could account for the pulsations you're feeling. I experienced that effect many years ago (i.e., pulsations on the track when everything was heated-up and I had pad deposits on my rotors). I can't recall now if that went away after the rotors and pads had cooled off.

Can you take a close-up photo of one or both front rotors so we can judge whether or not they have pad deposits on them (at this time)?

----------------------------------------

Just saw your 2nd post. "Judder" is the word for the phenomenon, all right. The Hawk Motorsport chart tells me that on a race track you want a pad on the order of the DTC 60 or the DTC 50. Note that on that page you can compare compound qualities by clicking on the white, bold-faced names with black backgrounds of multiple compounds. That might be useful, especially if you want to run the same pad on the street and the track and have considerations about noise and dust on the street.

Something to be aware of: if you increase the braking capacity of your pads by running a genuine track pad, and you're running a street tire like a Michelin Pilot Super Sport or Pilot 4S, you need to consider upgrading to a stickier tire. That is, the braking capacity of your pads must be reasonably matched with the tires you're running to get the most out of each.
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Last edited by dradernh; 06-22-2021 at 04:41 PM..
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      06-23-2021, 07:44 AM   #5
smchuck
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you nailed it. I thought my rotors were clean but a friend stopped by last night and looked and I definitely have deposits. I figured, with my skill level, I could get by another season with hybrid street/track pads, but I think I've surpassed that possibility. thanks for help.
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      06-23-2021, 09:55 AM   #6
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Ferodo ds2500's worked very well for me as a street/track pad, if you need s/t that you don't need to swap out for street use - I also replaced the factory brakes w/ the MP BBK. If swapping pads for the track, then go with a more dedicated track compound as noted above (or run those on the street too, and just deal w/ the noise and extra rotor wear).
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      06-23-2021, 10:20 AM   #7
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Quote:
Originally Posted by Maynard View Post
Ferodo ds2500's worked very well for me as a street/track pad, if you need s/t that you don't need to swap out for street use - I also replaced the factory brakes w/ the MP BBK. If swapping pads for the track, then go with a more dedicated track compound as noted above (or run those on the street too, and just deal w/ the noise and extra rotor wear).
I'm a huge fan of the DS2500s for my 228i.....no street noise, low dust and I can still track them at a high level with no issues....easy on rotors too!

Ken
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      06-23-2021, 10:49 AM   #8
smchuck
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Quote:
Originally Posted by Maynard View Post
Ferodo ds2500's worked very well for me as a street/track pad, if you need s/t that you don't need to swap out for street use - I also replaced the factory brakes w/ the MP BBK. If swapping pads for the track, then go with a more dedicated track compound as noted above (or run those on the street too, and just deal w/ the noise and extra rotor wear).
thanks.
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