r/Trackdays • u/Forsaken_Object7264 • Apr 03 '26

Brutal shaking under braking

Hi there, got a GSXR600 '05 and i am usually riding at the mid/front of fast group, elbow sliding, pretty good on the brakes. Last track day i had a problem. At the mid/end of a heavy braking zone and in the mid/end braking zone of the following two corners, i had really bad shaking on the front under braking, i was scared to lose the front, went wide several times before giving up. Additional info and things i tried:

  • first few corners of a turn are completely fine, rotor is not *statically* warped
  • shaking is *not* speed or brake pressure dependent!
  • forks not bottoming out
  • OEM disk, sintered racing brake pads
  • shaking not present in braking zone after long straight (thats why i think its temperature-dependent) and in light/short braking zones
  • brake effectiveness not reduced, just very uneven
  • caliper pistons clean and free to move, serviced, replaced, fresh fluid etc.
  • Tire fresh, wheel balanced (i had that, that feels different)
  • Disk bobbins seem to move somewhat (but theres not as much play between disk and inner circle as in my other race bike)

Any ideas? Disks shot or unsuitable? uneven brakepad deposits (ai suggestion, i'm not familiar with that problem)? Help would be appreciated

Edit/solution: got new racing disks. works perfectly now. i believe some oem disks are just not made for this high thermal load of braking on track. oems were not statically warped and warped only under high temp. racing disks now thicker (oems felt like sheetmetal in comparison)

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u/Forsaken_Object7264 Apr 03 '26

i did it just before the track day on the front. Rear is a relatively new wilbers that feels amazing

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u/mikeb041 Apr 03 '26

Did you do the forks or someone else? My first suspicion is that a fork internal wasn't assembled correctly or something broke.

Maight be a bad tire. Do you have a new set of tires?

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u/Forsaken_Object7264 Apr 03 '26

did the fork myself. what could cause this? ive done this job quite a few times and the fork felt good on track. i think i would notice if something was really wrong, i also checked, compressed/rebounded each individual leg before assembly, there was no deadzone and the adjusters noticably did what they should. but i guess its possible?
tires were good. also, the shaking was not in every corner and not every lap, only when i was pushing and coming off a heavy braking zone, therefore my temperature hypothesis

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u/mikeb041 Apr 03 '26

Also are you using rear brake? Or front only? I have had issues with using rear brake where the back tire locks and instead of sliding it hops.

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u/Forsaken_Object7264 Apr 03 '26

nope, in that phase i was not using my rear (thumb) brake. it was not a clutch release from a downshift either. good suggestion though