Stoptech Rotors: To Turn or Not to Turn - that is the question

[matteni]

Early this year I upgraded my front rotors to the Stoptech Rotors and replaced the rears with slotted rotors. I put new Axxis Ultimate pads on and bled and bed them in per specs.

I did a HPDE event and last month. It was a beautifal day (no water on the track and very nice all day). In my last session and on the way home felt some shutter in the front (at least I think it is in the front). It almost feels like rocks are moving around under the brake peddal.

After the problem did not go away I bled the brakes, put new Hawk pads on (because I like them much better - not that there was anything wrong with the Axxis pads).

The chatter did not go away again. The car brakes straight and well but the chatter is consistent and feels like it is coming from the left front more then the right front (but it feels like both).

Any ideas? Should I turn the fronts? All 4? Measure something? Replace something?

I did a search and it didn't turn up anything - any advice is welcome - especially from those who track their cars.

 

[nsxtasy]

I track my cars and use the Stoptech two-piece rotors.

The shudder - which manifests itself only when the rotors get very hot, such as on the track - comes from a lack of uniform pad deposits on the surface of the rotor, as described on the Stoptech website here (and can occur with any kind of rotors and/or pads). They describe the proper bedding procedure to avoid this; the purpose of proper bedding is not only to get the surface of the pad and rotor to mate, but also to leave a uniform layer of pad deposits on the rotor.

The article implies that if you bed your pads properly any time you are changing pads or rotors, you will never have shudder. Although the bedding helps, I am not convinced that that is true. Other measures, such as installing cooling ducts, can also help. Also, you can re-bed your pads (same procedure) if you are experiencing shudder, and that may or may not make it go away. You can also try polishing the surface of the rotors with garnet paper or scotchbrite pads to buff off any unwanted pad deposits.

I turn my rotors as a last resort, if none of these steps helps. I realize that this makes them thinner and more susceptible to problems afterwards, although I try to take off as thin a layer as possible. I usually turn the Stoptech rotors once during their life.

In my experience, the ENTIRE shudder is caused by the front rotors, and the rear rotors have nothing to do with it.

 

[polar]

try go follow the bed in procedure and bed in the pads again. NSXdreamer2 have simular problem with the axxis pad, but he is using the one piece stoptech rotor, (not aerorotor)
I ran dedicated track pad (cobalt spec VR) on track and I never have chatter problem.
When exactly did you went to track? last month could be just 3 days ago
the chatter problem that NSXdreamer2 experienced lasted almost 2 weeks after track event.

 

[matteni]

Thank you for your replies! The artical NSXTasy linked to was especially informative.

I will try to re-bed the Hawk pads per the StopTech recommendataions and let you all know if I eliminated it on my own.