braking shimmy

[nsxtasy]

What else could you do if the rotors have measurable runout other than turn them or replace them?

My point was, there are downsides to turning them; you may be better off replacing them.

When I was having shudder problems, I was experiencing first hand the difference in life between turning them (newly turned rotors lasting for 1-2 track events before shudder became unbearable) and replacing them (new rotors lasting 4-5 events).

I also found that the problems were not due to warping (since the rotors wouldn't shudder when cold), but due to "hot spots" which expand at different rates from the rest of the rotor (see Bill Zachar post above). So turning didn't help anyway.

[This message has been edited by nsxtasy (edited 14 November 2001).]

 

[sjs]

Not to argue, but rather to share experiences. I had what by all evidence was the hot spot problem on OEM rotors. They were also slightly warped cold, but not enough to cause shudder until hot. They cost me about $10 each to turn them and it completely solved the problem for quite awhile. No shudder even from 120+. If you do your own work and don't mind the time to pull them off, and you aren't concerned about the last bit of heat absorption, you might want to turn them. (Assuming they have enough thickness to remain within spec) On the other hand, rotors aren't really all that expensive.

 

[cobalt]

There are three types of rotor warpage. One type is what I call "cold warpage" and the other is "hot ghost warpage". Cold warpage is a permanent warpage which you will feel at all speeds and temperatures - it is typically the result of poor casting and quality control. Since you are only experiencing a brake shudder when the rotors are hot/heated up after a hard brake application, and since PF has incredible quality control on their rotors, you do not have "cold warpage". "Hot ghost warpage" becomes evident only when the rotors reach a certain temperature, such as when they become hot after hard braking; it results from uneven heating and cooling during the heat tempering process and/or the final cryogenic treatment of the rotor. This type of warpage in the rotor is NOT evident when they are cold - you can literally put the rotor on a lathe with a feeler gauge at room temperature, and it will spin true...but heat it up to some arbitrary temperature, say, 500deg, and the warping becomes evident.

Now, there is a third cause of brake shudder, which is NOT caused by a warped rotor, but can often lead many to believe that their rotors are warped. This third cause is "friction material film transfer", which is essentially the irregular, non-uniform deposition/transfer of brake friction material onto the rotor surface. All high-performance compounds exhibit this phenomenon to a certain extent at various temperatures, with some compounds being very hard offenders, indeed. When the brake friction material is deposited or smeared onto the rotor surface in an irregular pattern, upon application of the brakes, the brake pad will "grab-and-release" on the film transfers due to chemical adhesion, resulting in a brake shudder, and thus simulating what is often assumed to be a warped rotor.

With Best Regards,

Andie Lin

[This message has been edited by HomeDepotNSX (edited 28 November 2001).]

 

[Yellow Rose]

Originally posted by F=MA:
[I know this is heresy (and inviting flame), but I sort a wish I would of bought a Porsche.[/B]

Or, take some of the cash from your Porsche sale and invest in a big brake kit. There are a lot of NSXs with superchargers and turbochargers, yet the OEM brakes are still on the car. Yikes!! There is a reason why Porsche and Ferrari equip their +/-400HP cars with big brakes - shouldn't you owners of forced induction NSXs be thinking along the same lines?

Stepping down from my big brake kit soapbox, I'd like to now comment a bit on what Andie points out regarding shuddering. I had two problems - ghost warped the front rotors and film transfered from the pad to the rotor on all four corners. After sanding the old film transfer off of the rotors and changing pad compounds, there was still a little shudder until the new pads scrubbed the old pad film off. Now I can brake like PD - well sorta.

 

[nsx1164]

Originally posted by HomeDepotNSX:
Now, there is a third cause of brake shudder, which is NOT caused by a warped rotor, but can often lead many to believe that their rotors are warped. This third cause is "friction material film transfer", which is essentially the irregular, non-uniform deposition/transfer of brake friction material onto the rotor surface. All high-performance compounds exhibit this phenomenon to a certain extent at various temperatures, with some compounds being very hard offenders, indeed. When the brake friction material is deposited or smeared onto the rotor surface in an irregular pattern, upon application of the brakes, the brake pad will "grab-and-release" on the film transfers due to chemical adhesion, resulting in a brake shudder, and thus simulating what is often assumed to be a warped rotor.

I've seen this happen firsthand when breaking in NEW rotors with the AP Racing BBK (I have the one from RM Racing). In my case, both rotors and pads were new.