[s-cars] The front brake upgrade grinds forward

[Theodore Chen]

--- Taka Mizutani <t44tqtro at gmail.com> wrote:

> Evan-
> Thanks.
> 
> I meant, what are the advantages of a floating 2-piece rotor versus a fixed
> 2-piece rotor? In terms of noise, durability, truing issues, replacement
> issues, etc.

the advantage of a floating rotor is mostly theoretical.  a fixed
rotor works pretty well with a fixed 4-piston caliper, because the
pistons themselves float and allow the pads to track the rotor.
the main advantage is in reducing coning as the rotor expands from
heat.  however, this isn't as significant if you use aluminum hats
because although they run cooler than the rotor rings, they have
a higher coefficient of thermal expansion so they grow with the rotor
rings.  a lot of full-on race cars don't bother with floating rotors.

the primary disadvantage is that the floating rotor tends to wear the
mounting pins.  be prepared to replace parts often or put up with clunking.
this isn't much of an issue with a race car (NVH doesn't matter), but it'd
drive me nuts on a street car.  having said that, i think the euro M5
uses floating rotors - but i think clunking is a common complaint, too.

> As for brake ducting, yes, it does matter to me. I'm not fading my brakes on
> a regular drive, but I have experienced brake fade on the street. I don't
> think I'd see brake fade in the STi (3300 lb. car with 326x30 front rotors)
> but I think it is very possible with the Miata (tiny rotors, albeit 2400
> lbs). I know brake ducting solutions are soon to be available for the STi if
> not already, don't know about the Miata- I wanted to hear some discussion
> about brake ducting and proper application of such.

brake ducting can only help, and it's relatively cheap.  however, you
will probably find it tricky to get decent ducting in there.

brake ducts are not legal in spec miata, if that's what you were wondering.
i haven't been getting brake fade in the SM.  that's a dinky little car
with a lot of stick and not much power.  if you get brake fade in the
miata, you're using the brakes too much.

> As for track use, I faded the Porsche 996 caliper / MBZ 320x30mm rotor
> running Hawk HPS pads at the Glen. Repeated 135 to 60 on the back straight
> and 100-110 to 60 on the front straight caused major brake fade by the end
> of a session, major "check your shorts" moment on the front straight when
> the pedal went to the floor and I had to look for a suitable place to crash.
> Fortunately, I was able to scrub enough speed w/ understeer to be able to
> keep the car on the track. :-)

what kind of brake fluid were you using?  fresh?

-teddy


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