[s-cars] Cracked Big Brake Brackets - ECS Stage 2

[Eric Phillips]

Guys:

I think that it's a design flaw - due to *materials choice*.

Aluminum is the material from which this - and other - BBK brackets
are made.  Aluminum has no fatigue limit, which is engineer-speak for
being able to take ZERO stress without weakening the part made from
aluminum.  Different alloys have different fatigue strength, which
tells you how many cycles it takes to break that material.

http://www.sv.vt.edu/classes/MSE2094_NoteBook/97ClassProj/anal/kelly/fatigue.html

Steel has a fatigue limit, which means it can take an infinite number
of stress cycles below the that limit, and will only begin to fatigue
when the stresses happen above the limit.

This is the simplified version - but it is the basis for which I have
decided to always recommend against BBKs with aluminum brackets.  Of
whatever alloy.

Brake brackets get stress in two directions every brake cycle.  In
addition, one has to be careful about the torque put on fasteners
around aluminum.  Too much can create a stress riser that will lead to
cracking.  So, if your torque wrench isn't calibrated properly, you
could initiate a crack on the first install of a new BBK.

On any other automotive system, I don't think it'd be that big a deal.
 But brakes are *the* primary mechanical safety system.

The next problem is corrosion.  The environment in the wheel well is
pretty harsh.  Aluminum is more reactive than steel, by it's nature.
Surface treatments and alloying mitigate this, but don't eliminate it.
 Add to that galvanic corrosion from marriage to steel fasteners, and
all of a sudden you have a potential problem.  And that's before any
addition of road salt.

The reason to use aluminum in this application is price.  Cheaper to
make stuff out of aluminum than steel.  Who wants to pay $600 for a
pair fo steel brackets for a BBK?  That may be an exaggeration, but
not by a large amount.

Maybe somebody could run an ECS, MoVit, StopTech, BIRA or other such
aluminum bracket on their BBK forever without any worries - especially
on a street-only daily commuter.  Maybe it would take over a million
cycles to even approach the fatigue strength of the brackets.  I don't
know.  But that's not something I'd like to find out by accident, pun
intended.

So, now to the opinion part.

I wouldn't run aluminum brake brackets on my car.  Any of them.  And
my car will never see the track.  Even the spirited driving I do is
pretty mild.  During my research on BBKs, I came to the conclusion
that the 993TT caliper, RS2 (steel) bracket and A8L D2 rotor was the
way to go.  From a price and hassle standpoint, the ECS kit is the
best choice.  But I just couldn't bring myself to put an aluminum part
there.

With the RS2 bracket and the A8L rotors, some material has to be
machined away from the bracket where it contacts the strut - about
1mm.  And the stock bolts (35mm) have to be cut down to 25mm, but that
costs about $20 and takes all of two hours for any machine shop that
can do it.

Rotors are available and relatively inexpensive, and you can get them
plated and slotted from Apikol, if that's your thing.

Also, you can run Porsche 993TT rotors on custom hats.  Then you
wouldn't have to machine the brackets at all.  And the rotors are
wider, so you get more life out of the pads, and the rotors are MUCH
lighter than the big A8 boat anchors.  Custom hats are in the
neighborhood of $450 for the pair.

So, my opinion, FWIW, is to go 993TT calipers, RS2 brackets, and some
flavor of rotors that suits your fancy.

You could change over for as little as $350 - $200 for the brackets,
and $150 for the pair of rotors.  I would consider that cheap
insurance, but again, that JMHO.

YMMV, does not include batteries, may contain nuts, etc, etc.

Eric

> Date: Mon, 23 Oct 2006 08:30:21 -0700
> From: "Alvin Labonite" <alabonite at gmail.com>
> Subject: Re: [s-cars] Cracked Big Brake Brackets - ECS Stage 2
>
> I heard that chatter too and was very concernd. during that time, I had a
> shop installed my RS2 turbo and EM and they brought up the crack brackets
> too upon seeing them on the net. Mine turned out ok and they suspected that
> over-torquing may have played a factor. but who know's it could also be poor
> design.
> On 10/23/06, manuelsanchez at starpower.net <manuelsanchez at starpower.net>
> wrote:
> >
> > S-heads,
> >
> > I was having my tech inspection for upcoming VIR school and found that
> > both of my ECS Stage 2 caliper mounting brackets are cracked. Based on some
> > recent internet posts on the subject, I made sure the tech checked
> > carefully.
> >
> > I spoke with Gary at ECS, he was very nice and did some checking with the
> > returns department. He told me he thougght this was an isolated incident. I
> > mentioned that I was clued into this potential problem from chatter on the
> > net, but he said he had never run across the issue and he handles 50% of the
> > calls.
> >
> > I would be interested to know how many others have had this problem and
> > what you did about it (contacted ECS?).
> >
> > I asked if the design had changed at all, and he said no. I suppose it
> > could be an isolated manufacturing defect, but I wonder if it is a design
> > issue. Obviiously I would prefer that this not happen again, and a design
> > revision would probably make me sleep better.
> >
> > So check you caliper mounting brackets.
> >
> > Again, Gary was very nice and helpful, and ECS will warranty the brackets.
> > I need to buy new brackets, returned the cracked ones, and then they will
> > refund the cost of the replacement brackets.
> >
> > I'm wondering though what my other options would be for a 993TT Big Red
> > brake kit. Any thoughts?