[s-cars] About RS2 ebrake

joeamund joeamund at online.no
Fri Nov 1 12:26:15 EST 2002

I both agree and disagree on the RS2 e-brake comments. I have tested several
RS2 with poor e-brake, and also rebuildt a couple of them with exellent result
with locking power up to 50mph on dry pavement with little force. I believe if
the rotor and the e-brake shoes are truely grinded and matched to each other
it is a superior system compared to the "childish" stock URS4/6 one piston
combined caliper as an e-brake.

What we do is to grind a drain-groove on the aluminium carrier so the
water/salt/dust and whatever have a chance of escaping the system. You might
try that on our car as an improvement.

Of course there are cons and pros to installing such an expencive system,
compared to other options, but it is like asking: do we need 400+++HP, and how
often do the car see some track sessions? How important is the e-brake system
in this discussion? When testing several S4's with Brembos front and rear I am
really impressed how well theese cars handle the extra braking power, but not
too impressed with the separate e-brake caliper systems.

I am only supplying the details for such an installation, and the owners make
their own choices. I like the way this list is acting where everybody
contribute with their experience and engineering skills, but I am not looking
for a discussion on "how to RS2 on the rear", ala the bolt/torque treads going
on right now. Hopefully by next weekend all drawings and photos will be sendt
to Darren and availiable for all.

I  also believe there are numerous owners with different "spare" parts in the
garage as calipers,rotors,e-brake systems that would like to have a way to
have them used, and also have the splendid look of the red calipers both front
and rear.

Of course I realize we are discussing two items here, one is the upgrade of
the rear braking system, the other is how to solve the e-brake challenge.

I am not sure if it is neccesary to install a proportional valve at all on the
cars with the 3-way ABS, or let the brake computer(ABS) take care of the
mistakes we as drivers make. On the 4-way ABS systems it would be an overkill
for sure.

When adjusting rear/front brake power on my car, I am using a loadcell between
my foot and the brakepedal and check the force applied compared to brake power
(on a brake testing-dyno) on the front wheels vercus the rear wheels. Current
ratio is 65% front and 35% rear which I find serves my driving style, other
may find other good ratios depending on their setup. I strongly advice those
who rebiuld or modify their brake systems to check real braking power on all
wheels after the modifications. "Big Reds" are a lot more than one caliper, it
comes in all shapes and dimensions with different piston dia, different pad
area etc, as do the different rotors, and I also hope those on the list
modifying their system seek expert help if needed.(I am no expert at all, but
got some good advices from Movit)

After trial and error for some months now with the RS2 adaption to our URS4/6
knuckles, I'm convinced its a good system and with minor modifications can
adapt to our cars, and it has to be the Porsche 180mm ID in order to clear the
knuckles.. if the desicion is "go for it"! When testing I borrowed a knuckle
from a salvage yard and fabricated a "dummy" bearing without the pressfit
which saved a lot of work.

Hopefully the beast will act as a track animal when properly

Best reg,Joern MTM RS

>===== Original Message From Jani Peltopuro <jpeltopuro at yahoo.com> =====
>a comment about the RS2 ebrake: a sh*t system. :-)
>Most common failure of the RS2 is that it is not
>functional. Even after rebuild I struggle to lock rear
>wheels in snow, and after a while, the ebrake has no
>effect whatsoever. So at least it needs frequent
>maintenance (not just use!) to work.
>I know Dave E. has a functional ebrake in RS2, but I
>don't think his car meets snow, salt and slush.
>So to anyone living in "quattro"-climate, and thinking
>of a rear brake upgrade, I'd consider a separate
>caliper for ebrake.
>In general to rear upgrade, at least RS2 with 993tt
>caliper (44/36mm pistons), 322x32 discs and rear
>299x24 discs with 968CS (30/28mm) brakes works great.
>No fading at all on track, though the car weighs 1650
>I know some people say you shouldn't upgrade rears,
>causes instability. RS2 weight distribution is
>56%f/44r. The brake balance is a little oversteery if
>applied abruptly in corners, not disturbingly, just so
>you can use it to your advantage. I think in a
>straight line the rears do help braking more than
>you'd initially think.
>RS2 -95 mtm 380+
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