The
evolution of my beetle has seen many modifications, and when you have
made a car go fast the other half of the equation is to slow it down
fast as well. I thought I would share with you some of the experience
I have had adapting Porsche brakes to my car. Currently I have 944
brakes at the rear and standard disk brakes at the front. The resulting
combination is good. Although a lot of the magazines say the modification
is a simple bolt on operation, quite simply that is not true!
Yes
the brakes bolt up, but there are some things you should know! Lets
start with the rear trailing arm from the Porsche 944/924. Well,
when you compare the I.R.S. trailing arms of these models with the
Volkswagen I.R.S. trailing arm they are almost identical, except
the Porsche version is a little stronger as it has some additional
webbing inside it. Now you don't have to use the entire trailing
arm, in fact if you have a swing axle of course you can’t, you’ll
only want the aluminium calliper bracket and calliper/discs, yet
most wreckers charge you just as much, so you may as well buy the
entire arm. I got 2 complete arms with all brake hard ware including
handbrake cables for $600.
I
am going to concentrate on the I.R.S conversion as that's what I
have, but the conversion is pretty much the same for swing axle
cars and is actually a bit easier. Why? Well, because the I.R.S
arm on a Porsche has a different pivot point and this is the basis
of the first myth of being a simple bolt up operation. This Porsche
pivot joint must be replaced with the larger V.W. pivot joint. It's
a little bit of stuffing around but once you have done it the arms
do in fact just bolt on. On my conversion I went a little further
and had the rear arms narrowed by Peter DeBiasi and employed shorter
axles from a Type 3 (23mm/side shorter) so that I can fit my big
Fuchs 8 inch wheels under the guards.
The
only snag you run into is the handbrake, or lack of it! You must
modify one of the Porsche handbrake cables and get one made up so
you have a set that will hook up to the handbrake and work properly.
This is done through a process of holding the standard VW cable
against the Porsche one to determine the correct length, but you
must take into account the different thread lengths or you can end
up with the correct length cable that just wont work! Why? Because
the VW thread at the handbrake end is a particular length to allow
it to slide through the tunnel. The after market threads the cable
manufacturers use and press onto your new cable are longer and wont
slide through the curved tunnel tubing near the frame horn unless
its the same length as the VW one. Yet having the cables simply
cut the correct length must also be correlated with the new threaded
end. The cost of the new cables is about $30-40.
Things
to take note when you locate the brakes is to ask the wrecker if
the deal includes the aluminium wheel spacer . This will enable
the use of a 6J offset wheel such as the Porsche Fuch and it will
fill up standard guards nicely. If on the other hand you have widened
guards or you don't use the spacer be aware the studs will be too
long and will have to be replaced, or as I have done, shortened.
I simply shortened mine as they are $10 each!
The
final modification was to send the discs to Harrop Engineering (they
are the boys who look after the V8 touring cars) in Melbourne to
cross drill and slot them. This mod cost $150 and allows greater
water dispersion from the discs as well as cooling, which increases
brake efficiency when worked hard.
So
what did it cost and how does the setup go?
I
can say, I ‘m very happy with the setup, because it looks great
with the cross drilled and slotted discs, and it’s a well balanced
system that I don't think needs any brake bias adjustment between
front and rear. The 19-mm VW master cylinder is well matched to
the Porsche callipers. Remember the front brakes and not the rear
in fact do most of the braking, but it has certainly been an improvement.
I’m sure matching it with 944 fronts would be simply awesome.
So
two complete I.R.S arms with everything should cost about $600.
Cross
drilling/slotting about $150-200.
Brake
cables about $40.
So there you have it, my experience with Porsche rear brakes on
a beetle. I hope that if any one else does the mod to their car
they are a little better informed.
Stay enthused Volks!
David
Gluyas.
