Trev's VWRX Project
Brakes-Suspension
Quick links to latest updates (or
you can just scroll down!):
3-6-2003:
Suspension:
An IRS conversion of the standard swing axle floorpan
is planned, along with dropped spindles at the front. The front axle will
have all the bits required to fine tune the suspension i.e. uprated anti-roll
bar, axle adjusters, extra-eccentric camber adjusters etc.
Brakes:
Braking will be taken care of by a pair of Subaru 4-pot calipers and Kerscher
vented disks on the front. At the back, I'll probably use Golf or Passat rear
calipers (the Subaru rear calipers have no accommodation for a hand brake)
on custom brackets with the Porsche 914 rear disk set I already have. An uprated
master cylinder will be required to push enough fluid to the calipers.
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Subaru 4-pot front and single pot rear calipers
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Front
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Rear
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Wheels:
Wheels are to be fitted to custom drilled hubs, and will most likely be OEM
wheels from a modern luxury car manufacturer (not Porsche!) I have my eye
on some stock BMW 5 series 5 spoke wheels. They are different widths front
and rear, which should be ideal. I'll probably use widened rear wings to clear
them.
28-7-2003:
Suspension:
I've decided that a 1303 would be a better base car for this project than
a standard beetle. The reasons for making this decision are based on the superior
front suspension of the 1303. Coupled with the factory installed double jointed
IRS suspension this decision takes some of the labour out of the equation
and removes the possibility of me not welding the rear semi-trailing arm brackets
in right and ending up with dodgy chassis geometry. At least if it's as it
left the factory, I'm guaranteed it's right. The front suspension, being McPherson
strut based is more tunable than the torsion bar suspension and OEM Porsche
components can be used on the rear to upgrade it (i.e. anti-roll bar, adjustable
springplates).
Since large diameter wide alloy wheels are planned, and more than likely the
bodywork will be kept stock, slimline struts will be needed to prevent fouling
with the wheels.
Topline in the US make just such a strut, which I
will probably resort to.
Brakes:
With the decision made to go 1303, it's too hard to ignore the bolt-on simplicity
of the Porsche 944 components. While the Kerscher disks, custom drilling to
BMW pattern and custom made adapters for the Subaru calipers sounds great,
in reality the extra initial expense of buying the Porsche components would
more than likely be met by the cost of custom machining. Add to this the availability
of spares if something breaks and it would be foolish to dismiss the Porsche
components without first giving them some careful consideration. From the
research I have done, it appears that with small modifications to the ball-joints
of the Porsche front spindles, the whole front braking and part of the front
suspension system will fit directly to the 1303 front end.
Wheels:
If Porsche brakes are used, then I am limited to using Porsche wheels. While
this isn't a huge problem (they're loads of styles of Porsche wheel, most
of them quite handsome) it knocks the BMW wheel idea on the head. Even though
the BMW pcd is 5x120 versus the Porsche pcd of 5x130, the Porsche hubs can't
be redrilled like might be done on the old VW hubs. Either way, the wheels
will be 17" in diameter and are likely to be quite wide, especially at
the back. The Subaru motor is usually driving 4 wheels, it will be driving
only 2 in my car, so the more rubber in contact with the ground, the better.
12-1-2004:
Suspension:
Well, I finally got the brakes and rear suspension components I bought from
the UK a few months back. I knew the trailing arms were the later aluminium
versions before I bought them, but I was unsure whether they were the early
or late version of the aluminium arms.
The 944 throughout its life was subject to ongoing development of its mechanical
parts, the rear suspension being one of the developed areas. It started
its production run with steel trailing arms that are visually the same as
the 1303 items, but have extra internal bracing for extra strength and slightly
different inner bushes. These retain the same rear track as using the standard
1303 arms. In 1985 or so the steel arms were swapped for cast aluminium
versions, and again later on for wider versions of the cast aluminium arms.
The narrow and wide versions pretty much look the same as each other except
the narrow ones have a round "flat" cast into them on their upper
side for a rubber bump stop to bear on. The wide ones don't have this flat.
The narrow ones will increase the rear track by 43mm per side whereas the
wide ones will increase the rear track by 74mm per side. (Thanks
to "Superman" at the Germanlook.com forums for this info).
Luckily I got the narrow ones. This will leave more room in the wheel
arches for wider wheels or wheels with a standard Porsche offset of 52mm.
I would have had to hunt around for wheels with bigger offsets to keep the
wheels under the arches if I got the wide arms. These wouldn't be as common
as the ET52 wheels. The 944 spring plates were also included in the deal.
These differ slightly from the standard 1303 items in that they offer a
small amount of ride height adjustment. This is to fine-tune the car's height
from side to side and to help balance corner weights for the car. I also
got one driveshaft from an automatic transmission 944 in the deal. It is
an odd length compared to all the other 944 and 1303 drive shafts and is
therefore not suitable for use in my project, but it will yield a pair of
CV joints to use while setting up the gearbox location in the car.
Brakes:
The brakes I got (below) are from a non-turbo 944 and as such feature single-piston
sliding calipers as opposed to the big cast aluminium 4-piston calipers that
were used on the Turbo cars. I plan on a conversion to the bigger calipers
when money allows. It's probably overkill on a light car like a beetle and
especially when the national speed limit is 60MPH, but they look soooo cool
when painted red and behind big diameter Porsche wheels.
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Front brake assemblies
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Right
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Left
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Single piston calipers
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Spindles bolt onto the 1303 with minimal modifications
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Aluminium rear trailing arm, drive shaft and springplate
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Rear disk/hub assembly
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Wheels:
I need to find some wheel nuts before I can get wheels. I also need to do
my homework about which wheels and what offsets will fit on properly.
27-1-2004:
Suspension:
I placed the 944 arms beside some spare 1303 ones I have and noticed something
that will cause me a problem. The inner front pivot of the arms is mounted
differently in the two cars. The beetle uses a very thick stepped bolt
to secure the arm. It in turn has a correspondingly large hole in the
rubber bush. The 944 on the other hand has a small internal diameter bush
which will not suit the VW bolt. The VW aftermarket shops carry Urethane
bushes as an upgrade for VW rubber items. Luckily they will fit the Porsche
arms too so they will help to get over this problem.
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Steel VW arm bush
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Aluminium Porsche arm bush
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Comparison between Porsche alu arm (top) and stock
VW side by side.
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23-2-2004:
Suspension:
I sourced a set of the urethane replacement bushes and went about fitting
them to the Porsche arms. The bushes come with the steel sleeve with
the correct internal diameter for the VW bolt. Removing the rubber bushes
from the Porsche arms requires a pair of screwdrivers to lever and wiggle
out the bush from the first side, then a hammer and drift to knock out
the other one. It takes a bit of muscle work, but a bit of a no-brainer.
Putting the new bushes in is easy too, simply pressing them into place
and a bit of gentle persuasion from a hammer for the last few mm. Maybe
some lubricant would have made the job easier...
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Stock Porsche rubber and steel bushes in place
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Porsche bushes removed, urethane ones ready to
go in.
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One down, one more to go!
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21-3-05:
Suspension:
Since I'm holding off buying wheels til the very end, I have
bolted up the 944 rear trailing arm and brake assembly on the
left hand side only and fitted the 996 spare wheel to it to
check for clearance. Even though the wheel is only 3.5"
wide, the 996 spare protrudes beyond the edge of the wing by
approx 25mm due to the fact that the offset for this wheel is
only 18mm and the 944 arms are wider than the stock VW ones.
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996 spare wheel offered up to 944 brakes
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Wheel protrudes by approx 25mm, despite
being only 3.5" wide. The offset is shallow at 18mm
however.
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7-5-05:
Suspension:
I got the 944 trailing arm bolted up to the other side of the
chassis and the drive shaft bolted in place. The springplate
adjusting bolts foul the inside of the shock tower so I'll have
to figure a way around that problem. Since I'll be using coil-over
shocks and not torsion bars, the adjustability of the 944 springplates
will be defunct, but they do provide a mounting point for the
anti-roll bar. Some people have reshaped the stock VW springplates
to suit the 944 trailing arms. Since they're spring steel it
mustn't be easy, but obviousyly achievable. I'll have to decide
what to do eventually.
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right side suspension installed
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stock VW IRS springplate (top) compared
to 944 adjustable springplate (bottom)
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right side with spare wheel fitted
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spare wheel with stock wing fitted
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12-6-05:
Brakes:
I bolted up the 944 brakes to the front of the bug this weekend.
It was a fairly straightforward affair, but that's because they're
not properly on yet. The stock VW balljoint that connects the
track control arm to the bottom of the spindle is not suitable
for the Porsche spindle in that it has a 15mm diameter shaft.
The hole in the Porsche spindle is 17mm so I'll need to get
conversion balljoints from Kerscher in Germany to sort this
problem. Another thing that isn't a straight "bolt-on"
is the track rod. The bore in the steering arm of the VW spindle
has a taper machined into it to suit the track rod end. The
track rod end fits into the VW spindle from the top, but fits
the Porsche spindle from below. To facilitate the trial assembly,
I had to loosen the locking nut on the track rod end and turn
it upside down. I also had to wind the track rod ends out of
the track rods to lenghten them, but they're wound out so far
they're only held in by a couple of threads. This is not safe
for driving on the road, so a pair of anti-bump-steer bushes
will have to be fitted to the Porsche spindles to regaind proper
steering geometry and safety. Another thing to note if you think
the Porsche spindles are a straight conversion is that the Porsche
spindles will have quite a bit of positive camber when installed
in place of the 1303 spindles. I presume it's due to the 944
having a wider track or more of an angle on the struts. I can
either lengthen the track control arm or make adjustable strut
top plates to reduce the camber. More research will have to
be done to determine which is the best option.
Wheels:
I located a pair of 944 Teledial wheels in 7x15" with an
offset of ET53mm. I bolted these to the back of the car to check
how the clearance was with the inner bodywork and the wheel
arch lip. These wheels protrude by approximately 2" outside
the wings. I will need to take some measurements and see what
wheels are available and in what offsets before making a purchase.
I also think I will have to get wider wings to cover the wheels.
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| Porsche brakes all round! |
wheels stick out a bit! |
same on the other side |
944 non-turbo brakes
on front |
11-5-06:
Front Suspension:
Since the oval body is now going over the 1303 chassis and I'm
retaining the struts, obviously I'll have to build in some accomodation
for the strut tops. To this end, after looking at the Bugformance
strut-oval project, I reckon I can do something similar
in mine. The basis is a tubular frame that goes roughly around
the fuel tank hole and carries the strut-tops. This is tied
down to the chassis to keep the struts independent of the body
and ensure no suspension loads are transmitted to the body.
After measuring up a strut top, I put together a cad drawing
for a pair of plates to accept the strut tops and fix them to
the tubular frame. I had them laser-cut from 5mm mild steel,
along with some reinforcing gussets. While I was at it, I designed
them so they could be adjustable for camber.
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Camber plate assembled
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with clamping plate removed
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slots allow camber adjustment
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assembled, close-up
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Steering:
Since the oval shell is left hand drive and the chassis is right
hand drive, a steering rack on custom mounts is a good upgrade
over the stock steering box and a way of overcoming the differences
between the shell and chassis. The rack is from a Mk2 Golf and
with a steering column from a torsion bar bug, auniversal joint
from the 1303 and the rack from the golf, if can all be hooked
up together to work nicely. I'll have to get the front suspension
installed and settled before fitting the rack to make sure I
retain good steering geometry. Speaking of the front suspension,
I'm going to try my hand at making a pair of adjustable struts.
Threaded sleeves are available from motorsport suppliers that
come with lower spring seats and a locking ring for 2.5"
diameter springs. With the lower spring seat cut from the stock
strut, the sleeve can be welded in its place and the narrow
spring set in place. Along with shorter shock absorber inserts
it makes for an easily height adjustable strut using th original
struts. Watch this space for progress...
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Steering rack and steering column
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1303 steering UJ will make them work
together
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lower spring cup removed from strut
on right
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Rear Suspension:
I've fitted a pair of stock rear wings on to see how much wider
I'll need to getto cover the wheels. The left rear wheel is
a 924 turbo wheel measuring 6J x 15, ET53 and protrudes beyond
the lip of the wing by about 35mm. The right rear wheel is a
Boxster cup front wheel, measuring 7.5J x 17, ET55. It sticks
out beyond the lip of the wing by about 55mm. The reason for
this is the aluminium trailing arms being wider than the stock
VW steel ones. I'll need wings approx 3" wider to make
sure everything is undercover.
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Left side, 924 Turbo wheel
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Right side, Boxster front wheel
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28-5-06:
Front Suspension:
This week the 1303 shell was sent to it's new home. I've taken
all I need from it and made jigs from it to adapt the front
suspension to the oval shell so the time was right to move it
on. Micheal Wroth from Cork is the new owner, it was bought
to replace the rotten shell on his race-car build. He's building
a 1303 to compete in classic car circuit races and my shell
was suitable for his needs, despite the huge holes I had cut
in it! Best of luck with it Micheal, I guess this shell was
destined to drive fast, one way or another!
So as soon as Michael had packed the shell onto his trailer
and headed on his way I got back to work: I refitted the jigs
to the oval shell and offered up the camber plates I had made
(see above). I needed to enlarge the holes in the front quarter
panels of the oval to allow the camber plates through, but with
all three pieces of the jig in place and centred, the plates
look like they'll do the job nicely. I'd like to fit a wing
up just to check that it all fits under there but I'll have
to tack weld them in place first as the jig prevents the wings
from being bolted up. Next step is to make the frame inside
the bonnet to support the camber plates. Once made, I'll have
to fix that frame down to the hammerhead of the chassis and
the chassis cross member at the front of the pan. Still have
to figure that bit out but it shouldn't be too difficult.
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Shell off to a new career as a circuit
racer
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camber plate held in place by jig
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jig assembled and holding plates in
position
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it should fit under stock panels!
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10-7-06:
Front Suspension:
Well, the struts are in! I thought the day would never come!
I built a frame inside the bonnet area with the same internal
dimensions as the hole in the body where the fuel tank goes.
This way I can use the stock fuel tank in it's normal location,
just 2 inches higher. Once this frame was made, legs were made
and welded to plates that bolt to the chassis at the old body
mount locations on the hammerhead and the front corners of the
floor pan where the frontmost body bolts are. The legs bolt
to the frame as I want this to be removable. If I welded it
in place now I wouldn't be able to get the body off to do the
repairs that are necessary. Once the frame and legs were sorted
I fitted up the jigs I made from the 1303 shell to locate the
strut tops. The plates were fitted in place on the jigs and
the ribs I had laser cut at the same time as the plates were
trimmed to suit. The plates and ribs were welded to a length
of 50mm angle section steel so the assemblies can be unbolted
from the frame when the body needs to be removed. Once everything
was tack welded in place I was able to remove the jigs and offer
up the struts. Everything fits and looks like it's all in the
same orientation and alignment as it was in the '03. Just what
I was aiming for! ;-)
I feel like I should have a cross brace to strengthen the assembly
diagonally side to side and front to back, so this is the next
thing to do. Even when this is all welded together I'd feel
better if I had the whole thing braced diagonally, especially
considering that the assembly it bolted together, not welded.
Watch this space!
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Frame under bonnet
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Strut top held in place by jig
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Jig removed, strut top tack welded together
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Trial fitment of struts, looks good!
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Et voila! Oval shell over 1303 chassis,
retaining McPherson struts!
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