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Suspension Tuning Tips for Type 1 Swingaxle Beetles, IRS Bee

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Suspension Tuning Tips for Type 1 Swingaxle Beetles, IRS Bee

Post by LhYnxz on Thu Nov 27, 2008 3:42 pm

My name
is Greg Ward, I am a guest writer for Aircooled.Net, and I have a 69’
Std Beetle with IRS rear that I run in the Hillclimb circuits in Australia.
Some of you may know of me from my posts in several of the Volkswagen
related forums on the Internet...


My car
is powered by a 1915cc (69 X 94mm) engine, is road registered and driven
to and from each race event. In 2001, I won the New South Wales State
Hillclimb Championship with 8 wins out of 9 events, was runner-up Australian
Hillclimb Champion, and finished 3rd in the Queensland State Hillclimb
Championship in June, with the help of my sponsors, Stan Pobjoy’s
Racing Engineering and Aircooled.Net Inc.


I have
been racing these terrific cars for the last 12 years and hope to relay
some of my knowledge on how to make these cars handle, corner, and stop
well. I have broken it down into the 2 combinations I’m familiar
with; Ball Joint Front with either a Swing Axle or IRS Rear. Let’s
get started!


Swingaxle Beetles

The following
discussion assumes you are starting with an unmodified Ball Joint front
end, and a Swingaxle rear end. That means, NO lowering, NO dropped spindles,
NO narrowed beams etc; just stock suspension components. The Swingaxle
Beetle is the more commonly found rear suspension design outside of
the USA. This rear suspension design is notorious for not wanting to
go around a corner fast, and has special difficulty with high-speed
handling. Quick jerky movements like avoidance maneuvers are prone to
upsetting the car’s balance.

At
my first opportunity I acquired a 1970 Beetle with a Balljoint front
end, and Swingaxle rear. I then installed a reasonably mild 1915cc engine,
running 9:1 compression and dual Kadrons. It had more than enough grunt
to move the Beetle reasonably well and my testing began.


Though
it wasn't mandatory at the time
(the
car wasn’t that fast yet)
, I immediately
installed a roll
cage in the car. I believe safety to be of paramount importance
-- anything designed to protect me in the event something bad happens
is a good thing, in my opinion! An added benefit of the roll cage installation
is a "bracing effect" -- it effectively ties the floorpan
to the body and helps to make the entire car more rigid.


Since I'd
be competing in Hillclimb, which isn't all perfectly smooth asphalt
surfaces, my car would need to handle rough road, curbs, and might hit
other things (many of the races here are actually on public roads).
With
the type of power and speed I needed to compete, I felt it was necessary
to have front disc brakes.

BRAKES!
Another must have safety item! It might seem extremely obvious, but
I believe it is often overlooked.
What
do brakes have to do with handling, you ask? There is no point having
a car able to turn corners fast if you can’t stop when you need
to, right?


The easiest
thing for me to do was to replace all the brake components with new
hardware. I saw no real point in re-machining old discs and drums when
the price of good quality new components was reasonable and they were
readily available. This also meant I actually knew what I was starting
with from the very beginning, which eased my mind. This way I knew EXACTLY
how long I had a component, and the mileage and abuse it had, thereby
knowing when it should require a check up and or replacement.


So I bought
brand new front discs (SuperBeetle,
Std
Beetle/Ghia) which included new wheel inner
and outer
bearings and grease
seals. I retained the drum brake system in the rear, but also gave
it a complet overhaul. I installed new rear
drums, shoes,
rear
wheel bearings, rear
wheel cylinders, replaced the master
cylinder
,
brake
lines
, and rubber
front
and rear
brake hoses
(or
you can consider a sweet upgrade to braided
Stainless Steel Hoses)
. Most people
don't realize how effectively the stock braking system operates when
everything is in good condition -- most cars only get one or two of
the brake system components replaced at a time, even though the others
are also due for some attention.


Next I
replaced the steering
box, steering
damper, and all the tie rod ends.
NOTE:
Treat all of the above work very seriously! It is mandatory to the overall
performance of the car and its handling. “OK” or "So-so"
is NOT okay, you want your stuff to be in GOOD or GREAT shape.

And finally, it was time to start on the the actual suspension
work!


I
didn’t consider narrowing the beam as it would make the car twitchier
and make the rear more susceptible to sliding, (I knew from racing Superkarts
that if you wanted to make it slide you would narrow the front track
and widen the rear. Conversely, you would widen the front and narrow
the rear if you wanted steering and traction, which is what we did when
it rained.)

My first
move was to weld Sway-A-Way
adjusters into both top and bottom tubes of the beam.
I
was told you can get away with just one adjuster, but I figured it would
be more adjustable if there were two, and I wasn’t sure where the
suspension should sit yet.

I also
installed a set of caster
shims to keep it straight at speed. Next was a set of camber
adjusters, which gave me more than stock tuning.


After putting
all this back together and adjusting the ride height, I had the car
about three inches lower at the front than the rear. I lowered the rear
to suit and ended up with the front being 1 inch lower than stock. I
chose a rim size of 14”x 6” with 195/60/14 front tires, and
205/60/14 rear, and a basic set of Cofap gas shocks in front
and rear.

_________________

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Suspension Tuning Tips for Type 1 Swingaxle Beetles pt2

Post by LhYnxz on Thu Nov 27, 2008 3:46 pm

After the
required wheel alignment the settings were as follows.

FRONT


  • -1 deg
    camber (negative camber) /--\\

  • 3 deg
    caster

  • 5mm
    (3/16”) toe in

  • Rear
    –1.5 deg camber

  • 2mm
    (1/16”) toe in



The car
turned relatively well, but the rear wanted to slide out on every application
of the throttle around a corner. I tried it in the wet one night after
lowering the front another inch and put the car into an almost uncontrollable
fishtail. #$)*&)@* that, it was dangerous!! So I went completely
the opposite direction and made the front 1” higher than the rear,
now it was much more driveable.


A couple
of weeks later I found a small secret!


I was driving
with a friend riding shotgun, and two passengers in the rear seat (I
drive the car). I had good quality tires on but certainly not race quality,
and we were on our way through the mountains. I found that I could corner
at speeds not even dreamed of before, especially with these tires.


I learned
that because the car had more weight in each corner and in the back
because of my passengers that:


The car
was slightly lower and consequently also had more negative camber
The Z bar on the rear was activated when the passengers sat in the back.

So I shimmed
the Z bar with two pieces of water pipe and washers so it was pre-loaded
the whole time. I then installed a Sway-a-way
Camber compensator to minimize any wheel tuck.


These steps
weren’t quite enough since the car still oversteered, but it sure
helped! I knew that to correct the rear wanting to overtake the front,
the front needed more stiffness, and this was accomplished by the installation
of an 18mm
front sway bar.


I never
considered a rear sway bar. A friend had attempted this before and the
car was a death trap, adding more stiffness to the rear in a car that
was already able to oversteer at will is not a good idea! Just remember
that the Swingaxle is a unique design, it is not like a solid differential
rear car whose axles are in the same plane all the time.


On a Swingaxle,
if one axle has positive camber its because the other has negative camber,
just picture in your head what’s happening to the axles when you
turn a corner. One wheel gets more weight and one gets less, the angle
of one wheel has positive camber and the other has negative, and adding
a sway bar make this situation even worse.


All successful
autocrossers and circuit racers know that to increase oversteer (the
rear of the car losing grip) you need to stiffen the rear or loosen
the front. Conversely, to increase understeer (the front of the car
loses grip/pushes) then you simply increase the front stiffness or loosen
the rear. You accomplish this change in stiffness by increasing or decreasing
the size of the sway bar (sometimes also called anti-roll bar), even
to the extent of removing the rear, as in the case of a Swingaxle Beetle.


After a
few races I dialed in the camber so the car had –2 degrees negative
on all four wheels, and found that at really tight tracks toe-out was
needed to help the Beetle turn otherwise it would just understeer.


Another
thing that I did to fine tune the car was to have the spare wheel in
or out. To increase front grip the spare wheel should be in, to decrease
the front grip I simply left it out.


So this
was the furthest I could take the development of the Swingaxle. I couldn’t
wring any more out of it because the car already had negative camber
before anyone even sat in it. The idea was to start on the negative
side, by having force on the camber
compensator initially, and then cornering hard around a corner the
car could never get into a positive camber situation. The problem with
this was when accelerating from a dead stop, especially up a hill, the
car would squat even further, which caused the rear tires to only be
using the very inside, which left no traction during acceleration.


This did
nothing for my times in Hillclimb, which is really a drag race with
corners. It was very safe however, you could drive it at 90MPH into
a hairpin and be completely assured it would not want to roll.


So the
problem was on one hand I needed the negative camber to go around corners,
but I wanted the car not to squat off the line. Little or no camber
at the rear is good for drag racing, so long as limiting straps are
involved so the car can’t get positive camber, but it wouldn’t
work for cornering. I realized I could never get the best of both worlds
with the Swingaxle. I could have removed the Z bar, I’m not sure
of its effect, but this combo worked so I left it alone.


If anyone
wanted to take this development further, then they could always remove
the Z bar and replace it with a small diameter rear sway bar.


Have you
ever seen a Formula V? They have massive negative camber at the rear
and most that I have seen run a small sway bar that has brackets made
up that effectively mimic the standard mounting points of a Z bar. These
cars also handle well simply due to their lowered center of mass, all
forces act through the center of mass, and this is why simply lowering
a vehicle can make it handle better.


So to sum
up for a Swingaxle:


FRONT


  • 2 Sway-A-Way
    adjusters top and bottom. Cofap
    or KYB Gas shocks

  • 2 extra-eccentric
    camber
    adjusters.

  • Front
    –2 degrees negative camber

  • At least
    3 degrees (preferably 5) positive caster

  • 5mm
    (6/32-7/32”) Toe-out

  • 18mm
    (3/4”) Sway bar

  • 195/60/14
    tires

  • Front
    MUST be 1” higher than the rear ride height.


_________________

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Suspension Tuning Tips for Type 1 Swingaxle Beetles pt3

Post by LhYnxz on Thu Nov 27, 2008 3:47 pm

REAR


  • Sway-A-Way
    Camber Compensator. Cofap/KYB
    Gas shocks only

  • -2 deg
    negative camber

  • 2-3mm
    (3/32-1/8”) Toe-in

  • 205/60/14
    tires

  • Shimmed
    up Z bar

  • Rear
    MUST be 1” lower than the front ride height.





Independent Rear Suspension (IRS) Beetles and Buggies

The next
step forward for my car’s handing from the Swingaxle was to move
to the Independent Rear Suspension (IRS). This type of suspension involves
the use of two completely independent trailing arms suspended from points
near the torsion bar.

The gearbox
is completely different, since it now has Constant Velocity (CV) joints
with short axles that couple to a second set of CV joints (wheel end),
along with a small stub axle inside the housing of the trailing arm.


This design
is meant to provide better handling due to a relatively straight up
and down motion of the wheel and suspension rather than the wildly changing
arc of the Swingaxle design.


I had seen
many a successful conversions from Swingaxle to IRS by welding in the
necessary parts, but was not really in the position nor had the time
available to take this route before the next seasons’ racing. I
was a full 3 seconds/run slower than 2 other Beetles at most Hillclimbs.


After seeing
an IRS floorpan for sale in the paper I immediately bought it. It was
a 1969 Semi-Automatic pan that had been converted to manual. This was
great because it had the IRS rear and Ball Joint front. I never had
seen a VW pan just sitting completely bare but I realized that this
was the basis of the whole car and I could simply swap my body and other
bits onto it; Aren’t VWs great!?


I prepped
the pan, had a few rust holes welded (there were very few, I was lucky),
and while I was at it I had the whole pan seam-welded to strengthen
it up; underneath from the cross hatch of the main tunnel all the way
along the pan halves. This continued on the top, around all of the seat
mounts and rails (near any possible stress points).


I also
knew of one of my friends who had crashed their IRS Beetle in a race
and it had jumped in the air and landed hard. It twisted the chassis
and broke it at some critical points like the rear torsion housing.
So, I made some braces for the front from the tunnel back to the firewall
and then to the pan with round steel tube, triangulating these areas.


At the
rear I had two box tubes per side welded between the pan and the rear
torsion housing, further strengthening it.


After the
body swap all other front-end bits installed onto this pan, and the
rear end had new bearings installed and the rear brakes were upgraded
to Type 3 units with new parts. Type 3 rear brakes are almost 2X as
large to stop those heavy vehicles, you can never have too much braking
power!


I also
sifted through a box of used CV joints and washed all the cages and
balls in Kerosene. Each piece was inspected for wear and dumped if pits
or galling were present. 4 of the best groups of components were selected
and put together with Moly CV-grease and installed. These were put together
in 1993 and I’ve never broken or changed them, or had to do anything
to them since then!


Because
the car was now IRS I also decided I would change the shocks. With some
help from the other Hillclimbers I decided upon a set of Bilsteins front
and rear. These are a gas shock and were re-valved to provide a more
even rebound than stock units. This meant they were much stiffer, but
not so overwhelmingly that it felt like you had no dampening at all.


A much
more serious engine was also put in the car this time, it was still
only 1915cc but had bigger heads and a much larger cam, along with dual
44IDF’s and a 1 5/8” full merged exhaust.


The first
test at the track was interesting. I could immediately corner faster
on gentle turns than the best with the Swingaxle, and the takeoff from
a standing start was much better as the whole contact patch of the tire
was on the ground due to the IRS. However my main problem was in tighter
corners; the car simply wanted to go straight ahead, massive understeer.


The problem
in this situation is that understeer has only one method of recovery
and that is to take your foot off the accelerator. This is why most
manufacturers these days set up cars to understeer slightly from the
factory. This is no good for a fast time around a course, so I had to
figure out what to do. I still had the 18mm sway bar on the front, so
I took it off completely. This helped immensely, but then meant I couldn’t
take other corners as fast.


I ended
up borrowing a box of 20 different swaybars from a friend and spent
most of the day swapping them back and forth till I could go into a
corner as fast as I dared and still make it out the other side! It was
a real eye opener, with certain combinations you could enter a corner
at no more than 20MPH before the rear would break away.

Conversely
the opposite combination would mean the front would lose traction.

_________________

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Suspension Tuning Tips for Type 1 Swingaxle Beetles pt4

Post by LhYnxz on Thu Nov 27, 2008 3:48 pm

So this
is what I concluded from these tests:


If you
want to make an IRS Beetle slide from the rear (oversteer) you can increase
the sway bar size on the rear. A bigger bar on the front will make the
car understeer.

The ultimate
goal was to get both the front and rear in sync and be able to turn
the corners as fast as possible.


I like
driving with oversteer rather than understeer, it is faster and I believe,
more controllable. You can then control the car with the throttle to
good advantage. So after many combinations I ended up with a 22mm ((7/8”)
Sway bar on the front, and a 28mm ((1 1/8”) bar on the rear. These
may seem quite large but they were in proportion to the way I wanted
to drive the car. A good combination for the driver who doesn’t
necessarily want to race the car but wants more control would be an
18mm (3/4”) front bar and perhaps a 22-24mm (1”) bar on the
rear.


The stiffness
of the bar rises substantially with the thickness, so my 28mm bar is
very stiff. Now that I knew what I needed, I was able to purchase the
right thickness of bar but I got the fully adjustable versions; a row
of holes drilled in the arms of the bars which gave me infinite tenability.
I could now dial in the handling to suit each track and hill, and adjust
it as needed.


The first
race meeting proved that all was on track, the car was 3 seconds faster
at the same track than when Swingaxle equipped. However, it had a curious
lack of traction when accelerating out of hairpin corners and a weird
feeling on the steering wheel.


It kind
of felt like the body was not connected to the floorpan. Well my pit
crew and the later video revealed that when turning say a left hand
corner the inside front wheel was a good foot, sometimes more, in the
air! This of course also took the weight off the same side rear tire
and it was smoking up quite badly. This looked bizarre on video, kind
of like a wheelstand and a burnout at the same time!


The only
fix for this was to change the rear torsion bars. We elected to use
the torsion bars from Squareback, since they were 2mm (from memory)
thicker than what I was using (factory type 1 bars).


This lowered
the front wheel during hard cornering a little but not enough, so a
set of Sway-A-Way rear torsion bars were bought and installed. Looking
at the application chart Sway-a-way had at the time I concluded that
they should be somewhere in the 1300lb range.


That indeed
fixed the problem, and I also added 2 sets of caster shims worth of
caster to give a bit more feeling to the steering wheel for some faster
corners, which also required the longer bolts, but this resulted in
around 5 degrees caster and worked very well.


In the
quest for better cornering (And to make use of the newer stickier Bridgestone
RE610S tires that we had bought for the season), the camber was increased
again front and rear. The front now got –4 degrees negative camber
and the rear increased to –2.5 degrees negative.


The IRS
suspension was very good at maintaining the angle of the wheel around
corners, but the type of racing and limits that the car was now being
pushed to, showed it could still push the wheel into positive camber
in very hard situations. The new camber settings countered it effectively,
and no loss of traction was noticeable due to the increased camber at
the rear.


All this
meant that I was now only ˝ second behind my nearest competitor
and now I was in front of the Escorts and Datsuns. There was only one
Beetle to beat! So the last thing on the agenda was to install a close
ratio gearbox and a Limited Slip Differential.


I used
a 4.375 R & P for its low ratio, and even though it is the weakest
of the R&P’s, it can be made to work well with all the other
right bits in the box and some tight tolerances.


The gearing
was 3.40 1st, 2.21 2nd, 1.58 3rd, and a 1.21 4th, along with an abused
ZF LSD. The ZF was set up for approximately 60% grip and 40% slip, in
other words it wasn’t allowed to lock the wheels immediately upon
wheelspin.


After this
last change, the car then won 4 out of 5 races in 1994. Unfortunately
the car was smashed on the street early in 1997, which broke the front
beam in half and destroyed a rear-trailing arm. It sat in the garage
and I raced my Formula 2 open-wheeler.


No other
major changes were made until 2000 when I tried a different front beam
set up with a single Avis adjuster at the top, and changed the front
shocks to adjustable Koni’s. This was to try and restore some handling
to the car and I was prepared to try something different on the advice
of others. It turned into the worst nightmare ever!


The front
of the car was raised and would not lower, the rear was raised to compensate,
the car would wheelspin at will and would not turn a corner, even a
mild one, at any speed without wanting to go straight ahead (MASSIVE
understeer).


A 40kg
(90lbs) bag of cement placed in the spare wheel well was about the only
thing that mildly cured it. I couldn’t race it with a bag of cement
in the front though, so a spare tire and 18kg (40lbs) of lead was strapped
in the front for 3 races.


Unfortunately
I lost every race miserably even though the car was producing more horsepower
than ever thanks to a new set of heads and that 1 5/8” exhaust
with Phat-Boy.


This made
it an absolute pig to drive and I was fed up; I had all the power I
ever dreamed of, and it was slower than ever! :-/


I’m
not saying that Avis adjusters or Koni’s won’t work, but I
didn’t have the time to go through trying to re-tune a new combination.
2 Avis adjusters would have been better than one, but I didn’t
like their design for what I was doing, I was fearful a decent pothole
or curb hit would collapse the unit and the Koni oil was not stiff enough
for the rest of my combo.


So, I took
a week off from work and went back to my old and successful combination.
I installed a new beam with 2 Sway-A-Way adjusters. I dusted off the
Bilsteins and put them back on, then the car was lowered to where it
should be and –5 degrees negative camber was the standard on the
front.


You could
turn any corner, at any speed and all was back to normal.

_________________

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Suspension Tuning Tips for Type 1 Swingaxle Beetles pt5

Post by LhYnxz on Thu Nov 27, 2008 3:49 pm

So, for
a race setup for an IRS Beetle:


FRONT


  • 22mm
    (7/8”) Adjustable Sway bar

  • -4/5
    degrees negative camber

  • 5 deg
    caster

  • 5mm
    (6/32-7/32”) Toe-out

  • Beam
    cut and welded with 2 Sway-A-Way adjusters.

  • Bilstein
    Gas shocks

  • Extra
    Eccentric Camber Adjusters

  • Ride
    height 1” higher than rear

  • Corner
    weights approximately 160kg (350lbs) per wheel.

  • 195/60/14
    on a 7” rim tire pressure 24-26psi





REAR


  • 28mm
    (1 1/8”) adjustable Sway bar

  • -2/3
    degrees negative camber

  • 2-3mm
    (5/64-13/64”) Toe-in

  • Sway-A-Way
    heavy-duty approx 1300lb Torsion bars

  • Bilstein
    Gas shocks

  • Corner
    weights approximately 240kg per wheel.

  • 205/60/14
    on a 7” rim tire pressure 28-30psi



For a nice
street setup that will provide good handling and lots of fun, simply
tone down the settings, which results in:


FRONT


  • 18mm
    (3/4”) Sway bar

  • -1.5/2
    degrees negative camber

  • 2mm
    (5/64”)Toe-out or straight ahead zero Toe.

  • Any
    good set of gas shocks, or stiffer than original oil shocks.

  • Extra
    Eccentric Camber adjusters

  • Ride
    height 1” higher than rear

  • 6”
    rims 14 or 15” height



REAR


  • 20mm
    (3/4”) Sway Bar 22/24mm if you want it stiffer.

  • -1.5/2
    degrees negative camber same as front.

  • 2-3
    mm (5/64-13/64”) Toe in


  • **The
    rear should always have toe in, it is more stable, you can imagine
    if you had toe out that the wheels would want to travel in that direction,
    so when you turn a corner the car actually loses the rear end and
    ends up in a slide.


  • Any
    good set of gas shocks, or stiffer than stock oil.

  • At least
    a set of rear torsion bars from a Type 3 Wagon.

  • For
    the more adventurous choosing a set of Sway-a-way bars designed for
    a little more stiffness would work even better.

  • 6”
    rims 14 or 15” height




IRS buggies
can use toned down settings from the above data. Since buggies are usually
made shorter than a beetle, the rear suspension needs to be less stiff
as being shorter the buggies already have a tendency to oversteer.


Additional
weight in the front will also help, since we constantly have trouble
keeping the front wheels on the ground with even limited horsepower
in a friend’s buggy.


Always
remember it doesn’t matter how trick all the whiz-bang components
are that you buy for your suspension if you have other more important
parts that are worn out!

So things
like brakes, tie rods, steering boxes, steering couplers, wheel alignment,
and tire pressures are equally if not even more important.


The basis
for improving handling is probably that the driver wants to push the
car a bit harder, maybe just to enjoy those winding mountain roads a
bit more, not necessarily all out racing, the safety factor applies
even more for the road than the controlled environment of the race track.


I sincerely hope that this article has given you some help describing
things this way instead of just a listing of parts to bolt on. Now you
know what to do WITH the parts you need!


See you
at the track (behind me)!


Greg Ward,
Aircooled.Net Guest Tech Writer

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Re: Suspension Tuning Tips for Type 1 Swingaxle Beetles, IRS Bee

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