Suspension Tuning Tips for Type 1 Swingaxle Beetles, IRS Beetles and Buggies (Street and Auto-X)
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. 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!
written by Guest Author: Greg Ward
Suspension Tuning Tips for 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 floor pan 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 (Super Beetle, 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 complete overhaul. I installed new rear drums, Super Stopper Rear Brake Shoes, outer rear wheel bearings, inner rear wheel bearings, Super Stopper Rear Wheel Cylinders, replaced the master cylinder, brake lines, and rubber front brake hoses and rubber rear brake hoses (or you can consider a sweet upgrade to Stainless Steel Braided 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.
After the required wheel alignment the settings were as follows.
- -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.
Recommended Setup Summary:
FRONT – SWINGAXLE BEETLE
- 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.
REAR – SWINGAXLE BEETLE
- 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.
Suspension Tuning Tips for 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.
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 ½ 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.
Recommended Setup Summary:
FRONT – RACE SETUP IRS BEETLE
- 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 – RACE SETUP IRS BEETLE
- 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 race settings, which results in:
FRONT – STREET SETUP IRS BEETLE
- 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 – STREET SETUP IRS BEETLE
- 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
ADAPT SETUP FOR IRS BUGGIES
- IRS Buggies can use toned down settings from the above street 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!
The basis for wanting to improve VW handling is usually that the driver wants to push the car a bit harder, not necessarily for all out racing performance, but maybe just to enjoy those winding mountain roads a bit more. The vehicle systems safety factor applies even more for the road than for the more controlled environment of the race track. In your quest for improved suspension and handling, don’t overlook the more mundane, but important, things like brakes, tie rods, steering boxes, steering couplers, wheel alignment, and tire pressures!
I sincerely hope that this article has given you a clear picture of the ‘how and why’ instead of being just the typical listing of parts to bolt on. Now you should have an idea of what to DO with the shiny new parts you were itching to order!
Greg Ward’s car is powered by a 1915cc (69 X 94mm) engine, is road registered and driven to and from each race event. In 2001, he 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. He would like to thank his sponsors, Stan Pobjoy’s Racing Engineering and Aircooled.Net Inc.
originally posted date: article posted: July 24, 2003
article edited: Sept 25, 2019 (by John Connolly, Aircooled.Net)