Introduction to IRS for Split Screens
Lowering a split screen bus can be a pleasant experience once you are aware of the good points and the bad points. The front is very much the same as a bay window bus, as it too is torsion leaves and adjusters can be fitted, then you set it where you want.
Lowering the rear however is not so straight forward. Split screens as we know, have a swing axle rear end with reduction hubs. If I can explain, swing axle has an axle tube with a live axle inside, and pivots from the diff centre and is supported at the wheel end with bearings. The reduction hubs, are as they sound and reduce the revs per minute at the rear wheels for better pulling power from smaller engines, but with no top speed.
Swing axle though great in standard form, are not a good set up for lowering. As we know the swing axle set up has axle tubes, with wheel bearing at the end of the axles, right behind the backing plates of the brake drum. When we lower the rear of the bus with the standard reduction hub axles still on the bus, it puts the axles up to high and while driving, the gear oil from the reduction hub gets pumped back into the gearbox and leaves the reduction hub and the 4 bearings inside to run dry. Need I draw a picture? The swing axle conversion achieves a simular situation, not quite so radical but still causes the wheel bearings to run hotter than normal, because of the angle.
The other draw back with swing axle, whether in standard form or a swing axle conversion, is the tuck under that the swing axle creates/suffers.
Because of the wheel alignment requirements for the rear of an independent rear suspension car, the rear wheels try to over steer the rear of the bus in certain situations, especially once they are lowered.
No matter how low we have taken split screens with swing axle conversions, we always end up with positive camber, and hot wheel bearings. After many years of testing we have found the only way to enjoy your split screen long term is to use an independent rear suspension (IRS) set up with CV joints.
IRS Conversion: Independent Rear Suspension Conversion.
If you have ever driven a split screen bus for more than a few blocks in today’s traffic, and round quite few roundabouts that seem to be littering our suburbs now days, IRS will settle your nerves. The dreaded tuck under can really unsettle your nerves on a wet day, or even a dry day.
Our IRS Conversion Kit includes two Bolt On Adjustable Pivot Boxes, two Control Arms, two Bolt on Shock Mounts, and two bolt on Bump Stop mounts. There is a full set of instructions, and a full list of parts required to complete the installation of the Independent Rear Suspension Conversion.
The idea of going the extra mile and making our kit bolt in came about because of the following reasons.
1. We have been around long enough to know, welding in the rear control arm mounts can never be accurate, and a truly correct rear wheel alignment can never be achieved with a weld in setup. We have tested this in the past many times. We have also checked other weld in IRS Conversions that have been taken from the Bay windowed bus that resemble a home made set up, with no good results.
2. Bolt in has that benefit of the perfect wheel alignment. Once the bus has been set up and aligned, if the owner wanted to lower the bus more and changes the rear ride height, the bolt on pivot boxes are extremely adjustable making the alignment very easy for the wheel alignment expert.
3. As most of you would know, we not known here for being purists, but permanent damage to these old buses has never been an option. We have always felt that if you really want to enjoy an old 40 plus year old bus and didn’t want to hurt it, why not unbolt all the "hard to get" bits, like the reduction hub transaxle and the king and link pin front beam, wrap it up and leave it in the garage where it will gather no miles.
Then bolt in a Ball Joint front beam and an IRS Conversion, leave it at standard height, if that’s what suits you, and ENJOY the bus. Now it goes round corners, now it stops, now it will keep up with the traffic, now you’re not hurting it by driving around on the original suspension. Once you have finished with the bus, the entire Bolt In Suspension can be removed, being the Ball Joint Beam, and the IRS Conversion, and all the original parts can be replaced, while NO HARM has been done to the bus while you were enjoying. You would either have a complete IRS Kit to resell, or reuse in your next project.
Note: Kits are supplied only with Exchange controls/trailing arms supplied from a 72 to 79 T2 ONLY.
Please note that fitting an IRS Kit is a modification to your vehicle and will require an engineer’s report once fitted for it to be legal in your state for registration and insurance purposes. No warranty will be entered into unless the vehicle modified has had an engineer’s report certifying the installation.
