If you look around the internet, there is a lot of advice and conversation around castor correction for the front radius arms following a spring lift. However there is a lot less discussed about rear axle correction. Clearly "castor correction" does not apply to the rear but there is still an adverse effect due to a spring lift. There are two main effects, the nose of the differential is at the wrong angle which increases the angles the propshaft has to cope with and the spring mounts are not aligned top and bottom resulting in "banana" springs.
In rummaging around in my garage, I was fortunate to find two sets of corrected rear arms that had not been sold when Off-road Armoury stopped production of their Jimny arms. One of the sets was for a 3" lift and one is for a 4.5" lift. The picture shows the three different arms including a standard arm (painted blue).
Although it is not 100% clear in the picture the key difference is the different angle relationship between the axle end mounting points and the chassis end mounting point which rotates the axle slightly. However the 4.5" arms are also quite a bit longer.
Also the arms are of slightly different generations with the 4.5" one including mounting points for the ABS wiring. If you are purchasing the equivalent of these arms (as stated these are no longer in production) then check they are:
1. Very heavy duty. They take a lot of stress and a simple tube variant (with no re-inforcing) is not going to be any good.
2. Have the fitting points you need i.e. the handbrake cable mount and ABS wiring mounts.
Of course, the arms do not come with any bushes fitted so I took the opportunity to replace them. The old arms do have bushes fitted but after a season or two underneath the car they are very difficult to remove. I once went to a workshop to get some pressed out and as the press passed 38 tonnes pressure people began to leave the workshop for safety. Shortly after there was a loud bang and the bush shot out of the arm!.
You can buy a selection of bushes from a number of suppliers (including Bigjimny). Very popular are bushes based on Polybush material. These can be easy to fit, particularly the split push fit ones. However for me they are too firm. You will see from the end picture below that the original Suzuki and some equivalent bushes have slots cut in them, deliberately to improve the ride. There are also Eastern European copy rubber bushes around which, whilst made of rubber, are solid and do not have the slots. Its a personal view but, if Suzuki designed in slots and provides instructions on how to orientate them, it must be significant to the ride and I therefore stock bushes that have the proper slots in them.
There are three different bushes, the first is the chassis end bush. This fits both the front and rear arms at the end that connects to the chassis rails. At the other end there are two bushes that connect to the axle. There is a different design of bush for the rear axle and the front axle.
I am fortunate enough to have a press, so I can put the bushes in myself. However, in the past I have managed to persuade local garages to press them in for me. As the arms are new, the edges of arms where the bushes fit are blunt 90 degrees meaning it is hard to get the bushes started in the hole. I therefore chamfered the edges with a stone fitted in an electric drill. This puts a small chamfer that the bush can sit in before being pressed in.
The first picture below shows me creating the chamfer. In the second picture you can see an attempt at recreating the Suzuki bush fitting tool. It consists of a sleeve to hold the bush straight and a die that fits over the bush to press it in with. Whilst the pressing pictures show this working I actually prefer to use an old propshaft flange and visually watch that the bush is straight. THE BUSH HAS TO BE COMPLETELY STRAIGHT otherwise it will damage itself when being pressed in.
As mentioned before, the axle end bushes have slots cut in them and Suzuki provide a diagram of how the bushes should be orientated. The first picture is the diagram and the second picture shows the slots in the bush. It is quite difficult to get them perfectly aligned but I work on the principle that close enough is good enough.
As you can see from the pictures below, the press only required 3 tonnes to put the bushes in. I managed to get the slots orientated fairly well although there was some movement early in the pressing. The last picture shows the axle end bush.