My latest endeavor rebuilding the IRS I picked up a couple of months ago. I got the big bushing out and pressed in the new one, only to discover I may have pressed it in upside down.
How did I do it? I used the new bushing to press out the old bushing. I used a steel plate with 3 spacers between the low spots and the plate on the new bushing then pressed the old bushing out and the new one in at the same time. Safety 3rd right?
I can’t remember if the hole in the radius arm is on one side only…in which case it should be on the bottom to drain water… But from memory I pressed the bush into the arm from the underside with the retaining flange on the topside.
I think you should have the cut outs aligned with the length of the arm …because the cut outs reduce the stiffness in this direction and this is needed to allow the bush to “flex” in this direction. The suspension arm moves vertically and the radius arm pivots so something has to “flex”.
The “easy” way to do it is to get a bit of bar stock slightly larger than the outside diameter of the large bush retainer and machine a hollow in it which just fits the outside diameter of the bush retainer. This holds the arm safely in the exact position while you do the pressing. Then machine a further hollow a smidgem larger than the bush diameter and deep enough to contain the bush width. You can then press the bush out of the arm into the hollow in the bar stock . I tried several times to press with steel on the thin rim of the arm but pieces flew everywhere so I went with plan B.
There isn’t a picture other than the radius arm being pinched at the big end between two mandrels.
When I re-read the refitting bit. Or actually read it and didn’t just skim over it, I noticed the bit about the holes in the rubber. The green bible states should be centerline. I’m debating on sacrificing this bush in order to get it right. The other came out in bits. From several failed attempts.
The hole lining up will make a difference on the torsional twisting of the radius arm. The way it is now, it’s going to put undue stress on both bushes. Do I care? Right this minute. NO. Will I later? Count on it.
Fitting the bush with the “cutout” orientation perpendicular to the radius arm center line is how the XJS Sportspack did it, slightly firmer suspension and a bit more “passive rear steering” effect, as the forces will be compressing the rubber instead of flexing it.
Well this is intriguing. holes parallel to the front and rear of the car or perpendicular. I am a spirited driver, and enjoy tossing a car into the corner waiting for a bit of oversteer. Though It’s been my experience in a Jag, specifically My XJ-S when the oversteer comes into play it happens very quickly and if you’re not on your toes, you’ll be facing where you were. Does "passive Rear Steering help negate some of the “BOOM!!! you’re facing the opposite direction” or intensify it?
That being said, I don’t know what you mean by “passive rear steering”.
back to kinda the original question. or atleast one of them. is there a top or a bottom to the Radius arm? or is it strictly based on bush orientation?
I’ve laid the arms side by side, on the floor, and if I turn one upside down from the other, there is about 3/16 of an inch height difference between the two radius arms. though I can’t tell if it’s related to the bush orientation or if the arm itself has a slight bend to it.
They didn’t design this for dummies like me that would state “TOP” on one of the sides.
I just had a look under my XJS. I put it back the way it was assembled. The arm has holes top and bottom so draining water is no issue. Mine is assembled with the retaining lip on the large bush end on the bottom.
The photo in the Haynes manual (Page 263) looks like it is the other way around with the retaining lip on the top.
This sorta makes sense because it means that the arm cannot slide down off the bush…but there is a strap there to retain the whole thing anyway…and… it took about 10 tonnes to press it into position so nothing is moving anywhere in a hurry!!!
Either way won’t make a scrap of difference to the mechanism…
The bottom suspension link is mounted on bearings attached to the diff. There is no “flexibility” in this connection apart from the deflection in the arm itself…so I don’t think there is any “passive steering” designed into the mechanism.
The trailing arm is there to help absorb the thrust from accelerating and braking.
But the Jag arrangement has the bottom link taking all these loads so
the outside end of the arm is pushed and pulled by the wheel PLUS it is twisted in both directions by the wheel…this is why it is quite a big thick tube of steel!!!
All these loads are transferred into the diff housing by two bearings which have to absorb the thrust and torsion.
The trailing link is such that it can’t help with the torsion loads but can help with the thrust loads…except that it is designed to pivot so rigidly connecting it to the back axle …which moves straight up and down…would bend something…so there is a large flexible bush there which absorbs the movement.
It looks like there are compromises there to make the system work …but it does work although the complexity makes it quite difficult to maintain the rear suspension and very difficult and time consuming to get it set up correctly!!!