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I was doing some mock up and taking measurements and realized the angle for connecting the trailing arm to an existing braket is too great for the heim joints I have, even with high offset washers. Since the X frame is full width after the axle, I was wondering if it was a bad idea to flip or reverse the LCA so that the trailing arm now goes to the back of the frame rather than the front of the frame?
Here is a pic:
Thoughts?
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There's nothing wrong with running the trailing arm to the rear rather than the front. Ralphy posted this photo of an application that I,ve seen in my
own searches:
On page 3:
Have a good look at the products and installation example onSnow White's website. Study their installation instructions and view their "gallery". They've been doing these for 30 some years. The only thing we over here at the IRS Forum disagree with is their suggestion that the rear axle should angle downward towards the hub by 2 degrees.
Quote:
Normal Attitude For Jag 1/2 Shafts at Ride Height: 1/2 Shafts "Hang Down" Approximately 2 degrees (Outer Ends Lower Than Inner Ends)
That's a whole nuther discussion.
Ken
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The Jag LCA has a droop in the fork area where it attaches to the differential mounted brackets. This was done to clear the inboard disc brakes. I also read in an old HP Book; "The Street Rodders Handbook" that stock Jag LCA's have a small amount of toe out built in to allow for acceleration loads. The stock Jag trailing arm has compliant rubber bushings to prevent binding, so I am sure the LCA flexes around quite a bit under acceleration and braking. So, if one flips the LCA's side to side they would toe-in and if you flip them upside down in they would also toe in. Can anyone else in the forum confirm this?
6Speeds suggestion looks good and you will notice the radius rods are attached to the LCA outer pivot via a custom
bracket. This would leave the old trailing arm attachments available for you to attach a a sway bar, maybe.
I am the forums "Devil's Advocate" when it comes to angling the half shafts downward. I am attaching a link to a thread called Wobbly Knee Jag IRS that is fun reading.
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irstang,
You're quite right. My bad. I forgot to consider your mentioned characteristic of the LCA such that you can't just" flip it over". Welding a new bracket on the rear side of the LCA for the radius arm is a small task.
Thanks for the T Bucket link. I hadn't seen that discussion before. But I wouldn't necessarily agree that the Jag "bum", (differential), must be mounted using rubber bushings. That poster, tedabrown, may have just not gone far enough explaining that you need the compliance if you run your radius rods straight forward from the LCA rather than at an angle forward to line up with the inner LCA pivot point. That concept has been beat into our brains over and over again.
Anyway, 303Radar, does that help you at all?
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You can't flip it but you can swap them. That will maintain the bend in the arm and position the bracket on the back side. I don't think there is any toe built in to the arms. especially since the differential pivot end parts are cast with the boss to have the radios rod threading on either side. I taped in to that boss when I made the second mount for my sway bar mount. slight toe is added by shimming the differential bracket.
Last edited by Daze (4/01/2012 8:29 am)
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6 Speed, that does help quite a bit. I do have access to a tube bender through my neighbor which would help. I will look at sending the trailing arms out the back just because they would be straight rather than an angle.
The bracket coming out of the bottom of the hub, is that something custom for the application? Something like that would sure help not having to deal with the limited and tight space between the shock mount and the hub mount.
Thanks again!
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303Radar wrote:
I will look at sending the trailing arms out the back just because they would be straight rather than an angle.
Just keep in mind that if you do not angle them so that the inner wish bone pivot is in line with the trailing arm mount that you will need to use over sized rubber bushings as Jaguar did or your mismatched arcs will bind
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Here is some more Jag IRS Cobra eye candy. A better shot of the rearward facing radius rods and a nicely done differential support, as well.
Thank you 6 Speed for taking us there.
Last edited by irstang (4/02/2012 5:58 pm)
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I took some more measurements tonight and I'm glad I did. Sending trailing to the rear would bind like crazy! I can see on the above examples why they don't, they give a pivot point close to the pivot on the LCA. For me to do that, I'd have to put another cross member between the frame rails.
I've decided to send them to the front and grow the existing bracket out about four inches. Shouldn't be too difficult, I'll re-inforce the plate on the back side to the frame with round or square tube.
Thanks again for the links, the pics and the info.
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The issue I see with that link? Is that it has to be placed in line with the inner pivot, this means all three planes. You would need to be able to draw a straight line through all three mounting points. Both bone inner mounts and the fixed link end when finished. Trying to find a way to mount the link as low as what's pictured? That's a tough task for most cars? No? If the fixed end of the link were above? You would get roll steer and some bind a bit. Higher would be more/greater RS/bind. If you can do it, your in!
Last edited by Ralphy (4/03/2012 7:20 am)
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The pivot point for the radius rod should be on an extended line along the axis of the LCA to differential fulcrum shaft. I located my pivot points by leveling the LCA's to the ground. Then with a piece of string, a level and knowing the measurement between the left and right LCA I defined the extended axis. Then it was easy to see if there was clearance for a rod to run from the arm attachment point on the LCA to some point along the string. I used the Jag hard rubber bushing at the LCA and a Heim joint forward. The forward pivot point is no lower to ground than the Jag differential. It is at the same height from the ground since the LCA's are set up level, front to back, at ride height. In fact, I double checked the location br measuring from the ground.
Here is another way of locating the pivot points using some solid bar stock.
Last edited by irstang (4/03/2012 8:43 pm)
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I located mine by extending the Jag pivots with a 1/2" coupler and some 1/2" all thread.
Last edited by Daze (4/03/2012 8:26 pm)
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