Ball joint extender bumpsteer.

here's the general guideline sketch for setting rack location/tie rod lengths. Tie rod should share the same instant center with suspension arms. Not being familiar with your setup, most likely there is ackerman built into the upright, in your case it (front steer) it means the outer tie rod pivot is outside the line defined by the upper and lower upright mounts, ie displaced outside. The inside pivot location should be similarly displaced outside so that the tie rod has a similar arc. I think the best way to build these systems is so that the rack is nearly directly in front of one of either the upper or lower pivot locations on the chassis. Then camber adjustments should be made at the other pivot location so that such adjustments do not affect toe to any appreciable degree.
 

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Tom, about my setup. Its Jaguar XJ6 series2 based. KVA aparently did try out something back in the days.

Been googling this noon to find more Jaguar information.

Most pics about the jaguar suspension I find on google shows the upper wishbone pointing down like mine but I can't verify this in real as I don't have a XJ6 nor a XK-E near by.
As I found out the Jag XJ6 has steering on the back.side of the hub with shorter arms.
jaguar XK-E on the other hand has the steering up front like mine but steering rack sits way higher with the tie rods upside down.

I am on the hunt now to find some Jaguar geometric information.
 

Mike Pass

Supporter
Remember that you have the setup on a relatively light and empty front end whereas the Jaguar XJ6 is a big heavy car with a big heavy lump in the front.
Cheers
Mike
 
I'm confident that with some investigation, you can come up with a combination of part changes and suspension mounting that will get you close to the theoretical optimum.
 
Some more measuring today using a digital angle finder, to find out what effect raising the steering rack has. Raised it another 7mm, to find out that the trackrod angle just changed 0.5º. The get the required 8º track rod angle Ill need to raise the rack another 4cm or extend the ball joints with 4cm.

I don't fancy. going the uniball route. So repositioning the upper wishbone is the route to go.
 

Ian Clark

Supporter
Hi JP,

A lot of great suggestions and information coming in to help you through your front end. It's more challenging in that you have an unusual combination of components in very low volume version of the KVA. No doubt it will get sorted.

It's not clear to me from the pictures that you have the car supported in air with the desired ride height set as your base line. If it's on the money, carry on... if too high or low the correct settings will elude you.

Just saying, it's easy to chase your tail or make overcorrections when the baseline is off. Done it myself on this exact problem (before getting a surface plate).

Cheers
Ian
 

Terry Oxandale

Skinny Man
Some more measuring today using a digital angle finder, to find out what effect raising the steering rack has. Raised it another 7mm, to find out that the trackrod angle just changed 0.5º. The get the required 8º track rod angle Ill need to raise the rack another 4cm or extend the ball joints with 4cm.

Please don't take the 8º noted in my previous post as a solid number. It was more an example from using the photos in this string, plus assuming the rack's joints were positioned exactly midway vertically between the upper and lower arm pivot points. You'll need to determine exactly what that value should be through careful measurements. And once you change the mounting locations for the upper arms, that will all have to be remeasured and calculated all over again. Just a word of caution. You can't change one thing without considering all the other things that will be changed as well.
 
Terry, don't worry. 8º is just a guideline. Ill measure things twice and check every change in settings with laser to make it insightfull. Small steps are easyer to go back.

Just purchased a couple of uniball's to make an expirimental adjustable tie rod drop kit. Just to make a test setting to see how much degree drop of the trackrod is actualy needed to eliminate bumpsteer. To make it insightfull.
 
Problem solved.

I made a bolt on thick steel adapter bracket to lower the upper wishbone to correct the suspension geometrics which also made it possible to set camber settings to GT40 specs. Bumpsteer gone, fabulous to drive now.

Thanks all who contributed to this solution.
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1654617272742.png
 

Terry Oxandale

Skinny Man
Getting closer!! But...I'd like to offer one more suggestion on this (unless this is solely a temporary mock-up). The (what I would call) cantilevered mounting off the 1" square tubing (which is unfortunately already distorted or compressed by the bolts, from what I can tell in the photo) concerns me...a lot. Lateral and braking forces, I feel, will eventually result in an unsafe or failed upper suspension component because of this. May I suggest at minimum some gusseting between the new thick vertical mounting plate, and the vertically oriented steel upper shock mount material. Yeah, the 3/8" (?) plate is robust, but high lateral forces could play havoc on the way it is mounted.
 
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Davidmgbv8

Supporter
I agree with Terry, that is great for mock up and testing and confirming the theory around the block once or twice but you really should have someone fab up a better mount with gussets to the top shock mount and tie in behind the plate to the chassis somewhere to stabilize the back of the plate where the new mount point is.
 

Chris Kouba

Supporter
Why bother with the bolts at all? If the geometry is satisfactory as-is, use them to hold in place and weld in a properly triangulated/reinforced mount. The plate you have there will wreak havoc as predicted, specifically those bolts without crush tubes will see the "square" tube looking less and less square as you start to enjoy your vehicle's new-found capabilities.

See if you can tie it into the lower A-arm inboard mounts too.
 

Neil

Supporter
In Costin & Phipps book, they point out that the loads on the upper a-arm are much lower than on the lower one. A sleeve through a tube will allow you to tighten a through bolt without squeezing the tube flat. It's just good practice.
 
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