Club Cobra - FFR Arms on a Classic Revival Chassis

Hi All,

After reading Sjelby's Front end geometry thread I thought I'd post a quick update on what I've been messing round with.

A while back I bought a pair of Factory 5 upper control arms with the intention of adapting them to my CR chassis. They are a really nicely made piece and should give a lot of front end adjustability. They have left and right hand threaded sections that allow you to dial in camber and caster adjustments with the turn of a spanner.

Here's how the original Jag arms bolted up. You can see that shims are required to get camber and caster settings right. The Jag arms are also a bit tight for clearance around the coil over shock making changing springs etc a bit of a pain. I had to machine a chamfer on the pivot bar because the coils hit against it.

http://www.clubcobra.com/photopost/d...pper_Arm_1.jpg

There are a few things that need changing to adapt the FFR arms. The mounting hole widths are much wider on the new arms so new chassis brackets needed to be fabricated and welded on. Also the Jag arms are not symmetrical like the FFR arms so the mounts needed to be moved forward on the chassis by about 10mm.

While I was at it I thought is would be good to add in a bit of extra adjustability. By making the new mounting so I can pivot the arm I can adjust the amount of change in caster angle as the suspension compresses.

Here's the new arm and mounting installed and set for minimum change in caster angle.

http://www.clubcobra.com/photopost/d...FFR_Arms_2.jpg

Here it is set for max increase in caster angle.

http://www.clubcobra.com/photopost/d...FFR_Arms_1.jpg

You can see the slotted front hole that lets you adjust the angle of the arm. Excuse the stack of washers on the back. They are just there so I don't have to tighten the nylock up completely while I mess with it.

http://www.clubcobra.com/photopost/d...FFR_Arms_4.jpg

So why would you want to adjust this? Well think on it this way, as you front suspension compresses under hard braking the front of the car drops and the rear of the car lifts. This effectively reduces the amount of caster you have in your front suspension. Caster helps to self center the steering and it also adds camber as you turn the steering. The amount of caster angle you loose when the front dives depends on how much your car pitches forward and that's dependent on spring rates etc. Setting the front arm at an angle means the caster angle increases as the suspension compresses. Not knowing the ideal setting for my setup I figured making it easy to adjust was the go.

Another thing that needs changing is the taper on the upper ball joint. The Jag taper is different from the FFR taper so an adapter needed to be machined and pressed in to the suspension upright. The FFR ball joints are a bit longer than the Jag ones so I raised the mount on the chassis to match and keep the geometry roughly the same as original. I've still got to trim the thread down on the FFR ball joint an install a nylock nut rather than a castle nut.

http://www.clubcobra.com/photopost/d...FFR_Arms_3.jpg

Cheers