I changed directions. Instead of bending the bar to match the C3 width, I'm in the process of making some custom links to attach the wider C4 bar to the lower A-arms. It's a little more work, but I'm just curious about this bar.
I'm currently running a 1.125 C3 bar on the front, and the thing understeers like a pig. The amusing part is that, with the C4 suspension under the car, I'm running basically the same wheel (spring) rates f&r and front bar size as I had with the C3 suspension, but the balance is completely different. Perhaps the C4 rear is just biting more than the old C3 geometry would allow.
So, I need to reduce the front roll stiffness. I'm using this bar as it's left over from when I bought the C4 suspension at a swap meet years ago.
This bar is 24mm in diameter, and apparently '96 was the only year it was offered. It's a little small for my taste, but it's darn lightweight (5.5 pounds versus the 11.5 pound 1 1/8 inch bar) and at first glance it will reduce the front roll stiffness too much. One thing in its favor is that the torsion part is similar length to a C3 bar, but the arms are 13% wider (43' versus 38"), attaching further out on the lower A-arm. This should, if I'm correct, mean that the bar will twist more for the same amount of wheel travel, mimicing a stiffer bar.
Depending on the amount of front roll stiffness I lose, I have two other avenues I'm exploring to recover some of it back. Pre-'96 model C4s offered a 26mm bar, so I could try to find one of them down the road (I haven't done the math yet to see what the rate difference would be), or I could step up the front (coilover) spring rate, which I've been mulling around for quite a while. I've got 375# springs on them, and if my calculations are correct, these give me roughly the same wheel rate at the 550# springs in my original C3 suspension.
