New Z-bar

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Joined: March 24th, 2008, 2:14 pm

New Z-bar

Post by bill_browne »

I know most of you run zero roll, but there was talk awhile back about sharing performance upgrages, so I thought I share my story.

I was having a problem with what I call 'snap spins'. Feels good...feels good...feels good...backwards!! I thought the springs were bottoming out, so I borrowed a set of stiffer springs, but that didn't help.

I have a buddy that road races vees, but he runs zero roll too. So he talked to the guys running vintage and they said I needed more z-bar preload. The z-bar that came with the car seems to be made of a hard aluminum. What ever it is, it's way too 'springy'. By the time I got it tight enough to stop the snap spin, it was fighting the springs...pulling the rear down while the springs were trying to pick it up. Made the car crazy loose. I checked into having a new bar made...getting it bent was no problem, but the oven time for heat treating was crazy expensive. So I made one:


I know, it's ugly. But it's not finished. I'll clean it up during the off season.

I made it out of 4142CFHT steel, which seemed appropriate because sway bars are made of the stuff. There are hexes cut in the ends that that arms bolt on to. I would have prefered splines, but that's a little out of my machining ability at the moment.

Before the last event, I went back to the softer springs. I set the rear chamber to half a degree negative. When I pick the car off the ground, the chamber goes to 2 degrees positive. I have the bar tightend up just enough to take the slack out of it. No snap spin. First of the year, I was 8.3 seconds behind the CM car I get bumped with. Last event I was 3.8 seconds behind on a comparable length course. I know that seems like it took a long time to figure out, but there was some engine trouble in between.

The back end will still break loose first, so I'm going to try a stiffer swaybar up front.
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