KTM has the right solution for this, if you don't support this area it will fatigue and break over time with large swaybars on your car.

It's a trade off. Don't run the sway bars and scrape the door handles with the excessive body roll, or run the sway bars and have eventual damage to the frame rails (or take the time to beef up the rails when installing the bars).

As John alluded to, you can also run stiffer springs to combat the roll. In general the rule is stiffer springs and relatively soft bar(s), or softer springs and relatively stiff bar(s).

No. Those are fine for a car running the factory springs.

Since my project is pretty far along, I feel a little less stress now. But I'm using Stage 1 European springs. Any problem in combination with these sway bars?

Thanks for the reply.

Fixitman

I reinforced the frame rails where the bars connect using 1/8" steel plate shaped in a U-section.

I actually did the same thing back in the mid 70's after I pulled the captive nuts and frame (unibody) apart with my front bar. Of course it handled great up until theit pulled apart. :classic:

The Euro springs are only aobut a 10% rate increase over the USA OEM rate so they are fine with the bars you have.

About damaging the frame rails, early 240s were not delivered with a front sway bar anyway???

"early 240s were not delivered with a front sway bar anyway"

That may be true, but I have seen my share of early Z's and they ALL had front swaybars. I do not think that swaybars were an after thought on the 240Z.

Keep in mind that these cars were designed to last only so long, and they are well beyond what the original manufacture envisioned as the practical useable life of these cars.

The problem, (as I understand it), is not that the frame rail box structures aren't strong enough, but that the spot welds holding them together are too far apart. Stress causes the them to flex and the metal distorts around welds. This flexure eventually breaks the welds and the frame rail fails.

I'm having my body guy stitch weld the frame rails. Did this on my previous 240Z and had no problems.

Of course, I'm talking a street car here. On a highly stressed auto-cross or track car, I'b beef-up the structure as described in KTM's post above.

On my old street car 240Z I had the frame rails spider crack apart directly above the swaybar mount, even though most of the spot welds were still holding and this was 15+ years ago. So even a street car can wear out the stock mounts and frame rails.

If you look in this photo next to the Mallory Coil there is a dark area on the frame rail, and that is where the frame cracked, and where we welded it up.

http://www.classiczcars.com/photopost/data/500/932strutbar4.JPG

The PO of my car welded plates under the frame rail. They were removed during the rebuild to find that they covered torn frame rails. Sway bar size up front is 25mm.

Nissan knew that this is a weak point as they fitted an internal brace to help transfer the load up to the top section of the rail. It appeared that the brace is spot welded in after the rail was bent.

Did the HLS30 have internal frame rail reinforcement?

What handling characteristics would be expected with lareg bars and stiff springs?

Did the HLS30 have internal frame rail reinforcement?

Yes, they do have the reinforcement, it just isn't enough.

What about adding 2 strut bars, one front and one rear then?? Can it helps?