What do you have for chassis stiffening? Options

[Justinp71]

I put some more horsepower in my car, so far I have just autocrossed it on street tires. I have the bolt in roll bar that has the mid bar going to the floor.

Besides that my chassis is stock and I am wondering what I should do for more re-enforcement... so I can comfortably run on slicks.

Below is a photo of the roll bar. I don't consider the roll bar to give to much chassis stiffening, but it just might help with cracking the longs.

Edit: I mainly just use the car for street and the occasional Autocross or DE

[John]

An area that seems to crack and few discuss is where the rear shock towers are supposed to attach to the rear portion of the longs. To really fix, some of the cross-members should be opened up so that the shock tower can be attached to the inner long.

The inner longs could also be braced together better. The cross member between the rear shocks is important as it attempts to keep the two longitudes aligned with each other. The next forward cross member is the lower firewall. From what I have seen, the Engman kit has a well thought out piece that welds into the inner lower firewall (that ties the two longs together).

Over time, without sufficient bracing, the metal that makes up (or attaches to) the cross members of the cars will fatigue and crack. The cross members (or areas that attach to them) that show this the worst are the rear cross member/rear trunk floor where the rear shock towers attach, and the cross member just in front of the seats (close to where the parking brake indent is in the longitudes).

The other areas cracks seem to be common are the rear suspension inner ears. In these areas, the attachment to the long seems solid enough, but over time the sheet metal part itself fatigues and cracks form just above the trailing arm attachment bolt hole. The braces that can be mounted between the lower firewall (cross member) and the inner ear (dog ear) help a lot.

The factory stiffening kit may help a little, but cars still crack with them installed. I have tracked the same 914 for over 20 years and have found and addressed all the cracks (and most of the cars crack in the same spots).

Nobody mentioned the fatigue cracks in the lower windshield pillars. I have seen many many 914's (not even track cars) that show these cracks. My windshield frame is welded to the roll cage to keep it from moving around and rubbing on the cage (which it did prior to welding it).

The more you can remove and the less you add back (stiffening) will benefit you on the track. (a 10,000 RPM race engine wouldn't hurt either).......


my 0.02