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

[charliew]

What makes these little cars attractive is their light weight. But the power levels when they were designed was lower and the tire tech has gotten so much better. The tricky thing is to only add as much support as is necessary to the exact weak spots that are known. This is where you originally started your quest. You seem to be off to a good start as the some of the smart guys have already assisted you a lot.

I would bet that in a lot of cases the fractures started before the reinforcements were added. You know some of these cars started as just two or three times a year racers and then bigger and sticker rubber was added and then more power and so on till it got serious and the cracks started appearing so then the repairs and stiffening started where it was obviously needed but then that moved the stress to the next weakest area and so on. If you start out knowing what the bad areas are and brace them before the stress is applied it will end up much better.
I know this is what you are doing and the reply about the cage tieing the cab up tight helped the long area a lot. The suspension ears are a problem all by themselves and need to be braced and thickened to spread the load out over a larger area.
I would like to do a permanent brace from the targa to the windshield but I don't think the windshield is strong enough as it is. I don't think there is enough room for a cage in a street car without wearing a helmet all the time. But that is the best bracing solution. Of course a exoskeleton would be the best but how stupid would that look on a street car.
I have lots of studying to do it seems.
The safest thing is to do the mods you listed and only run about 9 inch wide tires and keep the power below 250.
I find it hard to believe that these cars don't get real crooked on a rotisserie when the whole long is cut out on one side even with the diagonal brace that is used between the seat belt point and the kick panel.
I may persue the idea of a 1-1/4 tube cage that is tight up against the body at the windshield and targa and nothing overhead on the outside but two connecting tubes in the middle away from your head. This would not be as good as over the side windows but would be where maybe your head couldn't contact it in a wreck with the seatbelt on. I would also like to angle the windshield back some and that means a lower roof line but that might be asking too much.
I'm only 5'8" but both my sons are taller and they may want this car when I'm done with cars.
I have fieros and both my son's think they are too confining although I know some 6 footers with fieros.

These cars are very thin sheetmetal boxed sections and sometimes the spot welds are not as good as the engineers planned. Seam welding is the time proven helper on all unitized cars used in motorsports. I know the seam sealer is a pain but it might have come loose because of some of the twisting, where it's loose might give a indication of where the most twist is at stock levels.