So I'm not a big fan of drilling a bunch of holes in my floor for sub frame connectors. I did have a full cage in my 93 and I don't want to go in that route in a street car. I looked on the internet for about 2 hours tonight and found 2 examples of what I was thinking. But both went to the mirror mounting area. I was thing has anyone made a roll bar, then added bracing that goes from the roll bar to where the hardtop mounts go, just to stiffen up the chassis and NOT for roll protection. If anyone has thought of this or tried it please share. I was thinking of 3 bars total 2 going straight forward to the hard top mounts but tucking up next to the hard top. One other bar going from drivers side roll bar to the passenger side A pillar to help twisting force.

 

Its not a smart thing to do if you like your own safety, but I've seen it done once on a car that was fully caged a year later. Connectors made from light exhaust piping. In terms of stiffness the car with connectors was very close to the fully caged one.

 

Forgive me for my ignorance. Really hoping to learn some more about this myself.
I thought sub-frame connectors were only attached under the car, like the butterfly brace. Do you have to drill holes in the floor for them?
Also, this is probably not what you want, but I was told adding door bars to a roll bar adds a good bit of stiffness. If you are already putting in a roll bar, but don't want a cage, would door bars be a good compromise? Can always take the time to seam weld. Wouldn't have holes in the floor going that route.

 

Frame rails are cheap, proven, and don't interefere with the driver or cause safety issues. They dramatically stiffen the chassis. The holes in the floor are not a big deal at all.

 

I was reading about someone that installed a set of door bars and what he said was that if you have crank windows. You will have to open the door a smig to roll up or down the windows.

 

Yes, how do you think they would install and provide a benefit otherwise?

This.

 

I have frame rails and door bars and they both helped. The door bars helped more, I think.

 

I've never had frame rail reinforcements, but adding door bars to my setup made a great change on my somewhat worn MSM.

 

I never did door bars, but the frame rails + butterfly brace was a HUGE improvement.

 

Door Bars > Frame Rails. Both help but the bars make a bigger difference in my experience.

 

Blackbird has done a couple of "street" cages, not exactly what you are talking about, but may be worth a look.

https://www.miataturbo.net/race-prep...eth-you-67640/

https://forum.miata.net/vb/showthread.php?t=454185

At the risk of speaking for Moti, I am pretty sure he would be willing to do some different things with the door bars.

 

I had door bars in my NA which made a drastic difference in terms of rigidity. It was however a pain both to enter and exit the car. This time around, I have the FM frame rails on my NB and while not quite on the same level as the door bars, there is definitely a noticeable difference.

+1 for frame rails especially considering its a street car.