So I'm planning on having a roll bar built for my car. According to SCCA rules, the rear bracing should be >30 degrees from vertical. I know a lot of cage builders extend these bars into the trunk. I can imagine that the larger angle would be better to prevent forward/backward movement of the main hoop but is there any other advantage? Worth the extra cost?

Here's a quick drawing of the design I had in mind.

 

diagonal needs to be the other way. It should extend from the top of the drivers side to bottom of passenger side

 

haha yeah i realized after i drew it that its going the wrong way and i didnt feel like redoing it. thanks though!

any input on the rear bracing?

 

Rear bracing looks good. Same as many top end race cars.

 

My question is the angle of the rear bracing. Is there an optimal position? I've been looking at various cages from SpeedStar to Science of Speed and a bunch of others and they run the rear bracing into the trunk but it seems that the position varies.

SpeedStar rear bracing goes to the beginning of the trunk well:


Science of Speed has theirs well beyond:


TC Design has theirs going to the shock towers:

 

The main structure of the rear of the car is two beams that run toward the back. In all those pictures, the bar has been welded to the top of those two beams.

There is no particular advantage to running the bar back beyond the rear suspension. My stays come down to those beams right by the top mount of the shock tower. Anything else is too far back, IMO.

You have to work around the fuel filler tubes (assuming you plan to leave the OEM tank and fuel system in place).

 

I think the reason why they put it so far back is to avoid the fuel tubing.

 

If you want to place 2 diagonals from the main hoop to the rear bars (as shown in OP drawing) you will need to go into the trunk area to clear the fuel cell and filler lines.

If you want tp place 1 diagonal from the main hoop to the rear bars you can mount the rear bars closer to, at or infront of the shock tower. You can see in the pic below, this is the path I took. It's hard to see from the position I took this pic but there is a diagonal running from behind the driver head of the main hoop down to the rear bar on the passenger side.

 

It was my understanding that integrating the roll bar to the shock towers increase chassis rigidity. Truth or hogwash?

 

I didn't have any diagonals on the stays. IMO, it's not necessary for just a roll bar.