View Full Version : Roadracing/NHRA roll bar questions

12-28-2004, 11:32 AM
I am just getting started on my first pro-touring project and would love some advice on the roll cage. Some of the goals for this car are to at least break in to the high 11's in the 1/4 mile and race in the Grand Sport division in MKM open road races. The car in question is a '71 Cutlass Supreme (A-body) and will probably weigh in around 3400-3600 lbs. I'm really more interested in the road racing than drag but since I'll need the cage for one I figure it's smart to have it legal for both.

1. Will a cage suitable for GS division meet NHRA spec for the 11 sec. bracket? What will it take for the cage to be acceptable for both?

2. Are bolt in door bars acceptable for both? Since the realistic time spent racing will only be 5% of the time spent driving, it would be nice to avoid the contortionist act 95% of the time.

3. Can the bars be mounted to the body, legally? I have in mind to use solid body mounts anyway and am thinking how much easier installation not to mention later modifications would be if the body could still be removed from the frame.

I really appreciate the resource that this site is. If anyone thinks that this post would be better addressed by breaking the questions into individual topic I can do that. Thanks, guys.

12-28-2004, 11:38 AM
Get rule books for every sanctioning body you plan to run under! There's a lot more than just cages/bars to consider.

And NO you can't weld a cage to the body. It has to be welded to the frame.

Nine Ball
12-28-2004, 05:21 PM
Just a heads up, but NHRA has lowered their cage requirements for 2005. It used to be mandatory for a 5-point cage at 11.99, but now it is 11.49 before you need one.

Ralph LoGrasso
12-28-2004, 05:25 PM
Check out some of the rules over at www.openroadracing.com. You will probably find that their tech requirements are much more strict than NHRA. Especially with regard to cage designs, tubing sizes and wall thicknesses.

12-28-2004, 05:27 PM
You can weld the cage to the body....kinda. It has to be welded to 6X6 floor plates with 6X6 plates to back them up and bolted to the floor with at least (8) grade 8 3/8" bolts. I think the floor plates have to be at least .120 plate but better check first. This wil pass tech for SS or MKM, any level. I do not know about NHRA/IHRA tech.

12-29-2004, 08:24 AM
Well I've looked at the openroadracing.com rules and it looks like a 6pt. cage made from 2" .120 wall mild steel would be sufficient for the rules. Is that enough to really be safe for a 168 tech speed? I would like to have the car to have the ability to eventually run there. It will probably take longer for me to get ready than the car!

I figured that with the proper construction the frame could be attached to the body. After all that's how the pony cars HAVE to do it. What are the reasons not to do it this way? Plus how do you account for frame to body flex if the bar goes through the body?

Thanks for the advice guys,

01-05-2005, 10:11 PM
Check this site for 2005 cage rules:


Hopefully this will be accessible...

01-06-2005, 09:22 AM
How many of you guys drill holes into your tube's for you roll cage so they can check how thick it is?

01-06-2005, 09:45 AM
I've only dealt with NHRA tech inspections, but they use sonic testers. No holes required.

Also, NHRA's spec for mild steel is 1 5/8" x .118". You have to keep in mind that they check all the outsides of the bends in the cage too. Because of that, you need to use thicker wall tubing, so when the outside wall stretches around the bend (and gets thinner), it'll still pass. The norm is .134" wall to meet a .118" wall spec.

A friend of mine just had his home made tube chassis certified up to 8.49 ET's, and everything passed fine, except for one bend. It measured .120". .002" away from failing a complete chassis!! For reference, the paper in your printer is about .004" thick.

Again, you need to get rule books, and you need to call them with every single question that you have. Message boards like this are a great resource, but you should allways check with the source first. Allways.