View Full Version : Rear down bar question
i have another post discussing the project, but this is a specific rules clarification question.
https://www.pro-touring.com/threads/117380-55-Chevy-truck-nothing-vs-roll-bar-vs-cage
for the rear down bars, i am looking at the diagram below. the bars do not tie into any node on the cage, and they are bent in the middle. these slope away from the cage, then straight down to the floor. if i was to use the exact same bars, but flip them around, they would go straight down from the cage, and then slope down to the rear floor. exact same bars tied to the exact same points. i could then triangulate the bend into the harness bar for extra strength at the bend. this seems simple, but is there any specific statement in the rule book that would disqualify that execution?
the reason i ask is for the other picture below (not my truck but same thing). this would allow me to bring the rear down bars thru a lexan back window, instead of cutting up the top of the cab.
https://static1.pt-content.com/images/noimg.gif
https://static1.pt-content.com/images/pt/2015/10/Chev55halfStepGrn12-1.jpg
TheJDMan
10-09-2015, 01:06 PM
It depends on what rule book you are referring to. Both SCCA and NHRA specifically state that the rear down bars must be straight with no bends. As such the above rear bars are not competition legal in those sanctioning bodies. Also, many smaller organizations use SCCA rules rather than developed their own, so those down bars might be problematic in those events as well.
Here is a pic of a NASCAR truck series truck. I know these are full tube chassis but it also clearly shows the straight rear down bars.
https://static1.pt-content.com/images/pt/2015/10/163_news090225_00z2Bnascar_camping_world-1.jpg
However, if you are just building something for a street driver or autocross it probably won't make any difference what you do. Just my opinion, an inverted rear bar will not gain you much. IMO, you would be better off with a conventional double loop headache bar that mounts in the bed and could be attached to the frame if you wanted to.
https://static1.pt-content.com/images/noimg.gif
straight bars, check.
as for the bed mounted roll bar ... while my head is pretty much against the back glass in this cab, i really didn't think that i could get it within the 6" limit from the drivers head. guess i should measure that out, might be ok.
HandOverFist
10-13-2015, 09:07 AM
In some circumstances you can do without any rear bars in trucks if you utilize the correct SFI cage.
Per NHRA -
"Steel-bodied pickup trucks (7.50 seconds and slower), roll cagesare permitted with no back braces if the roll cage satisfies SFI25.1, 25.2, 25.4, or the roll cage consists of a 4-point (door car)cage with a complete SFI 2.4, 2.5, 2.6, 2.7 dragster, SFI 10.2,10.3 altered, or SFI 10.4 street roadster roll cage/driver’scompartment incorporated into and attached to the 4-point rollcage. An upper windshield bar is mandatory.Non-steel-bodied pickup trucks (7.50 seconds and slower), rollcages are permitted with no back braces if the roll cagesatisfies SFI 25.1, 25.2, 25.4, or the roll cage satisfies therequirements for SFI 2.4, 2.5, 2.6, 2.7 dragster, SFI 10.2, 10.3altered, or SFI 10.4 street roadster roll cage/driver’scompartment. No 4-point (door car) cage is required and noupper windshield bar is required."
holy crap. while that gets around the rear brace issue, that REALLY hinders the daily driver aspect!!
but good to know thought, i'm slowly learning these asphalt rules.
HandOverFist
10-13-2015, 11:14 AM
Yes, that is the reason I decided against putting the El Camino on the track...it was just too nice a vehicle to begin punching holes in and I absolutely refuse to run bars thru the back glass. I'll just do what I can tolerate and run classes that do not require a roll bar...pretty sure I will enjoy the car even more being able to drive it on the street as well.
Yes, that is the reason I decided against putting the El Camino on the track...it was just too nice a vehicle to begin punching holes in and I absolutely refuse to run bars thru the back glass. I'll just do what I can tolerate and run classes that do not require a roll bar...pretty sure I will enjoy the car even more being able to drive it on the street as well.
i agree with that statement. i will also have this entire chassis in 3D when i'm done, no reason i couldn't just build another track-only version later!!
72BBSwinger
10-14-2015, 06:15 PM
http://www.nasarallysport.com/rules-forms/2012-NASA-Rally-Sport-GRR-Appendix-B.pdf
These are cage rules that apply to a road course car.
HandOverFist
10-14-2015, 09:14 PM
http://www.nasarallysport.com/rules-forms/2012-NASA-Rally-Sport-GRR-Appendix-B.pdf
These are cage rules that apply to a road course car.
Just my opinion mind you, but it is like pissing in the wind trying to have it both ways. It is either going to be a race vehicle or a street vehicle...the real definition of compromise is where neither party is satisfied. Surely there are classes of competition available where street driven vehicles can participate without such strict safety mandates.
z28cp
10-27-2015, 12:35 PM
http://www.nasarallysport.com/rules-forms/2012-NASA-Rally-Sport-GRR-Appendix-B.pdf
These are cage rules that apply to a road course car.
Not sure exactly what these rules are for... Rally Sport? The NASA version of RallyCross?
The applicable rules for road course cars are on page 43 of the NASA CCR. https://www.nasaproracing.com/rules/ccr.pdf
HandOverFist
10-27-2015, 10:03 PM
6DoF - You do not have to attach those rear bars to the top of the hoop. You are allowed to weld them on the sides of the hoop within 5" of the top. That might give you the room to avoid the cab portion and continue thru the back glass. I can see the difficulty with that small rear glass...you can cross those bars in a X fashion which might allow avoiding the cab sides while passing thru the window space. Ornery, but doable if you are intent. :secret:
Edit: Putting some more thought into it...I have not seen it done, but what about adding another cross bar straight across the hoop 5" down? That way you could run the rear bars off the lower cross bar closer together and straight out the rear glass into the bed. Hmm...I may have just out tricked myself lol.
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