[Ron Sutton]

Hey Mike,

Thanks for putting your name in the post. I always feel weird referring to someone's "street name".

Originally Posted by glassman

Ron, regarding that "common" drawing from two posts above, what is the point of diminishing return regarding lowering the triangulation from the door entry?

in other words, how low can it go, mostly you want the safety first, but entry dynamics come into play from the pro-touring vs racing side. I've seen alot of them run parallel to the running boards, which only help, i believe, in torsional rigidity, but not rollover protection. Is that part of the cage designed to help keep the main hoop from crushing?

I noticed its at the height of the harness bar, how much lower can it go while still retaining most of its integrity, while still being able to climb in ok (think wifey). 90% of my car is built for street, but track 10% of the time, i dont want to sacrifice safety, but ????? how low can it go?

thanx, Mike

Well ... what it was designed for originally ... could be open to interpretation. I can only share with you my experience & points of view from that experience.

For safety purposes, it does two key things, by priority:

1. It is to prevent mean things from coming into the car & killing you. Unfortunately, I know from first hand experience where guys died from side impacts with trees, telephone poles, ends of concrete barriers, other cars, etc. So it needs to come up high enough to protect the driver & passenger's bodies from impacts.

Look at the illustration I attached here ... from the NHRA rule book ... and see where the driver is in relation to that door bar. The door bar acts as a barrier between the driver & passenger's bodies and "stuff." If that door bar is 1-3/4" x .095" Chromoly ... it can take a hard hit & bend a few inches. In faster, harder side impacts .. the object may very well come in much farther, but the tube will help slow the object. This can mean the difference between broken bones & death.

So, to answer your question about how high it needs to be, varies with your seat mounting. The key is to make sure the Chromoly tube is a barrier for the driver & passenger's torsos when they are in the seat. I like to make sure it is protecting the majority of their body, as shown in the illustration. This varies with seat height, angle & placement ... and is usually lower than this drawing.

2. It is the only thing preventing the roll bar from folding in the middle in a hard flip or roll over. It turns a triangle into a double triangle, sort of like making it a truss.

But I don't set the height for this role. I set as outlined in #1.