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Discussion Starter #1
I'm making good progress with the chassis updates for my dragster, but I've run into one area that I have a question on. In the spec book, it outlines the max height of the roll cage in relation to the shoulder hoop, which for my case is 18". That allows me to use 1 1/2 x .058 tubing for my shoulder hoop, which I have, and 1 1/2 x .065 for the cage. I'll be using 1 5/8 x 058 for the cage instead, which is ok by the spec. Any higher and I have to use 1 1/2 x .065 for the shoulder hoop, which I have as well if I need it. Here's the question. The spec book says the height cannot exceed 18" as measured from the centerline of the shoulder hoop to the centerline of the roll cage hoop. That part I get. The part it doesn't clarify or outline, is exactly where this measurement is taken from. As with any dragster chassis, my upper frame rail and shoulder hoop are sloped in a downward direction to the front of the car, where the bottom frame rail is flat. Now I would assume that the measurement would be taken vertically from the highest point of the front hoop, but if the rear bars on the cage are at the exact same height (mine will be) as the front bar (parallel to the bottom frame rail side to side and front to back), couldn't this measurement be taken from the rear of the shoulder hoop at it's highest point in the chassis? What I mean here, is that if I measure the height of the front hoop straight down to the shoulder hoop, I can have 18", but if I measure from the highest point of the shoulder hoop to the highest point of the front hoop, it's going to be less because of the shoulder hoop sloping upwards towards the rear. I'm going for the 18" height, but if the measurement can be taken from the tallest point of the shoulder hoop to the tallest point on the front hoop, that would give me a bit more room inside the cage when finished, and if I'm right, would still meet spec (2.5c by the way). I'm just confused as to where to measure for the height.

Hope somebody here can clarify this for me. Thanks guys!
 

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Discussion Starter #2
I just had a thought, and correct me if I'm wrong, but would that measurement mean anywhere along the shoulder hoop? As in, measured from any point on the shoulder hoop, the roll cage cannot exceed the 18"? If that's the case, I could build my cage sloping down from the rear towards the front, and still meet the 18" spec. That would be a funny looking cage though, although I've seen a few like that at the track.....................
 

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Discussion Starter #5
Just so I'm clear with this, if I'm at the spec as measured from the highest part of the shoulder hoop (and parallel to the bottom frame rail), and the measurement is greater than spec measured straight down from the front hoop, I'm ok, right? I just want to make sure that's right before I start cutting and notching tube, definately before I start welding. Thanks again for the infor guys.
 

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just measure from the back of the shoulder hoop to the highest point of the cage. If your under 18 inch then you are ok with 1.500.065 if above 18 inch then 1.625 .058. I always use 1.500 .083 on roll cage on a dragster.
 

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Discussion Starter #7
Thanks for the info. I'm using the 1.625 x .083 for my cage ( I just realize I posted 1 5/8 x .058 before. I meant .083). The main reason I was asking is because when our tech inspector first looked at the car, he measured the cage from the shoulder hoop along one side of the car to the top of the cage, not at the rear. He also measured from the top of the tubing to the top of the tubing, even though the shoulder hoop was 1.375 at the time and not the 1.500 and the cage was 1.625. I know the spec calls for measuring from centerline to centerline of the tubing. I'll keep it the same way, I just don't want to get into an argument with the guy who will be putting the certification sticker on my car about what's legal and what's not. It's taking alot of work to get the car ready and I don't want to piss off the guy who's giving me the sticker I need. I will have the book right there when he does the inspection though, and I just want to be clear on some of the measurements so I know I have them right. Thanks for the help and info. I might hit you up again if I have more questions if you're good with that.
 
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