Cage Tubing Dimension Changes for 2008?

[ScottL]

I had a cage built for my car this year. My intent was to have a cage that complied with ITS, SpecE30, and KP classes (SCCA, NASA, BMWCCA, respectively). Unfortunately (or fortunately, as it may be), I ended up with a cage that is not legal for ITS according to the 2008 GCR.

Until 2008, 1.5 x .120 mild steel was acceptable for a car with a class weight of 2750 lb. That's what I have. Now, the minimum is 1.750 x .090 (GCR 9.4.F)

I don't have a huge problem with this; it's my job to check the rules and tell the builder what I need. I'll run E Production if I have to (the car would not be competitive in ITS anyway).

But I'm curious. Does anyone know why the cage rules were changed for 2008?

[JoshS]

But I'm curious. Does anyone know why the cage rules were changed for 2008?

As I understand it, the goal was to normalize the cage rules across all of the classes. There was no good reason to have different rules for each category. This way it eases transitions of the same car from one class to another.

[ScottL]

Thanks, Josh.

Doesn't make too much sense, though. They still allow two different dimensions for 2700 lbs and up. And if you refer to 9.4.5.E, you'll see that formula cars and sports racers still have three equivalent dimensions for cars over 2500 lbs:

Up to 1500 lbs. 1.375 x .095
1500-2500 lbs. 1.50 x .095
Over 2500 lbs. 1.50 x .120, 1.625 x .120, 1.75 x .095

Where's the normalization?

[DoubleXL240Z]

The rule you are looking at is basically aimed at allowing the GTA/cup/nascar stuff to fit in somewhere. The Formula/Sports racer specs are that way because the vast majority of the chassis are "certified" by the constructors. That is, that the constructors build them to certain specs etc.
And finding a formula/ sports racer over 2500 lbs would be pretty tough.

[ekim952522000]

The way I read the rules is that 1.5 x .120 should be fine for 2750lbs?

[ScottL]

If you look at the June update of the 2008 GCR, rule 9.4.F.2:

Up to 1700 lbs 1.375 x .080
1701 - 2699 lbs 1.500 x .095, 1.625 x .080
2700 lbs and up 1.750 x .095, 1.625 x .120

Note that the original 2008 GCR did not include 1.625 dimension:

Up to 1700 lbs 1.375 x .080
1701 - 2699 lbs 1.500 x .095
2700 lbs and up 1.750 x .095

[seckerich]

Also remember that is weight without driver and assumes 180# for driver.

[ScottL]

Also remember that is weight without driver and assumes 180# for driver.

Can you point me to the relevant section in the GCR that confirms your statement?

This is an interesting point because, first, I see this:

9.3.48. WEIGHT
All cars shall meet or exceed the minimum weight specified with driver, exactly as they come off the race circuit, at the conclusion of a race or qualifying session.

And then then I see this:

2. The following table shows the minimum allowed tubing outer diameter and wall thickness by vehicle weight: [table of dimensions - heading reads "GCR vehicle weight"]

So, I think GCR weight = vehicle weight + driver. The roll bar specs have to consider the forces exerted on the car during a crash and the mass of the vehicle. Driver would have to be included in that mass to do the math accurately -- but whatever.

I'd still like to know why they changed the minimum dimensions...

[ScottL]

Holy crap, the formula/sports racer cage specs say:

c. For purposes of determining tubing sizes, the vehicle weight is as raced without fuel and driver. The minus tolerance for wall thickness should not be less than .010” below the nominal thickness.

WTF? Which is it for GT/Production cars then? With or without fuel and driver?

[Greg Amy]

I haven't pored through the new rollcage rules (it's one of my winter projects) but I think the prior allowance of doing the rollcage tubing based on IT minimum weight minus 180# was rescinded, and replaced with purely minimum legal weight as raced.

Ergo, unless otherwise specified, the minimum rollcage tubing size for required elements is dependent on the minimum legal weight of the car, with driver.

Ignore the formula car rollcage rules. They are entirely, fully, and utterly irrelevant to your situation. If it makes you feel any better, take a big black marker and cross through all those lines, and remove them from your brain...

[ScottL]

Ignore the formula car rollcage rules. They are entirely, fully, and utterly irrelevant to your situation. If it makes you feel any better, take a big black marker and cross through all those lines, and remove them from your brain...

Thanks Greg. I was just quoting the formula rules for the sake of comparison. I guess it's apples and oranges though, so not relevant to my situation.

[Z3_GoCar]

I think it's a shame that the 1.5x0.120 tubing option was taken away, because there are a lot of smaller chassis cars that could use the extra room and weigh more than 2700lbs, think S-2000 and Z3's. At least I already have a log-book for my cage....

James

[ekim952522000]

So wait a minute which one is the cage rules I need to follow for IT.

9.4 roll cages for GT and Production based cars.

or

APPENDIX G. 2007 ROll Cage Rules.

Getting cage in 3 weeks and am now kinda confused?

[JoshS]

So wait a minute which one is the cage rules I need to follow for IT.

9.4 roll cages for GT and Production based cars.

or

APPENDIX G. 2007 ROll Cage Rules.

Getting cage in 3 weeks and am now kinda confused?

Mike, you need section 9.4. Appendix G is still there only for cars that were registered under the old rules.

[ekim952522000]

Thanks Josh I will make sure to use those.

[ScottL]

Well, it's a done deal. The CS is not letting me run the car in ITS even for the driver school coming up this month. Unless I can scrounge up a fuel cell and fire system in short order (to make it an E Prod car), I'll have to postpone my plans to get a comp license until next season.

SCCA has some flawed logic in the rules here. I could build a 2-ton E Prod BMW E30 325i and still run 1.500" tubing in it -- because the "GCR weight" for that car is 2300 lb! It wouldn't be safe, but it would be legal. If they have all this wonderful crash data that says a 2700 pound car should have 1.750 tubes, then cage construction should be based on the actual mass of the car, not on some theoretical minimum class weight!

Anyway, my bad. I'll STFU and get on with it... hope to see some of you IT guys at the races next season.

[Z3_GoCar]

A fire system isn't a big deal, actually they're down right cheap for a decent manual AFFF system. I got mine from Bimmer-World.

As for the fuel cell, quote 9.1.5.11a; to paraphrase, you can use the stock plastic tank if it's between the front and rear axle and frame rails. I believe that's under the rear seat cushion on the e-30. The spec line says "trunk mounted fuel cell allowed" So where is a fuel cell manditory for the e-30 325? You should be able to school in your car if they're having one this fall.

James

[Greg Amy]

So where is a fuel cell manditory for the e-30 325?

James, his cage doesn't meet IT specs, and he needs a fuel cell and fire system to be able to run EProd...

What about ITE or SPU or any of the other myriad "catch all" classes? Can't you find one where you can lower the minimum weight just to "get out there"?

GA

[ScottL]

What about ITE or SPU or any of the other myriad "catch all" classes? Can't you find one where you can lower the minimum weight just to "get out there"?
GA

Regardless of which IT category I run, I believe the car has to weigh less than 2700 pounds for me to run the cage I have. Correction: it must have a "GCR weight" of less than 2700 pounds.

Speaking of that, where are the rules for the regional classes like ITE, GTP, and SPU? They're not in the GCR...

[JoshS]

Speaking of that, where are the rules for the regional classes like ITE, GTP, and SPU? They're not in the GCR...

Since those are regionally-defined classes, you will find the rules for those classes at your region. Check their website.

Although many regions have a class called "ITE", they do not all have the same rules.