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1.625 vs 1.75 rollbar tubing


heavy85

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Looking at SCCA / NASA rules and the rollbar can either be 1.625x0.120 or 1.75x0.095. Since the 1.75 tubing is lighter and more stiff I dont see any reason to go with the smaller 1.625 tube. Before I start ordering stuff is there anything I'm missing why you would want to use the smaller tube?

 

Thanks

Cameron

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You can download the SCCA GCR free from their web site. The pertinent section is "9.4 Roll Cages for GT and Production Based Cars" and it starts on page 93.

 

The minimum allowable tubing sizes (as of 2008) are:

 

0 to 1700 lbs (without driver) - 1.375" OD x .095" wall.

1701 - 2699 lbs (without driver) - 1.5" OD x .095" wall.

2700 lbs and up (without driver) - 1.75" OD x .095" wall.

 

If the tubing used is .250" larger in OD then required, the wall thickness can be reduced to .080".

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I must have been looking at an old copy plus I had 1.625 instead of 1.5 stuck in my head. NASA looks to have somewhat recently changed as well:

 

1501 - 2500 lbs. (was 2200)

1.500” x 0.095” Chrome-moly / Seamless mild steel (DOM)

1.500” x 0.120” ERW* (No issuance of log books for cars with ERW cages 04/30/03)

 

2501 (was 2201) - 3000 lbs.

1.500” x 0.120” Chrome-moly / Seamless mild steel (DOM)

1.750” x 0.095” Chrome-moly / Seamless mild steel (DOM)

1.750” x 0.120” ERW* (No issuance of log books for cars with ERW cages 04/30/03)

 

Looks like I will be going with 1.50x0.095"

 

Thanks

Cameron

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  • 4 weeks later...

OK so doing some more research and found where I got the original data. The 2008 SCCA solo rules say:

 

a) Over 1500 lbs.-min. of 1-1/” 2 o.d. x .120" wall or 1-3/4"

o.d. x .095" wall

B) Over 1000 lbs.-min. of 1-1/4" o.d. x .090" wall

c) Under 1000 lbs.-min. of 1" o.d. x .060" wall

 

I wonder if the solo rules are now superseded by the GCR?? I'm confused.

 

Cameron

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