Can you mix cage tube sizes?

[Jake]

My MR2's cage is a 1.75" tube - but 1.5" is all that is required.

I still need to add the extra door bars for the rule change this year.

Can I use 1.5" tube for this even though it's connecting to 1.75" tube?

[Rabbit07]

3. Minimum tubing sizes for (all Showroom Stock, Touring and Improved Touring Category auto-mobiles registered after June 1, 1994) for all required roll cage elements (All dimensions in inches):
Up to 1500 lbs. 1.375 x .095 DOM / Seamless / Alloy
1501-2200 lbs. 1.500 x .095 DOM / Seamless / Alloy
2201-3000 lbs. 1.500 x .120 DOM / Seamless / Alloy
1.625 x .120 DOM / Seamless / Alloy
1.750 x .095 DOM / Seamless / Alloy

You need only meet the minimum, if 1.50 is all that is required then use it! Be careful though 1.50X.120 wall is heavier per linear foot than 1.75X .095!

[Speed Raycer]

Carefull though.... I'd look into WHY the cage builder went with 1.75 if 1.5x.095 was the min. tube spec'd. IF the main hoop couldn't meet the 4 bends & 180 +/- 10 rule, then the entire cage has to be upped to the next size tubing. Now, unless the rules changed since the last time I read that section of the rules, it still required ALL tubes to be the up size even with the changed wording last year for required tubes to meet the minimum.

Don't have the GCR in front of me .... sorry.

Also... IIRC, required tubes must meet the same size as the main hoop, so you might be SOL.

Again... search the GCR as I'm stuck at work ;)

[Speed Raycer]

:D I forgot that I had the GCR on my backup drive:

9.4.1.F.3
Main hoop: 4 bends max., totaling 180º ± 10º
Front hoop: 4 bends max.
or
Front downtubes: 2 bends max.
Rear hoop supports: No bends.

If any of the above bend requirements cannot be met, all components of the roll cage shall be fabricated from the tubing size(s) listed for the next heavier category of automobiles.

9.4.2.C. For tubing sizes for front and main hoop and all required bracing, see 9.4.1.F.3.

[Jake]

Interesting about the bends. I think I have 3 bends in my front down tubes. There are pics here...
http://www.racerjake.com/Vehicle_Mods.htm

Now here's anther question -

"If any of the above bend requirements cannot be met, all components of the roll cage shall be fabricated from the tubing size(s) listed for the next heavier category of automobiles."

So does that mean that if I go to thicker tubing I can go apeshit with bends? (8 bends here, 9 there....)

[Speed Raycer]

Well, you could... but think of bends as "Fail Here" points in a rollover or side impact ;) Which would you rather have, 3 or 9?

[Jake]

Agreed. But you could get a bit creative trying to keep the tubes away from the old noggin.

[Speed Raycer]

Well, in that case, if you're going to redo the cage, you can go with a Halo design and use the 1.5x.095 tube ... per the rules, no min. # of bends in a halo & you still get the 2 bends in the downbar

[Jake]

Well, in that case, if you're going to redo the cage, you can go with a Halo design and use the 1.5x.095 tube ... per the rules, no min. # of bends in a halo & you still get the 2 bends in the downbar
[/b]

U mean no max bends in the halo right?