RX-7 Roll Cage

[jwesleyc3]

I am ready to purchase the material for my roll cage for my 1st gen RX-7. I have been searching and found that Jegs sells material for a 2nd gen RX-7. Do you think with a little fab work I can get this to fit? I have a friend that is helping me weld and do the bends but I do not want to cause more harm if I was to order it from Jegs.

[joeg]

Just make certain it is DOM and not ERW.

[jwesleyc3]

Just make certain it is DOM and not ERW.

It is seamless or DOM mild steel tubing. 1-5/8" x .134 wall is the size. I called them to double check. Thanks for the heads up.

[x-ring]

1-5/8" x 0.134? That seems heavy to me.

[jwesleyc3]

1-5/8" x 0.134? That seems heavy to me.

I really do not mind if it is heavy being a newbie to the sport. I am all about safety and passing tech so the size of tube I love. I need to know from other 1st gen racers if they think that this cage will fit a 1st gen with minimal fabrication work? My friend said he can make it work but since he is doing this for free I do not want to make more work than neccassary. Nonetheless waste money on this kit from Jegs.

[jrvisual]

The width of the main hoop is the determining factor.

I don't know RX-7s but if the main hoop is to wide it is useless. All the other parts can be cut at one end or the other to fit, the hoop must remain a single piece so if it is too wide it is scrap.

[Knestis]

If you're talking about a kit that's pre-bent to fit the 2nd Gen RX, I'd be VERY surprised if it fit without a lot of massaging.

Part of a "good" cage is the fit - how close it is to the shell. I had to re-shell my first Golf when I rolled it because the cage had gone in with a full interior (showroom stock), which we subsequently took out. This left enough space that when it went over, the body shell deformed way more than it would have if the cage had been tight.

If you and a friend are doing the project, you need to get very, VERY familiar with the rules that apply. (I'm assuming one or the other of you has really good fabrication skills - big tubing doesn't by itself make a safe cage.)

K

[Streetwise guy]

The 1 5/8 x .134 would be NHRA legal, so its a bit bigger than we need. I would find a second gen car and do some width measurements before I ordered it, just opinion, but I think the first gen were quite a bit smaller car.

[DoubleXL240Z]

J, A few things to consider on this:
Is what dies does your friend have for bending?
The weight difference is pretty substantial, approx. 2.133 lbs per foot for 1 5/8 versus
1.425 lbs per foot for 1 1/2
figuring 85-90 feet of tubing in a cage and you've added about 58-63 lbs, a lot of it up high, not where you want it.
also it sounds silly but bigger tubing will fill up a cockpit pretty quik, meaning less room for you.
Build it right... build it once!!
Also the last cage someone brought me from Jegs was mild steel not D.O.M. it had a seam inside of it, Not legal... he was a drag racer so it didn't matter for SCCA.
Try checking out stockcarsteel.com if you are going to build it yourself, real reasonable prices
YMMV

[Speed Raycer]

There are plenty of good cage builders in your area. Jegs isn't on that list If you're going for prebuilt, go with Kirk Racing. Also, take your time and shipping into consideration. Lots of times, it pays in the end to let someone else do it.

[mustanghammer]

I really do not mind if it is heavy being a newbie to the sport. I am all about safety and passing tech so the size of tube I love.

As someone that owns an IT7 RX7 with a cage that has over-spec tubing (1.75" x 0.120") I can tell you that you really want to avoid this. The weight penalty is not worth it. While I can't tell you if the bigger tubing provides more safety but I certain that the extra weight does cause increased tire wear, brake pad wear and a slower car.

A cage is really hard to do over so my advice is to get the correct stuff the first time. A properly built cage made of 1.5" x .095" DOM will be fine. I have seen RX7's crashed with this size tubing and they held up very well. So the SCCA spec is right in line with what you need.

All that asside - welcome to the sport. An RX7 is a great car and you'll have a blast driving it!!

[jwesleyc3]

Thanks for the advice forum members. I am going to order an Autopower U-Weld cage along with the race roll bar and go from there. There cages are legal in the SCCA so I am settling for this. I found these guys in back of an old Grassroots magazine.
Thanks again for the quick replies.

[lateapex911]

Some gneral comments:

1- DO NOT buy a cage designed for another car. period. It will be HARDER than starting from straight tubes.

2- A custom cage often is safer, roomier and in the long run better than a pre bent one.

3- Thick/heavy tubes are only one indication of safety...design is as, or more important.

Remember in high school when you had to build that bridge using only a certain number of balsa wood sticks?

4- If you go the pre bent route, consider gusseting and extra triangulation. Often this requires no bending, but adds significant strength. Remember, triangulation is key, and give loads a route to follow. Also, attach the downtubes to multiple and vertical sections whenever possible.