tube80z

.095 1.5 inch tubing should be fine. I have seen many cars built that way at a shop near me that have won many championships. For your weight target be prepared to bolt in weight. My project is an EMOD V8 powered autoxer. All the pieces (complete frame) and everything else piled on the car weighs 1640 pounds. It is built with .095 for the outer sections and main cage tubes and a lot of .064 and .049 used as bracing for sections that showed low stress in simple FEA tests. You will need to check on materials if you plan to roadrace. I'm pretty sure all the tube needs to be the same thickness in GT and DOM. Cary

Is 90 degrees a misquote? Because if that's it I wouldn't bother. A fluid recirculator would be a much better option. Cary "had glowing red rotors on my autox car this past weekend :-)"

You all should really listen to Jon. There are two types of padding I see on cages all the time. The first, often called pool noodles, really should stay near the water. The second is SFI approved and is a more rigid foam. It, HOWEVER, is intended to be hit by your helmet, not your skull. I know of no foam that is designed to deal with your head hitting a bar. Cary

I need to read the rules again. I didn't realize you could get away with such a big doubler plate. I wonder if you can flange holes in it to help make it stiffer? Cary

Reading this I see that I told you a lie. I don't do area. I've been doing 4 times the size. So for a 1.5 inch tube I've been doing a 6x6 pad. You wouldn't know I had a math degree I'll plug weld those too to make the stick better.

yep, that makes sense. I would close the gap across the lateral tubes to the floor rather than just use a couple of stands. That makes the floor a shear panel as Jjohn mentions. It would seem like it would be harder to rip out too. Figure in a wreck (worst case) that you might see some rather large forces on those mounts. And having more area will lower the load, or some my feeble thinking goes. Cary

I'm not completey sure I follow. Are you putting this tube across the car or lengthwise? If across I would use sheet metal to hook to the floor just like the stock piece, similar to what John mentions above. But I'm may not be following what you're doing here. For the tubes I try and do 4 times the area of the tube. Not sure why but somewhere along the line I picked that up. At least one of us is out in the shop working Cary "stuck at work"

What about FIA seats that don't require a backbrace?

John is right. The end links stack up and your spring analogy goes out the window, just like tender springs. This only changes the rate of change, not the rate. Cary

If you plot bumpsteer every 0.1 inches you'll get a curve. It depends on the curve whether you change the inner pivot point or the outer pivot point when trying to minimize bumpsteer. Cary

Oddly enough I've gotten it to work well. If I were to continue to run this car I would widen the front to be wider than the rear, if for no other reason having a fat but makes getting around cones a lot harder. The EMOD car is wider in front if that is any consolation. It's not normal but I thought I'd throw it out there. Cary

Hmm, I guess I won't tell you that my car looks like a 911 I would widen the front track but I've found that wider rears work for me. Cary

.5 to .7 times the corner weight figuring in motion ratio. I don't know about street ride but that would give you a starting baseline that should be decent for radials for a track car. I'd then do 20 percent variation from that to see which way to go for sure. Cary

Helped a friend with this just this past weekend. And I managed to dig out some 240 stuff I had to take a look at tonight. They won't work. At least what I have would require a different backing plate. And to change that won't be so easy. Cary

The car is an L-series with the motor set back per GT rules (#1 cylinder is inline with the front axle line). The PO did this and it was a botch job par none. I've cleaned up numerous bits but this is a parts car that turned into something more. The steering is stock but the rack has been moved back as far as I can. If I were to keep it I would be changing the front lower control arms to be much longer and adding more ackerman to the mix. The tube frame car is built around a Ford 5.0 but if I were to do it today I would use a LS-1 Chevy. A friend of mine put one in a Z and it is sweet (the red one at Shasta) Cary

Okay, so a few others have questioned this. I'm here to say BS. You aren't going to go a lot faster with some magic suspension under your Z compared to what you have. Will it be better, maybe, but it's a package deal. You need everything to work together. I have a 71 240Z that's not in very good shape I autox. The car was totalled 2 or 3 times before I got it. I use this a testbed for ideas to put onto my EMOD car. The car runs in SCCA prepared classes and so far this year has been TTOD at all but one event ( I got beat by a cart so technically I was still the fastest car) and won PAX at all but two. This 30 year old technology worked significantly better than man tunered STIs, EVOS, etc. It beat Vipers, ZO6s, ... This isn't meant to sound like bragging. But an old car with less than 10K in it is creaming cars that have as much as $50K in mods. How is this possible? It happens because I spent a lot of time fine tuning what is there to get the most out of it. You need to understand the limitations of the Z's suspension and work around them. The Z has a large advantage in weight and size over a lot newer cars. Don't screw that up. Cary

As you mentioned the stock rubber rotates the bushing in torsion and is a relatively low friction bushing. Poly bushing rotate on the metal tube that is rigidly clamped in place. Cary