tube80z

I used turnbuckles and cables from the hardware store. The only reason I did this was thinking about it while I was working out on my blowflex, which has a lot of cables and associated hardware. The turnbuckles allowed me to accurately set droop/preload on the springs. I think both Jegs and Summit sell a kit for drag cars that would work. I attached the top to the strut tower wtih a metal strap that had holes and bolt that was welded to it. This was then had the turnbuckle attached to it. The bottome had another bolt that had a clevis end welded to it and then cable down to a bracket on the TC rod. Other options would be a mechanical stop against the bottom of the swaybar. I thought about this for some time and chose the cables because I wasn't sure any of this would work when I first did it. Now that I know it works I could see investing more time in a better solution. Cary

Can you turn one of the rod ends 90 degrees. Maybe the top one on the end of a slider adjustment? I personally think you have way too much droop. Look at late model bimmers and porsches. They have a lot less. Cary

What happens if you put the channel on top of the TC mount? Does that gain you anything? And for droop, how much do you have? If you're springs come unseated you can limit to that with no real change in how the car works. Cary

For what it's worth the swift manual I have recommends 28 PSI when running these tires on an oval using max downforce (3450 lbs) on a ten inch rim. Cary

I think a lot of it depends on tire construction. The FA tires I use on my car seem to work best for me at 18 PSI HOT. I generally start in the 16.5 to 17 range with them cold. I've never had a tire come off the bead but a few of the hoosiers had issues with not holding air. Well after that fact I heard they may have had a construction problem. A lot of this depends on how much your car weighs, etc. If you want to get real tricky you can play a couple of games with your tires. You can paint them with latex and put them on paper to look at how the contact patch changes with pressure, camber, etc. This is best done by using a modified press. Or if you need to see an actual pressure distribution you can use Fuji prescale pressure sensitive paper. Cary

IR guns aren't very useful for tires. The surface temps drop too quickly and they have a tendency to even out before you see the real trends. They are very useful in taking track temp measurements. You really need a good probe pyrometer. Just remember for autox you'll never see the core temps that road racers speak about. If a hoosier R25A slick will show you core temps in the 100 to 125 range when it is working good. When you get over that you'll find they are getting greasy. When taking tire temps remember to take 5 tire readings. What I mean by this is start with one tire (always the same one and usually a front), work your way around the car, and then take the temp of the tire you started with. This will let you see how much temps are dropping as you go. You can use this to guage if a tire that you took the temp of later is actually hotter. In general, once I have established that I don't have an outside edge hotter than the middle or inner I will usually only look at the middle and inner for what needs to change. Remember toe-out heats the inside and toe-in heats the outside. This can mask how the tire is used. For autox pressure rise is a better indicator of how the tires are being used, IMHO. Work to get the front and rears to come up the same amount. You'll also have a target hot pressure that you'll find that works best. You'll need to adjust the starting temp based on ambient temp. Always use the driest air you can in tires. Any water that is condensed and turns to vapor will cause an abnormal amount of pressure rise. Adjust pressure in 20% increments to figure out what works best. That will quickly let you see what you need to do. Cary

It would appear I lost most of my pics when I lost a hard drive last year. I do have some from when I started my experiments that would give you an idea of what I did. The u-shaped piece seen in the photo below had a top, which is in the second photo. Unfortunately I don't have anything close up or of the holes I put in the engine compartment. All I did there was put 3 inch holes in the inner fender in front of the strut (3 on each side) and flanged teh edges. Cary

I just got a new book from Simon Mcbeath called competition car aerodynamics. You may want to get a copy before going too far. They did a number of CFD studies on a generic shape that's close to a Z on the front. It shows airdam, airdam with belly pan, splitter, and splitter with diffuser. They all work a little differently and change the flow around/under the car. Simon writes the aerobytes column in racecar engineering. This book is basically those columns expanded. I'm pretty sure all the Z's had a splash pan. I put holes in my inner fenders to help vent the engine compartment when I ran a belly pan. I then used gurneys on the front of the fenders to help create more of an extraction, which helped to lower the engine temp. I also created a simple diffuser in front of the radiator. That's another thing you can try to make things more efficient and make the entire openning smaller in the front. Cary

I'm not really sure what you're talking about on F1 cars. They all use torsion bars these days and you can't change the rate of those unless you change the bars. That said most can be pulled out in about 15 to 20 seconds and a new one installed. I'd be curious to see the pic if you can find it. Cary

A few years back there was system that Eibach was using on a F3 car that allowed for adjustment by stacking to coils and usiing a special cylinder that put preload on one of the coils. Because the springs were stacked this is how the rate could be varied and it allowed it to be varied over a range if needed through having one of the coils stack solid. It's an intersting idea but I think it has some problems. From the drawing it looks like it is designed to screw up and down a spring. This will limit it to a certain rate as most springs have different pitches and diameter if wire. My second concern would be that this may cause the spring to put more side load on the shock since it isn't using the regular closed end. If you want to see what a coilspring does head over to hyperco and look at the video of their hydraulic spring seat in action. I think you may find it interesting to see how much the spring roates (it's basically a torsion bar). Cary

Looks good to me. Just think even with a little boo boo it's much better than most of the bars people have on their cars. You saw how easy it is for a lot of this stuff to bind and you've taken the time to fix that. Cary

It looks like you came up with a solution. I use 3.8 tap tube from coleman and left right taps for this. The taps weren't that bad and I've used them enough to pay for themselves. I also have the 5/8 and 3/4 tap tube for suspension bits. It's come in very handy over the years. Cary

I can't say I can end this debate but I weighed a 280 motor (can't remember if it had a flywheel and clutch or not) but had most everything else. It was very close to 500 lbs (~227 Kg). I also had acess to a normal SR20 (not turbo) and that engine weighed 325 lbs (~147 Kg) and I can't remember if that had a flywheel and clutch either. Hope that helps, Cary

Does it bind from being too short? That's what I'm guessing. I'm also guessing that it's a lot easier to tell when it binds with your new setup. Cary

So when this all started did you think you'd be building a trans-am car Cary

If you were to run the car in a way that you actually used the bumpstops as a tuning tool then I'd look into the late model VW stuff, which is pretty trick. It sounds like you'll only use them to keep the insert from self destructing and poly should be fine. When I went a lot stiffer with springs I quit touching the bumpstops and now I only have them in place to save the inserts. I shortenned mine up a bunch and if I were to hit them it would probably feel like they were solid steel. Cary

Most of the race shops sell them. They aren't that hard to make if you have access to thin plastic sheeting. Truchoice has them in their catalog but they are very proud of them. C

A packer is usually a small plastic bit you put around the shock shaft to change the spacing to the bumpstop. It looks like a C. The idea being if you couldn't find longer bumpstops you could use these as spacers. You can insert them through the springs with needle nose pliers to adjust when you hit the bumpstops. And speaking of bumpstops are you using something like the VW soft foam versions? Cary

What about using packers? Cary

Yep, and he's a bastard! Cary

I think Vic's car was fast because he was the first guy to start playing with some stiffer rates and getting them to work. Locally we have a number of Zs that have copied this (including the red one in your earlier pic, which belongs to Dave Kipperman) and they have all responded very well. Before we started doing this we all got beat by Miatas, vettes, RX-7s, etc. You'll also notice Vic doesn't have any bumpsteer spacers and appears to be using an EVIL underground front RC, which I have found to work very well for me in autox. What isn't mentioned is when you hook the sway bar to the strut it acts like it is larger because of the reduced motion ratio. I think you'll find a 7/8 about equivalent to a 1 inch bar in the normal locations. Cary

This should work fine. I agree you really want the lever on the sway bar to be at a 90 to the linkage that goes to the lower control arm. In your previous example the bar looked to have a falling rate. In the past I've made a few adjustable bars like this by grinding a falt along one side of the bar and then placing the 1/4 plate on this and welding along the edges and a few plug welds too. You can put build all the anlges you need into the plate. I hope that makes sense, or you'll force me to make some poor drawings too Cary

You'll also be adding dive if you drop the front location down. Cary