tube80z

Why don't you do what a lot of racers do. Convert the struts into uprights and make a top and bottom a-arm. May not be as good as a dedicated piece but you can use the stuff you already have. Unless you have nothing and then you're free to put what ever you want on the car. I'm with John on this. I don't know why you'd want to put Pinto pieces on your car and expect it to handle any better than a Pinto. To do this right you really need to design pieces to work with the rest of your car. Otherwise you end up with an expensive project that won't work any better than plain ol' struts. Cary

I thought VDP was velocity dependent pitson, learn something new everyday. I run the low buck ground control advance design shocks with custom valving. I would love to have been able to use Penskes or Ohlins T44s but they were well outside of my budget. Do you set those up with internal droop limiters? I'm currently running around just under a quarter inch in front and about one and a quarter in the back. Cary

Okay, I came to the game late. Is the 55/45 discussed above front to rear or rear to front? I was a little lost on that one. For what it's worth I ran at the Bogus Basin hillclimb with my car, which is L6 powered and 2 percent heavy with me in it to the rear. My first run up the hill was faster than any I've seen from previous results from Kim. While this doesn't mean anything it seems to be the argument that he uses for why rear weight isn't needed. Forward weight bias for hillclimbs is generall seen in Pikes Peak cars. If you look at the 4WD monsters this is how most of them are setup. I think it has to do with trying to get equall traction from the tires at a dynamic state. Not really something we'd see translate over to paved hillclimbing. Most of the fast EMOD cars autoxing are heavy to the rear. They do this to help with traction out of corners. They generally try and hit a 45 front to 55 rear target and work well. My tube frame car is built to try and hit this number and the back of the engine is 1.5 inches of the car centerline (completely behind the firewall with a 5.0 Ford). Good discussion though. It seems to validate my weird little view of the world. FP Z car using GT engine setback and little 13 inch wheels and tires. The only thing I saw missing here that relates to PMOI is gyroscopic forces from the rotating components. Which is why I think 16 inch wheels are wrong for an autox car. Cary

For the record that was the front roll center. I have never used a rear RC underground. I should also point out that my car was using 20 inch tall tires at the time. With the current 22 inchers the RC is actually above the ground. It seems to be a common notion that getting better camber compensation will solve a lot of problems with our cars. I have tried this numerous times and never seen the results it would indicate. What I have found is that you're better off not worrying about that and trying to keep the tire from laterally scrubbing. At least in my experience that did more for grip and overall driveability. If you can go with a longer link then you have a little more freedom to play with this. What ever you do in the back of a Z think really hard about making the outer strut pickups double shear. In the stock setup you can see a lot of flex that changes the toe setting. If you have an automatic car (stick would probably work too) try adusting your rearview mirror to watch the tire and powerbrake the car. What you see may surprise you. Instead of alternate holes make the design so that you mount it using spacers. This is a quick and easy way to make changes. Cary

The clevis is bolted down and is solid when tight. The difference is one bolt versus two on the stick TC rod. That can have a tolerance too, but when you tighten it it doesn't move around. I guess you forgot the rubber bushing that's usually at the end of all this that moves around a half inch or more. And even if you did install delrin or some other ball and socket option it will flex too. This is a proven and tested design, which in my opinion is a lot better than what Arizona Z offers.

650 was my upper limit. That would be 1.5 times the corner weigt on the EMOD car. To get there will require more development work on the shocks I think. Last year I ran 1 to 1.2 times the corner weight on the unibody car. Right now it has 400 lb springs all around from an event we ran late last year where it was cold. Cary

The weak link is on purpose. This is what lets the motor exit out the bottom of you really stuff the car. Welding in the crossmember will make the front a lot stiffer but if you get in a serious accident the motor will be coming through the firewall. It's your choice. Cary

I think it depends on what you do with your car. John had good info below on what he did on an actual racing course versus what I do in SOLO II. The tube frame car will have an underground front roll center too. But the 1 inch below ground RC is on my unibody Z car. It has a cage that ties into the stuts. When I got the car it had above ground front roll center and some weird spring choices. It was fast but was hard to drive. I gave up trying to make a three wheeler work and decided to try some advice I'd seen on the FF underground about using spring rates that were some portion of corner rate. I started with 400 lb springs, AD inserts, and GC camber plates. The rest of the suspension is monoballs in front and the delrin bushings in the rear, altough I want to change that to monoballs too. Front roll bar is 15/16 and rear is 5/8. Nothing too out of the ordinary. I guess I do have one thing that is a little different. I droop limit the front suspension, which has a major effect on the roll center. I have tried up to 600 lb springs on this car and it seemed like a good direction to go. Part of the problem is I can't lower the car enough to isolate for the spring change to say that's exactly what it is (I'm assuming people know that you have to change ride height to isolate spring changes). A lot of this will depend on tires too as you have to take into account their spring rate to determine the actual wheel rate. The one thing I do a lot of is change chassis rake to balance the car. And this does change the roll couple. So I agree that it has a major influence on your car. So we are in definite agreement that this is a key tuning tool. I just happen to play in a different speed range with my toy. Hence my advice is for SOLO II. I'm just offering it as something to think about. So what are normal Z spring rates these days? Cary "who only wishes he could afford to play on real tracks"

Good info. For what's it worth my car rarely gets over 80 MPH and never in a corner. At most course I run the average apex speed is 45 MPH or less. Which may be why I like this. Cary

Okay, I was a little harsh on that one. But you can get all this for a lot less in other books. It's still a good one to have but it doesn't need to be one of the first purchased. Cary

Lengthening the control arms is a good thing. Remember the TC rods and tie-rods too. Cary

I think Race Car Vehicle Dynamics is a great book, but it really doesn't tell you anything about struts other than give you basic definitions and tell you they suck. Before I bought that I'd look at some more basic books like Staniforth's Race and Rally sourcebook or Haney's book on tires. Those at least have some useful info for the DIYer trying to make their car go faster. Cary

The reply on RCs had a lot of good info in it. I think you can't go wrong with that advice. Some other rules of thumb to help you set things up: Scrub -- no more than 20 percent wheel width or tire width (which ever is bigger). For a ten inch wheel that's 2 inches (and ideally you want less). Caster -- one half the measured steering axis inclination trail -- around 3/4 to half an inch RC lateral migration (20 percent of track width) Vertical migration -- make sure it doesn't cross ground level in any real world condition. If this happens in a corner the car will momentarily lose traction. This often feels like a sideways hop and can be very unnerving. In general you want to run an RC that is close to the ground with the front slightly lower than the rear. Low is somewhere in the neighborhood of less than 5 inches off the ground. It depends a lot on the rest of your setup. High RCs will lead to large jacking forces, which is like a big lever trying to turn the car over as you enter a corner. They manifest themselves as a lifting that increases with corner force. Old triumphs, volkswagens, and corvairs had swing axles that were notorious for this. Just remember that everything is interconnected to the strut on these cars. You can't make on thing perfect without really screwing something else up. It's all a matter of coming up with the best compromise. Good luck, Cary

There's some good advice from John. I would also recommend that whenever you do this you spray weldthru (3M product) on the area to be welded. This is a very important step in making sure you keep rust away. One good point about seem welding that hasn't been mentioned is that if you ever wreck you car it is much easier to pull the parts back out. If you have simple spot welds they will often pop when you try and do this. I would recommend seam welding on any car the will see a V8 or hard use. Many times the spot welds will not all be holding on our older cars. This helps to ensure that the panels are all glued together. Cary

I have the GC AD inserts and I'nm generally happy with them. The bump adjuster as three positions but it makes little difference which position you use. There's just not much adjustment. The rebound is very adjustable and this what I spend the most time messing with. Given your location I would recommend a set of Konis or similar with the digressive valving. I think being able to get parts in a timely manner would be very good. A local shock expert told me that Koni's would have been cheaper than what I paid for the AD inserts but provided no real details. So you have a lukewarm recommendation from me. They do work, there's little bump adjustment, and parts are hard to get if you need them. otherwise they do work well and will allow you to run proper spring rates for a racing Z. Cary

Actually you want the control arms to be very near level to work best. This will help to reduce the jacking forces and scrub the tires less. If you want to adjust camber it's best to add it statically as you can't really get much back from the suspension without compromising other items worse. Cary