clarkspeed

Jon, you just gave away every race engineer's secret! Just kidding, but that is where every great set up starts. Once your setup is in the ball park, test sweep the tire pressures and sweep the camber. Make large changes so you have an obvious change. Data collection helps if you are not a consistent driver. Maximizing the grip of the tire pays huge dividends. When a pro team buys a new car, they go to the track to test and run sweeps.

100% agree books are not going to help much if you already understand the concepts. My shelf is also heavy, I think I have the Costin book but not the Rally one from Roberts. My fallback has always been Puhn's How to Make Your Car Handle. It's an old one but i think it covers the basics well. Tuning a race car is not covered in any books that I know of. Someone will probably write it eventually or even post videos, but for now it is reserved for seminars and consulting (some online!). My advice is keep doing what you are doing. You have not gone off the tracks yet.

Hmmm, the perfect question for this forum. Gotta love that conversion. Reminds me when a guy ask me to recommend a clutch for his 1000HP 2JZ. There is just not a cheap solution for that. If you want to do it on the cheap, go with a live axle conversion. If you just want to do a lot of skinny tire smokey burnouts, you can probably keep the IRS with some upgrades. If you want to put that power down at a drag strip with sticky tires, and keep the IRS, you have a mountain to climb with every step built on a roll of cash.

5. 350 is not super heavy but probably a good place start. I forgot to mention grip level affects camber also. You will have a lot more body roll with super grippy EP cantilever slicks than with a 200TW street tire for example. Make sure you can get to 3 degrees, you may need it. 6. Yes the Futofab TC's look decent but I have never run them. I had some TTT TC's on another and they were solid for sure, and heavy as hell.

See, I told you it was a little complicated. Especially since 1 change affects many others. And add the fact there are multiple designs available to make the changes, and you end up with a post that is too long for me to sort out. Mostly all good advice above. I commend JHM for trying to put all that together! I am not going to endorse any supplier solutions since there are so many different designs out there. I have not had any beers tonight so I will try to simplify some of this: For the front suspension in my order of importance 1. A means to lower the car. Adjustable coilovers. Or the cheap garage solutions of cutting springs or lowering and rewelding the spring perches. If you do these remember front and rear are different. And unless you shorten the struts, you may run out of shock travel and bottom out. Rule of thumb is lower the car until something scrapes and then raise it back up a little. 2. Eliminating bump steer=high priority and needed on all race Z's. You are trying to make the control arm and tie rod operate in parallel. Must be estimated to be adjusted and there are some easy/cheap ways to do this. I use plywood on a piano hinge with 2 screws that touch the wheel. I adjust until no gap. Or you actually measure it with a nice tool and dial indicators. May be accomplished by spacers at the tie rod end or slotting/enlarging the inner control arm pivot hole in the cross member. It does not take much on either end, maybe 3/16" max and usually less. Slotting not legal in most classes, but an offset bearing is another option. Perhaps a bigger hole or smaller bolt? Tie rods with rod ends can be purchased and you can straight drill through steering knuckle. Or you can build one yourself by cutting off the end of a stock inner tie rod and welding it into some tubing. Thread adapter on the other end for the rod end. I prefer using Pinto bumpsteer kits with a tapered bolt rather than drilling out the knuckle. Be careful the bolt/spacers do not hit the wheel. 3. Roll center is important but not important. Most conventional setups will try to keep the RC just above ground which means the control arms are slightly pointed down toward the wheel. I posted a roll center calculator in the forum somewhere and it is accurate. But running the roll center below ground is also possible. I think the general rule is not letting the RC move through the ground plane during operation. And never run a high roll center (more than 4"), it puts much of the loading back into the chassis which is not a fast recipe. Roll center location is very dependent on wheel/tire diameter and lowering the car. There are a couple ways to move the roll center. Different wheel/tire and ride height as mentioned above. Also again slotting the cross member to raise inner control arm hole. A more common solution is to add a spacer between the ball joint/steering knuckle and strut body. There are various lengths available including offset ones. And you can weld 2 together for a longer solution. On the tube car I am building I put a bolt here and will use spacers similar to a bump steer kit combined with a spherical bearing as my ball joint. Either way, to change the control arm angle you either must relocate the inner pivot or the ball joint in relation to the chassis. 4. You will want to run as much track width as possible but will be limited by rules or fenders or geometry. Rear track does not need to equal front. More track with in front is a good thing. Longer or adjustable control arms or wheel spacers can work here. 5. Normally a means to adjust the camber is needed. Many solutions here also. If you lower the car just right and run bias ply tires, you can get away with nothing. Otherwise, depending on spring rates, you probably need between 0.5 and 3.5 degrees of camber adjustment. Bias tires 0.5-1.5 and radials 1.5 to 3.5. Softer the spring, more camber usually required to get a good tire contact patch under full G load. Camber can be adjusted by moving the upper strut bearing (camber plate) or extending the control arm. 6. A different solution for the T/C rod. Rubber bushings are not acceptable for road racing. They will make your butt tighten up on heavy braking. Poly is almost acceptable but still wallows a little under heavy braking and has lots of sticktion. The Delrin ball aluminum cup works well but the Delrin doesn't last long and will really scare you (and drivers near you!) under braking when it cracks up. A common solution is replacing the joint with a rod end. But most of these involve bolting a clevis into the pocket which moves the pivot point slightly outboard. I never liked that but it is better than nothing and you can add couple degrees of caster at the expense of pushing the wheel forward in the wheel well. Seems like I saw some vendor did this correctly but I can't remember which one. More caster is good, but if you push the limits and add lots of caster here be very careful of interference. 7. Weight. There are some cool control arm designs out there. Some of them weigh many pounds more than stock. I always ask myself, if the stock stamp steel stuff is plenty strong to race with, why do I need extra thick wall tubing to replace it with? It is not good to add 5 more lbs of unsprung weight. Some of the more popular vendors use very heavy designs because they are designing for street cars and extra safety. That's when building your own starts to look attractive. 8. Eliminating friction or "sticktion". Replacing the stock control arm inner bearing with a spherical bearing or purchase of a control arm with rod ends. 9. Steering knuckle - driver preference, some road racers shorten but not that many. Many autox'ers do but not all. That's all I can think of for now.

Shit gets complicated depending on diameter of your wheel/tire combo, spring rate (wheel travel), ride height and desired roll center.. I replied somewhat on my thread. But there is a lot more involved. Tube control arms dont solve for any of those challenges. For a race car, you want to run as low as you can with no bumpsteer. There are many ways to skin that cat. I can only recommend what I have used in the past depending on your diameter.

I keep a close eye on suspension anyway. I made them fairly tight so they need to loosen some. For front LCA's it depends on what you need. If you have camber plates you dont really need adjust at the arm. And I normally use a wheel spacer to adjust track. Personally I just pop a spherical bearing in a stock arm and slot the cross member vertically about 1/8-1/4 inch to adjust out bump steer. (You can cover that with a washer if needed!) The only reason I built for this car is I replaced the t/c mount with a rod end in the exact same location.

This is the body kit I have decided to build around. I had a full 5 piece IMSA GTU bubble fender wide body set and sold it when I found this G-nose based kit. I bought it off a guy in Tampa and I have no idea where it came from or how old it is. I have never seen another one like it. I came with 4 fenders, G-Nose, cowl induction hood, and whale tale spoiler. Not the best gel coat finish, but I can work with it. I like it because it widens the fenders out exactly 2 inches all the way around. Very subtle. No wasted drag. And I intend to run 15x10 wheels square, so perfect fit. I am convinced I can get some gains out of 15" wheels/tires as opposed to the 16x10 and 16x12 setups common for this type of build. They are mounted using 1/4 turn fasteners for fast removal. You can see a 15x9 inch wheel fit up.

Here are some details of my rear suspension redesign. My goals were using the modified rear control arms I already had and having an adjustable roll center in the rear. I never liked the idea of welding or bolting on another tube at the bottom of the strut to drop the outer pivot bolt lower. And my rear control arms had the restriction of the 1" tubing inner pivot. After a lot of thinking, I came up with these Delrin bearing holders that raise the inboard roll center about 0.7" . I can shim them down if I want to reduce it. Light weight, low friction. This also eliminates the big ass bolts with a fore/aft brace that keeps the bearings centered. I think I am going to change them to something a little beefier in the future. As you can see, raising the inner pivots quickly jams the control arm up into the tub. So I cut out some clearance holes and added another brace there.

At some point I built this rotisserie. It saved an unbelievable amount of time with this project.

Awesome update. I traded off my "street/track" Z for a race prep Z many years ago, got my license, and never looked back. Most fun you can have with your pants on and very addictive. No real allegiance to the Z car, just happen to have a lot of parts lying around and know how to work on them blindfolded. We had a little Toyota sports racer around for awhile and that was a blast too. I can attest it is much much much easier and cheaper to purchase a race car than to build one.

Lots of info on this forum on the doggone support. On other cars I have tied it into a bushing on the mustache bar studs. I WAS planning to run my R200 diff raised slightly to get level halfshafts after lowering and keep the u-joints. Another cheap, light, reliable, and effective solution. But now I am considering the Ford 8.8. I saw Tube80 post this control arm years ago and could not resist copying. Such a simple solution, but just a little heavier that stock. Something lighter than that formed steel stock arm that includes adjustment would be an accomplishment.

Here is my rear control arm design I lifted from this forum. Using the original arms saves much weight. You can also see where I raised the cross beam clearance and added support to the dog bone uprights.

I have been using these Mazda throttle body flanges for brake cooling ducts. I found them on amazon super cheap. They are cast aluminum and I just drill them to fit the holes for the OEM backing plates.

Wow I missed out on posts for the last couple days. Some interesting techniques I need to try out. I tend to use very thin sheet to fill body panels, sometimes even thinner than the Datsun panels. No gap, low heat, and typically a "pearl necklace" finish like you mentioned. Although I would never use that phrase. I always check the back side for overall good pen, but not every mm, grind to finish, and then thin bondo along with a backside coating. I rarely hammer the welds or shrink metal, just smallest negative profile I can attain (less than 1/8"). Small pinholes everywhere. But keep in mind, I build race cars, not show cars, so I'm not to concerned about getting an all metal flat finish like the guys do on TV. As long as I can duplicate the contour, no one will ever check it with a magnet. Race cars always stay indoors, and tend to be repainted often. I've never had a bondo crack or rust break through, without direct contact of course ,

And here is the driver's door. Car came with the door fully cut out and it was floppy. I have seen these wrinkle up on other race cars and God forbid if someone accidentally leans on it. Anyway the cage sits very close to the skin, so I got creative with a some bent sheet metal and 3/16 rod. It is as rigid as a complete door now. The upper hinge was milled out, but I ended up blasting out the lower hinge with my $400 plasma cutter. I added a 3D printed inside door handle. I can sell these if anyone is interested.

Maybe this gives a little sample of just how rusty this tub was. These are some of my repairs along with patches over previous repairs. Please don't comment on some of the poor welding. Many of the welds were not clean on the backside and these are not structural. If you notice, I cut out the entire storage box area. I have the weight savings written down somewhere if I can find it.

I measured my Sweet steering shaft. It looks like 28 collapsed and 34 extended. And that includes the steering wheel QD spline on the end. Like I mentioned, it is just a little on the long side . I would say 25 to 26 collapsed would be optimum. I also use a flat steering wheel. If you use a dished or deep dish steering wheel, take that into account.

Great job on developing this! I am considering for a road race build. But have a couple questions. Strength is not a concern for me since I can make it fine with an R180 and u-joint axles. But I like this option due to cheap parts availability and virtually unlimited ratios. Weight is a concern. A R180 is a little over 60lbs and an R200 is just over 70 dry. Best I can tell the Ford 8.8 is 65 in aluminum and 85 in iron. Does that sound right? If so that is a pretty simple trade off. Do you know how much your cradle and uprights weigh? The cradle is a weight adder, but it looks like the uprights could be a reduction. Thanks for your attention.

Not sure on the length, I can measure it next time I am at the shop. It is a little on the long side because I need to collapse it quite a bit when installed so it only leaves a couple inches of "crush" zone. I will also try to get an estimate of the weight. It is a solid steel rod. Greg's EP car is refined to a point. He spent probably 20 years developing it. He doesn't make any more major changes to it and uses a similar formula to build other cars for himself and customers. However it is surprising how much OEM stuff he uses and simple common off the shelf parts.

The car is mostly cage, it has very little rigidity left in the tub. Between the rust and everything I have already cut out, I am more worried about panels wrinkling up than providing any structure. That is one of the reasons I have not cut it out yet. The front pillars are already tied to the cage, and it is connected to the rear main hoop above the side window. Vibration is not normally an issue on a car car. You tend to rev right through it.

I am pushing the CG down as low as I can go. Exhaust exits side so no problem there. Flat bottom floor all the way. I think it will work ok. I have been staring at that damn cross member for months. Started to cut it out couple weeks ago and declined. Do you think it weighs enough to make a difference? Looking closely at it, it didnt look like that much metal. I am also staring at the drip rails.

Next up is the floor and interior structure. I never noticed before until I started building this thing that the floor bottom on a 240Z is actually lower than the rocker panels. This car only came with rocker panels, nothing more. When I got ready to try and locate driver stuff I quickly realized that I couldn't just run a flat panel across the bottom. Turns out I needed to drop the floor roughly 1-1/2". Again all measured to the FSM datum points. So that meant building a frame around the tub. I used fairly thin square tubing since I already had plenty of structure above it. Again you can see the square tubing running fore and aft that represents where the bottom of the floor should be in relation to the chassis points.

In the tube car I am running a used Sweet column I got off eBay. I'm not sure it is that much lighter than stock. But it is adjustable and mounted with sphericals. Do the fit checks with the actual seat you will use. Usually end up as far back and as far to the center as possible. Then it's a matter of getting the rake to your liking. You can drop the steering wheel down but taller drivers will then bitch. But be careful of blocking yourself from getting in and out of car. One thing I did after moving the seat to the right was add some spacers under the flange at the bulkhead and slot the u-bolt more to kick the steering wheel toward the right. That always felt better to me than not having it centered.

Thanks for the offer. Yes I plan on getting a small lathe maybe later this year. I am forever needing a special bushing or spacer. I just got my home built CNC mill running and it seems to cut 6061 aluminum very well. This thing is so cool and opens up another world for me. I will cut these top hats as one of my first projects on it. Check out The MPCNC website from V1 Engineering.