Things are getting serious. Chassis/Suspension

The second I started hacking off sheet metal on the Z, I was confident I could tackle building this car. I feel like I’m a pretty good mechanic. I have a saying that I often use “It’s just nuts and bolts” and I applied that same mind-set to the cage work, “It’s just metal.”. Basically, don’t over think it. I did extensive research on tube chassis builds, materials to use, and I read the FIA, Global Time Attack and Pikes Peak cage/chassis portion of the rule book a hundred times. Like I mentioned, I’d never built anything to this caliber but I felt confident. Remember, “It’s just metal”. Very expensive metal… So don’t $%*& it up!

So I called my local metal yard. After I freaked out on the cost of 4 22′ sticks (not nearly enough) of 1.75″ .120 wall DOM steel, I place the order and a few days later the metal showed up. I built my front frame rails and bolted on the front 240SX (S13) front crossmember. I took all of my mock-up measurements from my temporary OEM 240SX shock towers and started bending away on my new Protools 105 HD tube bender that I converted to air over hydraulic.


I want to talk about a tool that made a lot of tricky cuts and coping cuts a breeze. It’s called a Pipe Master. It allows you to figure out your coping cuts without a bunch of eye balled cuts and grinding. Simply push the needle rods around your tube contour, then slide the Pipe Master over the tube that you want to cope and trace the profile. Click the link and watch the video. If your going to do cage work it’s an inexpensive tool you gotta have. PIPE MASTER


Once I had the front frame rails and front tube work tacked together, I moved to the “Main Hoop”. This is the back bone of the cage. The FIA rules state that you cannot bend the main hoop more than 180 degrees total, cannot use more than 4 bends, and have to use a single piece of tube. 240Z’s are pretty small. I had to have the main hoop VERY tight to the body to make sure I have as much room as possible.


I was really happy with the main hoop and that I got it right in one shot! I moved to the “front hoops” next. These are the tube that run along the roof line and down the “A” pillars. Once the front hoops were tacked in place I added the windshield/roof bar and added gusset bars to triangulate the front hoops and windshield bar. Although it’s not a requirement at Pikes Peak and Global Time Attack, I took it a step further and added “FIA” bars. The bars add a tremendous amount of strength to the cage in the event of a roll over.


Up to this point, the body of the car had not come off the jig. It was pretty exciting to take it off. I called my good buddy Mike, who has been helping me with the car when he can, to come over and give me a hand taking the body off. Come to find out that this would be something we did a lot in the months to come. After staring at my creation for hours, I added the dash bar and tied the front tube work to the front hoops. I felt like at that moment it was really starting to come together.


I then moved my attention to the rear of the car. I had a lot of fun building the rear shock towers.



You can see in the photo below that the chassis was really starting to come together. The door sill, harness, diagonal, roof, and rear down bars were also checked off the list.  I was really close to having the car sit on its own weight. I was nearing a mile stone.


I’m sure you noticed suspension parts popping up throughout the chassis build and I wanted to talk a little more about that. Im always looking for a deal and I stumbled across someone on Craig’s List selling a brand new set of BC Racing coilovers with Swift springs and a full set of ISR tension, traction, toe, and camber arms for sale. I picked up all of the parts for a killer deal and then powder coated the arms my signature orange.

While I was mocking up the front suspension I needed to make some tension arm mounts on the frame. I made a quick cardboard cutout and then had a friend scan them, turning them into digital drawings, and then lasered them out of cardboard stock. I wanted to make sure the fit was perfect before I had them lasered out of steel. Once I had metal parts, I dimple died them, and welded them. image1[1].JPGIMG_3561.jpg

I set the cars caster for a race set up. The coilovers provide camber adjustment, but not caster. Caster is often overlooked, but this dictates how the car feels when dipping into corners and straight line stability. So I took down some measurements and lasered a shock mount template out of cardboard stock. Once I dialed in the fitment, I lasered the mounts out of steel. Now I’m able to fine tune my caster.


A rear shot showing off the GK Tech Lower control arms and BC Racing coilovers.


The factory front lower control arms flex a lot under track abuse and they use rubber bushings to attach to the crossmember. That wasn’t going to work for me. I installed new Moog ball joints on the knuckle side and cut the bushing side off. I replaced the bushing side with a beefy adjustable heim joint. This provides very smooth rotation and allows about 10mm+/- of track width adjustment. While I was at it I boxed and dimple die the bottom.


For the rear knuckles I chose 300ZX (Z32) units. I believe it shed about 8lbs. per side over the steel 240SX knuckles. I cut off any unnecessary tabs and had them powder coated satin black. I wanted to eliminate any rubber bushing in the suspension if possible. SPL PARTS is the only company that makes spherical bearings for 300ZX knuckles. It’s probably one of the better suspension upgrades I’ve made. Such a huge difference in rotation over the rubber bushings that were causing a lot of stiction. I’m very honored to have teamed up with SPL Parts. image7.JPG

So there you have it. The car is starting to finally take shape. What’s going to power this track monster? I’ll cover the power plant and setting the car on the ground for the first time on the next post. Make sure you don’t miss a post and subscribe! Feel free to ask any questions. Thanks for the read.


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