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Pan Car Build: Part 2

This is part two of our series of articles that demonstrate how to properly build a pan car to get the most out of the chassis. This time we're going to finish up the chassis by building the shocks and front end.

First, we're going to look at the side shocks. Lately, I've seen a few pan cars running different length side shocks. While the pod may still have some movement, it's not how the car is designed. On our example car, you can see the the two shocks suffered from this problem.
If your car's manual doesn't give a specified length for building the side shocks, you can get them in the ball-park using this method. First, extend the shocks all of the way out and use calipers to measure between the bottom of the shock and the top of the spring perch. This is the shock's stroke measurement. Since I'm using el-cheapo calipers from Harbor Freight, I'm just going to round our measurement out to 8mm.
Next, set your car on a flat surface and measure the distance between the centers of the two ball studs that the shocks mount to. Again, since I'm using cheap calipers, I'm just going to round to the closest number, which in this case would be 68mm.
Since the side shocks need to compress as well as extend, we're going to aim for the center of the total stroke, which is 4mm. We add 4mm to the total distance between the mounting points, which gives us a total measurement of 72mm from center to center on the shock's ball cups. You may need to trim a ball cup to get the correct length on your shocks, but the measurement between both shocks needs to be the same. On our car, using a pair of uncut Associated heavy duty ball cups came out almost perfect.
Our shocks are now the correct length, so we can take them apart and start rebuilding them.
Check your shock shafts to make sure that they aren't bent. If they're fine, go ahead and chuck them up in a drill or Dremel and polish them using the metal polish that you used for the t-bar balls.
When filling up the shock, only fill it to just a bit above the groove on the inside of the shock body. Make sure that you let any air bubbles rise up and out of the shock oil before continuing.
One important note about building pan car micro shocks - replace the seals every time you rebuild the shocks! The photo on the left shows what happens to the seals in these shocks after use. You can see that the used seals on the top have swollen after soaking up silicone oil from the shock. This can cause the shocks to feel sticky, and can also make them harder to reassemble correctly. Shock seals are cheap and are something that should be replaced instead of reused.
Follow the instructions for reassembling/bleeding the side shocks, and you should be left with two perfectly setup shocks that are the same length.
A good starting setup for the truck class is an Associated gold spring (12lb.) on the right side, and an Associated red spring (14lb.) on the left side.
For the center shock, make sure that you move the shaft up and down slowly after filling the shock with oil to let any trapped air escape from under the piston. Let all of the air bubbles rise up and leave the oil.
Place the bladder on top of the shock oil and press it down flat. Let any excess oil drain out from around the sides of the bladder.
For shocks that have a two-piece cap, set the plastic part (center) of the cap on top of the bladder and make sure everything lines up flat.
Screw the outer part of the cap on, and your center shock should be ready to go.
After putting the center shock back onto the chassis, check the rear pod for droop. In the photo on the left, you can see that our pod is pretty much level with the chassis (no droop). This will cause the car to bounce a bit and lose traction on bumpy tracks as the pod can't drop down to stay in contact with the track surface.
To adjust pod droop, you can lengthen the center shock by unscrewing the lower ball cup.
Now our pod has a slight amount of droop, which should help it out through the bumps on the track. Note: after you add droop, you'll need to increase the tension on the center shock spring to get your chassis back up to the correct right height. We'll cover that in better detail when we setup the suspension in a later article.
We're halfway finished with our chassis. The rear end should be clean, smooth, and tight. Slop free, but with no binding anywhere. Little details pay big in oval racing, so take your time and make sure everything is right.
The standard pan car front end. Just slap everything together and bolt it on the chassis. (Kidding!)
Just like with the differential, one of the most important parts to a good front end is keeping it clean. Dirt, carpet fuzz, and tire foam can all cause a front end to bind up. I've pulled my hair out trying to get a car to handle correctly only to find that cleaning the front end fixed everything. We're going to start out by disassembling the front end and go through each part to make sure that it's working at it's best.
First, we're going to look at the steering blocks. Take your 1/8" reamer and run it through the kingpin hole a few times.
Next, look at the tops of the steering blocks. Sometimes the blocks can bind up on the upper arm eyelets when running high amounts of camber (2°+), so some racers trim the blocks for clearance. The block on the right has been trimmed. We're going to go ahead and trim the other block just in case.
While we have the upper arms off, I want to point out that these parts are left/right specific, even though they don't look like it. The dots on the arm are the bottom of the arm.
Also, the upper eyelet is directional. The offset should be up, and the rounded edge of the eyelet should face down.
Now to make the front end butter smooth. This is where most of your binding is going to come from. Take a look at the hinge pins and kingpins in the left photo. They shouldn't look like this...ever. Before you spend your time polishing them, roll them across your flat surface to make sure that they're straight with no wobble. If a pin has any bend at all (wobbles), replace it.
Dremel/drill time. Chuck them up, and put a shine on them. You want to be able to see your reflection in the pins.
Original pins on the left, polished pins on the right. Much better.
Check the pivot balls in your lower arms and upper eyelets. If they feel tight, pop them in and out of the arms/eyelets a few times to free them up. Also, make sure that both the balls and sockets are as clean as possible. Motor spray and some Q-tips work for cleaning up the sockets.
While we're working on the pivot balls, let's talk about types of pivot balls, and where they should be used. I almost always run plastic or delrin pivot balls in the lower arms. If you want to run aluminum or steel balls, that's totally up to you, but you'll be polishing your kingpins much more often if you do. They're fine in the upper eyelets, but for the lower arms using a plastic ball will keep the suspension smoother for a longer period.
After snapping the pivot balls back into their sockets (be sure to check the orientation- the "step" faces the steering blocks) using our your pivot ball tool, take the 1/8" reamer and run it through both the upper and lower pivot balls at the same time. I run mine in a Dremel/drill at low speed and work it up and down through both pivot balls until it moves freely.
Reassemble your kingpins/springs and shim them according to whatever setup you're planning on running. Some folks also polish their front axles. Personally, I don't waste my time doing this on my own cars, because the bearings should turn by themselves, not spin on the axles like a bushing. I did give these a slight hand polish just to make them look pretty for the photo.
Our front suspension is now finished. Notice that the caster/camber gain settings on the two sides are very different from before. This chassis is meant to turn left, so your setup isn't going to be symmetrical.
Our front end is bolted back onto the chassis, which completes the chassis itself. All that's left is to install the electronics, tires, and setup the rest of the suspension. (camber, ride height, etc..) We'll cover setup in the final part of our series.

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