Now you know that hydraulics run on pressure, but what you may not know is that hydraulic fluid isn’t compressible. That means it has no give, which equates to a pretty crappy ride. There are lots of solutions to this problem, however, which is what we’ll be talking about today.

Old school lowriders, hoppers, and custom guys can run coils. There are lots of different ways to do this, but I’ll explain the two basic ones.

Coil under

Remember in the cylinder section how I mentioned a cup? Here’s how it works:

In the front of a typical rear wheel drive vehicle right now, there’s a coil that mounts between your frame and your lower control arm. What juice guys do is drill a hole in the shock tower, right where the shock stud was, the diameter of the cylinder. Then the cylinder is slid up through the hole so that the collar catches on the inside of the shock tower. At the bottom of the ram, a cup is mounted. Then the coil is placed between the cup and the stock mounting location on the lower control arm.

If you were to do this with a stock coil at stock height, you’d have a lifted truck that lifts even higher. That’s why most people run either shorter coils or cut stock coils to compensate. You cut the coil to the height you want, and then you’re golden.

When hopping, the spring rebounds with the truck, and it gets some major power, with the weight of the motor adding to it. If you run a different weight spring, you can get higher.

If you want to do this the new-school way, relocate your stock shock off to the side of your lower control arm, just like you would with airbags. This way you have a cut coil ride, which is better than most other setups.

Coil over

Coil over is just that — the coil is now over the cylinder.

Since there’s a collar at the bottom of the cylinder, that means there’s a place for the coil to mount. You can buy a piece of steel called a donut — it’s essentially a big washer that fits over the cylinder, but not over the collar. It provides a mounting place for the coil. The top of the coil is held in place by your upper mount, which is in the frame. Most examples of coil over are in the rear. You make a bridge that the cylinder mounts in. The top of the cylinder comes up through a hole, and the coil is in between the cylinder’s collar and the frame.

The downside is that the cylinder now moves, and moves a lot. That usually puts metal to metal, which means it’ll wear the outside of the cylinder against the frame. That rounds out holes and causes problems with the cylinder ballooning from a weak point. Coil under is neat, but it squeaks, and that’s irritating.

Accumulators

Accumulators are godsends.

Since a cylinder is a piston, it can travel up and down inside of the casing however it wants to. In a normal setup though, the pressure keeps it in one place. This is where accumulators come in.

An accumulator is placed in the system after the dump and before the cylinder. It has a piston inside of it, and a nitrogen-charged balloon. When the cylinder is compressed, it pushes fluid into the accumulator. The accumulator’s piston pushes into the balloon and rebounds off of it. The accumulator is essentially a shock absorber for hydraulics.

There are many different types of accumulators, but the most common are the little grenade-looking ones.

Your ride is purely based on the ratios between fluid moved, amount of travel, and pressure in the balloon.

Tired of us yet? Wait, there’s still more: part 10, putting it all into practice.

This entry was posted on Monday, February 11th, 2008 at 12:07 pm and is filed under Custom Ride. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.