If you're removing springs, working with the shock removed from the vehicle (i.e. with no weight on the springs) before you begin you must relieve any force on the springs. In a triple-rate setup with helper coil you can just slide the springs away from the lower spring seat by hand to remove any pressure on the lower spring seat. In a dual-rate setup you will have to either compress the springs slightly with a coil compressor, or raise the position of the upper spring seat, so that the coils don't apply any pressure to the lower spring seat.

Whether installing springs on the shock for the first time or removing springs, begin by tapping the lower spring seat towards the shock tube in order to dislodge it.

It helps if the shock is pressurized (which it would normally be) so that the gas charge acting on the rod provides some resistance.

To install the springs, gather together:

• the tender coil (at left in pic)
• the dual-rate slider (centre)
• the main coil (at right)
• the lower spring seat
• the O-ring; and
• the snap ring

Assemble the tender coil, dual-rate slider, and main coil, as shown at left.

Ensure the tender coil is on the top, followed by the dual-rate slider with the longer portion inside the tender spring, followed by the main spring on the bottom.

The springs should be installed so that the labelling on the spring can be read - i.e. with letter and numbers right-side up.

Align the bottom end of the tender coil and the top end of the main coil on the dual-rate slider such that the very ends of the springs are 180 degrees opposite oneanother. This helps the springs sit flat and helps to reduce the amount the dual-rate slider rubs the shock body during spring travel.

This is because the triple-rate slider that fits between the helper coil and the tender coil cannot slide over the stop ring, its inside diameter is too small to allow it to do so. In addition, the stop ring cannot be removed from the lower (rod-end) of the shock, because the threads on the cylinder do not extend all the way down, and the diameter of the cylinder is larger than the minor diameter of the threads.

The result is, the triple-rate slider can neither be removed from, nor installed on, the shock from the lower end. It must me installed or removed from the top. This means the remote reservoir hose must be disconnected, and therefore the shock must be bled after the helper coil has been installed.

The final assembly should look like this.

Before the main and tender coils can be installed and the shock used, however, it must be bled to remove any air that entered when the remote reservoir hose was disconnected.

The bleeding procedure is outlined below.

Thoroughly clean the entire shock so that no debris falls inside during the process.

Clamp the shock in a vice with the rod-end facing up. It is best to use a vice with soft jaws made from plastic or aluminum or the like. Alternatively, you can place a rag or even a piece of cardboard between the jaws of the vice and the shock body.

Remove the Allen-head set-screw from the bearing cap and set it aside.

Using an appropriate tool, loosen the bearing cap.

Note: This is NOT an appropriate tool - but it was lying around handy!

In all seriousness, many of the parts are aluminum and care should be taken not to damage them.

Unscrew the bearing cap from the bearing assembly and slide it up the rod. The wiper seal will hold it in place out of the way.

The bearing cap is sometimes also known as the "dust cap" or "cylinder end cap".

Bring the rod almost to full extension to minimize the chance of oil spillage when you remove it.

Push down on the bearing assembly to expose the snap ring.

Nomenclature of the piston-end of the rod and piston assembly.

The rod spacers (aka shaft spacers) serve to limit the extension of the rod which in turn limits the side force on the piston when the shock is at full extension. By preventing the rod from completely extending, they ensure the rod is supported between the bearing assembly and the piston. Without them, the extended shock could easily apply an excessive amount of leverage against the piston, causing damage to the piston from the resulting side load.

Do not try to create a longer travel shock by removing the rod spacers - buy a longer shock if required.

The black extension-washer located between the piston and rod spacers is also sometimes known as the "extension-stop" or "stop-washer". It is designed to prevent contact between the compression valve stack or piston and the rod spacers. Its purpose is to prevent damage to the valve discs or piston when the shock reaches full extension.

Press down on the remote reservoir end cap, the one with the Schrader valve, until the snap ring is exposed.

Remove the snap ring.

You will now be able to see the internal floating piston (IFP) or "divider" in the remote reservoir.

There should be no oil visible in the reservoir on this side of the IFP, as this is the gas side that holds the nitrogen charge. If oil is present, you will need to replace the seal on the IFP.

To begin the bleeding process, orient the shock and reservoir so that the reservoir is below the level of the oil in the shock tube.

Using a soft tool (here I am using a hammer handle), set the depth of the IFP by pushing it into the reservoir.

Each brand & model of shock will have its own precise specification for the appropriate depth of the IFP in the reservoir. Consult your shocks documentation of contact the manufacturer for the exact number. The exact spec is important as the position of the IFP determines both the amount of oil in the shock and the appropriate volume and pressure of the nitrogen charge.

If there is too little oil in the shock the shock can overheat and the IFP and nitrogen charge will not be able to do their job properly, leaving the shock susceptible to cavitation, foaming, and fade.

If there is too much oil in the shock, premature seal failure will occur when the oil heats and expands, and in some cases the shock can hydro lock (just like an engine with water in the cylinders), severely damaging the shock.

I simply marked the hammer handle so that I would know how far I had pushed in the IFP.

On a Fox 2.0" series shock, push the IFP approximately 3/4 of the way into the reservoir (8" in for an 11" long reservoir, 6" in for an 8" reservoir).

As the reservoir is (or should be) below the oil level in the shock tube, this will also force any air out of the reservoir.

If you push the IFP too far into the reservoir, you can usually retrieve it by reaching in with some long needle-nose pliers, grasping the centre piece, and pulling it back.

Here it is shown having been fully retracted to show the centre piece that you can grab with the pliers.

Be careful not to scratch the the reservoir walls with any tools.

With the IFP at the proper depth, top the shock off with the appropriate oil (in my case, Fox 5wt shock oil) to about 2" from the open end of the tube.

Carefully re-insert the rod and piston, making sure the teflon wear band is in place and not lying in a pile of metal filings under the bench (don't ask!)

To bleed the shock, gently stroke the piston up and down in the tube until no more air bubbles are present.

As you stroke, carefully rotate the rod to help dislodge any air bubbles from under the wear band.

Proceed with care and patience, as hammering the piston up and down can create more bubbles than it removes.

In addition, if you pump the piston too quickly you will force oil through the hose and into the remote reservoir, where, because the reservoir is uncharged, it will move the IFP out of position. If this happens, re-set the position of the IFP and begin again.

Once no more bubbles are present, check and re-set as necessary the position of the IFP in the reservoir.

Carefully top off the oil in the tube to within a 1/4" of the open end (don't pour it from a height and aerate the oil as you do so).

Gently lower the bearing assembly into place in the tube. As you do so, any remaining air and a little oil will be forced through the bleed hole in the bearing assembly.

You may loose half an ounce of oil or so as you insert the bearing assembly, this is ok.

If you're working on a shock without a bleed-hole in the bearing assembly, you can bleed the final bit of air as follows:

• Retract the IFP an inch or so and top off the shock with oil to within a 1/4" of the open end.
• insert the bearing assembly until just before the O-ring makes a seal.
• While you hold the bearing assembly in this position, have an a assistant carefully push on the IFP in the reservoir, forcing the oil, and any air on top of the oil, up past the O-ring.
• Once that is done, have the assistant set the depth of the IFP and hold it as the proper depth as you press the bearing assembly into place.

Depress the bearing far enough into the tube so that the snap ring can be re-installed.

Re-install the snap ring, making sure it is fully seated in its groove. This is very important as this snap ring holds the whole shock together.

You can easily install the snap ring using just your fingers, but I didn't snap a pic of that so I'm cheating and recycling the disassembly pic from above (Jeez, some of you guys have a sharp eye for details!)

Lube the reservoir end-cap O-ring with a little oil.

Re-install the reservoir end-cap and depress it into the reservoir far enough so that the snap ring can be re-installed.

Re-install the snap ring.

Fully compress the shock by pressing down on the rod-end until the piston reaches full travel. This will seat the remote reservoir end cap against its snap ring with a pop or snap sound. If you hear a crackle, it may be Rice Krispies - do not be fooled - check that the end-cap is seated!

Before you pressurize the shock, cycle the shock a few times by hand to make sure you have bled all the air out. If there are any air pockets, you will feel them as a sudden drop in resistance as you compress the shock. Also check that the shock compresses fully - if not, it may by hydro locking, indicating that there is too much oil in the shock (i.e. IFP was not at proper depth when shock topped off). If this is the case you will have to disassemble the shock, remove some oil, and begin again.

You will need a nitrogen tank, like the one pictured at left. They are available from welding gas suppliers.

DO NOT use air or CO2 or any other gas. Nitrogen is specifically used due to its thermal stability and the fact that its non-hygroscopic. That means it doesn't contain moisture (water vapour) like air and it doesn't expand and contract with temperature as much as other gasses. This is important because moisture inside the shock can cause corrosion, and excessive expansion of the gas will change the pressure of the gas and therefore alter the shocks performance as it heats up and cools down - which we want to avoid.

If you're assembling your own nitrogen charging setup, be sure to also use a high-pressure hose and not some flimsy plastic hose, as the pressure in the tank can be upwards of 2000 psi. I used a 2-wire hydraulic hose.

Of course, you will use the regulator to adjust the working pressure down and not be blasting the shock, or anything else, with 2000psi nitrogen!

Charge the remote reservoir to 200 psi. You can vary this pressure + / - 50 psi later, during shock tuning, to make very small changes in effective spring rate, but it is wise to only try this after you have tuned in your spring rates and shock valving.

If you do not have the means to charge your own shocks, many ofroad, motorcycle or snowmobile shops can do it for you. Take the shocks to them for this procedure, do not drive the vehicle with uncharged reservoirs.

Note: The following six pictures, courtesy of Dan Dibble, show a 2.5" shock as opposed to the 2.0" shock illustrated in the rest of the article.

From left to right: Locknut, piston & valve stacks, extension-washer, rod spacers, bearing assembly.

(photo courtesy of Dan Dibble)

Piston with locknut and rebound valving discs removed.

The discs, or washers, come in different diameters and thicknesses. A particular combination of discs is called a valve stack or shim stack. As the shock strokes through the oil, depending on the direction of travel, the oil passes throgh the appropriate orifices and then reaches the shim stack. The shim stack must then flex and "open" to allow the oil to pass out the other side of the orifices in the piston. By varying the number, diameter, and thickness of the discs in the shim stack, the pressure at which the stack flexes and opens to allow oil to pass is varied, and thus the shock damping is varied.

(photo courtesy of Dan Dibble)

Compression valving discs in place against back-side of piston. Note the rebound orifices not covered by the compression shim stack.

In a Fox shock, a particular shim stack is identified by a number that ranges from 30 to 120, depending on the diameter of the shock. The higher the number, the more damping force the shock will have.

For a 2.0" Series Fox shock, both compression and rebound shim stacks are adjustable from 35 to 90 in increments of 5.

(photo courtesy of Dan Dibble)

Compression valving discs and piston. Note the compression valving orifices now visible that are normally completely covered by the compression shim stack.

Note: rod side of piston -> compression discs -> innermost orifices are compression orifices.

For a 2.5" Series Fox shock, compression is adjustable from 30 to 120 in increments of 5, and rebound is adjustable from 30 to 105 in increments of 5.

We shall examine re-valving in detail in a later episode.

(photo courtesy of Dan Dibble)

In a Fox shock, the damping number is engraved on the rod-end of the shock, just under the rubber snubber. The first number identifies the compression shim stack, the second number the rebound shim stack. Thus 75 / 80 shown in the pic at left, signifies that this shock is currently valved at 75 compression, 80 rebound. The number is a relative number and not a particular unit.

Here we can also see that Dan has been busy tuning his shocks and experimenting with different valving, and each time he makes a change he engraves it on the shock.

If you have a Fox 2.0 coilover shock and there is nothing engraved on it, the shock has been built with the "standard" 40 / 60 valving.

(photo courtesy of Dan Dibble)

To give yourself some room to work, slide the springs towards the top of the shock a little and temporarily retain them there.

I found a soft-jawed clamp works well. Do not use any kind of metal clamp on the shock shaft. Alternatively you could tie the springs up.

I've used Eibach springs for many years with great success and have always been very impressed with them.  In fact, in terms of value and quality I don't think you can buy a better coilover spring.

They are also available in a huge variety of rates, diameters, and lengths  - as far as I know more than any other brand. All of which are listed, along with all the other necessary specs, in the excellent Eibach Racing Springs Catalogue.

They have a simple and very useful 11 digit part-numbering scheme that is clearly marked on the spring.

The part number is also marked on the box in which each spring comes. The decode is as follows:

• The first four digits identify the free length in inches, tenths, and hundredths.
• The next 3 digits identify the inside diameter in inches, tenths, and hundredths.
• The last four digits identify the spring rate in pounds per inch.

This spring in this box is a 14" long, 2.5" ID, 300 lbs/in coilover coil spring.

(if you enlarge the photo at left, you will see there's a typo on the box where the fine print actually states that the spring is 1400.00 inches long - but that's silly - it's almost 39 yards - it wouldn't fit in the box!)

When installing the new springs on the shock, make sure to do so in the correct order, with the springs and dual-rate slider the right way up.

The springs should be installed so that the labelling on the spring can be read - i.e. with letter and numbers right-side up. The DRS should be installed with the longer part up. The tender (top) coil goes on first, followed by the DRS, and then the main (lower) coil.

Align the bottom end of the tender coil and the top end of the main coil on the dual-rate slider such that the very ends of the springs are 180 degrees opposite oneanother. This helps the springs sit flat and helps to reduce the amount the dual-rate slider rubs the shock body during spring travel.

With the shock and springs re-assembled, we come to the worst part of the procedure  - fishing the little misalignment spacers back either side of the the rod-end and between the shock mounting tabs, while keeping them aligned with the holes in the spherical bearing and the mounting tabs.

An extra pair of hands, or patience, is extremely helpful.

If you find yourself working with neither, as I frequently do, I have found that beer helps.

What I wouldn't give for a shock with spherical bearings with integrated misalignment spacers...or more beer!

Once you do get the little devils in place and lined up, reinsert the mounting bolt and torque to spec with a locking nut or thread locker.

Repeat as necessary to get the perfect balance of ride and handling.