Suspension school · Progression & Volume

Brand Systems Compared: Fox, RockShox, Marzocchi

Blue spacers, grey tokens and clip-on rings, and the maximum counts that matter

Every brand's volume system does the same thing, but the parts, the fitting method and the limits differ. Knowing your own fork's factory count and maximum is the difference between a five-minute tune and a jammed air spring.

Fox: blue volume spacers

Fox uses blue plastic volume spacers that clip onto the underside of the air-side top cap and stack onto each other. They are chassis-specific, so 34, 36, 38 and 40 spacers are different parts and do not interchange. You remove the top cap with a cassette-style socket after releasing all air pressure.

The Fox 38 is the clearest example of counts varying by travel, because shorter-travel builds leave more room in the chamber.

• 38 standard, 160mm: ships with 3 spacers, maximum 6
• 38 standard, 170mm: ships with 2 spacers, maximum 5
• 38 standard, 180mm: ships with 1 spacer, maximum 4
• 38 E-Bike+, 160mm: ships with 4 spacers, maximum 6
• 38 E-Bike+, 170mm: ships with 3 spacers, maximum 5
• 38 E-Bike+, 180mm: ships with 2 spacers, maximum 4

Notice the pattern in the E-Bike+ versions. Fox fits one extra spacer from the factory at every travel, a quiet admission that a 20 to 27kg bike needs more end-stroke support out of the box. If you are setting up a standard 38 on an eMTB, that factory-plus-one is a sensible template to copy.

RockShox: grey Bottomless Tokens

RockShox uses grey Bottomless Tokens that thread into the air top cap, with additional tokens threading into each other to build a stack. The same grey token serves Pike, Lyrik, ZEB and their relatives. Fitting needs a socket on the top cap and, as always, full release of air pressure first.

Factory counts follow the same travel logic as Fox. A ZEB ships with 2 tokens at 160mm, 1 token at 170mm and 180mm, and none at 190mm. Maximum counts vary by model, travel and wheel size, and RockShox publishes them in its air, oil and token specification chart, so check the figure for your exact fork before buying a bag of tokens.

Marzocchi: clip-on spacers

Marzocchi, Fox's sibling brand, uses simple clip-on volume spacers. The dual-crown Bomber 58, rated for eMTB use and a common choice on heavy-duty builds, ships with 4 spacers fitted and accepts a maximum of 7. That generous factory count reflects the loads a long-travel gravity eMTB generates.

Thread-in vs clip-in

The practical difference shows up in the workshop. Threaded RockShox tokens cannot rattle loose or pop off, and the stack height is exact. Clip-on Fox and Marzocchi spacers are quicker to add and remove but must be seated firmly, because a loose spacer floating in an air chamber will damage the spring internals. Whichever system you have, cycle the fork gently and re-check sag after reassembly, and always pump back to your exact previous pressure rather than a guess.

Never exceed the maximum

Maximum counts exist because the air chamber must still have somewhere for the air to go at full travel. Stack past the limit and the fork can hydraulic against its own spring, spike violently, or physically jam short of full travel, and the pressures generated at bottom-out can exceed what the seals are designed to hold. If you are at the maximum and still bottoming harshly, the answer is more pressure, more compression damping, or a different spring system, and the ramp-chamber forks in the next article were built for exactly this rider.

• Release all air pressure before removing any top cap
• Count the spacers that come out and write the number down
• Change by one spacer at a time
• Re-inflate to your exact previous pressure, cycle the fork, re-check sag
• Check your model's published maximum, and never exceed it