Understanding the split helps avoid fixing one problem while creating another.
Different jobs in the fork
The base valve meters oil displaced through the cartridge at the bottom of the fork, while the mid valve rides on the damping piston and adds support as the fork moves through the stroke. Changing one side without considering the other can make the fork dive, spike or lose grip.
Tune the balance
A stronger mid valve can improve hold-up and braking support, but it needs enough base-valve flow and bleed to stay compliant. A softer mid valve may feel plush initially yet rely too heavily on the base valve for control.
Workshop checklist
- Identify whether the complaint is initial harshness, mid-stroke dive or end-stroke control.
- Inspect piston ports, bleed paths and shim condition before changing stack stiffness.
- Compare base-valve and mid-valve changes together, not as isolated parts.
- Test braking bumps, square edges and jump faces separately to confirm the balance.
Next step
Use the calculator for stack comparison, the handbook for deeper theory, or the workshop booking form when the bike needs service or valving work.