Basic rules for suspension tuning
Marc Salvisberg

Suspension isn't always THAT confusing, unless you jump in in the middle and try to create some "magic".

From years of doing tuning, I've almost always found that it's best to aim towards developing a "tuning plan" or a consistent series of steps that ends up allowing you to derive the perfect tuning settings (or as close as you can be) for the intended usage of the vehicle.

That holds true with suspension, dynamometer design, carburetion, bike control setup, engine building, chassis development and whatever else you are trying to assemble into a "good working pile" of parts and pieces.

By structuring testing and other evolutionary / empirical processes, you will be training yourself to rapidly identify problems, recognize trends and patterns and be able to create a possible path to improving whatever you are working on.

In suspension, the basic path is to do the spring rates and preloads and then do the damping.

Springs setup, front and rear, is to simply set "spring" both ends of the bike so that when you push down on the footpegs (where most of your weight is when you aggressively corner), both ends of the bike NEED to go up and down exactly evenly, both in travel and rate.

General order

Select a rear spring that will just bottom out over your harshest bump that you are riding over with "normal" sag. Soften it up till it just bottoms out, then tighten preload 1/4. Check the sag and see if it's in general range of 35mm to 20mm.
That's with no compression damping.

Select front fork springs that allow the front end and the rear end to travel equally and evenly when you bounce on the footpegs (helps to have someone hold the bike upright). That's after you have set the rear spring as in the above step.
That's with no compression damping.

Rear rebound: Use just barely enough to prevent wallowing in high speed sweepers.
I like to leave it just a teeny teeny bit "shy", so I always know I'm "right there". If it ever feels "totally" under control, I back off the damping a click.
That prevents the dreaded "over damped" rebound situation, where the suspension "packs down" in multiple ripples.

Front rebound: Use just enough rebound to keep the front end from topping out and drifting wide when exiting low speed corners at full throttle.
Same deal as the rear, I like it "ever so slightly" shy of totally controlled.

Compression damping, front and rear: The goal is to use as little as possible. Use the proper, perhaps heavier than stock spring to do the major work during non-braking mode riding - but never use a front spring that is stiff enough to be stronger than and mismatched than the required rear spring.

Use compression damping to trim if necessary and only if required.

Excessive dive under braking: Use increased oil level to firm the front end under hard braking. 5mm is a significant change in modern forks.

Goals are to always use the softest rear spring that works within "sag" range limit.

Use just enough rebound damping to control the springs.

Use as little compression damping as possible and only when required. Not everybody has a supply of alternate fork and shock springs, so you will probably have to improvise and use a bit of extra preload or a bit more compression damping to compensate for too soft of a spring.

All in all, there is nothing like heeling a bike over in a 120mph sweeper with a sharp edged bump in the middle of it and knowing that you can back of just a bit over the bump, get bounced in the air and calmly land heeled over, in control, unperturbed and remain at highest possible speed with no fuss or muss.

That just doesn't happen if the springs aren't perfectly matched!

Cheers and thanks to Steve McLaughlin for the mentorship back in the day.

Marc