The problem with Internet forums is they perpetuate myths and misconceptions. Motorcyclists are not immune to this behavior. Scattered among the idle chatter, sophomoric humor and bling boasting on any motorcycle forum, one finds recurring rants on tires, oils and octane along with testimonials on how stiffer springs greatly improve handling. True maybe, for real heavyweights, but often the writer claims such changes are necessary for anyone weighing more than 160 pounds. Sometimes these opinions resemble superstition more than knowledge.
I'm not about to comment at length on tires, oil and octane as the rantings on these subjects often approach a religious zeal, the ranters themselves immune to rational argument. Suspension and springs, though, are fairly easy concepts to grasp at a layman level. Here's the simple truth: springs absorb the shock of bumps and undulations while those things Americans call "shock absorbers" damp the oscillations of the spring. Suspension travel allows the spring to work. Too little travel or a too-soft spring allows the suspension to bottom too frequently. Too-stiff springs absorb shocks harshly and may not properly utilize suspension travel. Too little or too much damping will not control the spring properly. The whole point here is keeping the rubber in contact with the road.
Most riders of sporty motorcycles want to be fast on twisty roads. Despite widespread certainty among a large number of Internet forum members, these riders likely do not need to change or modify suspension components for street riding or amateur track days. The belief that suspension upgrades are mandatory prevails because some bikes lack the latest high-tech suspension components and adjustments. Race-replica sport bikes have these high-tech components with fully adjustable suspension front and rear because a few expert riders push the limits on the track. For these riders the suspension does need to be adjusted and fine-tuned. Lesser riders know this and believe it to be the secret of fast riding. Worse, some believe that if they can talk the talk, they will be perceived as knowledgeable and fast themselves. No mystery here; our ego, our culture, maybe human nature, drives us to learn the vocabulary and assume the role of expert.
It's common for riders to believe they would be faster with better suspension components. These riders often begin with replacement springs, especially fork springs, without first determining stiffer springs are needed. It's also common for riders to believe they are faster after changes are made even if the modifications were technically inappropriate. Seat-of-the-pants is a notoriously unreliable testing procedure. All riders wishing to improve their speed should first ask themselves: is this motorcycle faster than me (meaning, can a skilled rider go faster on this motorcycle, in it's stock form, than I can)? Do the engineers who designed this motorcycle know more than I do? (Yes I know they built to a price and designed for a mythical average rider). Can I answer these questions honestly? If the answer to the third question and either or both of the first two is "yes," then the rider should spend money on track days and good track schools, not suspension modifications.
Those are opinions, here's a fact: if static sag is correct or you can make it correct your springs are fine. The notion that stiffer springs are always better for fast riding is erroneous. Fact: I've been in Jason Pridmore's STAR track school on both an SV650 and DL650, riding among the leaders or leading in the slower B class, when Jason's instructors, some of whom are AMA racers, passed me easily on SV650's with stock suspension (before they were allowed by Suzuki, their sponsor, to modify the suspension). Obviously, a stock SV650 is faster than I am so upgrading the suspension would be a bit premature. At the track one observes that many riders have modified or upgraded their suspensions believing this will make them fast. With less than half the horsepower and no suspension upgrades I've passed many of these riders on tight tracks and I'm not good enough to move to the A class.
How does a rider know if the springs are correct? By the time-honored procedure of checking static sag with rider and gear aboard. The suspension must work both up and down from its normal position for the spring to absorb a shock, rebound and be subdued by the damper. Static sag is the measurement of how much the suspension compresses from being fully extended with wheels off the floor and partially compressed with rider and gear aboard. This measurement should range from roughly 25 percent of available travel for track to 33 percent for street. (NOTE: it has become common to recommend static sag settings as a measurement rather than a percentage, often 25mm to 35mm. This presumes that all suspension travel is the same. I prefer percentages.) If it's within that range, then the springs are correct for street and amateur track days. If it's less than that range then the springs may be too stiff. If it's more than that range, the springs may be too soft. Moderate deviations from that range can be corrected with preload adjustments. Most any motorcycle has preload adjustment on the back. Some do on the front. When adjusters are not provided on the front, preload can often be adjusted by changing the length of spacers above the springs. If static sag is excessive and can't be compensated with preload, then the springs are too soft. If static sag is correct then the springs are correct and stiffer springs are not desirable. Static sag comprises all spring factors: bike weight, rider weight, spring rate and suspension travel. Stiffer springs that are not needed upset this balance.
Once the static sag is correct, the burden of suspension tuning shifts to compression and rebound damping if adjusters are provided. If damping adjustments are not provided and the rider did not change springs, then the factory engineers probably chose damping characteristics that will work well for the real world. When adjusters are provided, rebound damping is often the more useful adjustment. With static sag set correctly, the rider should be finished with preload adjustment unless the load changes. Preload may be increased when carrying extra weight such as luggage or a passenger; it's important to remember where it was so it can easily be returned to normal.
Caveat: the above statements make a point; the real world is not so absolute. On public roads, a sensible motorcyclist rides well under their limits or the bike's limits, whichever is lesser, to allow room for maneuvering when encountering the unexpected. It makes sense for a fast rider who has not yet reached the bikes limits to upgrade and tune the suspension to increase the safety margin. Presumably these changes will be based on knowledge and understanding, not urban legend.
Footnote: before finishing this narrative, I put it aside to do the 600-mile service on my new Honda 599. After changing the oil and filter I measured static sag. The front measured 33 percent of travel, the rear 30 percent of travel. I weigh 200 pounds with riding gear. My rear preload is set at the 2nd of seven positions with higher numbers being firmer. I was not surprised. I already knew from a fast canyon run that the handling was exceptionally good, partly because the OEM BT56 dual-compound tires stick tenaciously even on cold winter pavement. The tires were able to do this, even on rough pavement, because the suspension was keeping the rubber in contact with the road. This bike is going to make me both smoother and faster and I do not need suspension modifications.
Footnote: a few years ago, I bought a new Buell from a Harley-Davidson dealer. Imagine my surprise when, during my first service, I was called to the service department and asked to sit on my bike, on the work bench, while the mechanic meticulously adjusted static sag both front and rear. I was impressed. The fact that most dealers, most brands of motorcycles, don't do this is not a sign that it isn't an important setting.
A brief how-to for the inexperienced:
(NOTE: let's understand that static sag has no meaning unless the rider is on the motorcycle. Static implies only that the motorcycle is stationary, not that the rider isn't aboard. Static sag comprises all spring factors: bike weight, rider weight, spring rate and suspension travel. Since useful sag measurements and adjustments must be made with the rider aboard, there is no purpose in first messing with sag measurements and adjustments without the rider aboard. The bike never goes anywhere under it's own power without a rider. This once was clear but recently some "experts" have come to believe that "static" somehow means without a rider aboard and sag with a rider aboard is "race sag" or "rider sag" or some other catchy phrase. If you understand why you are setting sag—to allow the suspension to work properly when the bike is in motion—then you won't suffer this confusion.)
• Assuming stock components, check a service manual for the amount of your motorcycle's suspension travel, front and rear. • Calculate 1/3 or maybe .30 of these numbers for the amount of sag desired. Record your numbers. • By whatever means works for you, raise the motorcycle until both wheels are off the floor with the bike more or less level. • Measure from something subject to suspension travel at the axle, such as an axle nut, to something inline with suspension travel and not subject to movement, such as the lower triple clamp in front and maybe the sub frame in the rear (be aware of the path the axle nut will follow in the rear as the swingarm moves). Record your numbers. • lower the motorcycle back to the floor, get on the bike, ideally with riding gear, and repeat the measurements. Record the numbers. This is easiest with a couple helpers but not impossible to do alone with rope, care and a little imagination. • The difference in measurement is your static sag. If these numbers differ significantly from the numbers you calculated above, then you need to adjust your preload or change your springs. Unless you are really a lightweight, it seems unlikely you will need softer springs. If you think you do need softer springs, consult a suspension expert. Most motorcycles have preload adjustment in the rear. Some do in the front. If you use nearly all your preload to obtain the correct sag, then you may need stiffer springs but know what you are doing. If you don't know, then consult a suspension expert. Don't just buy something because it's stiffer or someone on the Internet said it was trick.
Once you have static sag where you want it, set compression and rebound damping, if you have adjusters. For starters, I would set both compression and rebound damping as the manual recommends. If you increased preload significantly, I would increase rebound damping a click or two. If you changed to a stiffer spring in the rear, you may also need a new damper to provide adequate damping adjustment. That's the baseline. Fine tuning damping adjustments is not so straight forward and not so easy. It takes experience and knowledge to translate subtle handling characteristics to meaningful damping adjustments. If you lack this experience and knowledge, you need to find proven literature on suspension tuning or talk to a racer or other person who you know understands suspension setup.
Footnote: some riders find a plastic zip tie, snug but not too tight on the smaller fork tube (if exposed), a handy way to record front suspension movement. If you use this method, lower the bike and get on it carefully so you don't cause the zip tie to move beyond what your weight causes.