[motorcyclistonline] - Making Sense Of Suspension: SET UP FOR SUCCESS

[Ninjette Newsbot]

The past three installments of “Making Sense of Suspension” (CLICK HERE for Parts 1-3) were geared toward educating you about suspension theory and function. Now, in the final part of this series, we’ll give you some guidelines for applying that knowledge to your motorcycle so that you can optimize the suspension already on your bike.

What’s wrong with the setup your bike came with? Maybe nothing, but odds are it’s not optimal for you and your riding style, and if you have complaints about your bike’s ride quality or handling, you may be able to eliminate or moderate them by tuning the suspension. Invest a little time in setting up your suspension now, and it will pay dividends for thousands of miles to come.

The most common complaints are also the broadest: The suspension is either too harsh or too mushy. Let’s define the terms. When we say suspension is harsh that means it’s unyielding and road irregularities are transmitted almost unfiltered to the chassis and the rider. The worst cases may feel like there’s no suspension at all. The handgrips quiver in your palms and your backside gets kicked out of the seat. That’s harsh.

Harsh is when the suspension doesn’t move as much as it needs to. Mushy is the opposite, where the suspension moves too much—that is, it uses too much of its travel too easily or does so in an uncontrolled way. The bike may feel “floaty” like a boat. Hard braking makes the fork crash to the stops and the rear of the bike rise substantially.

The ideal suspension setup would see the wheels following the road perfectly and the chassis and rider remaining stable. Perfection isn’t attainable, but with careful setup and good components, it’s possible to minimize the compromises between comfort and control.

When it comes to straight-line ride quality, you’ll want to focus your attention on your springs and damping, with softer, looser settings offering a more comfortable ride. If you’re a fast, aggressive rider, a firmer setup is likely advisable, but beware going too stiff, which will impede traction; the reason we have suspension at all is to keep the tires in contact with the road.

Bear in mind that changes to spring preload will also affect steering and cornering behavior by altering ride height, rake, and trail. We’ll discuss that later, but first let’s look at a testing strategy for getting familiar with your bike’s range of damping adjustments and zeroing in on the best settings for you.

There’s no way to directly measure damping like we can with sag and travel (see “Travel Monitor” sidebar below for tips on monitoring suspension travel). Getting a baseline on your rebound damping was covered in “The Lowdown On Damping” (CLICK HERE), but compression damping is difficult to feel when shoving on the seat and tank, so some dedicated testing is needed to figure out what works best.

RELATED VIDEO: How To Dial In Your Damping

How should you test? The same way we do: on familiar roads that offer up the kind of curves and bumps that tax suspenders. The idea is to standardize conditions so the changes to the suspension are the variable. Riding the same road is critical so you can track changes accurately. Speaking of tracking changes, take copious notes. Check out the “Notes For Success” sidebar below for some tips. And resist the urge to change more than one parameter at a time!

Pack any tools you’ll need to adjust your damping and spring preload and head out to your test route. Now set all of your damping adjusters to the recommended baseline settings, which you’ll find in your owner’s manual. Now ride your route, taking note of how the bike responds to bumps, behaves on the brakes, steers, and tracks through corners. Then reduce the rebound damping at both ends to something close to the minimum and ride the route again. How does it feel? Now increase the rebound damping to something close to the maximum and ride again. Now go through the same process with compression damping. These large changes ensure that you feel them, and they will also reveal what your bike’s effective range of adjustment is. Once you know which of these very coarse settings you like best, you can go back and refine them until you’ve honed in on the optimal settings.

Once you have your damping figured out, you can play with ride height to alter rake and trail to see how that affects handling. Rake is the angle of a bike’s steering head from vertical, while trail is the distance from the front tire’s contact patch to an imaginary point where a line extending through the bike’s steering head meets the ground. Rake and, to a larger extent, trail influence the general steering behavior and stability of the bike. Less trail results in lighter steering but reduced stability, while more trail will improve stability but make steering heavier.

The easiest way to alter trail is to change the front ride height, which can be accomplished most easily by changing the spring preload. Remember, spring preload effects sag and thus ride height. By playing with front spring preload you can cant the chassis forward or back to alter your bike’s steering and cornering behavior.

Remember to recheck sag to ensure you’re within range, and if not you should shift the fork tubes in the triple clamps to achieve the ride height change you liked and then reset the preload to your original setting to restore sag. As a general rule, you would raise the fork tubes 1mm for every turn of spring preload you took out to achieve a desired trail setting or lower the fork tubes if you ended up spinning preload in. Be cautious of how much you raise the fork legs in the triple clamps so the wheel can’t contact the radiator or exhaust header.

We’ve mentioned this several times throughout this series, but if any adjuster is at its minimum or maximum, that’s a strong indicator that internal changes are required. Also be aware that damping rates don’t change in a linear way relative to adjuster position. If full in is 100-percent damping, one turn out might be 90 percent and two turns out could be 50 percent. Once you’ve played with the adjustments and noted the bike’s reactions, you’ll gain an idea of your machine’s particular non-linearity.

We developed the flow chart at the top of the page to help you work through some of the more common handling complaints, but bear in mind that the suggested fixes assume proper spring rates for your weight, as well as ballpark sag figures.

A reader recently wrote in to inquire if he should adjust his bike’s shocks to accommodate luggage. The answer is yes. You’ll want to check sag and tune damping any time your load changes significantly. Even changing tire brands or models may necessitate some suspension adjustment. Our hope is that you are now armed with the understanding and knowledge needed to tackle the challenge yourself.

BEFORE YOU BEGIN: The Pre-Test Checklist
Hopefully you’re excited to get out there and dial in your suspension using the procedure we’ve outlined, but there are some things to consider before you begin.

Is your bike up for the challenge? Tires play a huge role in how your bike handles, so it’s important that they’re in good shape with plenty of tread and the proper pressures. How about your chain? Does it have sufficient slack, and is it properly lubricated? Your fork and shock(s) should be in good condition, with healthy seals and smooth action. If your fork oil is ancient, check out the How-To HERE and change that fluid! Your swingarm and shock-linkage pivots need to rotate smoothly as well, so if there’s any binding in the back end, check out last month’s How-To for a rundown on servicing those parts.

Other important and often overlooked items that can have a huge effect on bike handling are the steering-head bearings. They should be properly lubricated and torqued so your front end swings smoothly, without any friction or slop.


NOTES FOR SUCCESS
When testing suspension, a systematic approach and good note-taking habits are key. Make changes one at a time, and write them down! At a minimum you should record your starting settings so you can return to them if you get lost, but the more info you take down, the better. CLICK ON THE PDF LINK BELOW for a printable suspension setup sheet.

mc_suspensiontuningsheet.pdf
RESTRICTED TO REBOUND: Just the Basics, Sir
Many budget bikes only offer adjustable spring preload and rebound damping and often only on the shock. Why? While the manufacturers are trying to cut costs they also want to offer some tunability, and changes to spring preload and rebound damping are the most noticeable and have the greatest effect on handling, ride quality, and the rider’s sense of traction and control.

TRAVEL MONITOR
A zip-tie around the fork tube is an easy way to see how much travel you’re using. Make a line with a dry-erase marker on the shock shaft rather than using a zip-tie, since the zip-tie could damage the shock seal at full compression.




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