FastDates.com Paddock Garage -Advanced Suspension Setup

Multiple World Superbike Champion Troy Bayliss and the title winning Ducati 999R06

Basic Suspension Setup and Tuning Advanced Setup Here
by Jim Gianatsis, former National Championship winning
Fox Racing Suspenion engineer for the AMA factory Superbike Teams

With so many suspension tuning variables available in a modern sportbike, in can take many days of testing and adjusting to dial-in a street or race bike from scratch. Adding to that equation is the fact most riders just don't have the years of experience in testing to fully realize what their bike might be doing wrong, which part of the bike's suspension that problem might relate to, and then how to proceed to correct or improve it.

A Suspension Test Engineer or tuner is an important part of any factory racing team, because even most top factory riders are not experienced enough to analyzise and offer suggestions on how to adjust their race bikes. That's why bike development and testing is usually left to Engineers who have worked with many different teams and riders, and to very experienced racers turned test riders like a Peter Goddard or Pier Frankie Chili who have more than 10 years of racing and testing experience to relate to. Their job is to ask a rider questions like "What's the bike doing?" And translate the rider's response of "The bike is bucking in corners!' to mean there's not enough high speed rebound damping in the rear shock and the internal valving stack in the shock will need to be changed.

But thankfully, when you purchase a production sportbike today, all that suspension tuning has been done for you. And the first place to start is with your Owner's Manual to confirm that your bike is set up to the factory recommended settings as the baseline and right place to start. From there you will adjust or chage the setting to suit your particular riding weight, riding skills, and street or racetrack conditions. You will want to record all suspension changes or adjustments you make in a diary, together with the results, for future reference. You also should be made aware that changing one type of suspension setting -say reducing front fork compession damping, will probably also affect another adjustment setting like fork travel and increasing fork bottoming, requiring an increase in fork spring preload (controling ride height or sag) to compensate.

Which brings us to the Golden Rule of Suspension Testing/Tuning:
"Never change more than one setting or variable at a time."

Then go out and test it and confirm that the change is going in the right direction or not. Then you can come back and trying changing something else. Because suspension setting are so interrelated between spring rates, ride height and damping, both at one end of the bike and even between front to rear of the bike, you will quickly become lost and confused in what you are doing if you change more than one thing at a time. In setting up your bike, here's where to begin:

Spring Rate
Suspension setup begins with confirming that your bike's spring rate is correct. In full riding gear and riding at your limit, the bike's suspension should travel through its full range of travel and just bottom slightly on the biggest bumps you'll encounter. Front suspension travel can be checked by securing a plastic zip tie on the front fork's slider tube and seeing how far the compressed outer slider tube moves it. Rear suspension travel is check by moving the rubber silastic bumper up the shock shaft, and seeing if riding it pushes it all the way back down the shaft without your encountering any "hard" butt pounding bottoming when riding. Most suspension product companiescan offer optional rate springs for your bike.

Ride Height
Setting ride height adjusts where your bike "sits" within its stroke of suspension travel and determines how much suspension stroke is available for absorbing bumps that push the wheels up, and hollows in the road which your wheels will drop into to maintain traction contact with the road. From the ride height point to full suspension compression (bottoming) is called available suspension travel, and the distance from full extension to the the ride height point in called sag. Ride height (or sag) should be set at 25-33% of the full suspension travel.

Determine total travel distance by either consulting your Owner's manual, or place your bike up on a stand and remove the springs from the suspension and measure as you push the suspension through it full distance of travel. if total travel os 120mm for example, the sag should be in the range of 30-40mm with your full riding weight on the bike, leaving an available travel of 80-90mm.

To set ride height you'll need to measure sag. At the front forks you can use that cabl-tie around one of the fork tubes. With the suspension fully extended (place the bike on a stand to get the wheel off the ground) slide the tie-wrap up against the fork seal. Next, with the bike off the stand, sit on the bike in the normal riding position (with a friend to keep you from falling over). the tie-wrap will be pushed along the tube to the new position. Now extend /top the suspension again and measure the distance from the fork seal to the tie-wrap. This distance is sag and should be adjusted with the spring's preload adjuster to 25-33% of total available travel.

At the rear suspension do the same thing. Place the bike on a centerstand (or have your buddies lift the rear end of the bike so the rear suspension fully extended. Measure from the rear axle center to some fixed point vertically above it on the chassis (see the picture above). Then put the bike back on the ground and sit on it while wearing your riding gear and measure again between the axle and the chassis point. Subtract the second measurement from the first to get the amount of rear sag. Adjust the shock's spring preload perch to get the right amount of sag.

If you ride harder than average, especially on the race track on race tires, your extra cornering speed will generate more centrifugal force and more weight on the springs. This will compress the suspension more than normal -possibly causing the pipe and/or footpegs to drag. You could add preload to counter this, but his is more of a band aid fix at the expensive of lost rebound travel. But to keep stock ride height and sag you might need to switch to stiffer springs. But if your springs are dialed in, you don't want to change them. A serious sportbike model will allow you to raise raise or the bike's ride height/ground clearance with an adjustable rear shock linkage and by raising or lowering the front fork tubes in the triple clamps.

Steering Angle
Adjusting your bike's fork tube position in the triple clamps, and raising or lowering the rear shock linkage in the opposite direct to the front has the added bonus of changing the steering angle slightly, and slowing up or speeding up the handling of the bike. Lowering the front end of the bike (raising the tubes in the triple clamps) has the effect of decreasing steering angle and speeding up the handling to turn quicker, at the expensive of stability. Many sportbikes use a steering damper to control stability with a steep steering angle.

Some of the higher priced sportbikes like Ducati and MV Agusta offer adjustable adjustable steering heads and rear shock linkages to alter steering angle and affect weight transfer even more. And the concentrick real wheel and swingarn pivot adjusters on these bikes also provide additional suspension tuning adjustemnts for ride height, steeling angle and traction under acceleration.

Damping
Before you go in and adjust any damping settings at either end of the bike you must have your spring rates and ride height dialed in first.

Damping is resistance or friction, and it is used in the motorcycle's suspension components to control movement of the springs directly, and the movement of the motorcycle indirectly. Remember Issac Newton and his theory 'A body at motion remains in motion...' -in a perfect universe without friction or resistance. So to prevent those springs (used in our suspension to absord bumps and irregularities) from continuously bouncing up and down after that bump in the road has been passed, we use damping resistance to stop the spring occelations.

We want to have just enough damping to keep the bike stable. Compression damping is usually only about 30% of rebound damping because you've got the spring rate working to absorb the bump in the road. Rebound damping is considerably more because it has to control the entire rate of the spring in rebound.

Damping is controlled by two systems working together in a modern sportbike's suspension, be in the front forks or the rear shock. 1). The first system is High Speed Damping (for big bumps) which is controlled by flexabile shim washer stacks covering big oil flow holes on a damping piston. This system is ideal in that it allows high speed piston movement through the suspension oil if the suspension encounters big, high speed bumps. And the damping can be made progressive for smaller bumps by fine tuning the diameter and number of flex washers that "flex" open to allow oil to pass buy. To adjust High Speed damping the suspension system must be taken apart and the valving shim stack modified.

2). The second system is Low Speed Damping (for small rolling bumps) which uses a needle valve screwed into a small orfice to control oil flow. This is adjusted by the external knobs or screws on the forks or the shocks. Your Bike's Owner's Manual will tell you which screws control compression and rebound and the best settings to start with.

If you can't tune the suspension the way you like it with the external screws, you'll need to have the internal valving stacks modified by an experienced race suspension tuning company. The cost to do this at the rear shock, though, will be half of what it might cost to buy a race quality rear shock, and the results still might not be as good as we want. Ohlins, Penske, Fox and White Power rear shocks all offer excellent damping designs and can be purchased pre-setup for your bike and riding ability. So if you are roadracing or you want a quality rear shock that is already tested and set up with the correct valving, ready to go, I really recommend just replacing your bike's stock Showa or Kayaba shock with one of the race brand shocks mentioned.

Up front, the stock forks are usually more forgiving and you should be able to get good results by just adjusting the external damping screws. Although revaliving serices are avaialble for them as well, and the ultimate E-ticket are replacement Ohlins fork legs.

To test damping you'll once again need to tke notes, and you'll only want to change one suspension setting at a time, on just one end of the bike. The factory recommend Owner's Settings and a "push test" with the bike off the stand is the best place to start. Adjust the Compressing screws so the front forks or the rear suspension compress down fairly easy as you shove on them, and then adjust the Rebound screws so the suspension returns to its stock ride height fairly quickly ( maybe in 05 m-1.0 seconds) without returning in a too quick bounce with no damping whatsoever.

Next move is to go out and ride the bike at speed with the use of zip tie indicators on a fork tubes, and a pushed-up stilastic bumper on the rear shock shaft. If you feel the front or rear suspension wallowing or bottoming hard, turn up the compression damping on that end. If you feel the suspension bouncing or kicking up, it needs more rebound. If the suspension is running out of travel and "packing down," the rebound damping is too stiff and the suspension is staying compressed, so soften up the rebound damping. Most riders aren't experienced enough to recognize these problems and know what to directly change to correct it. That's why we say to change just one setting, one or two clicks at a time, then go back out and try it again. If the bike's handling improves, then you're going in the right direction until it gets bad again. If you don't have enough damping adjustments available in the direction you're going, then the suspension needs to be revalved or replaced.

One big sportbike suspension problem in America, and especially in California are concrete freeway expansion joins and worn slabs which put the bike into a jerking, rocking horse motion. These can be dialed out in revalving, but unfortunately, only at the expense of high speed handling control. So just accept and live with it as the sacrafice to get to your favorite sportbike riding roads.

The suspension is dialed in correctly when you "can't feel it working." If everything is working as it should then the suspension feels smooth, stable, and so great you can't feel it moving or doing anything wrong..

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