ASK THE MXPERTS: HOW CAN I MAKE MY BIKE HANDLE BETTER?
What can I do to make my bike handle better? My bike seems to push the front end, not turn as well as it should and shake at speed. Everybody I ask tells me something different. What can I do to my suspension to get a handle on the handling?
Set aside the suspension for now because that needs to be dealt with once you get your bike’s balance and set-up spot on. Without the self-stabilizing forces that are built into a modern motocross chassis, your bike would handle like a wheelbarrow, which is what you are describing. The perfect steering geometry is the correct relationship between the bike’s head angle, weight bias, overall wheelbase, front center (distance from the front axle to the crank center), fork offset and trail. Changing any single number will affect all the others. How you set up your bike will alter its steering geometry—sometime for the good and sometimes to the bad. Something as simple as more race sag in the rear shock, a different tire profile or even lower tire pressure can be used to fine-tune the way the front end handles. Even sliding the rear wheel back in the swingarm changes the way your bike turns because moving the wheel back puts more weight on the front wheel; however, a longer wheelbase turns slower, tracks smoother over rough terrain and is less affected by rider position. Conversely, sliding the rear wheel forward makes your bike more responsive to weight shifts. It will make your bike turn quicker and ride rougher.
Here are the six basics of tuning your bike’s chassis:
(1) The weight bias and head angle can be influenced through preload adjustment, suspension settings, bar position and by sliding the forks up and down in the triple clamps. If you make the bike taller in the back and set the controls so the rider weights the front, the bike will turn quicker but be less stable at speed. If it’s taller in the front with a more rearward weight bias, the bike will turn slower and be more stable.
(2) Removing or adding a link in the chain makes it possible to lengthen or shorten the wheelbase. Short wheelbases turn sharper, hook up better out of corners and feel more nervous. Longer wheelbases are more stable. Be forewarned, adding a link or two to the chain will require a change to the shock’s damping settings.
(3) Aftermarket triple clamps are available in a wide variety of offsets. Depending on the fork offset, aftermarket clamps can speed up or slow down handling. Less offset results in quicker steering. More offset makes the steering more controlled.
(4) The center of gravity moves every time the rider moves. Rear-set footpegs can take the load off the front of a bike, slow the steering input and change the weight bias rearward. And, of course, the rider can move fore and aft on the bike to change the load on either end (steepening and slackening the head angle as he slides around on the seat).
(5) An aftermarket shock linkage can lower the rear of the bike to kick the head angle out. The rider can then raise or lower the forks to choose the head angle that he wants while also lowering the center of gravity.
(6) The most common and effective trick to improving handling is to slide the forks “down” in the triple clamps to lessen oversteer on corner entrance or reduce head shake across rough ground. It achieves this by making the frame’s head angle slacker. Conversely, if you want your bike to turn sharper, slide the forks “up” in the triple clamps, this will change the weight bias forward and steepen the frame’s head angle.
MXA test riders make constant adjustments to their chassis—after practice, after the first moto and often at home in the garage on a whim. That said, a lot of testing and engineering goes into the frame geometry of the modern motocross bike. Small changes will make a big difference in the way your bike handles. Most fast guys set their bikes up to reduce the negative effects of oversteer or understeer—not to get them to exhibit those characteristics.