Get the Engineers Advice on Motorbike Suspension

For more insight on how to tune your motorbike suspension, we asked the experts. The Honda Gresini MotoGP team have not only the support of Castrol and Honda but also an incredible team of world class engineers. If anyone knows how it’s done; it’s definitely the Gresini MotoGP engineers. With their help tuning your motorbike suspension is a far more manageable task.

The first step is to pinpoint the front and rear static sag levels of your bike, this important baseline will inform the rest of the process.

The Rear Suspension of Your Motorbike

The first step is to lift the rear of your back wheel. You want to lift it as high as it will go without lifting from the floor entirely. Measure the extension between these two points, from the spindle of the wheel to the tail. With the help of another person hold the rear of the bike while bouncing up and down on it to return the suspension to its resting position, which should be lower than when the rear of the bike was lifted or ‘topped out’. Now, by measuring the distance between the wheel spindle and the same point on the rear of the bike as before, you are able to attain the difference between the two points which is your static sag measurement.

The Front Suspension of Your Motorbike

As with the rear suspension, lift the front of the bike to measure the full extension of the wheel spindle and the bottom of the yoke. Again, you will bounce on the forks, ensuring that they return to their natural resting position. Now you can measure from the spindle to the yoke again, the difference between the two measurements will give you your static sag. Your static sag should measure between 20mm and 30mm on both the front and rear suspension. If your measurements fall within this range, tie a cable tie around your fork slider to see how much fork travel you are using when braking. Ideally this figure should range between 10mm and 15mm. 

Adjust, Measure, Ride and Repeat

Take your time when measuring your static sag to get accurate measurements. From here you can make adjustments and test drive your bike to see the differences. Remember to adjust measure and test when you have identical road and weather conditions, along the same route. 

Troubleshooting Common Problems

Chatter on the Brakes

If your forks bottom out, there is bounce or chatter on the brakes, add a preload to give the forks more support. After your test ride take note of where the cable tie is sitting, see whether it is sitting near the bottom of the fork past the ideal 10mm – 15mm. If the cable tie is past this measurement you want to add some compression and reduce a bit of rebound. If this doesn’t work you may require either harder fork springs or thicker fork oil.

THE TANK SLAP

If you are experiencing a tank-slap on your bike, this may be caused by the rear of the bike being too soft and squatting under power. By adding rear preload one turn at a time and a little compression you may be able to fix this. If this doesn’t work, try backing off the rear rebound. If you are still experiencing a tank-slap, you may either require a stiffer rear spring or your shock may require servicing. 

THE UNDERSTEER

If your bike cannot hold a line through a SuSpenSiona corner, the front of the bike is too high. You need to either add more rebound or rear ride-height. Without adjusting the ride-height you could try adding more rear preload.

The problem with too much preload, however is that it can lead to:

  • A lack of rear end grip. To remedy this reduce the preload by a turn and ease off the compression damping by a few clicks.
  • Understeer, a loose rear end and tanks slapping. This however, may also be a result of riding too close to the limit. Ensure that you always ride in a manner which is appropriate for the road conditions, and stick to the speed limit.
  • A lack of rear end grip. To fix this, reduce preload by a turn, then back off compression damping a couple of clicks.

Through attending to all these concerns, making adjustments and testing your bike, you can ensure that you are able to find the right settings and adjustments for you. In the end, all this extra effort will make your motorbike more enjoyable to ride.

The Most Important Motorbike Tips

There are always one or two things which may not be top of mind, but we’ve made a list of the most important things to take note of and attend to…

  • Always check your tyre pressure. The right tyre pressure goes a long way to ensuring your motorbike is handling correctly.
  • Don’t adjust your bike if it already feels fine.
  • Road bikes are made differently to race bikes, your adjustments are unlikely to make your bike unrideable or have a detrimental effect on the way it handles. Even the suspension components are designed to work over a range of different conditions such as wet or dry and one or two-up.
  • Adjusting the suspension on your bike is not a permanent solution, the settings can always be changed back to the way they were previously. To find your standard settings simply find them in your owner’s manual.
  • While you are making changes and adjusting settings, be sure to keep a log of everything you do. By noting these changes you can always refer back to your previous settings if needed.
  • The best way to work on your bike is with the help of a friend. With someone to assist you in moving the bike around, the whole process is much more manageable.

Mind Your Jargon

Preload: This is the tension a spring is set in before a load is applied by the rider or by braking. Without the right amount of preload; your bike may either sag under its own weight or the springs will offer no give at all.

Rebound damping: This is the adjustment which impacts the way your springs rebound after compression. Without rebound damping, your bike would bounce you straight off the saddle when you ride over even the smallest bumps.

Compression damping: This setting affects the speed at which the springs compress under a load as seen when braking, accelerating or riding over bumps. With too much compression damping you will find your bike to be too harsh when the compression damping is too low your bike will tend to bounce.

FRONT FORKS

Preload adjusters: These can be found at the top of the fork legs. Adjustments can be made using 14mm or 17mm spanner. The turns can be measured by the rings marked on the exposed area of the adjuster.

Rebound damping: As with preload adjusters, rebound adjusters are measured by turns and half turns which are made using the flat-headed screw nipples on the top of the fork. These adjusters make an audible click on some bikes, making the turns easier to count.

Compression damping: This setting can be adjusted via a small screw in the base of each fork leg. Adjustments are counted in half-turns and need to be made in equal amounts on the same side.

REAR SHOCK

Preload adjuster: On the rear shock you will find the preload adjuster collar, it will be located at either at the top or bottom of the shock absorber. Using a C-spanner this setting can be adjusted.

Rebound damping: This setting is customised using the screw adjuster which is found at the base of the shock absorber.

Compression damping: This setting can also be adjusted using the small screw which usually resides at the top of the shock or on the remote reservoir.

Ride-height: The ride-height can be shifted using the threaded nut adjuster found at either the top or bottom of the shock absorber. This setting lifts the back end of the bike to place more weight on the front of the bike, helping it steer more quickly. There are some more modern sports bikes which do not allow for the adjustment of this setting but many aftermarket shocks do have this adjustment.

Now, with all the important tips and tricks at your disposal you can toil until your heart is content to find just the right adjustments for your comfort and for your bike to reach optimal performance.