Once upon a time, not so very long ago, I met a true Suspension Expert.  Someone who lives and breathes suspension day in and day out.  I was passing through the small town of Christiansburg, VA and saw a big GasGas banner on the window of a motorcycle shop.  It was well after closing, in fact it was pitch dark.  Being a GasGas Trials Rider, and having never seen an actual GasGas Motorcycle Storefront, I just couldn't resist investigating.

 

Around the side of the building, I found a man and his son furiously packing their trailer....headed for Daytona Bike Week.  But not just to gawk at the scene.  He had a mission to watch the fruits of his labor out on the track.  He tunes suspensions for a living.  If everything is art, then he is truly a Suspension Artist of the finest degree.

 

We met by pure chance, but maintained contact by purpose.  Convinced of his expertise, I formed a plan to let him transform my WRR stock suspension into something special.....really special.  He asked me, "what do you want it to do?"  My reply was simple:  "Everything!"   He just smiled and then delivered a result that honestly exceeded my expectations.

 

His name is Travis Jones.  He owns "Go Race Suspension" in Christiansburg, VA.  You can find him if you want to.  Just Google him.  And remember, all his new found WRR knowledge was at my expense....

Since this is my first suspension article in a series, I think its best to get everyone on the same page....draw a baseline for common understanding.   Travis gave me some papers to read while he was working on my bike.  I'm assuming he wrote the material, but am not absolutely certain.  Nevertheless, I'll give him the credit for it.  I have re-typed it, cleaned up some grammar, and added a little explanation where I think some clarification was needed. I have decided to call it:  SUSPENSION 101 

 

by Travis Jones

 

Why concern ourselves with suspension tinkering and alterations?  Strong running engines are wasted if they cannot transfer power efficiently to the ground.  Rider talent and training will be minimized by a machine that wallows or rides too harsh.  Modern motorcycles have a vast assortment of adjustments but a rider must understand the basics before experimenting.

 

RAKE:  Draw a line down the forks to the axle center, then draw a line straight up from the axle center.  The angle created by these two lines is your bike's Rake measured in degrees.

 

- Less Rake  =  quicker steering and less stability at speed

- More Rake  =  reluctance to turn and slow steering at lower speeds

 

TRAIL:  Draw a line straight down the steering head centerline, and then draw a line straight down from the axle center.  The measurement of those two points is your bike's Trail.  The Trial influences the self steering ability of motorcycles.

 

- Less Trail  =  quick steering

- More Trail  =  slower steering

 

OFFSET:  Look at your top triple clamp.  The distance from the center of the steering head and a line drawn throught the center of each fork tube (measured straight out from the steering head) is the Fork Offset.

 

- More Offset decreases Trail

- Less Offset increases Trail

 

SPRINGS:  The function of the Springs is to suspend the combined weight of the bike and rider.  Determining your specific needs is important.  The best way is to simply contact a suspension shop and give them the Year, Make, & Model of your bike, plus your weight when fully dressed for riding (including any fanny pack, toolkits, bags, helmet, boots, etc).  

 

- Spring Weights: a 4.5kg spring will depress 1mm when 4.5kg is placed on it.  An additional 4.5kg will depress it another 1mm further.

 

STATIC SAG:  Also known as "Free Sag"....its the amount the unloaded bike settles on its suspension when lowered to the ground from a center stand.  This is altered by adjusting the large preload ring on the threaded section of the rear shock.  Ideally, it should be set for 10 - 25 mm of Static Sag.

 

RACE SAG:  Also known as "Rider Sag".....its the amount the bike settles when lowered to the floor and a fully equipped rider mounts it.  So, how do you measure it?

- put the bike on a center stand with both wheels off the ground.

- get a helper to hold the bike steady, while you sit in a normal riding position (not too far back or too far forward).

- measure from the axle center to a point on the body with the wheels off the floor.

- lower the bike to the ground and mount up again.  While holding it level, have your helper measure the distance between the same two points.

- the difference between these two measurements is the Race Sag.  It should be 1/3 of the total suspension travel (usually between 95 - 105 mm)

 

- if Static Sag is correct but Race Sag is LESS than 1/3rd of travel, you need softer springs.

- if Static Sag is correct but Race Sag is MORE than 1/3rd of travel, you need stiffer springs.

 

PRELOAD:  The loading of the spring from its static length.  Preload adjustment is used to obtain the correct Sag readings.  

- incorrect Preloads will affect both steering qualities and ride qualities.

 

DAMPING:  The term used to describe the controlling of the shock or fork movement during both compression and rebound.

- Low Speed Compression refers to the damping of the shock or fork during Slow Speed Compression such as when encountering gentle whoops at low speeds.  (Not the machine movement, but the suspension component speed)

- High Speed Compression refers to the damping of the shock or fork during fast movements, such as a hit from a square edged hole or log.

- Low Speed Rebound refers to the damping of the shock or forks during a slow return stroke.

- High Speed Rebound refers to the damping of the suspension during quick return strokes.

- Note:  High speed compression and rebound requires the channeling of large amounts of oil in a short time period.  Therefore, the component (shock or fork) opens larger passages than used for low speed actions.

 

STICTION:  Refers to the resistance to suspension movement or "sliding friction".  Can be attributed to fork seals, bushings, linkages, misalignment, wear, and damage.

 

PACKING:  Refers to the situation where the suspension component fails to rebound to a useful length before being compressed again.  It results in less and less travel with each compression of the fork or shock.  Too much high speed rebound damping is the usual cause.

 

G-OUTS:  Refers to the extreme compression of the suspension components in a low speed manner.  The bike will be moving quickly but the suspension compresses slowly (as in riding a fast bermed corner).  This is an extremely difficult action to control because the suspension must move a large quantity of oil through the low speed compression valving, which usually handles only small quantities of oil.  Due to the low speed action, the high speed valving does not come into operation.

 

STINKBUG:  Refers to a "Tail Low" chassis set up.  Its the result of insufficient shock preload, or the fork springs being too heavy.  The bike may "swap" and the cornering will be slow to react.  The front wheel will tend to climb over bermed corners.  Short riders often create this chassis as they attempt to lower the bike for a more secure "foot-down" seating position.

 

FAILS TO TURN:  Both Stinkbug setup (see above) and too much compression damping will prevent the forks from settling during braking (for corners).  This can make the bike difficult to turn.  Sometimes, raising the fork tubes slightly in the triple clamps will cure this ill (i.e. lowering the front end).    That resultant increase in rake allows quicker cornering and weight transfer to the front wheel for traction.

 

REAR WHEEL KICKS ON BRAKING:  Excessive compression and insufficient rebound damping on either the front or rear will fail to control the rear wheel action as the wheel brakes and reacts to trail bumps.  Should the front end dive excessively or too quickly, it will upset the chassis loading and cause a loss of rear wheel contact with the ground.

 

HANDLEBARS SHAKE AT SPEED:  This is caused by either too steep a steering angle (Rake),  or loose front suspension components.  The rear preload may be excessive and preventing the rear from settling slightly during acceleration (there is that "built-in increase in Rake" again).

 

WALLOWS IN WHOOPS:  Too soft a ride will create an increasingly imprecise ride through deep whoops.  Try more compression and rebound.

 

HARSH INITIAL TRAVEL:  Too much tire pressure, too high a spring rate, stiction, or too much preload &/or low speed compression damping will prevent suspension reaction.

 

HARSH TRAVEL FURTHER INTO STROKE:  Too high an oil level in the forks or excessive air trapped in forks will "lock" the front end.  Mid and High speed compression damping may be too high.

 

SWAPPING:  The rear wheel is not reacting to the trail surface quickly enough and this sends the rear from side to side in an increasing angle relative to the front wheel.  Not a good thing!  And "Packing" of the shock is the usual cause.  Swapping in "sand" can also be the result of too little low speed compression.

 

KICKING:  Should the front tire pressure, spring rate, preload, or compression damping be excessive....then the front wheel will not react to trail obstacles quick enough and the wheel wheel will bounce or "kick" back and lose contact with the ground.

 

 

GO RIDE:

Set out a short trail loop containing all the usual obstacles and trail conditions you encounter during a normal ride.  Turn each clicker to its end stop and back to the original setting to determine your initial setting (i.e. count your starting point and write it down).  Set the Static Sag and the Rider Sag to the correct range, as best you can.  Then, ride your loop and mentally evaluate suspension deficiencies based upon these explanations above.  Return to your the starting point of your loop, and make setting changes.  Turn the clickers 3 or 4 stops....to ensure a noticeable change, rather than single stops (clicks) that may not be distinguishable.  Go ride the loop again and re-evaluate the suspension performance.  Record all your changes in a notebook with a description of the result.  Don't be afraid to experiment with the extremes.

 

REMEMBER:  The machine SHOULD BOTTOM SOFTLY ON THE MOST EXTREME OBSTACLES.  Why have suspension travel that you do not use?  Double check your results after a riding break and be very critical.  You may end up back at the original settings but that is more desirable than not utilizing all of your suspension to its fullest potential.

 

SHORT INSEAMers:

Just because you are short in the inseam does not condemn you to boots with "lifts", or a life without trail bikes.  The suspension units can be correctly lowered to suit your height and confidence level.  It is better to surrender 2 - 4 inches of suspension travel and go ride, than to not ride at all  or at least dread the thought of stopping.  While it is a task best left to the trained suspension expert, that is something  indeed worth the cost.  Don't grab the bread knife and cut foam out of the seat or slack off the preload and slide the forks up the clamps excessively....thereby disturbing the bikes balance.  Talk to a suspension expert and let them evaluate the dilemma.  A properly lowered machine will have both good suspension travel AND good action.  You do not have to ride under-suspended, under-powered, beginners bikes....or ride machines too tall for you comfort.