Motorcycle Suspension Set-up Guide

Introduction to Suspension Set-up

The sun is out and armed with your screwdriver and spanner you're ready to start working on your suspension set-up. Stop. Before you even consider adjusting your motorcycle's suspension there are a few basics to sort out first. Check your tire pressures are correct; an under or over inflated tire does more damage to a motorcycle's handling than any suspension adjustment could ever do. Get online and check your tire manufacturer and ensure yourself that the tire pressure is correct. Next, find a nitebook and pen. Hopefully your motorcycle's suspension is set as the manufacturer intended, but anyway write down the correct settings so that you have a safety net should it all go wrong.

Suspension is generally set as turns form fully in, which means how many times the adjuster needs to be turned to reach the point it is at from being fully wound in (generally clockwise). The little dot stamped on the adjuster is your guide to turns so carefully screw the adjusters in, counting the turns. Write this figure down then return them to their original position.

Spring preload on the fork may be rings, which is the number of scored rings you can see protruding from the adjuster, turn or even length in millimeters the adjuster is extended. Check your owner's manual to see how your motorcycle's are measured, again they will generally be set from fully in. An older shock often has a 'stepper' spring preload, which is a series of steps on the collar that compress the spring, or will be measured in distance and adjusted via a C-spanner and two collars, again check your motorcycle's manual.

Why Replace OE Motorcycle Suspension

Mass-produced suspension, as featured on mass-produced motorcycles, lacks the infinite control and precision of elite aftermarket units. Straight from the crate, manufacturers have to accommodate a wide spread of weights and abilities that sacrifice the perfect set-up. Motorcycle manufacturers also have to buy bits in to meet a budget. To give you some idea of how shabby OE shocks are, there's a certain manufacturer who pays around 2500 THB for a shock. The others don't pay much more…

There's zero advantage to be had by getting wound-up with standard suspension's limitations, as you're not going to shave seconds off your personal best. Unless you've just parted with a lot of money, all you get from standard clickers is RSI rather than any decent set-up. What you need to make the grade is a fork cartridge kit and shock to fling in.

The Front End

Fork Spring Preload

Where? The large nut adjustor on the top of the fork (not Big Piston Forks or motorcycles that split the damping between fork legs).

Too Hard?

Symptoms: The motorcycle turns into corners slowly and doesn't feel settled. Once on the power the motorcycle runs wide.

What's actually happening?

Spring preload adjusts a motorcycle's static sag. Indeally this should be set at 25 to 30mm and so increasing the spring preload reduces this sag by raising the front of the motorcycle. This puts more weight on the rear end which slows down the steering. People think that spring preload makes the front stiffer, this isn't true, it just alters the height of the motorcycle's static sag. Most motorcycles run linear rate springs which means increasing or decreasing the preload can't alter the spring's stiffness.

Too Soft?

Symptoms: The motorcycle turns almost too quickly into turns, giving an unsettling feeling and causing you to sit up and re-adjust your line.

What's actually happening?

By reducing the preload the static sag has been increased, which sharpens the motorcycle's handling and puts more weight over the front end. This can lead to a nervous feeling from the front in corners as the motorcycle's geometry and weight balance had been tilted too far forward.

Too Soft?

Symptoms: Once off the brakes the motorcycle pings back up on its suspension, unsettling it at corner entry and making the motorcycle feel high at the front. Once on the throttle mid-corner the motorcycle starts to run wide, forcing you to adjust your exit line and making cornering a case of constant readjustments rather than a smooth, single process.

What's actually happening?

This is a very common complaint and riders often confuse too little spring preload with too soft rebound damping as they have similar effects. Once the weight is reduced on the front, by the throttle being opened, the forks extend too quickly, which makes the motorcycle run wide. You also find that many riders complain the motorcycle doesn't flick from left to right if the rebound damping is too soft.

Fork Compression Damping

Where? The screw adjustor at the bottom of the fork leg (not with Big Piston Forks).

Too Hard?

Symptoms: Under braking the motorcycle hardly dives at all, feeling completely dead and devoid of feedback from the front tire while delivering a harsh ride. The motorcycle fails to track over bumps and even the smoothest of roads feels like a moon landscape.

What's actually happening?

With too much compression damping the fork's movement becomes stiff and harsh and it doesn't ride bumps well as the small amount of initial damping that deals with bumps is taken out. Too much compression damping also reduces the weight over the front wheel which makes the motorcycle kick off small bumps and feel twitchy and nervous under acceleration.

Too Soft?

Symptoms: When hard on the brakes the forks dive too much and feel they will bottom out.

What actually happening?

Generally, having too little compression damping isn't a huge issue but if your motorcycle's fork springs are too soft the fork can bottom out if there isn't enough damping. Use a cable tie on a fork leg to see if you are bottoming them out. If so, increase the damping or look at fitting stiffer springs.

Fork Rebound Damping

Where? Screw adjustor at the top of the fork.

Too Hard?

Symptoms: Under hard braking, the rear feels unsettled and the motorcycle drops into corners with an unpleasant flopping sensation. Over bumps the ride is harsh and the front sometimes patters.

What's actually happening?

The rebound is holding the forks down in their stroke and not allowing them to recover. This puts too much weight over the front wheel which makes the rear light and the forks too rigid, transferring any bumps directly from the tire to the rider. In addition, should you hit a series of bumps while the forks are compressed they will have no more movement left, which creates a pattering sensation as the front hops over the bumps rather than damps them.

Too Soft?

Symptoms: Once off the brakes the motorcycle pings back up on its suspension, unsettling it at corner entry and making the motorcycle feel high at the front. Once on the throttle mid-corner the motorcycle starts to run wide, forcing you to adjust your exit line and making cornering a case of constant readjustments rather than a smooth, single process.

What's actually happening?

This is a very common complaint and riders often confuse too little spring preload with too soft rebound damping as they have similar effects. Once the weight is reduced on the front, by the throttle being opened, the forks extend too quickly, which makes the motorcycle run wide. You also find that many riders complain the motorcycle doesn't flick from left to right if the rebound damping is too soft.

The Rear End

Shock Spring Preload

Where? Two collars compressing the shock.

Too Hard?

Symptoms: Under braking the rear feels wayward, swaying back and forth and losing contact with the ground. Bumps in the road kick you out of your seat and the ride is harsh and choppy.

What's actually happening?

This is a very common complaint. A motorcycle should have about 10mm of static sag at the rear, but most come with between 3 to 5mm as they have too much preload. Because of this, should you hit a bump in the road the force of the jolt causes the shock to full extend of 'top out' which creates a harsh ride. Should these bumps occur when you are approaching a corner you have to wait for the suspension to settle down before turning in, often forcing riders to miss apexes.

Too Soft?

Symptoms: The motorcycle is settled under braking, but during turn-in feels lazy and once on the power the motorcycle has a tendency to want to run wide. Any throttle movement mid corner causes the motorcycle to squat with a vague, squashy sensation.

What's actually happening?

The lack of preload makes the motorcycle sit low at the back which reduces its turning capability. Once on the power, the weight transfer is too great to the rear which makes the shock squat and sometimes bottom out causing the motorcycle torun wide. The best way to use the preload is a fine tuner for the spring. If your motorcycle is unsettled in a corner the best thing to do is swap the spring for one that matches you weight then use the preload to perfect your set up.

suspension_setup.txt · Last modified: 2014/04/15 17:50 (external edit)
 
Except where otherwise noted, content on this wiki is licensed under the following license: GNU Free Documentation License 1.3
Advertising

Poll

How many times have you crashed your motorcycle in the last three years?

  •  Never
  •  Once
  •  Twice
  •  Three times
  •  Four times
  •  Five times
  •  More than 6 times
  •  More than 10 times
This poll has 0 more questions.
Results
Other polls | 8,369 votes | 19 Comments
TMEA MEMBER
Thai Motorcycle Enterprise Association
Events
Site Events
Wednesday 30-Nov - Monday 12-Dec
Motorcycle Thailand on Facebook
Motorcycle Thailand on Facebook
My Account