[mad_mardigen]

A few articles I wrote for my CBRTech web site a long time ago, in a galaxy far far away

Bike Sag
There are two types, Static and Loaded.

Static sag is the amount the bike suspension settles under its own weight.

Loaded sag is the amount the bike suspension settles with a rider on board.

Road bikes have a wide range of bumps and potholes to negotiate so the suspension needs to be set slightly soft. Race bikes on the other hand are set up harder than road bikes because the race tracks they ride on are generally smoother and void of potholes.




The correct settings are: (this was for the CBR1000RR)
Static Street Race
Front 20-25mm 10-20mm
Rear 15-20mm 10-20mm
Loaded Street Race
Front 35-50mm 25-35mm
Rear 30-40mm 20-25mm



Most of you will find that you will need to change springs to get into the right range.

Without the sag set correctly the damping will never be able to work effectively, because the suspension will be trying to overcome the effects of an incorrect spring.

So how do we set the sag and determine if we have the correct springs?

First off you will need the following.
A tape measure. (that reads in mm)
A pen and paper.
Tools to adjust the front and rear preload. (in your Honda tool bag)
Two strong friends.

Static Sag
Lift the back wheel of the bike off the floor with a floor jack.
With the bike on the side stand, place the jack under the oil pan (put a piece of wood between the jack and the oil pan) and raise the wheel just a hair off the ground.

Now, using your tape measure, take a reading from the centre of the rear wheel spindle to a point on the tailpiece that is directly above the spindle. Write down the rear no load measurement and assign it as reading A.

Next, raise the rear wheel about 2 inches off the ground and get your friend to push down on the passenger seat - this should unload the front forks.

Measure from the bottom yoke to the top of the stanchion. Write down the front no load measurement and assign it as reading C.

Measurements A & C will remain the same throughout the procedure so you only need to take this reading once.

Now put the bike back down on its wheels and hold it upright. The bike will settle under Its own weight. Measure the distance from the spindle to the tailpiece. Write down the rear Static measurement and assign it as reading B.

Subtract B from A. This is your rear static sag. Keep a note of it just in case you want to change it back. Ideally you are looking for 15-20mm on a road bike and 5-10mm on a race bike.

Either compress or loosen off the spring to get into this range using the tool supplied in your tool kit

Perform the same operation for the front, Measure from the bottom yoke to the top of the stanchion. Write down the front Static measurement and assign it as reading D.

Subtract D from C. This is your front static sag reading. Keep a note of it just in case you want to change it back. Ideally you are looking for 20-25mm on a road bike and 10-20mm on a race bike. Either compress or loosen the fork springs with the supplied honda tool to get in this range.

Loaded Sag
Sit on the bike with your riding gear on and have one friend steady the front and the other ready to measure. Sit the bike upright. Now WITHOUT touching the front or rear brakes bounce up and down a few times on the seat and then assume your normal riding position. Measure the rear of the bike as before. Write down the rear loaded measurement and assign it as reading E.

Subtract E from A and this gives you your rear loaded sag. Try and get between 30-40mm on a road bike and 20-25mm on a race bike by adjusting the spring preload as before.

Now do the same for the front. Write down the front loaded measurement and assign it as reading F. Subtract F from C and try to obtain 35-50mm on a road bike and 25-35m on a race bike.

If you can't get in these ranges for both Static and Loaded sag then you will need to change the springs for a harder or softer ones.

 

[mad_mardigen]

Suspension Damping

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First things first its called Damping not Dampening

Unfortunately there is no documentation that I can give you for the perfect setup. Suspension setup is individually dependent on the rider (style, preference) and road conditions, that vary from place to place. I can only give you guidelines for the suspension setup of your bike.

The suspensions role is to support the tires to create the best possible traction. For this reason the suspension plays it's most important role in corners, acceleration and braking. In the straight line the suspension is set correctly if it can absorb the bumps without causing instability.

So what does this all mean. Well there are 2 types of damping, rebound and compression they both work to counter the effects of a spring... well, acting like a spring.

How rebound damping affects traction.
Imagine you're riding along and you hit a bump. When the wheel hits the bump the shock is compressed. Then the wheel extends without any control; in fact, it extends too far. Because the sprung weight of the chassis has mass and is moving upward, it wants to pull the wheel off the ground, thereby losing traction. Rebound damping slows down the spring return to counter this effect.

With a light rebound damping setting, the wheel moves very quickly and the feeling is plush and mushy. As rebound damping is increased, there is more and more resistance to movement, and at maximum damping the wheel is "packing" so much, that the chassis is sucked down in its travel because it has not recovered for the next bump. This means the following bump has to overcome the added spring force due to this compression and the result is a jolt to the chassis upon impact.

Setting rebound
Mount your bike and quickly compress and release the front forks while holding the front brake. The forks should come up, and slightly settle only once. If you have too much rebound, the forks won't reverse direction. They'll just come up and stop.

Note: this is not the exact setting just a place to start

How compression damping affects traction.
Again, imagine you're riding along and you hit a bump. If there is no compression damping, the wheel will not meet resistance as it compresses the shock spring. No energy is dissipated at the crest of the bump and because the wheel itself has mass and the mass is moving upward, it wants to remain in motion and continue to move upward, compressing more than the amount required to handle the bump. This means the tire will lose contact with the ground as it crests the bump. This produces a loss of traction. Compression damping is used to dissipate the upward force just enough so the wheel will remain in contact with the road.
Here is where it gets complicated - Too little compression damping, the wheel moves up farther than it should, while with too much compression damping, the entire chassis moves vertically. In either case, you lose traction.


Now a lot of riders have mistaken ideas about how much damping should be used. They think the faster they are, the more damping they need. Nothing could be further from the truth. In fact, after a certain point, traction, control and ride quality (plushness) are all sacrificed.

Below are some tips to help you dial in your suspension and remember to take it slow. Suspension tuning is an art.
NOT ENOUGH COMPRESSION DAMPING ( Front Forks )

The front end dives excessively while on the brakes.
The rear end of motorcycle wants to "come around" when using front brakes aggressively.
The front forks "bottoms out" with a solid hit under heavy braking and after hitting bumps.
The front end feel is mushy and semi-vague, similar to lack of rebound damping.


NOT ENOUGH REBOUND DAMPING ( Front Forks )

The forks offer a plush ride, especially when riding straight.
The feeling of control is lost.
The fork feels mushy, and traction "feel" is poor especially when the pace picks up.
The front tire tends to chatter or bounce when hitting bumps at speed.
The bike tends to feel loose or wallow a bit when flicking the bike into a corner at speed
Increased speed and aggressive steering inputs adversely affect chassis attitude and pitch causing front end feel to be lost after the bike is counter steered hard into a turn.


TOO MUCH COMPRESSION DAMPING ( Front Forks )

Very harsh ride, especially when bumps and ripples are contacted by the front wheel.
Bumps and ripples are felt directly - the initial hit is routed through the chassis instantly, big bumps bounce the tire off the pavement.
Brake dive is reduced drastically, though the chassis is upset significantly by bumps encountered during braking.


TOO MUCH REBOUND DAMPING ( Front Forks )

The ride is quite harsh - just the opposite of the plush feel of too little rebound.
Rough pavement makes the forks feel as if they're locking up with stiction and harshness.
The front end wiggles or tankslaps exiting bumpy corners under acceleration.
The tire feels as if it isn't staying in contact with the pavement when on the gas.
The bike is hard to control when riding through dips and rolling bumps at speed.
The suspension's reluctance to maintain tire traction through these sections erodes rider confidence.


NOT ENOUGH COMPESSION DAMPING ( Rear Shock )

Too much rear end "squat" under acceleration.
bike wants to steer wide exiting corners (since chassis is riding rear-low/nose-high).
Hitting bumps at speed causes the rear to bottom out, which upsets the chassis.
Chassis attitude affected too much by large dips.


NOT ENOUGH REBOUND DAMPING ( Rear Shock )

The ride is plush at cruising speeds but as the pace increases, the chassis begins to wallow and weave through bumpy corners.
Loss of traction over bumps under hard acceleration.
Rear end rebounds too fast, upsetting chassis with a pogo-stick action.
Rear tire chatters due to lack of wheel control.


TOO MUCH COMPESSION DAMPING ( Rear Shock )

The ride is harsh, though not quite as bad as too much rebound, however, the faster you go the worse it gets.
Harshness causes loss of rear tire traction over bumps, especially during deceleration.
There is little or no rear end "squat" under hard acceleration.
Medium to large bumps are felt directly through the chassis, when hit at speed the rear end tends to kick up.


TOO MUCH REBOUND DAMPING ( Rear Shock )

Very harsh ride, rear suspension compliance is poor and feel is vague.
Poor traction over bumps during hard acceleration due to lack of suspension compliance.
Bike wants to run wide in corners since the rear end is packing down. This causes a nose-high chassis attitude, which slows down steering.
Rear end tends to hop and skip when the throttle is chopped during aggressive corner entries.

 

[Kiwi Rider]

@mad_mardigen Thank you for posting this. I did a couple of similar posts in the race section recently but it's good to have some street set up advice too.

 

[Boat]

Too bad the Ninja 400 offers neither compression nor rebound damping adjustments...

I’d still like to know what the stock spring rates are...