GSX-S Suspension Sag Setup

GSX-S Suspension Sag Setup

What is Sag?

Sag is the amount that the suspension drops with the riders weight – It is the first thing that needs setting upon getting a new (new to you) motorcycle.  If the Suzuki GSXS Suspension Sag setup is incorrect then the suspension will be working in the wrong part of the suspension travel.  Any rebound and compression damping adjustment should not be done until sag is correct. Suzuki suspension setup is easy and only takes a few minutes.

Too much Suspension Sag means that the GSX-S risks bottoming out on large bumps or heavy braking, causing an uncomfortable ride and the risk of loss of control whilst bottoming out.

Too little Suspension Sag means the suspension risks topping out after bumps or accelerating causing loss of traction.

So ideal Suzuki Suspension setup for Sag means that the bike uses the correct part of the suspension travel.

Why to Adjust Sag, Motorcycle Suspension setup

The majority of sports-bikes, including the Suzuki GSX-S1000 and Suzuki GSX-S750 have adjustable preload on both front and rear suspension.  All springs are installed with some preload otherwise the springs would rattle about on full extension.

Increasing the preload squashes the spring more but does change the length of the shock or fork as they are already at full extension.  If you have a 10 Kg/mm spring and increase preload by 10mm then you are adding 100Kg to the force needed to start compressing the spring, after the inital 100Kg force is applied the spring rate is still 10Kg/mm, so the fallacy that adjusting preload makes a spring stiffer or softer is a fallacy, however the effective spring rate can be changed by the linkage arrangement, usually meaning that the effective spring rate increases as the bike moves down/swing arm moves up.

Preload: This adjuster bears down on the shock or fork spring and shortens or extends the spring accordingly. Many people think that changing preload affects spring stiffness, and while you can compensate to a certain extent for a too-soft or too-stiff spring by using preload, the right move in that situation is to change the spring itself. Preload is used to adjust the shock or spring to the correct range of operation within the suspension’s travel – more preload will raise the bike up on its suspension, keeping you near the top of its travel. With less preload, the bike sits lower and closer to the bottom of its suspension travel.

With motorcycle suspension setup Rider Sag is the difference between full extension (the bike lifted so the wheel is off the ground) and with the rider in full gear sitting in the normal riding position with feet off the ground. For most sports-bikes on roads Sag should be between 30 and 35mm front and rear.  The Suzuki GSXS1000 has 120mm front travel and 130mm rear travel so sag for the street should be 30 – 35 front and 35 – 40 rear

How to to Suspension Sag setup

Rear Suspension

Moving to the rear of the bike, extend the suspension and measure from the axle to a solid point directly above. Find an obvious point to measure from, I use the flat point on the rear bodywork by the light.  This measurement is L1.  As can be seen here 653 mm to the inside top of the axle.

GSX-S rear sag measurement

Measure again with one person holding the front of the motorcycle while the other takes the two measurements at the rear, first measure with just the weight of the bike, this is the free sag. Next measure with the rider in normal riding gear sitting in normal riding position, with feet on the pegs  Measure this (L2)

Sag is L1-L2

35 – 40mm of sag is a good starting point for street riding, 30 – 35mm for the track.

Calculate the static sag and adjust the rear preload accordingly – one click or position of preload usually equates to between three and four millimeters of sag. There are 7 settings for the preload.  The tool to adjust the rear shock comes in the standard toolkit.   Here’s a tip to check that your rear spring rate is in the ballpark. With your bike unladen, lift the rear end until the suspension tops out, then gently let it settle-how much it drops is the free sag, which should be approximately five millimeters. If the suspension doesn’t drop at all, you’ve dialed in a lot of preload and should consider a stiffer spring. Too much free sag is a sign that a softer spring may be in order.

Original Suzuki GSX-S1000 rear suspension sag setup
Original Suzuki GSX-S1000 rear suspension – Preload is set by twisting the collar to one of 7 preset positions

GSX-S rear shock preload adjustment

Ohlins GP suspension sag setup on Suzuki GSX-S1000
Ohlins GP shock on Suzuki GSX-S1000 Preload is adjustable continously via a hydaulic system

Front Forks

With a couple of friends helping, fully extend the front suspension and measure from the seal to the fork bottom. This measurement is L1.  As can be seen here 125mm.  To fully extend the tyre must be off the ground.

Suzuki Suspension setup
GSXS Suspension fully extended

Put on your regular riding gear and hop on your bike, assuming your normal riding position. Have one friend hold the rear of the bike or using a front wheel clamp so that you can keep both feet on the pegs. Your second pal needs to take the same measurement as in step one-once after pushing down on the front end and slowly letting it settle up, and again after gently lifting the front end and letting it settle down, These would be identical in a perfect world, but take the average (L2), Here 90mm

Motorcycle Sag setup
GSXS Suspension with Rider

Sag is L1-L2. Here 125 – 90mm = Sag of 35mm

Cable Ties Method

Alternatively use the cable tie method, this makes it easier to measure and can be used to check afterwards that you are using the correct travel.  With the suspension fully extended tie a cable tie around the inner fork leg and push the cable tie up as far as possible, The cable tie must be able to move freely but not move under its own weight.  Again the rider sits on the bike, again make sure the cable is snug against the upper fork leg.  Extend the suspension fully again and measure the sag, between the red lines, 35mm.

GSXS Suspension Cable Tie Sag setup
GSXS Suspension fully extended Cable Tie

The blue line shows max travel, here 120mm so 30% of 120mm gives 36mm so 35mm is close enough.

Suzuki GSXS suspension adjustment
GSXS Suspension Cable Ties Rider weight

Leave the cable tie on the forks for a week or so of normal driving, the cable ties should be between 15 and 25 mm from the bottom of the inner leg with the Suspension Sag setup correctly.  Any lower and fork springs are too soft, any higher and the springs are too hard for your weight and riding style.  Here i have about 22mm.

GSXS Suspension Cable Tie Travel
GSXS Suspension Cable Tie Travel

Aim for approximately 30-35 mm of static sag for street riding and 25-30mm for the track.  See the bottom of the page for more information

How to adjust Suzuki GSXS Suspension Sag setup

If you have too much sag, tighten up the front preload. Too little, and you’ll have to loosen the adjusters accordingly. One line on the adjuster will usually change sag by about two mm.  The adjuster is the black 14mm nut, clockwise, less lines showing gives more preload and less sag.

GSX-S Preload adjustment

Suzuki Fork Preload adjuster
Front Fork Preload adjuster
GSXS Front Fork Preload setting
Suzuki GSXS Suspension Front Fork Preload setting

 

Suzuki Suspension Setup

Tuning the suspension damping

The stock suspension damping adjustment is very limited in its adjustment. I upgraded to a K-teck SSK piston kit, huge improvement

Fork Rebound is adjusted using the slotted adjuster on top of the forks, clockwise is more rebound, i.e. slower for the forks to extend.

Fork Compression is adjusted with the adjuster near the base of the forks, clockwise is more compression, i.e. less dive under braking and firmer on bumps.

Standard Rear shock only has rebound adjustment, slotted adjuster near the base of the shock.

 

Too Much Rebound, Fork
* The ride is harsh. Rough pavement makes the fork feel as if it’s locking up with stiction and harshness.
* Under hard acceleration exiting bumpy corners, the front end feels like it wants to “wiggle” or “tankslap.” The tire feels as if it isn’t staying in contact with the pavement when on the gas.
* The harsh, unforgiving ride makes the bike 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.

GSXS Front Fork Rebound Adjustment
GSXS Front Fork Rebound Adjustment

 

Lack Of Compression, Forks
* Front-end dive while on the brakes is excessive.
* Rear end of motorcycle wants to “come around” when using front brakes aggressively.
* Front suspension bottoms, with a solid hit under heavy braking and after hitting bumps.* Front end has a mushy and vague feeling, similar to lack of rebound damping.

GSXS Front Fork Compression adjustment
GSXS Front Fork Compression adjustment
 

Too Much Compression, Forks
* Harsh ride, especially when bumps and ripples are first contacted by the front wheel.
* Bumps and ripples are felt directly; the initial hit is routed through the chassis instantly, with big hits bouncing the tire off the pavement.
* The bike’s ride height is affected negatively; the front end rides too high in the corners; bike may want to drift wide in corners.
* Brake dive is reduced, though the chassis is upset significantly by bumps encountered during braking.

Lack Of Rebound, Shock
* The ride is plush at cruising speeds, but with increased speeds the chassis begins to wallow and weave through bumpy corners.
* Poor traction over bumps under hard acceleration; rear tire starts to chatter due to reduced wheel control.
* Excessive chassis pitch through large bumps and dips at speed; rear end rebounds too fast, upsetting chassis with pogo-stick action.

GSXS Rear Shock rebound Adjustment
GSXS Rear Shock rebound Adjustment

Too Much Rebound, Shock
* 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 forces a nose-high chassis attitude, which slows steering.
* Rear end wants to hop and skip when the throttle is chopped during aggressive corner entries.

Lack Of Compression, 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, which upsets the chassis.
* Chassis attitude affected by large dips and G-outs; steering and control become difficult due to excessive suspension movement.

Too Much Compression, Shock
* Ride is harsh, though not quite as bad as the too-much-rebound situation; but the faster you go, the worse it gets.
* Harshness hurts rear tire traction over bumps, especially during deceleration. There’s very little rear-end squat under acceleration.
* Medium to large bumps are felt directly through the chassis; when these are hit at speed, the rear end kicks up.

More information from Sport Rider

How much travel, spring rates

 

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