Setting rear suspension sag (Laden Sag)

If you want your bike to handle like it should, then checking and setting up your bikes suspension to ensure its operating at its optimum is crucial.

There are three types of ‘rear shock’ suspension Sag to check:

A) Free / Un Laden Sag
B) Rider or Laden Sag (Ride Height) rider onboard.
C) Static Sag – The amount the bike sags under its own weight stood still – No rider.

Checking your bikes sag is simple and costs nothing other than time adjusting and setting the stiffness of the rear shock. Adjustments as small as 5mm (¼) will have a dramatic effect on the way the bike performs. Once set, you can check other stuff such as rebound / damping etc.

Follow the three simple steps below to see if your suspension is set according to your weight. A bike with a standard spring will be suitable for a rider of average weight: 75 – 85kg?
If you are unable to achieve the correct Sag rates (B & C) for your weight you may need to replace the spring on your rear shock for something harder or softer, depending on your results.

Items needed:

Centre stand (Both wheels need to be off the ground)
Tape measure / Pen and paper
Willing assistant – to help you measure and balance while you are sitting on the bike
Your riding gear including backpack with usual contents drinks / tools etc
The printout of this page, keep it handy for referrals
Your manual
C spanner (preferable) or flat blade screwdriver and hammer

Note: Both sags, (rider and static) need to be in the correct range to operate properly. Once set you can adjust your rebound and damping clickers to suit.

Before You Start:

Check that your ‘Rebound’ and ‘Compression’ clickers on both your Front Forks and Rear Shock are set to their standard settings. If you don’t have a manual, just set them half way between hard and soft.

For All Measurements: Mark a point vertically above the rear wheel spindle on the rear mud guard. Measure and note the distance between the spindle and that point.

A = Free / Un Laden Sag

B = Rider / Laden Sag

C = Static Sag

Measurement A: Free / Un Laden Sag

Place bike on a stand ensuring both wheels are off the ground un-weighted; record and note your measurement.

This number will not change as sag is adjusted. All future sag adjustments will be based on this number

Measurement B: Rider / Laden Sag

Next, with your bike off the stand, sit centrally on your bike in ALL your riding gear including backpack etc. and let someone hold you in a balanced position or lent slightly on a wall etc.  Bounce up and down a couple of times to settle the suspension ensuring your feet are on the pegs.

Your assistant will need to measure and record the same two points as before.

  • Linkage bikes: 95-105mm rider sag
  • Non linkage: 105-125mm (KTM, Husaberg etc)

Measurement C : Static Sag

With the bike off the stand and the rider off the bike; push down on the back end a couple of times and let the bike come up by itself. Measure between the same two points as before.

Note: If you set your rider sag and your free sag does not fall within the recommended range,       you may need to change your spring.

  • Linkage bikes 25-35mm
  • Non linkage bikes – PDS – 30-45 (KTM, Husaberg etc)

Note: Less than 25mm of Static Sag generally indicates a stiffer spring is needed and more than 35mm indicates a softer spring is needed.

Adjusting ‘Rider’ Sag

There are two spanner type nuts on your rear shock holding the spring at the top end. First loosen the upper one (the lock nut) and then adjust the lower one accordingly.

Winding the nut down will compress the spring, and raise the rear ride height. Unwinding the nut will soften it and lower the rear ride height.

Making small changes at a time (3-4mm) re check as you go, getting back on the bike and re measure as per step B taking note of your new figure. Keep doing this until you achieve the required setting. Then tighten the lock nut!

How Does This Affect My Bikes Handling?

Adjust spring preload as necessary to obtain the desired handling results:

  • Decreasing the race sag dimension improves turning ability for tight terrain at the cost of slightly reduced straight line stability.
  • Increasing the race sag dimension may improve stability on faster terrain with less turns, but will reduce turning performance slightly and may upset the balance between the front and rear suspension, producing a harsher ride. This will happen if the adjustment shifts the effective wheel travel toward the more progressive end of its range

Can’t Achieve The Correct Settings?

Too much rider sag indicates you must increase pre-load to the spring by turning the Spring / Pre-load Adjuster clockwise – decreases rider sag measurement.

Too little rider sag indicates you must decrease pre-load to the spring by turning the Spring / Pre-load Adjuster counter clockwise – increases rider sag measurement.

Your static sag should be within the limits given in your owner’s manual. If it’s not, you have had to set too much preload to get the ‘Rider Sag’ in spec. This means your spring is too weak. If there is too much static sag, the spring is too strong.  You may need to change your spring to achieve the correct settings.

A good suspension shop should be able to tell you what spring rate you will need, based on your bike make and model, and on your weight. When you get all this right, your bike will perform the way it was designed

Things to Remember About Sag

  • High speed shock compression adjusters will affect sag settings.
  • Track riders should experiment with setting sag from a standing position instead of seated.
  • Off-road riders are usually better off using measurements from a seated position.
  • There is no magic number for your bike. Experiment, and use what works best for your riding style.
  • Springs can settle and adjustments will change slightly over time. Check your sag settings often.

The above settings which should be used as a guide only were provided by: K-tech Suspension Specialists