Suspension Setup

This article describes a baseline suspension setup.

Sag

Put the bike on the center stand to get the rear wheel off the ground and extend the suspension.

Use a measuring tape to measure from the center axle up vertically to a point on the chassis. Measure in millimeters to make doing the math easier. Record this measurement and label it M1.

Take the bike off the stand and have a couple of folks help hold the bike up while you get on it in riding position. Have a third friend push the rear down about an inch and let the rear come back up slowly (don't bounce it). When the suspension stops, measure from the center axle to the chasis point you measured to before. Record this measurement and label it M2.

With you still in the riding position get your third friend to lift up on the rear of the bike about an inch and let it settle slowly (still no bouncing). Then measure again from the center axle to the chassis point. Record this measurement and label it M3.

Calculate your static spring sag using this formula: M1 - [ (M2 + M3) / 2 ]

Ideally, your sag should be set somewhere around 28-33% of total travel for street riding (front and rear) which translates to somewhere between 30 and 35 millimeters. Too much sag means you need more preload while too little sag means you need less preload. If you run out of adjustment and still have too much sag, you'll need stiffer springs. If you run out all your adjustment and have too little sag you'll need shorter or lighter springs.

You'll want 30-35 millimeters of sag on the front as well. Since the ST doesn't have front suspension adjustments, you may find you need to adjust the thickness of the oil, add spacers, cut the springs (not likely), or get different springs in order to get a good sag set-up.

Doing the above will give you a baseline suspension set-up for front and rear. You can then adjust that further based on your riding style and preferences. If you're planning a track day, you might want to stiffen things up and run it in the 23-27% range (25-30mm) because you're not worried about road bumps or uneven pavement. For daily riding, you might decide you want things to run a bit softer and run your sag closer to 33% (35mm). Then for twisties you might decide to run in the 27-28% range.

Rebound Damping

It's important to remember that the REBOUND DAMPING is NOT weight sensitive. I've adjusted over 25 ST's over the past two years teaching the Total Control Advanced Riding Clinic and, without fail, proper rebound damping has been at ~1 & 3/4 full turns to 2 full turns out from full hard on a stock shock. Any harder than that and the rebound is too slow (bounce on the rear with it set at full hard and you'll see how slow the bike rebounds - looks almost like it's sticking).

Set your damping to full hard and bounce it. You'll need a friend to help stabilize the front and hold the front brake while you stand at the back and give the suspension a good push down. When you release it just let it rise on it's own. Set at full hard, it will look like the suspension is sticking as it rises up.

Set it to full soft and bounce it again. It will pogo so fast that it actually pulls the wheel off the ground and oscillates.

Turn it back to full hard and dial it out 2 full turns. Bounce it and it will come up and settle without oscillating. If it oscillates, turn it a 1/4 turn towards hard and bounce it again. This will be close to "just right."

Adjust in quarter-turn increments to get it dialed in perfectly. It should come up and just settle without looking like it's sticking and without oscillating.

Once again, there are only adjustments for the rear suspension. You can do the same measurements for sag on the front and check the damping on the front but you can't change it unless you upgrade the suspension.

Reference Material

• CalSci:
  • How your suspension works: http://www.calsci.com/motorcycleinfo/Suspension.html
  • Adjusting your rear suspension: http://www.calsci.com/motorcycleinfo/Suspension1.html#AdjustRearSuspension
• Total Control by Lee Parks: http://www.leeparksdesign.com/eshopprod_cat_530-3637_product_72946.Total_Control.htm

Source: http://www.st-owners.com/forums/showpost.php?p=548341&postcount=4

-- MarkFeit - 18 Sep 2008