Back to basics: setting static sag
It defines how well any suspension adjustments work. It’s that important
SOME TIME in the 1990s, adjustable suspension on sportsbikes started to become the norm. Far beyond the preload-only adjustable shocks of previous decades, suddenly we had the capacity to fiddle not only with spring preload fore and aft but also with the damping too, compression and rebound now being able to be addressed separately whereas before, if it was found at all, it fell under the combined umbrella of ‘damping’.
Sometimes the differences that could be wrought from these set-ups were minimal. In other cases it was often easily possible to completely ruin the handling through inept and ill-advised fiddling.
By the end of the 1990s however, stock adjustable suspension was generally pretty decent. For those who found standard suspension wanting, a huge aftermarket grew up with kits available to respring, revalve and revive sportsbike suspension.
Often these made cheap mass-produced suspension components work a lot better. They did of course take owners far beyond the realms of the settings in their manuals. For the purposes of this feature we will stick to what the various adjusters do so you can embark on your own adventures in suspension adjustment. Start with stock setting, work in small increments and remember you can always return to stock.
To achieve best results, suspension components should be services and in good working condition.
Tools for the job
Steel rules or measuring tape. Cable tie. C-spanner. Screwdriver(s). Spanners.
1 Measure up
First off we’ll look at rear static sag, that is how far down the suspension’s total stroke the bike sits at rest. You need to establish two points to measure between – one on the swingarm and a fixed point on the bike. We’re going from the top of the swingarm to the shock reservoir.
2 Ask a friend
Get a mate to lift the bike upright and bounce it up and down a couple of times to settle the suspension. Measure at rest and with the rear end fully lifted. Note down the difference between the two measurements. Do it several times in case the bike isn’t settling in the same spot.
3 Rear preload
There’s a C-spanner lurking in there to loosen off the locking ring to then move the adjuster ring. To increase the amount of sag, less preload is required. We’re aiming for a figure between 10mm and 12mm of rear static sag for the ZX-6R. We had to back the preload off to achieve this.
4 Front sag
A call to Darren at MCT Suspension suggested 26mm of static sag at the front. Butt a cable tie against the fork seal with the bike at rest having first settled the suspension then have your assistant lift the ’bars to fully extend the forks and measure between seal and cable tie.
5 Front preload
The ZX-6R’S front preload adjusters require a 17mm spanner. Adjust both legs evenly until the correct amount of static sag is achieved. As at the rear, less preload means more sag. Adding preload does not make springs stiffer, it merely changes the moment at which the spring compresses.
6 Rear compression
The ZX-6R’S shock has compression damping adjustment on the remote reservoir. Too little compression damping and the bike will be reluctant to turn in and the rear will tend to squat. Too much and it will be harsh and kick off bumps while too little squat will lead to loss of traction.
7 Rear rebound
You’ll usually find the rear rebound adjuster at the bottom of the shock. For illustrative purposes we’re showing the one on this old Yamaha shock. Lack of rebound leads to wallowing while too much rebound damping stops the rear recovering quickly enough forcing the bike wide in turns.
8 Front rebound
The front rebound adjuster is concentric with the preload adjuster. Too much rebound causes a harsh ride to the point where the tyre struggles to maintain contact with the road. Too little and the bike will wallow and tend to run wide coming out of turns.
9 Front compression
Too little front compression damping and the bike will tend to dive and may even bottom out. Too much compression and the bike will again tend to run wide as it will sit too far up the stroke. Set your suspension to the manual stock settings then make small tweaks to your taste.
Mind the paint with that steel rule, son