The table was taken from an Ohlins Spring Manual.
You’re correct though, the accepted range of values is typically 1/4 to 1/3 of total travel so 32mm to 42mm would be correct for your Showas for the street.
If you preload to get 32mm of sag then the rider’s neutral position is closer to the fully-extended position so you increase the tendency to hit the top bump-stop but the suspension moves less, resists the larger forces generated by the higher speeds, and giving better handling. That’s why this is a good track setting.
With less preload you’ll get 42mm, which softens the ride considerably for rider comfort but increases the tendency to bottom-out on severe bumps. If you want a plush ride without bottoming-out then you shouldn’t buy a sportbike.
In short, when you set sag, you are determining how much suspension travel will be available for bump absorption. The maximum travel is decided by the bike designer, i.e. a lot is needed for off-road bikes, very little for track bikes because of the smoother surfaces they encounter.
So a 996’s stock suspension would bottom-out regularly off-road, but allow too much squat and dive on a typical track - which is why recommended sag values for the track are lower than street values.
That means that a sag value for a given suspension travel can be selected to maximize comfort at the sacrifice of larger suspension movement that limits handling performance. Bryan’s original concern arose from a question of comfort to avoid “kidney shake” so it would be better to err with a higher sag value than a lower one.
Shazaam!
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