Author Topic: The Preload Adjuster Myth (by Elvin Rivera)  (Read 5258 times)

Offline elvin315

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The Preload Adjuster Myth (by Elvin Rivera)
« on: May 17, 2011, 07:30:24 pm »
It is a common belief that adjusting the preload of the fork will stiffen or soften the springs. That's simply not true. Preload is the amount of force a suspension provides to support the unladen weight of the bike and still allow for the travel of the suspension components. The weight of the bike is accounted for in the design of its suspension and the spring rates are chosen accordingly. The spring rate is determined by the temper of the spring's steel and the thickness of its coils. It's measured in pounds or kilograms of weight per inches or millimeters of compression. Adjusting the preload doesn't change this regardless whether the springs are progressive, straight, or dual wound. Preload adjusters are just that. They adjust the existing preload. The adjusters can increase preload or decrease it slightly to compensate for the load placed on the bike by passengers and cargo. Simply put the adjustment affects the bike's ground clearance.

The confusion lies in the terminology. Compressing and stiffening are not the same. Yes, the adjusters compress the springs but they do not stiffen them. Through the law of "action & reaction", you've applied a force by compressing the spring and the spring responds with an opposite force of expansion. When you screw down the adjusters that force is passed through the spring and pushes the slider down. That, in turn, raises the bike up. All you've done is add to the length of the length of the spacer. You can screw the adjuster down to where the fork won't bottom under braking and think the fork is now stiffer but all you've done is extend the fork so there's more tube length to travel. The only way to truly stiffen the fork, meaning to increase the spring rate, is to install stiffer springs.

I hope this helps dispell this "old biker's tale".

« Last Edit: May 21, 2011, 12:14:34 pm by elvin315 »