The screw at the bottom is a pre-load tensioner for the elastomer inserts. You should adjust it for your personal preference, but the more you tighten it, the less shock absorbancy you get. This means that the saddle height should be raised to allow for compression. If you tighten the preload t oo much, you lose the advantage of this shock absorbing post.
The preload adjuster is located at the bottom of the post and is adjusted using an Allen wrench. Clockwise adds more preload and counter clockwise lessens the preload. The preload adjusters [sic] intended purpose is to allow each rider to set up the amount of cushion they prefer. Always begin testing the adjuster 1/2 screwed in.
Tamer posts don't have an internal spring. Instead of spring tension, the screw at the bottom adjusts "pre-load." This type of adjustment (absent on many suspension seatposts) allows you to get rid of "sag"; the amount of suspension travel that results from merely sitting on the bike. Reducing sag has two benefits. First, unless a suspension has adjustable "rebound" (and bicycle suspension seatposts don't) "pogo-ing" and sag are inextricably related. Pogoing is not only annoying, it reduces efficiency and control. Second, sag diminishes the amount of travel left for absorbing bumps (if you have 4cm of travel and 1.5cm is used in sag, only 2.5cm of travel remains to cushion bumps). While some stokers like the "Charmin" effect of lots of sag, reducing sag to below 0.5cm will improve over-all performance.
The other adjustment on newer Tamer seatposts is obtained by changing elastomers. Current Tamers are factory-equipped with 8 medium-density one-inch elastomers. By trading some or all of these for high or low density elastomers you can obtain 15 different settings. A ride kit includes eight elastomers of the same density (high, low or medium) and costs ~$15.
Because adjusting preload or changing elastomers produce similar results (either will make the ride firmer of softer), less sophisticated customers will probably be happy to merely adjust the preload to accommodate different stokers and terrain. This method (the best you can hope for with most brands of suspension seatposts) is far from optimal. Pre load should be adjusted through the aforementioned "sit on it while it's stopped" method. Optimal elastomer density should be determined only after using the post during normal rides.
How do you know which elastomers to use? This depends on weight and terrain. If you remain on pavement and your captain continues to avoid and/or call-out the worst potholes, lighter elastomers give a softer ride (without pogoing). If you ride off-road or have an insensitive captain, you'll need firmer elastomers to keep from constantly bottoming out.
Santana sells an advanced version of the Tamer that includes a simple gauge that allows you to accurately determine sag (to adjust preload) and maximum travel (to suggest different elastomers). The gauge indicates the maximum travel used since the last reset (kind of like the max speed function on your computer). Unless you're consistently using most of your travel, switch to lighter elastomers for a softer ride. If the gauge shows you're consistently using all your travel, firmer elastomers will keep you from bottoming out.
Three popular ways of "testing" a suspension seatpost should be avoided. First, using arm muscle will only work if there's too much sag. Similarly, bouncing up and down on a stopped bike should not produce much movement. Finally, while intentionally running into obstacles seems amusing to some, it's about as intelligent as butting your helmeted head against a brick wall.
As was alluded to above, there are various versions of Tamer suspension posts and Santana prefers a special lighter version with maximum travel-to-height ratio, sealed (no funky boot) construction and the aforementioned built-in gauge. The price of the best version for diameters other than 29.8mm is $130. If your seatpost measures 29.8, (newer Santana and Trek tandems) you can opt for Tamer's exclusive-to-Santana "ShockPost"--no shims required. The ShockPost includes further advanced features and sells for an additional $50.Back to Tech Tips!