Cycling 201: Dropper posts Explained

New technology and deviation from the norm are often met with reticence among those who have charged themselves with upholding cycling’s “traditional values.” Two recent examples include the furor over mountain bike wheel sizes and resistance to the inevitable change to road bike disc brakes. One technological advancement which has been whole-heartedly welcomed, however, is the adjustable-height, or “dropper” seat post. In fact, dropper posts have been embraced so enthusiastically that riders are willingly shelling out hundreds of dollars to add up to a pound of weight to their bike. Can the expense, both in cash and grams, be worth the performance gains? Well, once you try one, you’ll likely never want to ride without one again; which is why we present this guide to dropper posts, with the goal of helping you decide which one is right for you.

While the advantages of using a dropper post are many, there are only two real negatives, but they are notable: cost and weight. With the most affordable posts costing $260, and the high-end offerings hovering around $500, the price of entry into the dropper post market makes any argument moot for many riders. Also, the act of weighing down your bike with an extra 400 grams of metal and hydraulic fluid by replacing a part that already does its job just fine is anathema to the dedicated XC riders among us.

If you have been saving your pennies and don’t keep track of your bike’s weight to the gram, then you are probably ready to enjoy the benefits bestowed by dropper posts. In this writer’s opinion, the dropper post is no less a game-changer than sticky rubber tire compounds, enabling increased overall speed, flow, and fun on any ride.

turnLowering seat posts for descending is nothing new, as the added clearance allows you to get lower and farther back on your bike for better high-speed control, the ability to use the length of your bike for optimal weight distribution, and clearance on jumps and whoops. Dropper posts allow you to lower your saddle on the fly, and also fine-tune saddle height for “in between terrain,” which is flat enough to pedal but requires maximized bike handling for the most fun. Plus, when short, steep, technical sections appear on the trail, instead of dismounting before and after to lower and raise your seat post, or conversely fumbling through with a raised saddle, a flick of the thumb will have you crouched and able to attack the section and immediately get on the gas after. When climbing, instead of sliding up to the saddle’s nose on short steep efforts, which effectively lowers your saddle height, some riders drop the saddle a touch in order to stay seated on the comfortable end of the saddle. Dropper posts enable you to optimize your position on the bike in any situation, enabling better traction, increased responsiveness, and maximizing fun!

While there are several important distinctions between dropper posts, the most important feature to consider is the difference between fixed and infinite positioning. Fixed posts generally have three preset positions to choose from; fully extended, fully lowered, and somewhere in the middle, usually closer to the top than the bottom. While three positions is the norm, there is at least one manufacturer with a four-position fixed post. Conversely, seat posts with infinite adjustability can be positioned anywhere in the post’s range of travel. These posts allow minute differences in saddle height for varied terrain, and don’t require “hunting” to find the middle spot. Most fixed position posts have to be finessed into the middle position—time which could be spent pedaling—while infinite posts will immediately go wherever you want them.

KS LevIn addition to deciding on an infinite or fixed travel post, you’ll have to choose between internal/stealth versus external cable routing and remote or post-mounted actuation. Here’s a hint for the latter—go with the remote option. Remote actuation levers are mounted on the handlebars next to the grips, making raising or lowering the post a risk-free, immediately executable operation. Conversely, actuators mounted on the seat post require you to take one hand off the bars and reach under your saddle to lift a lever. This makes fine-tuning saddle height much harder than it should be, discouraging use of the post. While actuator location is up to you, your frame largely decides between internal or external cable routing. If it’s equipped with an internal cable path, go with a compatible post. Your frame will look much cleaner and you won’t have to worry about cable rub marring your bike’s finish. If you decide to go with an externally routed post, there are a few factors to weigh. First, which location attachment is best? Generally, cables are either attached at the seat post’s saddle clamp or on the seat post tube itself, usually just above the frame’s seat post clamp. Attachment points at the saddle clamp force the cable housing to move up and down with the saddle. This can cause the housing to rub against your frame during movement, or possibly make the cable to bend outward and contact your leg or catch trailside debris when the post is compressed. Attachment at the post’s tube fixes the cable housing in a permanent position, free from movement when the saddle is raised or lowered. This attachment lets you precisely fit housing to your frame and ensures the housing will never rotate outward.

Next, decide on your travel needs, determined by frame size and riding style. Longer travel bikes benefit from a longer travel seat post. These bikes reverbwill usually be tackling varied and technical terrain, which is easier to negotiate with a lower center of gravity coupled with the ability to get farther off the back of the bike. Larger sized frames will almost always require longer travel posts to facilitate proper leg extension in the raised position. Sometimes, 150 millimeter travel posts will be too long for smaller sized frames. If weight is a concern, seat posts with less travel, thus shorter, are generally lighter as well.

By now you are probably ready to lay down your credit card and wait for your new post to arrive, but there’s one more item to discuss, and that is the internal mechanism of your post; hydraulic, mechanical, or a hybrid of the two. Full hydraulic systems, like the Rock Shox Reverb, require bleeding to maintain long-lasting, like-new performance. Don’t let this scare you off, however, because the bleed procedure is easier than a brake bleed. Hydraulic posts make up for the necessity of bleeding by offering smooth, infinitely adjustable travel, and do not require the use of a shift cable between the remote lever and post. Mechanical posts use springs and locking mechanisms to vary travel, and are usually in the fixed position category. Hybrid seat posts, such as the Kind Shock LEV and Integra, along with Thomson Elite Dropper Posts use mechanical actuation to open and close a hydraulic cartridge for height adjustment. This set-up offers infinite adjustment, smooth travel, and easy maintenance, since the hydraulic cartridge is closed and does not require bleeding. Some hybrid posts, like the Kind Shock e10, feature an air/spring hybrid system. Cables are used to remote actuate hybrid and mechanical posts, and are subject to the same degradations in performance as shifter cables. When deciding between hydraulic, mechanical, or a hybrid post, consider whether you would rather change cables every few months or perform a bleed twice a year.

Finally, it’s OK to shim your seat post if needed, since there are many seat tube sizes and limited dropper post diameters. If you have to go this route, try to avoid shimming posts with collar/clamp-mounted actuators, and remember; there are no 30.9 to 31.6 shims available.