Avoid Dropper Post Installation Mayhem or Do the Opposite with These Tips!

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See this post at its original home on Bicycle Times.

You ride up to a red light and all the other jokers in the bike lane line up in various states of immobile balance. Someone has both feet flat on the ground and bike in between, reminiscent of the kid who drops his shorts all the way to his ankle at the urinal; another has one leg down and one up on the pedal, like a Lycra flamingo; the worst of them tries to track stand, fails, lurches forward a pedal rotation then tries again but halfway in the intersection this time.

You’ve seen it; you’ve been there.

Now imagine if you could just flip a switch to lower both feet onto the ground without removing your butt from the saddle. Imagine: stoplights become a pleasure, a chance to sit comfortably and inhale the vibrant world around you. Imagine the awe of your fellow commuters, watching, transfixed, as you lower yourself like some kind of technologically advanced alien sex god.

This dream can be your reality, but before you jump straight into the bike tech avant-garde, here are some of the little details people tend to overlook that will determine your success with the drop.

Before you buy, these are the measurements you should take.

Tools needed: Calipers and tape measure. Maybe some hex keys.

1. Stock seatpost diameter and/or seat tube inner diameter. If they don’t make a dropper post to match your frame: dang.

2. Distance from seat tube collar to saddle rails. Seatpost companies advertise 100mm drop or 120mm drop, but that’s just a measure of how much the saddle goes up and down, it doesn’t account for the size of the saddle cradle or the crown at the base of the stanchion. The minimum height for the “100mm” dropper post in the picture is actually 158mm when fully extended.

3. Internal seat tube depth. There are mysteries inside the bike frame. I’ve found Chinese candy wrappers, cigarette butts, and all kinds of mischief in brand new bikes, but if you have a small frame the most worrisome obstructions are the things that can’t be removed: water bottle bosses and fender braze-ons. To find what’s in there, loosen your seatpost collar and let your stock seatpost drop as far as it can, then pull it out and measure the distance between the seatpost collar and the base of the seat post. You might need 250mm or more to fit a dropper.

4. Handlebar clamp diameter. Stock dropper post control levers are usually made for 22.2 handlebars, so a lot of drop-bars are too big, even at their thinnest point, but some companies make a lever for 31.8 bars. If you’re tricksy you can retrofit a shifter to work as the dropper lever. There are guides on how to do that elsewhere on the Internet.

“But what if my post bottoms out on something inside the frame?”

Water bottle bosses are the most likely enemy. Sometimes all you have to do is take out the water bottle bolt and that’ll give it the room it needs. There might also be a burr down there, which you can remove using a cylinder hone on an electric drill. Do not use a reamer or any other cutting tool because seat tubes are wicked thin and you’re liable to cut right through.

“But what if the dropper post sticks up too far and my stinking feet can’t touch the pedals?”

How comfortable are you with cutting pieces off your frame? Some frames come with what frame builders call “smokestacks” – a section of seat tube that sticks out beyond the top tube junction. These smokestacks might be longer than necessary. Or, they might be exactly as long as they need to be. Only one way to find out for sure: use a hacksaw to cut a bit of spare stack away, then smooth it down with a file. Keep cutting, little by little, until you’ve effectively lowered the max saddle height, or until you’ve ruined your frame forever.

Now that you have the dropper post down in the sweet spot, lets figure out cable routing.

Tools needed: cable/housing cutters, 1.5mm to 4mm hex keys, zip ties? 

This is the fun part. The cyclocross frame in the pictures has an extra braze-on for top-swing front derailleurs so I was able to run the cables through there, easy cheesey.  Don’t have extra housing braze-ons? Don’t worry! Zip ties work fine. I suggest you tie up to the brake housing instead of the frame because it won’t move around as much. You can also buy housing guides that mount around the top tube.

Before you cut the cable and housing, make sure that you can move the handlebars back and forth, all the way.

PRO TIP: Dropper post cables often come with what nerds call “compressionless housing” or “shift housing” to the layperson. The problem with compressionless housing is that it isn’t very flexible. Instead, I use brake housing, which handles bendy routing a lot better. I use a 5mm to 4mm stepped ferrule at the end to fit the housing into the dropper post cable-stop and the lever cable-stop. The bad part about brake housing is that when you flex it a lot the metal coil inside lengthens, effectively pulling on the cable. To overcome this, install the cable with an itty-bitty-bit of slack. Also, the dropper post is designed to work with a thin cable, while the brake housing is meant for a thick one.  It’ll wear out quicker than normal. Deal with it.

Frequently Asked Questions:

“The saddle drops whenever I turn the handlebars. Whuddupwiththat?”

The housing might be too short, or the cable might be too tight. Make sure the housing isn’t pulling out of the ferrule when you turn. Also, installing a flexible elbow bend (sometimes called a noodle) might help.

“The saddle returns super slowly.”

You might just need to give the cable some more slack, or there might be some drag in the housing or lever. Might as well give up.

“I hit the lever but the shit don’t drop.”

First, try putting your weight on the saddle, dummy. If that doesn’t do it, then you might need to tighten up your cable, and double check that all your fasteners are tight too.

“At first it worked great, but now it keeps dropping when I don’t want it to.”

The housing might have dislocated from the ferule, so check that.

“My dropper post has an electronic/hydraulic lever so none of this applies to me, but I’m still having problems.”

That’s what you get for trying to be fancy. Did you plug it in? Try turning it off and on. Is there even fluid in it? Air bubbles? If it’s an electric dropper and there’s fluid all over, then you’re really in trouble. Good luck, sucker.