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Zero Offset Seatposts Make Zero Sense, Mostly

Zero Offset Seatposts Make Zero Sense, Mostly

Zero offset seatposts are a waste of nice aluminum. Zero offset posts were popularized when folks started to CNC machine seatposts in the 1990’s, when machining bike parts was all the rage. Machining a seatpost with offset is harder to do, and it makes it heavier. The whole thing in the 90’s was low weight CNC’d stuff, so obviously heavier was bad. Can’t forget that more time on the CNC mill means less profitability. Those are the main reasons why there are so many of them. It’s too bad because they kinda look cool.  

What’s the percent of the population that needs them? I’d say 5% is highly generous. Regardless, these posts are often found on mountain, gravel, road, etc. bikes. And they’re put there for two reasons: to control reach by putting your saddle closer to your bars, and to keep costs down.  

Unless you have a really slack seat angle (around 71 degrees, Hey! Isn't that the seattube angle of a Tanglefoot Moonshiner?) or really short femurs you want an offset post. Right now so few bikes have an angle that slack and there is no reason to run a zero offset post. None. It puts more strain on knees, hands and arms because it shifts your weight forward. For long distance comfortable riding: push your saddle back. Get a 20-25mm setback post. Don’t let a sales guy jam your saddle forward and tell you, voila, the bike fits! Pro tour riders all ride 20-30mm of setback. That number has been standard for 70 years for a good reason. Setback posts allow for your fit to be both powerful and comfortable.  

Good seatposts share a few design parameters:

Setback, forging, big bolts, nice looks, ease of adjustment, and ability to use a normal multi tool allen key to adjust them.  

The best posts are cold forged (the Nitto S83 is the best post on the market), and have 2 big bolts, placed front to back, not side by side. This means, for the saddle to slip, you have to break an M7 bolt, which isn’t going to happen. Cold forging means the aluminum is smashed into it’s shape by a huge press, and that smashing action aligns the aluminum’s grain structure along the curves of the post. Think: wood grain vs. poured concrete.  

 

Bad seatposts typically have some or all of the following traits:

Hard to get at bolts. If you can’t get in there with a multitool, it’s bad design.

Bolts that you access from the side rely purely on friction, (technically all fasteners rely on friction, but not in the same way that side loaders do) and it’s easy for the saddle to slip unless the bolts are seriously over tightened. I’ve used many, many side bolt seatposts over the years, none of them is as easy to adjust, as safe once adjusted, or as easy to readjust as a seatpost that has bolts that install from the bottom.

Side by side bolts are also a no-no. They’re just riffing on a single bolt seatpost, which uses the friction between the top of the seatpost shaft and the bottom of the saddle rail cradle to keep the seatpost head from slipping. It can still slip. Bolts that are loaded fore to aft do not have this issue. To have the seatpost head slip on a fore to aft bolt seatpost, the bolt has to snap. Not gunna happen.

Small bolts. Seatposts should be able to be field adjusted, which means no torque wrench. Small bolts have low torque specs. Thomson seatposts have a 7nm torque limit, plus they are hard to get at. That’s bad, and bad.

Hard to adjust. See: Bad design.

Bolts you access from the side of the post. These turn the head of the seatpost in a handy pivot, which activates when you wack a bump, causing the saddle to nose up in an alarming fashion. Terrible design.

Bonded heads. When the shaft and the head of the post are glued together, that glue can eventually give out. That’s bad.

Weird bends in the middle of the post, or aero shaping. These limit saddle height adjustment, and there is no reason for them except poor design. Why would you put a bend in a seatpost? It limits the amount of vertical adjustment you can get.