Seat Post Head Assembly by Fox

In this article, we’ll be discussing a Seat Post Head Assembly by Fox, US Publication 20210009224 (not granted yet). The publication date is Jan 14th, 2021 and the filing date is Sept 21st, 2020. This patent is a division of granted patent 10,780,933 filed on March 18th, 2018.

Edited: As noted by gregoryvanthomas in the comments, this is actually an Easton seat post head used in their EC70 and EC90, among others. I didn’t even realize they were part of Fox. I’m going to leave this up for future reference, but it’s definitely been released. Can’t win them all.

Brief Summary (tl;dr)

Fox have developed a new style of seat post head, where the pitch and fore/aft adjustments are independent of each other. The fore/aft position is adjusted similarly to current seat posts heads, with an outer through-bolt and two clamping components. The rider can loosen the through bolt and move the seat fore/aft. The pitch adjustment comes from two set screws in the front of the seat post head, which are forced against a rotating member inside the head (to which the through bolt is attached to). As the rider tightens and loosens the set screws, the rotating member… rotates, adjusting the pitch without affecting the fore/aft position of the seat.


I tell you what, one of the things I really don’t like about my bike (and every bike) is the way the seat attaches to the seat post. It’s such a pain in the ass to get that thing at the correct pitch and fore/aft position. I’m always dropping pieces somewhere and I’ve even lost a bolt at the bike park. Not fun.

The proper seat pitch and location are incredibly important for riding comfort and longevity. In my early riding years, I never paid much attention to the seat. The seat always hurt, and I just thought that was the way it is. I had some real gooch (technical term) issues, among others, and finally just sat down and started messing with the angle. All I had to do was lower the pitch a little bit, and I was good to go.

The current, widely used, system consists of two bolts, a top plate, and a convex base plate, as shown below of the current Fox Transfer to the left. The rider loosens the two bolts, which then allows the base plate and top plate to move freely. With the plates loosened, the seat can move fore/aft, and the pitch can be adjusted with the convex base plate. Neither the pitch or fore/aft can be adjusted independently; you’re always going to move both.


Fox are introducing a new seat post head system, where the pitch of the seat is a separate adjustment from the fore/aft adjustment. The rails of the seat are attached to the seat post in a very typical fashion, where they’re sandwiched between clamping plates and bolted to a rotatable core from the side. Set screws apply pressure to the completely separate rotatable core, and the pitch of the seat can be adjusted using the set screws. When the side bolt is tightened, the fore/aft movement is locked, and when the set screws are tightened into place, the pitch is locked. If the rider wants to only move the seat post fore/aft, they only need to unbolt the bolt on the side. If the rider wants to only change the pitch, they only need to adjust the set screws.

Intended Novelty

The intended novelty here appears to be the whole system, where Fox have a rotatable core, adjusted with set screws, and the rotatable core is attached to the seat rails via a bolt/shaft and clamping components. Really, it’s the set screws and the independently adjustable rotatable core that are novel here.


Fox explain the reason, which is pretty obvious to anyone that’s been on a bike in the last 20 years. Personal preference is the goal here.  

Seat posts are adjustable for fore/aft position and pitch adjustment of the seat. The adjustments can be for personal preferences, different bike geometries, different user geometries, different terrain, different performance characteristics, and the like. For example, a tall rider would prefer a further aft seat position than a shorter rider on the same bike. Similarly, a rider would likely prefer a first seat pitch when riding a bike on a road and a second seat pitch when riding the same bike on a BMX track.


Fox have a very concise line on the intent of this idea. They want to provide infinite pitch and fore/aft movement of the seat while simultaneously compartmentalizing the adjustments, so neither adjustment affects the other.

The following discussion provides a novel solution for a seat post head that includes the ability to allow “infinite” (un-indexed), adjustment of a seat’s fore-aft position while also allowing “infinite” (un-indexed), adjustment of the seat’s pitch, independent of one another. Moreover, the solution provides a mechanical stop for pitch adjustment such that accidental seat pitch movement is significantly reduced or even removed in normal and higher-than-normal seat loading scenarios.

Figure 2 shows an exploded view of the primary example in this document. Here, we’re focusing on the rotatable core 106, bolt 112a, shaft 112b, and set screws 114 and 116.

To adjust the fore/aft: Figure 6B shows a cut view from the front of the seat post. The screw and shaft are inserted into the head (and rotatable core) of the seat post, which holds the seat rails inside the clamps (108 and 118 above). The rider can loosen this bolt to adjust the fore/aft position of the seat without affecting the pitch of the seat.

To adjust the pitch: Figure 5B shows a cut view of the inside of the seat post, looking from the side. The set screws enter the head from the front, so they’re easily accessible and also well hidden. The process is pretty straightforward; the rider can tighten and loosen both of these set screws to adjust the rotating member, which will adjust the pitch of the seat.

When the set screws are tightened in place at the desired location, the pitch of the seat post is locked into place. You do not need to unbolt the clamping bolt to adjust the pitch of the seat. Fox have a great explanation of what is going on:

…by moving the [set screw] 114 and the [set screw] 116 into or out of their associated chambers the rotation of rotatable core 106 within cylindrical bore 103 can be adjusted. By adjusting the rotation of rotatable core 106, the pitch of the seat is adjusted. Moreover, since it is the rotation of rotatable core 106 that is adjusted to modify the pitch, it can be adjusted without affecting the fore-aft location of the seat. After the pitch is set at the desired angle, the [set screw] 114 and the [set screw] 116 are tightened against rotatable core 106. In so doing, [set screw] 114 and [set screw] 116 will provide a physical hard stop against a change in the pitch of seat in either direction.

Fox also show some other possible example of the final product, though they’ve been released. They all follow the same idea, but these don’t have an inner clamping component for the seat rails. Instead, the inner clamp is integrated into the rotatable core 106.


I’m a fan of this one. The bike world loves simplicity and adjustability, and I think this ticks both boxes. By simplicity, I mean simple actuation. I know there are more parts, but it should be easy to adjust. It seems like a great solution to isolate the movements of a seat. Does it look heavier? Maybe. It’s tough to tell from pictures. Will this be implemented soon? By the looks of the figures and the simplicity of this design, I’d bet that this is not conceptual. It’ll be available at some point in the future.

The current Fox Transfer has the head integrated into the upper shaft itself. This new invention would eliminate that, possibly saving some expensive machining costs. Though, this design appears to have more small parts, which could increase costs; so, it’s anyone’s guess as to the costs of this design. But Fox is Fox. They know people pay big bucks for their products, giving them a lot of freedom of design.

Either way, cool design, engineers.

4 thoughts

  1. Maybe they are already thinking a little bit ahead and securing a patent intended to rotate the seat accordingly to the height fo the post. Imagine an eletronic seat post with a rotating screw to get it up and down, and pitch the seat altogether.
    A rotating assembly is way easier to adjust than the screws directly attached to the post.

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