Everything You Need To Know About Wishbone Seat Stays

This post compares the advantages and disadvantages of wishbone seat stays.

FAQ: What are wishbone seat stays?

The seat stays of a bicycle represent the tubing going from the seat tube to the rear dropouts.

Anatomy of a Bike Frame

Regular seat stays consist of two distinct tubes welded or brazed to the left and right of the seat tube.

Wishbone seat stays, on the other hand, attach to a monotube which then connects to the seat tube.

The shape of mono seat stays resembles the wishbone of a bird which is formed by two collarbones.

This is the wishbone of my Centurion Futura

In the past, people believed that wishbones bring good luck. Currently, there’s a ritual/tradition during which two individuals hold a wishbone and think of a wish. Then they proceed to break the wishbone. The wish of the person left with the larger piece is expected to come true. (Hence the name wishbone.)

The Pros Of Wishbone Seat Stays

  • A Stiffer Frame

Wishbones seat stays do not flex as much as regular seat stays and make it possible to produce frames with stiffer rear triangles.

For that reason, wishbone frames are considered better for cantilever brakes because those brake models create lots of stress in the area during hard braking.

  • Simplified Production Process

Wishbone seat stays a.k.a. mono stays are sometimes chosen as a way to speed up mass frame production.

By relying on a wishbone, producers can use the same base and seat stays to produce frames of different sizes by trimming the monotube when building smaller bikes.

Another production advantage of wishbone seat stays is the absence of a seat stay bridge (the small tube connecting the two seat stays.

The above shortcuts may not seem like a lot when building a single frame, but during mass production, one less step results in a million saved steps over time.

  • Reduced Mud Accumulation On The Seat Tube

The monotube of the wishbone stay acts as a small mudguard reducing the dirt reaching the seat tube.

  • Another Place For Accessories

You can install clip-on seat post accessories such as rear fenders and lights on the monotube:

The benefits are:

  1. Extra real estate
  2. The ability to install or remove a seat post without having to take off the rear accessories
  3. The ability to use traditional seat post accessories even when the seat post is lowered all the way down for extra clearance
  • Unique Appearance

Wishbone seat stays are quite rare, especially these days. Truth be told, most people don’t even know that wishbone seat stays exist in the first place. Thus, by acquiring a frame with such construction, you will enjoy a bike with a unique appearance.

  • A Second Handle

When carrying the bike, one can use the monotube to lift the rear wheel. Some people will find that option useful and convenient.

The Cons Of Wishbone Seat Stays

  • Vertical stiffness

A commonly criticized downside of wishbones seat stays is that the monotube adds vertical stiffness to the frame without having a noticeable effect on the lateral stiffness.

In the world of cycling, vertical stiffness is not desirable because it reduces the compliance of the frame and makes the ride harsher.

This problem is more pronounced when the bike is equipped with thin tires operating at high air pressure.

If the bike has wide tires running at low PSI, the suspension effect of the tire compensates for the vertical stiffness introduced by the frame design.

  • Difficult Full Fender Installation

The mid-point of regular full fenders normally attaches to the seat stay bridge. In the case of wishbone seat stays, such a bridge does not exist. Moreover, the distance between the monotube and the tire could be quite small. As a result, it becomes increasingly difficult to install a full rear fender, especially if a larger tire is used.

Nonetheless, it’s still possible. I did it on my road bike by adding metal hooks made from a thick wire on each side of the fender. Then I secured the fender to the brake bolt via a zip-tie passing through both hooks.

Note: If the frame uses caliper brakes and has enough clearance it should be possible to install the fender normally.

  • Difficult Installation of a Rear Rack

Most rear racks have stabilization stays normally connecting to the seat stays.

Wishbone seat stays do not come with rack mounts. Consequently, one will have to look for an alternative solution.

One of the possibilities is to install a seat post collar with rack mounts on it. Another option would be to mount some sort of clamps directly on the monotube.

A seat post clamp with rack mounts
  • Non-classic Look

Some riders consider wishbone seat stays non-aesthetically pleasing due to their resemblance to a fork.

FAQ: I’ve had both standard and wishbone seat stays. Why can’t I feel a difference?

This is a common phenomenon and applies to most people. The overall performance of a bike depends on its entire geometry (not just a small segment), the used materials, the thickness of the tubing, the craftsmanship, the tires…etc.

The dissimilarities between wishbone seat stays and standard ones aren’t substantial enough to create an easily perceivable difference in behavior and performance.

For that reason, the choice often boils down to personal preference especially when it comes to recreational riding.

Summary: What You Need To Know

The pros of wishbone seat stays are:

  • Unique look
  • A stiffer rear triangle beneficial to bikes using cantilever brakes
  • Simplified production process allowing the use of the same seat stays for many frame sizes
  • An opportunity to install seat post accessories on the monotube

The cons of wishbone seat stays are:

  • Excessive vertical stiffness that can theoretically result in a harsher ride
  • Technical difficulty when installing full fenders and rear racks
  • Appearance that some riders do not like

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