Solving the biggest issue with Factor bikes

Factor bikes have been my race and training steeds of choice for the past 2 years. In this time, I have been hopping on board the Ostro VAM as my road race bike (now riding the second version), tested the LS and Ostro Gravel as my gravel machines and set some fast times on the radical Hanzo TT bike. All of these share very similar design concepts and frame characteristics and each belongs to the very best in their respective category. Unfortunately, they also share a serious design flaw that has been plaguing not only my ride experience, but also that of many riders around the world.

What is causing the issue?

The suspect part is of course no other than the notorious plastic seatpost wedge, which makes seatpost slippage a daily occurrence. I have already talked about it briefly in my extensive Ostro VAM review, so just to reiterate: on all Factor frames, the seatpost is held up by a sliding wedge that is pressed on to the seatpost itself by an M8 worm bolt threaded into the frame. Since this wedge is made out of nylon, it does not provide enough surface friction and/or stiffness to properly held up the post under load. In some instances, Factor has provided replacement framesets to deal with the issue, quoting problems with the threaded insert, but that is simply not the source of the problem, nor an acceptable solution.

Is there a simple fix?

On my first Ostro VAM, I have found a relatively straightforward solution. The seatpost held up just fine after gluing a strip of skateboard grip tape to the surface of the wedge that is facing the seatpost. I had been using it in that configuration for around 24 000km without any issues whatsoever.

The next bike I had received was the LS Gravel, and immediately the same problem has surfaced. Skateboard grip tape came to the rescue again, and things have been fine since. At that point I had realized that this is a widespread issue.

A few months after that, the Hanzo as followed. There I have applied the tape as a precaution and haven´t even ridden it without – things were perfect from day one.

The real problems appeared with the arrival of the Ostro Gravel. Again, I had started off with the tape application, but even this was not enough to secure the post over rough terrain. After some fiddling, I have also added a strip of grip tape to the back side of the seatpost itself, which has solved the issue.
Or so I have thought, until around 2 weeks before the gravel National championships. Things were already a bit iffy during my first gravel race. By the time I have finished, I had a weird feeling that I am pedaling somewhat low. In the subsequent training rides, the disaster struck and the seatpost started slipping uncontrollably, no matter what I have done. With the Nationals in sight, I was starting to panic.

What now?

Of course, my first thought was to get a warranty replacement for the frame and/or post. Due to the tight schedule, this was not a realistic option though, despite the fact that the distributor had the exact same frame in stock. Getting it shipped to me and rebuilding the bike would take too long, so I had started looking at other solutions.

The first thing I had noticed was that the worm bolt kept getting loose, no matter the tightening torque and the amount/strength of threadlock used. After consulting my friend who is an expert is manufacturing, we came to the conclusion that the lack of stiffness of the plastic wedge and the subsequent deformation allows for this loosening. Using a stiffer material seemed to be the obvious solution. Our idea was to replicate the shape of the standard wedge in machined aluminium, with additional ribs on the surface that contacts the seatpost for maximum clamping.

Because of the importance of the race and the rushed process, we have also designed and external binding clamp. This prevents the seatpost from sliding in, as it rests on the top of the frame tube. Later that week, the first prototypes have been ready for me to test. The first test ride has proven to be a huge relief. The aluminium wedge has worked it´s magic and held up the post even without the help of the binder.

Due to the accelerated process, not all dimensions of the wedge have been carried over perfectly. I had to make some adjustment manually using a handheld milling tool. Even though I have lost out on the title in the final sprint by just a few meters, the concept worked and my saddle height stayed unchanged throughout the super rough course. After a few more refinements and going back and forth with the testing, we have finalized the design and submitted it for manufacturing.

The result

After a few weeks of waiting, the first few production samples are finally ready – beautifully machined from high grade aluminium and guaranteed to keep your seatpost in place. All three of my bikes are already upgraded with the units. Luckily, the Ostro VAM, Ostro Gravel and Hanzo all use the exact same wedge, so they are all cross compatible. If there is enough demand, we could possibly design a different version for the LS as well – this could potentially also fit the O2 and O2 VAM respectively. The wedges are now available for you to order in our store. The quantity is currently limited, but we might manufacture more runs in the future depending on the demand.


The first batch of wedges has sold out within the first day. If you have missed out, we have opened a pre-order that will ship in January 2024.


In our conversation with customers, there were 2 common questions that have popped up:

1.) Does using this seatpost wedge void the frame warranty?
No, it is a plug an play part, and requires no modification of the frame. It also leaves no marks or damage inside the frame, the use cannot be determined. It is the same as if you used a different set of thru axles or an aftermarket derailleur hanger.

2.) Does the wedge leave a mark on the seatpost?
Yes, just like any other clamping mechanism on a painted surface, it will leave a slight mark on the post. Obviously this is nowhere near severe as the marks and damage caused by a slipping post – which can also damage the frame.

14 Responses

    1. Thank you Jordan, much appreciated! It is not a structural modification of the frame in any form, so it really should not mess with the warranty. Also, nobody will ever be able to tell if you used this wedge or the standard one.

  1. Hi Rony.
    Received my seat post wedges here in the U.K. today for my Ostro and Ostro Gravel. Although I have had no seat post slip issue with either bike I thought that this little upgrade would be worthwhile and avoid any possible future issues. I was pleased to receive them so quickly. As you say, they are beautifully machined. It is just a shame that they are hidden inside the frame and out of sight. Both have now been installed. Many thanks. Brian

  2. Hello Rony, do you know if it leaves any marks on the seatpost when tightening beacause it is made out of aluminum instead of nylon?

  3. Hi Rony, do you know if the aluminium seatpost wedge leaves marks due to tightening on the seatpost because the original one is made out of nylon?

    Thanks in advance,

    1. Hi Noah. It leaves a very slight mark on the top clear coat (like all seatpost clamp designs). Of course, this is much more subtle than marks caused by the post slipping down. Unfortunately it is not possible to clamp a painted surface without marking it.

  4. Hi Rony, I was wondering or do you already know around which date the new batch of the wedges will be shipped?


  5. Hi Rony,

    The wedge is delivered today. On the pictures they have a aluminum colour.
    Mine is black and the form is a little different on the sides.
    Do I have the correct wedge for my Ostro Vam?

    1. Hi.

      For the last batch, we were able to arrange anodizing the wedges with no extra charge for the customers. Every dimensional aspect is identical to the raw wedges.

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