Some background and history.
Paid for the $99 up-grade for the carbon fiber seat post (as well as $99 for the carbon fiber handle bar) and thought I was getting 100% carbon fiber product.
Been riding the Nireeka (initially as the Nature version and now as the Homie) since early March 2019. The Nireeka has done close to 2,350km on paved roads or cycle paths. It's never been on trails or the mountains.
Last week, went for commute ride with my work colleague along a well known bicycle path. During the ride, the seat post had sheared off at the top where the seat is attached. See above pictures.
I was completely shocked by this and carried out an emergency brake as my seat fell out below me. Travelling speed was around 30km/hr - I had purposely limited the speed to a maximum of 38km/hr and was mainly using the thumb throttle while pedaling. My work colleague and a few riders were very surprised on what had happened.
Examining the fatigue failure, I noticed there's an internal metallic (suspected to be low strength aluminium) tube with the carbon fiber skin as a wrap around. My initial thought was that this isn't what I paid for as it's not 100% carbon fiber. Looking a bit closer the design is quite clever into fooling people into thinking they paid for an expensive 100% carbon fiber seat post. When looking up from the bottom of the seat post, it's not possible to see the internal metallic tube. If one wanted to cut the seat post, most likely it'll be near the bottom where it's 100% carbon fiber - not at the top where it's attached to the seat.
The other thing is that the internal metallic tube is load bearing structure - as this is where the fatigue failure occurred.
In correspondence with Nireeka, they have confirmed that the carbon fiber seat post was sourced from an outside 3rd party. They are now investigating this.
I have two main concerns with the carbon fiber seat post offered by Nireeka.
(1) Provenance of a 100% carbon fiber seat post; and
(2) Safe and reliable use.
I'm also concerned about the same above issues with the $99 carbon fiber handle bar that's on the Nireeka.
Please note that I'm just a sample size of one of the 159+ others that got a carbon fiber seat post. Nicholas and Marvin thinks it's an isolated case and I happen to be the unfortunate one to experience this. My primary concern is the safety of other backers who ordered the carbon fiber seat post. If you're one of them, please consider to at least up-grade your disc brakes to larger diameter ones for emergency braking. I've up-graded mine to 180mm size and considering to go with the largest 203mm units after the seat post failure incident.
We're so sorry about what happened to you and we already apologized several times in emails and offered to send you a replacement and also gave you credit for the next products.
Of course, it has an aluminum insert for the upper part but not for all the tube length.
This is the lower part of the seatpost tube and clearly shows that all the tube is made of carbon fiber.
Thank you for the generous offer of a replacement carbon fiber seat post. However, I would like to know the outcome of the investigation with your 3rd party supplier of the carbon fiber seat post regarding fatigue failure.
Also would like to see some fatigue failure test reports conducted by in house by Nireeka or outside lab if Nireeka does not have the expertise to carry it out.
Will there be any means of checking the provenance of a 100% carbon fiber seat post? X-ray or ultra-sound testing are non-destructive methods to check.
Thanks for sharing the pictures and your experience. I'm sure it was frightening and I'm glad that you were not injured.
While I understand your assumption that the construction of the seatpost was 100% carbon fiber, in reality a seatpost has to contain metal parts for the clamping mechanism. Carbon fiber alone would not have sufficient tensile strength to tighten the seat clamps, that's why you see the insert(s). I'm not aware of any carbon fiber seatpost that is 100% carbon fiber.
Regardless, it does appear that the internal casting itself has failed, I would guess perhaps a flaw in the casting is the root cause. I'm sure Nireeka will want the part back to do a thorough investigation, (which is certainly warranted).
I disagree with your presumption that Nireeka in any way misrepresented the construction of the seatpost, as metallic inserts are part and parcel of the process.
Thanks for the concern regarding safety. When the seat fell out underneath me, was a bit of a shock to say the least.
Here is an example of a 100% carbon fiber seat post from Hope (UK): https://www.hopetech.com/products/accessories/carbon-seat-post/carbon-seat-post/
Write up by Road cc is here: https://road.cc/content/review/247267-hope-carbon-seatpost
This is a nice seatpost, but it certainly is not 100% carbon fiber. The engineering drawing clearly shows the metallic parts, and they even show the metallic seat clamp just to the right of the craftsman in the picture.
Believe what you're referring to are the visible external parts that connect the seat to the post itself. These are expected to be metal - in particular the screw (item 5 in Hope's exploded view).
Note that Nireeka's main post is a single piece unibody design. I'm expecting this to be made from 100% carbon fiber. The external screws (which go through the eyes of the main post) and the top plate is metal that clamps to the seat itself. I can understand these parts being made of metal.
What I'm referring to is the main post itself (or item 1 in Hope's exploded view drawing of their carbon fiber seat post). I expected the main post to be 100% carbon fiber. Not a metallic tube covered with a carbon fiber skin. This is what bothers me as I had been duped into thinking otherwise. Maybe you don't think its a big issue and happy to pay $99 for an inferior product. I disagree based on principal and waiting to see the outcome of Nireeka's investigation with their supplier.
If Hope had down the same thing and was caught - there would be complaints also.
How about the carbon fiber handle bar where no metal parts are expected? Note that if the same design principal has been carried over to carbon fiber handle bar, the result of a fatigue failure would simply be catastrophic during a ride.