Quote from: eins4eins on September 14, 2026, 11:17:40 PM
Yes, UD glossy. Incl DPD shipping, the price was 720USD.

Built it to see what it looks like and i thinks its a very nice machine.
A friend will eventually buy it, once my new bike is here.

Hey the wheelset looks very nice, can you tell me what brand that is?

Kind regards

UPDATE 4: broken RK Ultra Frame

I just received a notification from AliExpress regarding my case. Interestingly, they updated the ticket stating: 'We learned that the chargeback result favors you'.

It seems that after I escalated the case to PayPal and submitted my engineering report, the pressure worked. AliExpress has officially acknowledged that the outcome is trending in my favor.

I'm still waiting for the final notification from PayPal to see the money back in my account, but it looks like a 100% win. I'll let you know as soon as the case is officially closed!

Quote from: fhill on January 31, 2026, 10:24:04 AM
Keep in mind, at PayPal you can only start a claim till 180days after paying!

I also noticed that and have just filed a claim!

Quote from: fhill on January 30, 2026, 11:43:38 AM
How long ago did you buy the frame? Did you pay via paypal? make a claim over paypal thats way more effective to get you money back.

Yeah it's common that they let u pay for shipping

I paid for the frame in August, received it mid September 2025. I am waiting for the next reply by AE and then will file a chargeback with all the evidence on PayPal.

UPDATE 3: broken RK Ultra Frame

AliExpress initially offered a measly 106€ refund, which I obviously declined immediately. I've since doubled down and sent them even more evidence, including a full analysis of the stripped-down frame. I have all the time in the world to keep providing them with data until they get it right.

The seller, on the other hand, is completely losing it. He's now resorted to personal attacks, calling me a liar and even claiming I made up my engineering degree... lmao.
He's clearly mad because he realized I'm not just another customer he can gaslight with 'user error' excuses.

It's actually quite funny to see a business owner go into full meltdown mode once you hit them with actual physics and legal facts (EU warranty laws).
I'll keep you guys posted on the next move from AE!

Quote from: panel on January 29, 2026, 08:13:00 PM
insanetree , do you have the link to the store ?

https://www.aliexpress.com/store/1103851770

Quote from: Ludo on January 29, 2026, 08:04:29 AM
What a great analysis and great last post, I applaude this!

Thanks for the support! It's satisfying to apply my engineering background to a real-world problem, even if it's a costly one.

This failure isn't just about 'thin carbon'; it's about the unfortunate synergy of several design and manufacturing factors in combination with cyclic fatigue. The design combined a high-stress geometry with a low-strength transition zone. In engineering terms: the safety factor dropped below 1.0 under normal operating loads over time. It was a textbook 'planned' failure, just waiting to happen.

I'm glad this analysis helps shed some light on the 'why' things fail.

Quote from: Lotnik on January 29, 2026, 07:46:12 AM
I'm sorry for your broken bike, but this is what you can expect buying counterfeits. Someone stole a money from Factor to produce and sell fakes and the the same person doesn't give a damn about your issue. Your lesson cost you about 1k USD and you need to take it. Now you can turn your head for the reputable part of eastern manufacturers without that boutique writing on the downtube.

You are absolutely right. This experience has been a massive reality check. When you buy a replica, you aren't just buying a shape; you're gamble with the lack of engineering standards and QC that a proper brand invests in.

The next bike will definitely be from a reputable chinese brand with proven quality control. I hope for the best regarding the AliExpress dispute, but regardless of the outcome, this has been a $1,000 lesson for me.

By documenting this so thoroughly, I hope it serves as a warning to everyone else here: the 'boutique' writing on the downtube isn't worth the risk of a structural failure at 50 km/h. Engineering integrity matters more than aesthetics.

Visual & Acoustic Proof of Structural Failure (The "Paper-Thin" Carbon Issue)

I've recorded a short video to demonstrate why I'm 100% sure this is a manufacturing and engineering defect and not 'user error.' https://youtube.com/shorts/_mjw31EugHs?feature=share

• The Acoustic Resonance Test (Coin Tap): In the video, listen to the sound as I tap the seat tube. It starts with a high-pitched, solid 'ting' at the top. As I move down toward the wheel cutout notch, the sound becomes more resonant. This acoustic shift confirms a significant drop in wall thickness. While the frame's overall stiffness is mostly defined by its tube geometry (second moment of area, mostly shape of the tubing), the local strength depends on sufficient material (wall thickness) to handle stresses (flexing under finger pressure).
• The Flex Test: Watch how the carbon surface actually deflects under simple finger pressure near the crack. It's 'paper-thin' in that specific area. While tubing walls may exhibit some flex, the lack of structural backing here is evident. Beyond wall thickness, the layup orientation and carbon type (UD, 3K, 12K etc.) are critical. Carbon is anisotropic and designed to carry forces along the fibre direction, not perpendicular to it. The visible deflection under minimal point-loading proves a lack of supporting laminate layers in this high-stress zone.

The Engineering Problem:

• Geometric Stress Raiser: The concave notch for the rear wheel already features a higher wall thickness and stiffness, creating a point of high stress concentration at the transition to the thinner side wall.
• The 'Bottleneck' Effect: Combining a sharp geometric notch with a sudden reduction in wall thickness is a recipe for disaster.
• Additional Stressors: Near the crack are the threaded inserts for the bottle cage and front derailleur. These holes act as additional stress raisers in an already weakened zone, creating a cluster of failure points.

Conclusion: It's a critical failure of a primary structural component. The frame didn't fail because of a 'slipping seatpost' (which shows zero marks anyway), but because it simply wasn't built to handle cyclic loads in this poorly reinforced area.

One more detail for the technical crowd:
The concave cutout for the wheel (rear of the seattube) is reinforced with more layers, making it significantly thicker than the adjacent side wall. From a mechanical engineering perspective, this creates a stiffness mismatch. Under load (cyclic pedaling forces), the thin side wall undergoes higher strain than the thick concave section. This results in strain incompatibility at the transition zone. The resulting interlaminar shear stresses are concentrated exactly where the crack appeared. This isn't just a random failure; it's a textbook case of a stress raiser caused by poor structural transition in the laminate layup.

Please check the video
https://youtube.com/shorts/_mjw31EugHs?feature=share

UPDATE 2: broken RK Ultra Frame

Quick update on the communication with the seller – it's getting absurd. After I sent over my full Technical Failure Analysis Report, the seller's narrative completely shifted, exposing some major inconsistencies:

• The 'Vanishing' Factory vs. 'Direct' Warranty: Initially, the seller claimed he was just a middleman for a shop that 'vanished' and that he had no idea about the quality. Now, suddenly, he is offering a 'factory warranty' and claims he is in direct contact with the production line to resolve the issue. You can't be a clueless middleman and a factory-backed dealer at the same time.
• Deflecting Structural Issues as 'Optics': The seller tried to claim that the partially poor internal finishing I documented (fuzzy fibers, poor consolidation) doesn't affect functionality and is 'normal' for this price range. As a Mechanical Engineer, I find this argument dangerous. We aren't talking about paint chips; we are talking about delamination and manufacturing artifacts in a primary structural zone that lead to the exact type of fatigue failure I experienced.
• The 'Slipping Seatpost' Myth: He also tried to blame me, claiming the seatpost must have slipped and damaged the frame. I've already debunked this with high-res photos showing zero witness marks on the post and a consistent 17.5 cm insertion depth.
• The 'Compromise' Offer: He is now offering a replacement frame at 'cost price' or a new frame under warranty, but only after initially saying he doesn't know the quality.

My Stance: I have declined the replacement. I've lost all confidence in this specific product and the seller's transparency. I am pushing for a full refund through AliExpress mediation, using his own contradictory messages as evidence that he is evading contractual responsibility for a safety-critical defect.

I'll keep you posted once the AliExpress dispute team weighs in on the technical report.

Short and 'not so sweet' update:

The seller has officially shut down any further negotiation. His latest response to my demand for a full refund was simply:

,,Sorry, we can't meet that request."

It seems we have reached a complete dead end in direct communication. After he tried to deflect responsibility to a third party, blamed me for a 'slipping seatpost' (which I debunked), and offered a 'cost-price' replacement, he is now flat-out refusing to acknowledge the manufacturing defect and my request for a refund.
I am now 100% dependent on the AliExpress mediation team's decision. I've uploaded all the evidence. At this point, it's a waiting game to see if the AE mediators prioritize technical facts and safety-critical evidence over a seller's empty excuses. I'll keep you all posted on the final verdict. Thanks for all the support so far!"

UPDATE: broken RK Ultra Frame

I just received a very concerning response from the seller regarding the frame failure.
Instead of addressing the technical evidence in my report, the seller is now trying to deflect all legal and structural responsibility.

Here is a summary of what was said:

• Third-Party Sourcing: The seller admitted that the frame was not manufactured by them but was sourced from 'First-Class-Carbon'.
• 'Proxy' Selling: They claimed they were only 'helping' to sell the frame on behalf of 'First-Class-Carbon'.
• Zero Quality Control: The seller explicitly stated: 'I have no idea about the quality of your transaction framework'.
• Vanishing Partners: Apparently, the original source/store has shut down and 'vanished with the money'.

My Take:
This is a massive red flag for anyone buying from this store. They are essentially operating as a middleman without performing any quality control or taking responsibility for the products sold under their name.
When I confronted them with the fact that they are my sole contractual partner under AliExpress policy, they merely offered to sell me a new frame at 'cost price'. I have obviously declined this, as I cannot trust a seller who admits they don't know the quality of what they are shipping.

I have now further escalated this to AliExpress Support, including the screenshots where the seller admits to these practices. I will keep you guys posted on how the mediation team handles this 'proxy-selling' admission.

Quote from: offspring_fan on January 28, 2026, 04:47:55 AM
And this is why I'm not an engineer . Thanks for explaining. And I hope you get a satisfactory resolution from the seller!

Haha, no worries! It's definitely a rabbit hole once you start looking at stress distributions and carbon layups.

I really appreciate the support. Hopefully, the seller or the AliExpress team will see the technical evidence for what it is, a clear manufacturing defect rather than a user error.
I'll keep the thread updated as soon as I get a response regarding the refund.

Quote from: offspring_fan on January 27, 2026, 04:02:25 PM
This sucks, but also is a real puzzle.

I'm not an engineer and haven't worked in a bike shop, but I have snapped my share of frames. Two on the chainstays and one round the bottom bracket. But never in the middle of the seattube.

It's not a high stress area. It is hard to see what could have caused it apart from seat post impact unless the carbon was badly laid up and disasterously thin in that particular spot. Which is not impossible, because there's that frame in the TanTan thread that arrived with a hole in the chainstay... 

Actually, the mid-section of the seat tube is a highly dynamic area under significant stress.

While it might seem 'low stress' at a glance, the seatpost acts as a long lever arm. This lever generates a substantial bending moment that must be absorbed by the seat tube. As shown in my sketch (and demonstrated in the Peak Torque video linked below), the clamped seatpost (green) creates localized pressure points in the seat tube.





Technical breakdown of the forces (red):

• Torque Generation: The rider's weight (F_g) creates a torque that forces the lower end of the seatpost against the front internal wall of the tube.
• Geometric Stress Raiser: The crack occurred exactly where the cross-section changes and the geometry shifts significantly.
• Concave Notch Effect: The frame features a sharp concave cutout for rear wheel clearance. This design creates a massive notch effect, concentrating stresses in the exact area where the seat tube transitions.
• Cyclic Fatigue: Even with 17,5 cm of insertion, the tube is subjected to cyclic flexing.

If the carbon layup is inconsistent or thin in this transition zone, as evidenced by the internal artifacts I found (fiber breakout and poor consolidation), the laminate will eventually fail under these standard bending loads. It's not about 'impact'; it's about fatigue at a structural bottleneck caused by a combination of geometry and manufacturing quality.
I have also attached additional internal photos. While some sections show a decent finish, the laminate consistency is highly variable, with several areas showing poor consolidation and 'shoddy' workmanship.

Quote from: BeR on January 27, 2026, 01:05:54 PM
They sell the same products but They are not the same sellers and They don't share the same WA number.

For your information, the WA account of RK was active today.

Can you privately send me RKs WA contact?

Quote from: BeR on January 27, 2026, 10:52:59 AM
Send to the seller a message through Aliexpress or WhatsApp.

I have messaged them via AE and WhatsApp, but their WA account has not been online since October.
RK and First Class are the same seller.