Hi everyone,
I finally finished my very first bike build! Honestly, I was a bit nervous going into it, but everything actually went incredibly smoothly. I particularly want to shout out the Shimano manuals, they are incredibly detailed, easy to follow, and made the whole process a breeze for a first-timer.
In the end, the sizing feels absolutely spot on, and the overall ride quality is very good and comfortable. Plus, the custom paint job looks absolutely stunning out in the daylight!
For those interested, here is the full spec list of my build:
- Frame and Handlebar: Frame size 500 with glossy raw carbon + crystal purple paintjob and handlebar with 380 mm x 80 mm
- Groupset: Shimano 105 Di2
- Crankset: Magene PES 515 (165 mm) with Magene Chainrings (52-36T)
- Bottom Bracket: TOKEN Ninja BB47V24
- Wheelset: EliteWheels ENT 2.0 Disc (50 mm Front & Rear)
- Tires: Continental GP 5000 (32 mm Front & Rear)
- Tubes: RideNow TPU
- Brake Discs: IIIPro (160 mm Front / 140 mm Rear)
- Saddle: LightCarbon SD01
- Pedals: Shimano PD-ES600
- Bar Tape: SUPACAZ Starfade Purple (2.5 mm)
Regarding common build notes: I haven’t experienced any issues with a slipping seatpost. However, the latch on the down tube storage door did pop open once during my first ride. Luckily, I noticed it in time and managed to secure it before the door fell off completely.
Unfortunately, I also detected a major issue during that first outdoor test ride.
While taking some photos of the finished bike, I noticed a distinct mark/line on the right side of the top tube. I am completely baffled as to how this could have happened—I obviously haven't crashed (yet!) and the frame wasn't subjected to any impacts, drops as far as I know. I also obviously didn't clamp the top tube during the assembly.
The clear coat is split open and the line can be felt when running the finger over it.
When applying localized hand pressure, there is no excessive flexing (the tube still feels structurally firm).
But I also did the coin test and tapping along the tube sounds completely normal everywhere, except for that one specific grayish spot where the paint is gone. There, it emits a noticeably dull, muted thud.
I actually did another 2h test ride today after I have found the damage, and I didn't notice any issues, and the "crack" didn't seem to grow, but my confidence that the frame is safe is gone. This dead sound leads me to believe the carbon might actually be delaminated or cracked underneath, rather than it just being a cosmetic paint scratch.

I have already reached out to LightCarbon support to get their engineering team's assessment and discuss warranty/replacement options, but I would love to hear your thoughts. I think many of you know quite a bit more than me about carbon and could really help me determine the extent of that damage.
What do you guys think? Does this look like a structural failure to you?
Here is a Link to some high-res photos and a video of the area:
https://drive.google.com/drive/folders/1ZQ9Cr1hYwupFzodC7mv3nkZ7shksKPVc?usp=drive_linkThanks in advance for your input!