Are these shallow gouges and imperfections on a new carbon fork steerer benign or serious?

Question

I have never had a carbon component on any of my bikes, so I have no idea what sorts of imperfections are perfectly normal minor blemishes that pose no risk. I'm building the bike for a family member and don't want to install anything dangerous.

These photos are from a new fork we just received. It cost almost $300, which isn't high-end by any means, but it is triple what the low-end forks are costing, and it was from an eBay Seller with over 15,000 feedbacks and a 99.9% positive rating, so I figured there would be a basic level of QA that would prevent a defective fork from being sold, and I hope I was right about that.

Are the shallow gouge and the other blemishes on the steerer just above the crown benign?

P.S. I should also add that at 9 o'clock on the steerer, when looking down at the tube from above if you were straddling the front wheel, there is a palpable ridge that runs from the crown up the conical taper. The other side of the tapered section is perfectly smooth. I've added a picture that shows that palpable ridge.

Answer 1

I don't normally go around inspecting fork steerers, but I suspect that's highly abnormal and a significant cause for concern.

I don't clearly see torn fibers. If you did, that should mean the steerer got gouged in transit. Raoul Luescher is a carbon fiber repairer and consultant with extensive aerospace and bicycle industry experience. He describes some common manufacturing issues with carbon fiber. I think that the gouges might be related to porosity, which stems from improper compaction.

Basically, carbon fiber is a bunch of sheets of little carbon threads. These are immersed in resin, and then the assembly is baked at high temperature and pressure. The carbon plies and the resin are supposed to compact, i.e. come together. If are holes, i.e. porosity, this compromises the structure's strength. (Although normally I would suspect that porosity is inside the structure, not on the surface.) Alternatively, you can have areas that have too much resin, where the resin pooled and perhaps disrupted optimal compaction, or you can have areas with too little resin where some carbon fiber is left exposed. Either of these are bad as well.

Without a background in the subject, I can't be sure what caused these surface imperfections. They definitely look out of the ordinary for a new component.

I suspect you are correct that normal factory quality control would have caught this item and probably destroyed it. In theory, I have heard speculation that some people resell factory second items, like ones that were QC rejected. There are cases where factory seconds with only cosmetic issues get sold. To my knowledge, in the bike industry, these tend to be for accessories. For example, Spurcycle, which makes very high quality and expensive bells has an annual sale on what they call "Frankenbells". These have cosmetic but not functional defects. I haven't seen cosmetic seconds sold as new equipment in official distribution channels. It does seem possible that the rough spots in the steerer might only be cosmetic. However, that steerer is taking a lot of load, and I wouldn't chance it. This isn't a case of paint chips on a used carbon bike.

Answer 2

The first picture in particular, shows damage that extends far beyond the epoxy resin used to bind the fibers themselves. In pursuit of safety, I highly suggest you return the product if it is under warranty or simply use a different fork.

A fork that fails at the steerer tube is sure to cause an accident that would leave you injured and unable to ride for weeks. Further, now (during the pandemic) is not exactly the best time to get hospitalized.

Stay safe!