sanding carbon fiber for bicycle painting

Sanding to Raw Carbon Fiber? Custom Bicycle Painting Tips

There’s no doubt carbon fiber is sexy. When companies leave it exposed on a frame, there’s a sleekness added to the bike. Thus, when riders come to us for their bicycle’s custom paint job, occasionally some inquire about sanding the paint down to raw carbon fiber, with the idea of leaving it exposed. However, it’s not as easy, cost effective, or as aesthetically pleasing as you would think.

A little background

When bicycle manufacturers are building their carbon frames, there are a lot of seams/lines, epoxies, and “stuff” in the mix of the fibers. The structural carbon is unidirectional sheets being manipulated and laid in certain ways to create the desired shape/ride quality. The “stuff” I mentioned are resins or any fillers they use. They may not be black. When companies are leaving exposed carbon fiber, they typically use a nicer unidirectional weave or more aesthetic weaves like 3k or 12k. Since weaves like 3k and higher are used as the surface layer, they hide any imperfections in the structural carbon. Factories that leave exposed carbon fiber take a little more care in ensuring the seams aren’t too unsightly or glaring. However, when frames are going to be painted, most companies are not as concerned about where seams go, where extra resin goops up, or where any fillers are used.

Gerard Vroomen, co-found of Cervelo, and now co-founder of the mountain bike brand OPEN, was selling just black paint jobs until recently. Now they have black or white paint options and white is cheaper.

… so why is the white frame cheaper? Because it is, in a way, a defect. Vroomen explained that when the frames are being finished, sometimes a cosmetic defect in the surface makes it impossible to use the almost-clear black finish. These kinds of blemishes, though structurally inconsequential, would be visible and make the frame unsaleable. In the past, they would be destroyed.

But white paint covers up any blemishes, saving the frame from the trash bin. It’s good for the environment, Vroomen noted.

~Source: BRAIN


What about Carbo-Lift?
Carbo-lift created a product that supposedly could be applied to the frame and after a period of time, the paint could be lifted/wiped off. Therefore, leaving the raw carbon fiber and fillers exposed. However, when we wanted to order some, they disappeared. This led us to believe either there isn’t a large enough market for this product or it didn’t really work. Bummer!

Update April 2015: We tried a sample of the Carbo-Lift’s supplier’s product and were not impressed.

Here are the Following Reasons We Don’t Sand to Carbon:

  1. The labor hours required to sand the frame down to raw carbon safely and cleanly is not cost effective.
    We like our hands. We sand a lot as it is and while exfoliating your hands is good, this is the wrong kind.
  2. When manufacturers know carbon is going to be painted over, they do not care as much about where seams and edges are in the carbon. Aesthetically, it can be unattractive. We do not risk it.
  3. There may be bondo, fillers, off-colored epoxies, and other “stuff” in the carbon before a frame is painted to make it look smooth. If that is uncovered and removed, the carbon isn’t smooth and unsightly. We never risk the integrity of your frame.
  4. It’s out of our hands, it’s in the manufacturing process.

types of carbon weaves

Of Course, There’s Always Exceptions

Some bikes will have a nicer weave under the paint if it’s near exposed carbon. Depending on the desired custom paint job, select sections of the paint can be sanded away to the exposed carbon. When this is done, you really want a professional doing this or you could really be disappointed. Here’s why: When sanding, you have to be sure not to go into the carbon weave or it will begin to distort and ruin the carbon. As a result, the carbon will look damaged. Also, if you do not remove the paint well enough, the paint will have a tint to where the paint once was.

One of mantras of our company is that every bike leaves our shop better than when it came in. If you have exposed carbon fiber, we can work with it. If you don’t, do not fret or hesitate from contacting us about your dream paint job. That’s what we do day in and day out.

If you really desire a bike that has exposed carbon fiber, Kane Bikes is your company. We love carbon. Unlike the big boys, our carbon frames have an exposed 3k weave surface. Since every bike our customer’s design is a one off paint job, we start with a beautiful foundation.