Carbon Fiber Mountain Bike Frame Repair

(1st in a series of 3)

Before last weekend, I was the proud owner of a carbon 2011 Specialized Stumpjumper Comp. Since last weekend, I have been the proud owner of a cracked carbon 2011 Specialized Stumpjumper Comp.

Since paying people to do things is expensive (in the short-term....perhaps wiser in the long-term), I'm going down the DIY road. I figured I might as well blog it, so that those other fools who follow in my footsteps might have a little more light on their path.

My Stumpjumper suffered a broken chain stay while riding it 'normally'. I didn't crash it, or smash it on my way through a rock garden. One moment I was riding fine, the next moment I had weird tire-rub and noise behind me. It's worth noting that the crack is only on the inside, top, and bottom faces of the rectangular chain stay 'tube'...there is no problem with the outside wall of it. It's also worth pointing out that the crack appears to have occurred in the exact same location where Specialized has a seam between two parts in their triple monocoque construction:

My chain stay broke right at their seam. Hmmm...coincidence? I don't think so.

I am aware that there are several professional carbon fiber repair service options in the area (apparently Matt Appleman offers top-notch service), which may be the right choice for some people, but this blog is intended for armatures who want to DIY (trusting our lives with our own shoddy repair jobs, no doubt!)

So, getting started.... Here is a general outline of the process that I anticipate. I will try to blog about each step along the way. I don't want to duplicate the vast amounts of instructional information and videos out there that already cover the basic process for carbon fiber repair. But just for posterity, here is the basic process:

1. Take a deep breath, make a plan, and gather supplies! 
2. Prep the surface by sanding. Get down through the top coats to the actual cloth; go deep enough in the damaged area remove damaged threads; prep an area at least 2" beyond the damage on all sides 
3. Prep materials and "layup schedule". Determine wight, weave, sequence, & number of carbon fiber layers, and stack with peel-ply, breather cloth, and vacuum bagging materials (if vacuum bagging). 
4. Apply layup, vacuum or tape, & allow to cure; ensure no wrinkling, bubbles, etc. 
5. Remove peel-ply and work on sanding smooth transition to unaltered frame. 
6. Finish. Apply UV protective clear coat(s), work down to a fine wet-sand, polish, apply final coats &/or paint.

I have already completed step #2 above, and the "gather supplies" part of step #1 is proving to be pretty difficult, without breaking the bank.

For next blog post click here!