I have a 2002 K2 Attack 2.0 that broke its frame on the drive side chainstay, where it is welded to the drop-out end piece. The frame, or rather the weld, broke in two while trail riding after about 2 1/2 years of frequent use. The weld was probably weak as the metal of the chainstay tubing and the drop-out casting didn't show much heat penetration from the weld, it was just being held by the filet built up around the joint. I decided to try and salvage the bike as a winter training bike to use on an indoor trainer. The main triangle on the K2 has a five year warranty but the rest of the frame, on the full suspension portion, just had a one year warranty. My K2 dealer checked to see if a chainstay was available and found that K2 couldn't supply the part, and didn't have a complete frame to purchase either. K2 has recently sold their bike brand to Worldwide Cycle Supply, which also owns Iron Horse bikes, so K2 has gotten out of the bike business even though the Brand name survives
With an aluminum frame there are not many options for repair. After the frame broke, I rode the bike home 6 miles, and was able to see how the joint was being stressed, as it moved around while riding. Pedaling tended to pull the broken joint back together, while coasting let the joint and rear wheel wobble around more. To repair it, I drilled and tapped two holes in the drop-out casting and screwed in two 6 inch 10/24 bolts, so that the other end would slide inside the open end of the chainstay tube as the casting was put back into position. The bolts were threaded into the casting as far as the tap would go, about an inch and a quarter. Then I filled the chainstay tube with J-B Weld to glue the rest of the length of the bolts into the inside of the chainstay, and clamped the joint together. Since most of the stress from weight on the bike tends to slide the joint straight up, these bolts should handle the main stress on the joint pretty well. The bike is now relegated to the trainer, and the repair is holding. I don't think I would trust it back on the street or trail again, but it will be interesting to see how long the repair lasts. Either the epoxy will begin to wear around the bolts, or the drop out casting will start to crack around the treaded holes drilled in it. The trainer actually puts stress on this area of the frame as it is clamped in by the rear axle skewer. If it lasts the winter on the trainer, I'll be tempted to take it out on the trail again to see how long it will hold together. Maybe it will last 2 1/2 years.
Has anyone had any luck patching up an aluminum frame?
With an aluminum frame there are not many options for repair. After the frame broke, I rode the bike home 6 miles, and was able to see how the joint was being stressed, as it moved around while riding. Pedaling tended to pull the broken joint back together, while coasting let the joint and rear wheel wobble around more. To repair it, I drilled and tapped two holes in the drop-out casting and screwed in two 6 inch 10/24 bolts, so that the other end would slide inside the open end of the chainstay tube as the casting was put back into position. The bolts were threaded into the casting as far as the tap would go, about an inch and a quarter. Then I filled the chainstay tube with J-B Weld to glue the rest of the length of the bolts into the inside of the chainstay, and clamped the joint together. Since most of the stress from weight on the bike tends to slide the joint straight up, these bolts should handle the main stress on the joint pretty well. The bike is now relegated to the trainer, and the repair is holding. I don't think I would trust it back on the street or trail again, but it will be interesting to see how long the repair lasts. Either the epoxy will begin to wear around the bolts, or the drop out casting will start to crack around the treaded holes drilled in it. The trainer actually puts stress on this area of the frame as it is clamped in by the rear axle skewer. If it lasts the winter on the trainer, I'll be tempted to take it out on the trail again to see how long it will hold together. Maybe it will last 2 1/2 years.
Has anyone had any luck patching up an aluminum frame?