Frame Repair Question
Would like to solicit input from folks familiar with frame building and frame repair. I purchased a high end mtb frame from a very reputable builder ~ 1 year ago. Unfortunately the top tube of the frame has cracked on the underside of the tube just behind the weld to the head tube. I have no issues with the builder who is has been very responsive, apologetic and clearly intends to honor their warranty. After looking at the frame the builder has informed me that rather than replace the frame they intend to repair the frame by removing the cracked top tube and welding in a slightly larger diameter top tube with slightly heavier wall thickness. The frame is a Ti hardtail designed for racing and was built with light weight and stiffness as key objectives. The one concern I have with their proposed solution is whether any othe areas of the frame may have been comprimised as a result of the top tube failure. I found the crack as a result of the bike developing a creak which got steadily worse over a couple of rides. I suspect the top tube may have begun to let go some time ago and I only caught it when the tube was close to catastrophic failure and started to audibly creak when flexed (when I found the crack it extended for ~ 60% or more of the circumference of the tube). Given the tubing / welds on the frame are intended to work in unison to handle the stresses and load placed on the frame I'm now wondreing whether the weaker cracked tube may have transferred increased loads on other sections of the frame beyond what they were not designed to handle and flexed the frame in ways it typically would not be flexed or in amounts greater that it was designed to handle. Given the top tube may have begun to let go some time ago the frame may have experienced many cycles of unusual flexing / loading? Anything to be concerned about? My understanding is that typically this builder would just replace the frame but given it was the top tube repairing was a viable option for them and that thet have done this type of repair before. I should also note that I was assured that after replacing the top tube and refinishing the frame would look brand new and I believe this is likely true. Thoughts / opinions?
Andrew R Stewart
Some thoughts from a non TI hobby guy.
- Light weight VS stiff- Choose one.
- Failure mode- TI has a slow crack propagration mode. Chances the crack was there long before you noticed. This is good! No one wants a quick failure unless you buy Aluminum or Carbon...
- Increased stress elsewhere- Has the flexibility of the frame increased a lot? If not then the crack has not made the stresses fall on the other joints by a lot. If so then the other joints are carrying the stresses and because of their distance from the crack the amount of flex is greater.
- As long as the other joints are in good condition (cracks, bucklings and such) it is very doubtful that there is a concern with any potential added loads they carried.
- Warranties- This is the real issue as i see it. When you purchase a product you enter into an agreement. That means there is some expectation of acceptance on both sides as defined by the written warranty. Part of this is the understanding that life and man made stuff is not perfect but most all the time "good enough". If this is not acceptible then you need to have a different discussion with the next builder... The investment that the builder has in your frame far exceeds your cost to purchase it. Unless he is the exception, he is trying to balance refunding your purchase (which might be limited to only a portion of the total cost, components and wear possibilities), the reputation he has had so far and the intregrity of the frame.
- Unless you have any compelling information i'd go with what your builder has offered. If things go bad a year from now you can always trash him by name then. Andy.
Andrew R Stewart
I should have said this:
Light weight VS stiff VS strong, choose one.