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Friday, September 17, 2010

My Strong Frame is Dead

Dead Strong Frame

I was riding over to Google to visit some friends this morning, and when riding over a pedestrain bridge over 101, heard and felt this "snap!". I looked down at my bike and found that my bike had inadvertently shifted from the middle chainring to the granny gear. I shifted back to the middle chainring and things were fine, but the bike felt a bit funny.

At lunch, I looked at the frame and found that the chainstay where the spoke holder was was cracked. The crack didn't go all the way around the frame, but it was obvious that I wasn't going to descend Page Mill Road on the bike even one more time. After meeting various people (every time I visit, I run into so many people I know that it takes far longer than I expect), I visited Cynthia and she observed that the bottom bracket area was cracked as well, which it was, and almost all the way around. It looked like the weld had just about fallen apart!

The Bicycle Outfitter thought that the frame was not repairable, but Carl wants to see it anyway. In any case, I am very very grateful that my super fast descent on Wednesday didn't result in anything untoward!

I've never had a frame crack on me like this before, but this frame was my only single bike for about 2 years, surviving rough commutes, tours across France and Hokkaido, and of course, frequent rough stuff riding. On the other hand, my previous frames had done the same for many many years without any trouble. I'm not usually sentimental about equipment, but since I had a big hand in designing the frame, I feel the loss a bit deeper this time than previously. So here's a retrospective on the bike on this blog:
We'll see what Carl says when he gets it!


Allan Folz said...

Well that's pretty disappointing. My guess would have been the stress from welding the spoke holder in the same area as the fender bridge weakened the tube. Except that doesn't account for the bottom bracket being cracked. Was there ever an impact/crash to the cranks?

Also, in one of the earlier threads you talk about bike weight being more important that Grant allows, especially for lighter riders. Are you familiar with Jan Heine's thoughts on frame resonance (he refers to it as planing)? Could it be the issue is not frame weight, but frame stiffness as the two are closely linked?

Piaw Na said...

Carl says he thinks that the weld got contaminated: these failures don't happen to properly built frames. I will leave out the spoke holders for the replacement frame.

Tarik Saleh said...

You are a frame breaking monster!

I think that usually the best attitude to have. This probably should not happen, but they happen fairly often to even reasonably well built frames. I have broken two frames through the bottom bracket. One I attribute to poor joining, the other I attribute to a small undercut/contamination or other weakness in the weld plus a doozy of a rough cross race. Since your bike is a Ti bike it is much more sensitive to weld contamination than steel.

The poorly joined one was a lugged frame, but the crack is similar to yours but almost completely severed the bb from the frame by the time I discovered it. It was winter and coated in road muck and it had been riding funny for a while.