Sunday, May 09, 2010

Bad Design Not Covered by Warranty

Bad design is not a defect in material or workmanship. If it leads to an actual failure within the warranty period you may qualify for compensation, but if it manages to limp along past that to an annoyingly premature death just outside the official coverage period you just have to eat it.

Shimano's plastic-collared Altus brakes from the mid 1990s are a prime example of this.

I spent about five hours fixing the cable guide problem on that Specialized Roubaix this week. The rest of the tune up took about 45 minutes.

To release the frozen bolt and broken piece of the BB shell, I had to cut and pry the cable guide away. That allowed me to push the broken bit up into the shell. I hoped to grip it with locking pliers or something, but the curve of the shell prevented it. Instead, I was able to wedge it with an improvised pick I made by grinding the elbow of a broken spoke. I felt like a dentist as I juggled instruments in the open mouth of the frame. It was all the fun with none of the disgusting saliva, blood and food particles.

Once I had jammed the broken piece I was able to unscrew the bolt from it. This left a slightly ragged hole in the aluminum BB liner and a metal-lined hole that may be the remains of a Riv-nut in the outer carbon shell. There is also an unexplained pinhole in the carbon off to one side.

The bolt and insert

There is an air space between the carbon and the aluminum. I can see loose carbon fibers sticking into the hole where the cable guide was mounted. I would feel better if the bike had an inert layer filling that space, especially as the pinhole implies that moisture (and perhaps even liquid) could get in, creating a conductive environment that could lead to some sort of electrolytic interaction between the carbon shell and the alloy liner. The bottom of the shell is not as highly stressed as the top, but it is hardly unimportant. Also, could that unsupported air gap have led to the failure of the threaded insert spanning it?

I would have to grind away gel coat to inspect the site thoroughly to determine if that really was a Riv-nut. Is it important?

The new guide, with shim for added thickness

The front derailleur cable goes through the frame. To prevent abrasion of the frame material, the cable guide needs a tube that lines the cable passage. The only guide I had with the required tube was another thin one like the one that had not provided adequate protection originally. I shimmed it with a sizing sleeve from a handlebar-mounted mirror. The bolt threads into a t-back I found in one of our miscellaneous hardware drawers, that happens to fit the hole, more or less.

I don't know if I should worry about the long term integrity of the frame. If water gets into the layers of the bottom bracket shell it could freeze if the bike is stored in an unheated space during the winter. I have seen freeze damage to steel and aluminum frames when ice expanded inside small spaces like the outer ends of chainstays. In any case, what happened is not normal wear and tear. We'll see what Specialized has to say.

1 comment:

Steve A said...

Specialized Tricross V brakes from 07 to 09 are another example of bad design not covered by warranty. Fortunately, that is a design problem that is easier to remedy.