Thursday, September 03, 2009

Chain II

So, yesterday evening I spent a little time trying to adjust the shifting of the new chain on the rear cogs. Trying being the operative word here. FAIL describes the level of success. Now, the worn chain was still shifting perfectly on the rear - it was just refusing to stay on the big chain ring, so I started looking at everything a lot more closly, especially the new chain. The picture over there shows what I found. The arrow is pointing to a distinctly beveled edge. My first thought - taken from watching too many Mythbusters episodes - "Well, there's your problem!" Since I have been working as an engineer for, like, almost forever, and have some limited knowledge of how things are supposed to work, my thought process was that if I wanted a chain not to shift, I'd bevel it exactly like that. The only thing those can do is push the chain away from the cog you are trying to shift to.

Here is a picture of the (Forte) chain that came off the bike (it's a piece that came off when I shortened it - it was new this spring). Notice the nice, sharp, corners?

Armed with this new found info, I did a quick search on Wipperman chains and shifting. Guess what I found. Yeah, there are a LOT more reviews complaining about how badly this chain shifts than there are kudos on what a wonderful part it is. Imagine that.

On top of that, I found this, written by Jobst Brandt (for a little info on Jobst you can go here). The chain he is talking about isn't a Wipperman, but a Sachs, and it sounds like it's made the same way, with the same problem.

From: (Jobst Brandt) Newsgroups: Subject: Re: chain stiffness data Date: 2 Nov 1998 21:08:22 GMT Damon Rinard writes: > I thought some of you might like to know that I've just posted the > lateral stiffness of a few bicycle chains on my web site at: > I think this information would be more interesting if you had their lateral flex of each chain when new and when 0.5% elongated. This would reveal more about the consistency of performance during its usable life and might reveal what causes the change. I has always been my experience that the more laterally flexible a chain became the poorer it shifted. In fact that was one of the early criteria for replacing a chain when it no longer shifted easily due to its ability to snake over to the sprocket it was on even though the derailleur was aligned with the next gear. As I said previously, the new Sachs derailleur chain is the worst shifting chain I have come across because its pins and side plates are beveled to reject climbing to the next sprocket. The intent was apparently to allow extreme crossover gearing with 9-speeds and triple chainrings. I am not impressed. This is another case where the demands of the incompetent bicyclist has prevailed over the riders who use their equipment effectively. Jobst Brandt

Guess I'll be off to the bike shop for another chain, this time it'll be a SRAM, Shimano, or Forte. I'm planning on riding after work tonight, though, so I have at least one more ride with this chain. Saving $20 by choosing the Wipperman over the Shimano last Saturday turns into throwing away $50. Live and learn, live and learn.

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