[CR]Frame Flex

(Example: Production Builders:Tonard)

Date: Thu, 29 Sep 2005 10:55:08 -0700 (PDT)
From: "dan kasha" <dankasha@yahoo.com>
To: Classicrendezvous@bikelist.org
Subject: [CR]Frame Flex

I just have to laugh, so many different opinions and experiences. Here is one. First an opinion, then an interesting experience.

My most comfortable bike is my 1990 era Cannondale. Compared to my 1970 Zeus, it is a luxury ride. Compared to my Orbit Track bike, it is a luxury ride. It is not any harsher than my PX-10, except the Brooks saddle is really nice on that one, and I find toe clips/shoes more comfortable than look pedals. It is the road race geometry frame. Before the bent stays. I can ride hours on that bike. I blame the geometry of the bike, along with a good saddle (Selle Italia Turbo) and wheels (32 spoke, Mavic MA2, with Continental 28x700 tires).

But there is more....

I heard lots of talk about a test for frame flex being if it ghost shifts when you climb a hill out of the saddle. The twisting of the frame changing the tension of the rear derailleur cable, causing a shift. About 5 years ago I set up this cannondale with all vintage parts. NR derailleur and shift levers, Modolo Pro brakes, the wheels I mentioned. And first ride, I figured this was going to be great. And on every hill, I was getting a ghost shift. I couldn't figure it out, until finally I realized I had to tighten the shift lever a bit more. Once I got it right, the ghost shifts where gone. So, was it the mighty Cannondale twisting? No, it did not do it before with the indexed derailleur set-up. What I also realized is that it never did it if I was in the saddle, even if I had virtually no weight on the saddle. But once I was out of the saddle, I started to rock the bike laterally, and noticed that the lower portion of the chain now flops around some. I suspect that this puts an ever so slight force on the derailleur cage and moves it - especially if the shift lever is set at the limit of friction.

I tell this long dull story because I firmly (I should be careful using this word) think that there is a lot more faux stories out there than real.

I also have been wondering recently, why don't they make cross country skis out of a rigid structure, would be a much more efficient power transfer:)

Dan Kasha Seattle, WA

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