Originally Posted by
T-Mar
Tom, I'm going to have to respectfully disagree. Many tubing manufacturers offered seamed, butted, CrMo tubesets that used the same wall thickness and butt lengths as their seamless tubesets, resulting in comparable weights. The introductions of these seamed tubesets, in conjunction with component technology trickle down, allowed bicycle manufacturers to offer sub $300 bicycles in the mid-1980s that weighed around 25 lbs.
That's about a 3lb weight reduction with only a doubling of price over what was being offered a decade earlier. While some of it can be attributed to the components, notably the widespread adoption of aluminum rims and aluminum cotterless cranks, the deduction in frame weight is not inconsequenttial. Entry level frames with seamed, butted CrMo main tubes and hi-tensile stays were running around 5 lbs in a 23" size.
Okay, so, I read the comments related to my additional questions connected to the original posters questions. I agree with T-Mar's remarks to Tom's comments. 4130 Chromoly (aka bike tube chromoly) is 1.75 times stronger than 1020 high tensile (aka bike tube hi-ten). So, in theory, a frame made from chromoly could end up being 60% lighter. Chances are though, the difference is less. For one, standardized tube diameters and standardized tube wall thicknesses mean that you probably couldn't get EXACTLY the tubing dimensions that would be ideal. For instance, your calculations may say that the perfect seat tube (with a chosen wall thickness of .08") would have a diameter of .83467 inches. Well, .83467 isn't standard, so you would probably be forced to round up to the nearest standard diameter, say .875". Also, a lot of frames used chromoly tubing for the main tubes (which have approximately 1" diameter) but hi-ten stays (where, because of the comparatively smaller cross-sectional area of the tube, the weight savings would be more diminished, and the cost not worth the weight savings). I would like to know a comparative weight of a 23" size frame made with hi-ten tubing, anyone know? Plus, I have a KHS Classic bike, made with Tange #5 tubing (which I believe to be seamless) that has components with a 1981 manufacturing date. I assume that it was fairly "entry level" for it's era, with it's components being fairly closely matched to my 1977 Schwinn LeTour II (definitely near entry level specimen for it's day). So, I question whether the ability to create seamed chromoly tubesets was the driving factor for the reasoning as to why chromoly tubing became so affordable and widespread in the eighties. It seems to me, since Tange seamed chromoly tubing (like Tange 1000) showed up AFTER it's other tubing offerings (like Tange #3, which is quite similar in size/strength as Tange 1000, but seamless). So seamed chromoly tubing did provide lower pricing, but it did so after seamed chromoly tubing had already shown up. Any arguments to refute my claims (more like guesses than claims really)?