You invited a response, so I'm going to try and use some bicycle tubing data from Columbus to take a slightly different tack. It’s just easier for me to go through the exercise this way rather than try to follow your train of thought. I apologize in advance for any confusion. I certainly don't know everything, but as an amateur framebuilder (limited so far to brazed lugged steel), I'm pretty familiar with standard tubing dimensions (diameters, wall thickness, weights).

Most bicycle tubing has wall thickness in the range of 0.5mm to 1.0mm in the center (non-butted) sections of the tubes. It can be as thin as 0.3mm (Reynolds 953) and as thick as 1.22mm (18 gauge non-butted 1020 carbon steel used in late seventies Schwinn Le Tours, Travelers, and World Sports). A wall thickness of .08" (2.032mm) would be almost a millimeter thicker than the 1020 steel tubing used in these late seventies Schwinns.

Standard Imperial O.D. for the main tubes in the 1980s (pre-O.S.) were:

Top Tube – 25.4 mm (1”)
Down Tube – 28.6 mm (1-1/8”)
Seat Tube – 28.6 mm (1-1/8”)
Head Tube – 31.75 mm (1-1/4”)

Since the density of all steel alloys is virtually identical, a tube that's twice as thick as another with the same O.D. and length will weigh nearly twice as much.

Columbus SL is a double-butted chromoly tubeset used extensively in the eighties for competition bicycles, and the diameters, butting profiles, and weight of a raw tubeset (not cut to length and mitered by the framebuilder) are shown in the data sheet below.



Notice the weight of the raw tubeset is 1,925 grams (4.244 pounds).

Columbus Zeta is a straight-gauge carbon steel tubeset used in the eighties for lower end sport bicycles, and the diameters, butting profiles, and weight of a raw tubeset are shown in the data sheet below.



The weight of the raw tubeset is 2,440 grams (5.379 pounds), or more than 1.1 lbs heavier than the SL tubeset.

The Zeta tubing has a 0.9mm wall thickness, while SL is 0.6mm in the center part of the tubes and 0.9mm in the butts.

The 18 gauge 1020 straight gauge tubing in the late seventies Le Tours and Travelers had a wall thickness of 1.22 mm, which would add a bit more than a pound to the weight of the 0.9mm Zeta tubeset, putting it at about 6.5 pounds.

In contrast to the SL, Zeta, and 18 ga. 1020 tubesets, the new Columbus XCr for lugs stainless OS raw tubeset weighs 1,425 grams (3.142 pounds), or more than a pound less than SL.





Of course, these weights are for full length tubing, so the differences between tubeset weights will be less for smaller frames. Also, for practical purposes, let’s specify that the weights of lugs, dropouts, and BB shells will be the same for each frame.

Basically, my point is that the weight of a raw 1979 Traveler 18 gauge 1020 alloy tubeset at 6.5 pounds is going to be more than twice as heavy as a raw Columbus XCr for lugs tubeset and more than two pounds heavier than a Columbus SL raw tubeset.

This thread is wonderful.

I think the optimization of tube OD vs wall thickness was in practice more easily approached from the other direction. Pick any one of the commonly avialable tube OD sizes which were available in 1/8" incriments, and then optimize the diameter to thickness by reducing the tube wall thickness. For high-quality tubing, a fairly wide selection of wall thickness was avialable, custom builders will oftern mix-and-match specific tubes from different tubesets in order to finely tune the weight & stiffness of the frame. Much easier to fit OD of tubes into available lugs and to match established aesthetics by sticking to commonly available OD sizes. THe only bike part that cares about the exact tube ID is the seatpost and that is easy to specify (or to ream-out). I think that vintage road bikes largely arrived at using 1" TT, 1-1/8" ST and DT because the tube diameters were fairly well optimized to available CrMo. Even thinner CrMo tubesets were available then (such as columbus KL) but by all acounts made bikes that were too limber with standard size tubes and too fragile to use at larger OD.
Thickwalled hi-ten tube bikes probably suffered a bit from trying to conform to the standard tube OD of nicer CrMo bikes. The hi-ten steel was not strong enough to use as a thinner wall but they were overly stiff and heavy because they used such thick tubing. Probably would be possible to have built a slighlty more optimized hi-ten bike using smaller diameter tubing throughout.
Also note that as steel strength increased beyond that of plain non-HT CrMo, it became necessary to bump up the tubing OD by +1/8" and later +1/4" OD in order to better optimize the strength-stiffness-weight ballance to the material.


I have run across a few older mid-low end bikes that proclaim that they used butted hi-tensile tubing. Interesting to see that it was at all economically viable to produce butted hi-ten tubes to compete in the same marketplace as strait-gauge CrMo.

Correct and a quick sanity check shows this to be true. Let’s look at two tubes of the same length and a standard 28.6mm outer diameter. If you look at a Tange #5, plain gauge, CrMo seat tube which has a wall thickness of 0.9mm you get a cross sectional area of 78.3 square millimeters. Now, if we take a high tensile tube which has an inner diameter of 25.4mm (which is fairy typical), we come up with a cross sectional area of 135.6 square millimeters. Since all steels vary very little in density, the relative cross sectional areas can be equated to relative weight and the CrMo tube is 57.8% the weight of the hi-tensile tube. That’s pretty close to the 60%.

Yes, the difference will typically be less. Even if the manufacturer used a full Tange #5 tubeset, they would probably use lugs and shells that weighed the same or very similar. This will cut down on the weight advantage of the CrMo frame.

The better material frame will probably also have more fittings. The rear dropout will likely have a hanger that adds weight while the hi-tensile frame likely has a hangerless, stamped dropout. The better frame probably has shifter bosses, which weigh less than the cable stops for the stem shifters on the hi-tensile frame. The CrMo frame probably has an extra water bottle boss. Basically, the better frame likely has more convenience fittings which add weight and further compromise it’s weight advantage over the hi-tensile frame.

However, the biggest compromise are the stays and forks. In these applications CrMo’s potential weight savings cannot be fully realized because the forks and rear triangle would be too whippy. Stiffness in a round tube is a function of the material’s modulus of elasticity, its outer diameter and its thickness. In the case of CrMo and 1020 hi-tensile, the modulus of elastic are similar and the stiffness primarily becomes a function of diameter and thickness.

A main triangle can maintain good stiffness, primarily due to the larger diameter tubes. But shrink the diameter, as in the stays and fork blades and things start to get whippy. In order to maintain the necessary rigidity, Tange used CrMo stays that are about 80% the thickness of their hi-tensile stays. So, in these regions you lose about ½ the potential weight savings of CrMo. This is why designers often substitute lesser grade material in the stays and forks. It saves money without affecting the weight as much.

Then there is the whole question of how much the designer wants to push envelope in either direction. Does he want to go heavier than the norm, knowing it is more likely to be abused and used in all sorts of applications? Or can he make it lighter, knowing that it will be used only in certain applications and that the extra cost will result in better care? A designer of an X-mart bicycle is going to build in a heavier safety factor than a standard hi-tensile frame, while a designer of a time trial frame will build in a lot less than your typical CrMo frame.

Back in 1983, Bicycling did a comparison of entry level bicycles. A Pansonic Sport with a full 1020, 21"frame weighed 6 lbs 9oz. An identically sized KHS Citation (notice how I found a KHS for you) with a Tange #5 main triangle, weighed 5 lbs 9 oz. Obviously there will be some differences in weight savings due to actual tubing gauges, geometry, choice of lugs, fittings, etc., but it looks like a roughly 1 lb weight savings by going to plain gauge, CrMo, main tubes over hi-tensile.

Now, here’s the bonus. I found a road on a 1985 KHS Fiero with a Tange 900, seamed, double butted, main triangle. Frame weight was 5 lbs 2.5 oz and it’s a 2" larger frame. So you’d get about an additional ½ lb saving by going butted CrMo in the main triangle.

You’ve missed one very important point of my previous posts. I was referring to the cost saving of seamed butted CrMo tubesets. Butting is the most expensive operation of tube making. While there are savings in going from seamless to seamed in a plain gauge CrMo tube, they’re relatively small compared to going from seamless to seamed in a butted, CrMo tube.

Let’s take a look at the two previously mentioned KHS bicycles. In 1983 a KHS Citation with a seamless, plain gauge CrMo main triangle cost $219. Two years later the KHS Fiero costs only $20 more, yet it’s got a ½ lb lighter frame, thanks to going seamed, butted CrMo. To top it off, the rate of inflation over those two years was about 7.5%, so the adjusted price increase was only about $5. The components were comparable and, if anything, arguably better on the Fiero. They were certainly lighter based on overall weights.

Seamless, butted, CrMo tubes were pretty much restricted to mid-range and higher models. The best you got for an entry level price up to the very early 1980s was a plain gauge, CrMo main triangle. The mid-1980s seamed tubesets brought butted CrMo butted into the entry level. You got the weight savings of butted tubes but perhaps more importantly you also got their more resilient ride quality. A couple of years earlier you would have had to pay a lot more to get the weight savings and resiliency.

After coming across another KHS bicycle this week and was hoping to find more info on via the WWW, I happened across this thread. Even though it's been four or so years, I just want to thank everyone who offered up insights and observations to my questions. I really appreciate all the help and knowledge given without any attitude towards this novice. It creates a great community here on the forum, and I hope that sometime in the future, I get to meet some of you and thank you in person for all good you have graciously given me throughout my years participating on this forum. Thanks once again, you make this the best of WWW for me.

I thought all the early high end steel sets grew out of technology used from the aircraft industry but I could be wrong on this.