Does anyone have two (or more) frames of the same material (531 for example) but different sizes? I'm interested in how much frame weight difference there is between, say a 52 cm. and a 62 cm.

Hi,
Size is more important than weight, I should think! Differences in weight between identical frames of different sizes is negligable. After Losing access bodyfat, a light pair of wheels makes a difference, followed by other lightweight componentry. Extra fitness will greatly undermine any extra weight carried though!
Regards
Hope this helps
Michael

There are certain significant variables to consider, especially on older steel frames. I have a 59cm frame which weighs right at 4.5 lbs. and also a 53cm Paramount frame which weighs CONSIDERABLY more. Both have double-butted 531 tubes, Nervex Pro lugs, and Campy #1010 dropouts. BUT, the Paramount is fully chromed. Chrome plating adds a surprising amount of weight - even if only on half of the stays and forks. And, with pampered older bikes, there is also the possibility that portions had been re-chromed during their lifetimes which makes them even heavier. In fact, old time racers tried to avoid plating on their bikes for this reason. I have a late '60s Frejus 'Professional' (full Campy Nuovo Record) with no chrome at all. Generally, I would suspect the additional lengths of thin gauged steel tubes is a relatively small contribution compared to the combined weights of the BB shell and lugs (even a "light weight" lugged fork crown alone can weigh 3-4 ounces). ~~ Personally, I frequently do reduce the weights of my old steel bikes... by shedding a couple pounds of winter body fat.

Hi Michael67 & Stronglight,
Thanks for both answers - both excellent. I know I could probably lose an amount of body weight equal to my complete bike weight (21 lbs.) - but it's not easy. I'm a retired engineer so I'm interested in the engineering items - just my curiosity.
But as a data point: My completely stripped 1972 Italvega SuperSpeciale with double-butted 531 tubes with chrome on the stays and lugs and 56 cm frame weighs 4 lbs. 13 oz.
Thanks for your input. SM

I sorta/kinda remember a specs chart for a high quality steel frame that listed weights for sizes from around size 54 to size 62. For that frame, the weight difference between the small and large was around 6 to 8 ounces.

The use of longer tubes on larger bikes may not account for the entire difference in weight. Schwinn used different tube sets for Paramounts in the 1970's based on size. A size 62 racing Paramount had a straight gauge downtube instead of the double butted downtube used for smaller sizes. Schwinn engineers assumed that a size 62 bike would have a rider who was heavier and more powerful than a size 54 bike, and that a large rider needed a bike that would resist flexing or twisting at the bottom bracket.

I suspect many of the "smarter" bike designers who worked with the traditional diameter steel tubes of the '70's and '80's used similar techniques...the tubes on their largest road bikes were not just longer tubes, they might also use have thicker walls, at least for some tubes.

Our old friend Sydney used to "rate" thicker tubes as "inferior" and thinner tubes as "superior". I don't think Schwinn thought of the issue that way. Larger bikes and larger riders have different needs than do smaller than average bikes and smaller riders...the best bike is the one that mets a rider's individual needs.

And, given the ratio of frame weight to rider weight, the difference may be insignificant. A 160 pound rider on a four pound frame requires the frame to support forty times its own weight. A five pound frame with a 200 pound rider is also supporting forty times its own weight...the same rider to frame weight ratio.

Alanbike houston brings up a very valid point. In the case Columbus tubests, most builders would switch from SL to SP tubing, around 58-60cm, on the assumption of the larger riders being heavier and more powerful. Some of the borderline frames would use as SL/SP mix, with SP in the downtube and chainstays.