jimmuller 

Thank you for the reply. Yes, I understand that, and that's why I wrote "built for the same purpose" rather than "built with the same dimensions". Perhaps "same purpose" was too stringent still.

I was really asking the fundamental question of why you'd choose 753. If it was to obtain lighter weight assuming both bikes were as light as you make them for the purpose of, say, climbing the Alps, how much lighter would the thinner tube walls actually allow? 3oz? 6oz? 1lb?

Sure, the frame stiffness would be different. If you chose 753 for that purpose because the greater strength would allow it you'd still end up with a lighter frame. How much lighter?

To ask the broader question which was posed in a different thread but never answered (and quickly degenerated into weight-weenie bashing): What are typical weights of frames (all the same size of course) made from hi-ten, chrom-moly, 531, 753, etc?

I'm guessing the weight difference between 753 and 531 is small enough that it wouldn't matter for most of us recreational riders. I know how my bikes feel, but that's with them fully built-up. Hypothetically, were I to strip either bike down to "upgrade" the frame, and assuming I don't trash them so that frame strength per se is not an issue, what be the gain?

kroozer 

Those 3Rensho lugs are awesome, especially with the psychedelic paint job.

GrayJay

From the previously cited link in this thread, https://fivenineclimber.com/bikes/gaz...eynolds_80.htm
A bare 753 tubeset is approx 250gr lighter than a bare 531competition tubeset and the 531c tubeset is itself approx 250gr lighter than a CrMo 501 tubeset. Compelling reason to use the more expensive tubing (& if you are willing to sacrafice the stifness of a thicker walled frame) is that if you were to build a 501 or a hi-ten frame with the same thin tube deminsions used for 753, the 501 frame (with lower strength tubing) could reasonably be expected to develop cracks and fail catostrophically under same use much sooner than a 753 frame. Up to the instant that it cracked, there would not be a difference in how the two frames rode (provided that the tubesets were otherwise deminsionally identical).

Road Fan

Jim, there are sites that give the wall thicknesses for 531 SL and 753 tubings for each position on the bike frame. You can calculate a rough estimate for 753 and 531 based on the cross-sectional are of the tubes in both alloys, and divide one by the other. That factor is roughly the number you are looking for. CrMo and 531 are very similar in strength, though Columbus Cyclex (SL, SLX, and SP tubesets among others) is a little stronger than 531.

I also think you can just take the ratios of their tensile strengths and use those as rough(er) scaling factors.

If you want EXACT, you'll have to build four framesets to the same geometry and same features, using the four different alloys, then weigh all four on an accurate scale. I think my methods are easier.

Picchio Special

That's plausible to me - I owned and sold a well-documented, larger-size Raleigh 753R frame in Panasonic livery with the oversized caps - so what you suggest make sense, IMO. I don't know why you think the non-fastback sounds odd, as a matter of fact.

Picchio Special

There are a few Motobecane Champion Team 753 frames out there - rare, but they exist.

Picchio Special

Your LBS owner is full of @r@p and should probably retire or zip it.

Picchio Special

It's hard to assign "typical weights," since 531, 753, and pretty much everything else was available in a range of wall thicknesses, and therefore a range of potential frame weights, depending on the rider size, desired frame stiffness, riding style, etc. In other words, your "broader question" doesn't really have a meaningful answer (check out the weight difference between a 753R set and a 531Pro set with the same frame size, for example).

repechage

I would change that to a believer of Jan Heine. Any of the steel thin walled tube of the same outside diameter are going to flex just a bit more than one of thicker wall thickness and given equal build attention and care. Going oversize in diameter with thin walls gets you a stiffer bike. But, even with the more modern heat treated steels, air hardened etc, the thin wall thickness may also make the bike a bit more "fragile", easier to dent locally, more likely to fold up in a big crash.

One could probably save more frame weight by carefully selecting a pressed bottom bracket shell, fork crown, dropouts and lugs than going silly thin on the tubes. Silly thin tubes and light fittings will of course get one the lightest frame yet.

jimmuller 

Well, Jan, I hope you learned something about 753!

As for weights, I appreciate all the comments but I'm still in the dark, more or less. I don't need to know at all, but just would like to have a sense of perspective. I have never weighed a bare frame or the components which go on it. So though I can easily do the math for the relative weights of different wall thickness, I don't know a baseline. Or to put it another way, if I have a 22lb steel bike with decent components, I don't know how much of that is the frame and how much is the components. But it doesn't matter. Thanks anyway.

repechage

Think of it this way, what would the tubes weigh to get you from .4 mm to .6 mm wall thickness for the full length of the tubes, about Columbus SL to 753 thin stuff. In other words, probably 300 grams total at most, if that.

GrayJay

Good article with a bunch of comparison bare frame weights for otherwise identical columbus frames is at; https://www.habcycles.com/m7.html
The EL-OS and Neuron tubed frames were 4.0 lbs. EL-OS is fairly similar wall thickness to 753 and I would estimate that the larger OS diameter tubes add about 150gr in comparison to the smaller diameter 753 tubes. Should be possible to build a midsize 753 frame that is a 3-4 ounces shy of 4lbd.

Road Fan

Yes, I neglected to qualify my POV with teh caveat "with equal OD," since with early 753 and 531 SL, the ODs were teh same. In this situation, thinner wall would result in a less-stiff frame tube, and presumably a less-stiff frame. I never said anything about oversize tubes v. thin tubes, nor about other fragility factors such as tubing collapse aka beer-canning.

Road Fan

You're welcome?

I gave you a way of estimating the fraction of frame weight (actually the upper limit) that might be saved in going from tubing of wall thickness 1 to wall thickness 2. You say you are able to handle that. Columbus has said that SL (hope I am picking this out of the correct portion of my body) builds into a complete frame of about 2400 grams. Convert to pounds by dividing that by 2.2 lb per 1000 grams. Then apply the conversion factor you will derive. Subtract to find the absolute difference. Tell us what you learned.

Subtract that absolute difference in frame weight from the total weight of the bike to get the potential reduction in bike weight due to a "wave teh magic wand" upgrade from 531 or Columbus SL to 753. Any realistic frame changes will require a much more detailed calculation or an empirical weight analysis to get real numbers. Or just build two bikes and weigh them, accounting for any component differences between them as correction factors.

jimmuller 

I just learned this:
Thank you. (Reading through those tubing tables puts me to sleep. Too much is left to infer.)

bobbycorno

Which, for those of us who only speak English, is over half a pound (10.6 oz to be precise). Over 10% of the weight of a typical road frame. I'd call that significant...

SP
Bend, OR

GrayJay

Dont divide, multiply the 2400gr x 2.2 to get as pounds = 5.3 Lbs. That actually seems a bit on the heavy side to me for a SL frame. THere are many other variables such as frame size, lugs & dropouts used, paint, chrome plating that will effect frame weight too. In the "magnificent 7" comparison article, https://www.habcycles.com/m7.html they weighed a SLX frame (without fork) as 4.5 pounds and the SLX tubeset is only about 40 grams (1.4oz) heavier than an SL tubeset. Even thier Aelle tubeset frame was well under 5 lbs.

Picchio Special

In terms of bike performance, it's utterly meaningless.

seypat

Not 753 related but this might help with your question.

I took 2 frames/forks to the post office the other morning to see the weight differences before I built one up.
1st frameset - 21"/56cm 531DB throughout. This bike was the top of the line from its country during its time. Full Campy, tubulars, etc. This frameset had some success in the TDF, Giro, Pro circuit, etc. As tested in '73 it weighed 23lbs for the 21".
2nd frameset - 54cm low to mid level bike boom French bike with seamed "unfamous" tubing. Simplex Prestige FD, Suntour Honor RD, steel Rigida rims, kickstand, etc. This bike weighed in at 30lbs before I disassembled it.

So what did the scale read?
Frame 1 had a NR headset and NR BB/spindle on it and weighed 7lb 8.2oz.

Frame 2 had no headset/bb so I brought the ones that came with it plus a Stronglight Competition BB/spindle that was acquired for it. With it's stock headset and cottered spindle/BB(bearings included) it weighed 8lbs 3oz. With the Stronglight BB/spindle(no bearings included) it weighed 8lbs even. Not much of a difference!

Frame 2 will get a stronglight 93, 27" Wolber Super Champion Mod 58 and Suntour Vx derailleurs as upgrades. Frame 1 will be sporting it's original NR and 700 Wolber Super Champion 58 or comparable.(except when the tubs come out) I'm guessing when they are both completed they will weigh within a pound of each other. Less than the weight of a full water bottle. BUT remember, it was one size smaller.

Hopefully, this somewhat answers your question or gives you some perspective.

retrofit

Thanks for the instructive discussion; this is why I continue read C&V.

And as if on cue, a 753 bicycle is for sale in the BF Classifieds -- by its original builder...

E.G. Bates 753 Racing Bike built by Clive Bates

old's'cool

I'd like to give this thread a star for technical accuracy and astute inquiry. Keep it up!

One aspect I want to point out is, different parts of the frameset experience different types of critical loading and hence potential failure modes. The critical loadings on the fork I would assume to be bending and shear, due to vertical shock loads and horizontal braking or impact loads. So sheer and beam bending analyses apply when evaluating fork stress & failure. This also applies to the steer tube.
For the chainstays and seat stays, I assume the critical failure mode is buckling. Buckling analysis can be very complex, I suppose, especially when the loading is not pure compression but a combination of compression with bending, torsion,and shear.
The main tubes I assume see highest stress in torsion. There may be some significant sheer loads (due to road impacts) that need to be taken into account also. The downtube and top tube would see significant bending loads in event of a severe frontal impact, but since the fork & steer tube would probably succumb first, I don't think a frontal impact analysis would drive reinforcement of the top and down tubes, at least on a competitive racing frame.

The reason I mention all of this is, wall thickness, and hence wall stiffness, or lack thereof, plays a role when the loading is such that the wall itself is subject to buckling. So a shear, torsion, beam bending, or column buckling analysis may ultimately devolve into a wall buckling analysis, when lack of wall stiffness starts to become an issue.

All of the above is primarily addressing failure in yield, rather than fatigue, but since the peak and typical loads are qualitatively the same, a frame that has higher yield strength should also have greater fatigue life, generally speaking. Wall buckling is a bit of a grey area. If a wall buckles (wrinkles) elastically on infrequent occasions of high loading, can that potentially lead to a fatigue failure? I suppose, but does it happen in reality? No idea.

With respect to frame geometry, the above discussion applies to a classic double diamond frame and cantilever fork only.

twolegs

you see the gear shifters you got there.. well on the frame you have modified the old gear sticks so that the cables rest where they used to be.. would you mind telling me what that contraption is called? did you make it yourself or is it available to purchase.. i cant find anything like that online, and a name would be helpful. many thanks

Scooper

These are down tube shifter braze-on cable stop adapters. Shimano makes them with built-in barrel adjusters. Part No. 67B-9100 "SM-CS50" $14.99/pair

Shimano alloy braze-on down tube cable stops with barrel adjusters

They bolt onto the existing shifter brazed-on bosses. Here they are on my Waterford.

twolegs

thanks so much for that link for the down tube cable stops, thats really helpful, much appreciated

KonAaron Snake 

Campagnolo also has a version.