531 versus 725

[LittleWheelsandBig]

Imagine pinching an empty Coke can between thumb and forefinger...

[Cudzoziemiec]

Okay. As opposed to denting from an impact in one place, I presume.

[De Sisti]

Does Columbus steel tubing compare favourably with Reynolds?

[Brucey]

in very thin-walled steel pieces you can get Euler type buckling which can go on to initiate a collapse.  In practice steel frame tubes seem to  get too dent-prone well before they are liable to that kind of behaviour.


Much is made of stiffness and certainly having stiff chainstays seems to make for a good ride. But in the main triangle it is easy enough to overdo the stiffness in any (small/medium size)  frame that doesn't have to carry a load.   I find that even in the lightest practical standard gauge tubing (eg 753R) frames that are up to ~22" (with a horizontal top tube) are stiff enough for unladen riding.  Not that they don't flex, but this seems either harmless or may be helpful.   If a frame of about that size is built in oversize tubing it can very easily become too stiff, and soon becomes thoroughly unpleasant and plank-like to ride. However in larger frame sizes it seems very much easier to end up with a frame that isn't stiff enough.

My sensible materials scientist head says that (in comparable gauge tubes) there ought not be much difference between steels based on their yield strength; however some of my favourite framesets are built in steel tubes that derive a fair amount of their strength from cold work, and have been silver brazed so as to retain as much of that strength as possible.  Maybe there is something in the idea that yield strength has some impact on ride feel. 

If so this suggests that you might be better off silver-brazing a lugged frame every time.  The reasons for not doing this are a) the cost of the spelter and b) the fact that silver braze doesn't usually fill wide gaps very well.  This makes building the frame more difficult than it might otherwise be, but the post braze strengths of many common tubesets are considerably improved by so doing.

 FWIW one of the unseen but important aspects of lugged frame construction is how well mitred the tubes are; if poorly mitred (so the tubes don't fit one another inside the lug) then the lug is left 'to do all the work' and the resulting frame can be noticably floppier than it might be otherwise. The frame can also crack in the lug too. This is commonly seen in the lower head lug.

You can build  a nice frame in 725 tubing without a doubt. However the devil is in the detail. Choose your tubes with care.

cheers

[whosatthewheel]

The main characteristics of a frame are down to trigonometry... it's all in the angles.

Frame material is almost immaterial... steel wise, I've had 531, 725, 853 and Columbus SL... I wouldn't be able to tell the difference

[rafletcher]

  You don't see all that many 753 frames secondhand as the chainstays often rust out.

My understanding at the time was that the main triangle was 753, the forks and stays 653.

[rafletcher]

Maybe there is something in the idea that yield strength has some impact on ride feel. 

I don't see how. Elastic behaviour (as governed by Youngs Modulus) is similar up to yield.

[Little Jim]

Quite a while ago someone posted a link on here to a pdf of an article written for an American cycling magazine back in the 90's.  I know that doesn't really help but I can't be any more specific.

The premise was that they would get a well respected Italian frame builder to make about 7 different frames of identical size and geometry out of seven different tube sets ranging from gas pipe to state of the art.  They were sprayed identically except for a number applied to each frame to identify it.  They were then built up with the same groupset and the same set of wheels was swapped between bikes.  They were then ridden by the same tester around the same course and he had to rate them in order of preference and they also timed him.  In summary there was very little difference in the times taken to ride the course, although obviously you only need to be a second or so faster over a set route to make the difference between first and second.  The tester could tell the difference between the lighter frames and the heavier ones but could not rank them in the correct order and really struggled to say which one they preferred.

[whosatthewheel]

Quite a while ago someone posted a link on here to a pdf of an article written for an American cycling magazine back in the 90's.  I know that doesn't really help but I can't be any more specific.

The premise was that they would get a well respected Italian frame builder to make about 7 different frames of identical size and geometry out of seven different tube sets ranging from gas pipe to state of the art.  They were sprayed identically except for a number applied to each frame to identify it.  They were then built up with the same groupset and the same set of wheels was swapped between bikes.  They were then ridden by the same tester around the same course and he had to rate them in order of preference and they also timed him.  In summary there was very little difference in the times taken to ride the course, although obviously you only need to be a second or so faster over a set route to make the difference between first and second.  The tester could tell the difference between the lighter frames and the heavier ones but could not rank them in the correct order and really struggled to say which one they preferred.

Not surprised at all... if the geometry is the same, the frame is 99% the same

[mattc]

Quite a while ago someone posted a link on here to a pdf of an article written for an American cycling magazine back in the 90's.  I know that doesn't really help but I can't be any more specific.

The premise was that they would get a well respected Italian frame builder to make about 7 different frames of identical size and geometry out of seven different tube sets ranging from gas pipe to state of the art.  They were sprayed identically except for a number applied to each frame to identify it.  They were then built up with the same groupset and the same set of wheels was swapped between bikes.  They were then ridden by the same tester around the same course and he had to rate them in order of preference and they also timed him.  In summary there was very little difference in the times taken to ride the course, although obviously you only need to be a second or so faster over a set route to make the difference between first and second.  The tester could tell the difference between the lighter frames and the heavier ones but could not rank them in the correct order and really struggled to say which one they preferred.

They should have asked a magazine tester.

[Brucey]

the 7 frame test used 'ordinary Joes' as 'testers'. This is a bit like asking a bunch of novice violinists to give their impressions of how playing a Stradivarius differs from a lesser instrument, i.e. you would be lucky to get any sense out of it.  Any test riding on the road needs to be carefully designed in order that random factors (such as how many cars go past you) don't dominate the results.  A draggy climb at a fixed workrate seems like a good experiment and the route they used in the 7-frame test wasn't.

More recently BQ did a 3-frame, 3-rider test using more experienced cyclists, and the (blind-tested) bikes were weighted internally to be the same mass.  Of the three riders, two expressed a clear preference for the lighter-built frames and went faster on them (at a given pulse rate on a draggy climb). The third rider couldn't tell the difference but still went faster.

I think it is fair to say that different pedal strokes suit different frames better than others, and that (on the road) the crunch test is whether you are still pedalling nice circles or not after a day in the saddle.

My personal theory is that a frame without enough flex (lets call it 'flexless' although this is a slight misnomer) doesn't 'talk back to you' enough and thus when you get tired you are more likely to pedal badly.  But that is just a theory.

In terms of strength affecting how tubing behaves below the yield point; this can fairly easily be demonstrated. If you take two pieces of steel of the same geometry but different strengths, and suspend them so that they can resonate when struck (like a bell), you can hear a clear difference, even though neither is getting anywhere near yield stress when struck and remains undeformed.  This may translate into the efficiency of the frameset (as a spring) when pedalling.

cheers