Yet Another Cycling Forum

General Category => The Knowledge => Topic started by: Roy on 03 February, 2019, 06:55:50 pm

Title: 531 versus 725
Post by: Roy on 03 February, 2019, 06:55:50 pm
Is there any real difference to the ride / feel of a bike built around a 531 frame compared to one built around a 725 frame assuming everything else, wheels, saddle etc. were the same?
Title: Re: 531 verses 725
Post by: giropaul on 03 February, 2019, 07:10:36 pm
I suspect that the builder is more important than the tubing ( within the range of decent tube sets).
Title: Re: 531 verses 725
Post by: Ian H on 03 February, 2019, 07:19:31 pm
I suspect that the builder is more important than the tubing ( within the range of decent tube sets).

Yup. 

You *might* notice a slight difference if you lift them in turn.
Title: Re: 531 verses 725
Post by: mattc on 03 February, 2019, 07:29:56 pm
What would you think if the builder told you that?
"Oh I'm such a great builder, you don't need to worry about things like tubing choice. It'll be fine!"
Title: Re: 531 verses 725
Post by: ACyclingRooster on 03 February, 2019, 07:37:44 pm
Is there any real difference to the ride / feel of a bike built around a 531 frame compared to one built around a 725 frame assuming everything else, wheels, saddle etc. were the same?

Hi Roy. Is it your intention to build the frame lug-less or with lugs ?

The use of 725 was noted to have been used on lug-less frames and as such when compared with 531 it has slight weight advantage - frame for frame of the same size.
Title: Re: 531 verses 725
Post by: Roy on 03 February, 2019, 07:51:56 pm
Thanks for the replies. The frame would be built with lugs. So no real difference then?
Title: Re: 531 verses 725
Post by: Ian H on 03 February, 2019, 07:58:45 pm
What would you think if the builder told you that?
"Oh I'm such a great builder, you don't need to worry about things like tubing choice. It'll be fine!"

The man who is going to build my new frame is certainly suggesting that he knows best about tubing choices.
Title: Re: 531 verses 725
Post by: grams on 03 February, 2019, 08:25:48 pm
What would you think if the builder told you that?
"Oh I'm such a great builder, you don't need to worry about things like tubing choice. It'll be fine!"

Preferable to them prattling evidence-free nonsense* about slightly difference types of steel having different "feels", surely?

(* if they have evidence I've found my frame builder!)
Title: Re: 531 verses 725
Post by: Hot Flatus on 03 February, 2019, 08:33:24 pm
Is there any real difference to the ride / feel of a bike built around a 531 frame compared to one built around a 725 frame assuming everything else, wheels, saddle etc. were the same?

Hi Roy. Is it your intention to build the frame lug-less or with lugs ?

The use of 725 was noted to have been used on lug-less frames and as such when compared with 531 it has slight weight advantage - frame for frame of the same size.

Yes, it's TIG weldable.

725 is heat-treated 520, so Cro-mo, rather than Mang-Mo. Drawn thinner than 531.

Unless the tubes are OS (assuming they still do 725 OS) I don't know if you'd notice the difference in the ride.  Maybe slight weight difference.
Title: Re: 531 versus 725
Post by: rogerzilla on 03 February, 2019, 09:09:15 pm
How much do the tubing gauges differ in terms of total weight, tube diameter, wall thickness and butt length?  Those things will make a small difference to the way the frame rides.

Tony Oliver's book has a load of stuff about micro-yielding which suggests that the very strong heat-treated tubesets like 753 (which was the best available when the book was written, now long superseded) would waste less energy under high stress.  I don't completely buy it, but he was a materials scientist.
Title: Re: 531 versus 725
Post by: Ian H on 03 February, 2019, 09:25:26 pm

Tony Oliver's book has a load of stuff about micro-yielding which suggests that the very strong heat-treated tubesets like 753 (which was the best available when the book was written, now long superseded) would waste less energy under high stress.  I don't completely buy it, but he was a materials scientist.

Ha!  You've reminded me:  He built a tandem, for himself, out of 753.  I remember him showing me the yolk linking the rear cantilevers which he'd made to stop the seat-stays spreading under the braking forces.  He gave up making bikes many years ago.
Title: Re: 531 versus 725
Post by: rogerzilla on 03 February, 2019, 09:36:30 pm
Apparently the fumes from brazing were affecting his health.  His bikes/frames sell for an absolute fortune secondhand.
Title: Re: 531 versus 725
Post by: LittleWheelsandBig on 03 February, 2019, 09:52:39 pm
Same reason Bruce Gordon stopped brazing. Towards the end, he hooked up a breathing air supply.
Title: Re: 531 versus 725
Post by: Paul H on 03 February, 2019, 11:42:46 pm
Here's a Reynolds tube list, from 2013 but that's the latest Google would find for me.
http://www.torchandfile.com/assets/images/Reynolds/Reynolds%20Tubing%20Parts%20List%202014.pdf

You're not going to notice any difference between two tubes of the same diameter and gauge and as you can see from that list 725 and 531 are available in identical spec.  There is more choice with 725 and whether the frame builder makes use of the other options is something to discuss with them. 
Title: Re: 531 versus 725
Post by: Cudzoziemiec on 04 February, 2019, 01:32:02 pm
So what about people like eg Fairlight and Shand who mix different sets for different tubes? Markting bullshit? Weight savings? Money savings?

And what about the stainless tubes?
Title: Re: 531 versus 725
Post by: rafletcher on 04 February, 2019, 01:57:08 pm
Pretty much woo IMO. Digging waaay back into my memory (there are others here who are much more current), the "flexibility" of steels can be defined by the Youngs Modulus of Elasticity - the ease with which you can deform a material elastically.  It doesn't vary that much between different types of steel.  Nor does density, so similar sections have similar weights. As has been mentioned elsewhere, resistance to bending (which would be what gives a frame it's rigidity) is a factor of the shape of the section, and tubes of equal thickness and diameter (and Youngs Modulus) will have the same stiffness.  What varies with steels is the elastic limit and the ultimate tensile strength, the points at which a load causes permanent deformation and failure, respectively.  Provided the applied loads don't cause permanent deformation of the section, then the absolute strength doesn't matter - you're just closer or further from that point.

There are other charactersitics of the steels though - how easy it is to form the required sections, how easy to braze / weld they are, that could influence choice.

No doubt I'll be corrected in due course  :)
Title: Re: 531 versus 725
Post by: rogerzilla on 04 February, 2019, 01:59:28 pm
Some builders may want a thicker top tube for a touring bike for better load carrying/dent resistance, or may want a heavy tubeset that takes a common 27.2mm seatpost rather than an irritating 27.0mm.  Some tubesets also have silly overbuilt fork blades (531DB - not sure if 531C was exactly the same) which would ensure the frame, not the fork, was written off in a front-end collision, and this can be avoided by using someone else's fork blades (Columbus/Tange).

I suspect some builders also worked in total chaos and used whatever was lying around and took their fancy on the day- I've seen photos of Ron Cooper's workshop!  The outside diameters of traditional tubes are standardised, so there is no particular reason not to mix and match, since they all fit into the lugs.

The modern stainless steels are very hard and strong.  Reports are that they are not fully stainless, if you think you can treat them like titanium and ride an unpainted frame on salted roads.  AM-series stainless Moultons can suffer from surface rust, which is probably disappointing if you just dropped £17k on one  ;D



Title: Re: 531 versus 725
Post by: Frank9755 on 04 February, 2019, 02:05:21 pm
I recall reading somewhere that it was typical to use stiffer steels for the main tubes but not for the rear triangle or fork, where a bit more give would improve the ride, hence these would often be in eg 531 which is more springy.
Title: Re: 531 versus 725
Post by: rafletcher on 04 February, 2019, 02:17:35 pm
The modern stainless steels are very hard and strong.  Reports are that they are not fully stainless...

Makes sense. "Proper" stainless steels, which I would define as austenitic (316 for example) are pretty weak materials, much more so that the martensitic 420's used for sinks and swimming pool steps. You can tell how old my knowledge is, I've no idea what the current designation for the steels would be, and many would have been developed long after I stopped being a proper engineer! 
Title: Re: 531 versus 725
Post by: LittleWheelsandBig on 04 February, 2019, 02:19:30 pm
Different strength steels, as a rule, have differing corrosion and crack propagation characteristics, which link to stress concentrations, fatigue and hence durability. Ease of machining and ease of realignment post-brazing (cold-setting) also is a factor in why there can be advantages in using lower strength materials at each end of a bike frame, compared to the main triangle.
Title: Re: 531 versus 725
Post by: rogerzilla on 04 February, 2019, 08:35:05 pm
953 is a maraging s/s, which ISTR is a portmanteau of martensitic and ageing (or aging in USian).

Besides the micro-yielding thing, using a stronger steel means you can use less of it (thinner tube walls) and get a lighter, yet not significantly more flexible, frame.  One problem with the super-strength non-stainless steels like 753 is that rust is no respecter of fancy heat treatment and will eat through super-thin tube walls with glee.  You don't see all that many 753 frames secondhand as the chainstays often rust out.
Title: Re: 531 versus 725
Post by: giropaul on 04 February, 2019, 08:55:26 pm
I have some reason to believe that if you put , e.g. 753 transfers on e.g. a 501 frame elite riders will confirm how good 753 is compared with other tubing.
Title: Re: 531 versus 725
Post by: rogerzilla on 04 February, 2019, 08:56:56 pm
The scales would show it was about a pound heavier, though.
Title: Re: 531 versus 725
Post by: LittleWheelsandBig on 04 February, 2019, 09:15:50 pm
Stronger steels often corrode faster/ more easily than weaker steels. The lack of sacrificial wall thickness is the biggest factor though.

A stronger steel tube with thinner walls will be more flexible than a thicker walled tube of the same diameter but weaker steel. The only way around that is to bump up the diameter to compensate for the lost wall thickness but then that tube is more susceptible to 'oilcanning' and denting once diameter:thickness significantly exceeds 50:1. Stronger steel helps resist that behaviour a bit but doesn't rule it out.
Title: Re: 531 versus 725
Post by: Cudzoziemiec on 04 February, 2019, 09:45:03 pm
oilcanning?
Title: Re: 531 versus 725
Post by: LittleWheelsandBig on 04 February, 2019, 10:39:39 pm
Imagine pinching an empty Coke can between thumb and forefinger...
Title: Re: 531 versus 725
Post by: Cudzoziemiec on 04 February, 2019, 11:25:00 pm
Okay. As opposed to denting from an impact in one place, I presume.
Title: Re: 531 versus 725
Post by: De Sisti on 05 February, 2019, 06:03:25 am
Does Columbus steel tubing compare favourably with Reynolds?
Title: Re: 531 versus 725
Post by: Brucey on 05 February, 2019, 06:54:54 am
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
Title: Re: 531 versus 725
Post by: whosatthewheel on 05 February, 2019, 08:16:03 am
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
Title: Re: 531 versus 725
Post by: rafletcher on 05 February, 2019, 08:49:52 am
  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.
Title: Re: 531 versus 725
Post by: rafletcher on 05 February, 2019, 08:55:02 am

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.
Title: Re: 531 versus 725
Post by: Little Jim on 05 February, 2019, 09:56:26 am
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.
Title: Re: 531 versus 725
Post by: whosatthewheel on 05 February, 2019, 09:59:41 am
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
Title: Re: 531 versus 725
Post by: mattc on 05 February, 2019, 10:29:29 am
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.
Title: Re: 531 versus 725
Post by: Brucey on 05 February, 2019, 02:28:20 pm
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