Author Topic: 531 versus 725  (Read 1134 times)

Roy

531 versus 725
« on: February 03, 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?

Re: 531 verses 725
« Reply #1 on: February 03, 2019, 07:10:36 pm »
I suspect that the builder is more important than the tubing ( within the range of decent tube sets).

Re: 531 verses 725
« Reply #2 on: February 03, 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.

mattc

  • n.b. have grown beard since photo taken
    • Didcot Audaxes
Re: 531 verses 725
« Reply #3 on: February 03, 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!"
Has never ridden RAAM
---------
No.11  Because of the great host of those who dislike the least appearance of "swank " when they travel the roads and lanes. - From Kuklos' 39 Articles

Re: 531 verses 725
« Reply #4 on: February 03, 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.
Your ears are your rear-end defenders,keep them free of clutter and possibly live longer.

Roy

Re: 531 verses 725
« Reply #5 on: February 03, 2019, 07:51:56 pm »
Thanks for the replies. The frame would be built with lugs. So no real difference then?

Re: 531 verses 725
« Reply #6 on: February 03, 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.

Re: 531 verses 725
« Reply #7 on: February 03, 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!)

Re: 531 verses 725
« Reply #8 on: February 03, 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.

Re: 531 versus 725
« Reply #9 on: February 03, 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.
Never tell me the odds.

Re: 531 versus 725
« Reply #10 on: February 03, 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.

Re: 531 versus 725
« Reply #11 on: February 03, 2019, 09:36:30 pm »
Apparently the fumes from brazing were affecting his health.  His bikes/frames sell for an absolute fortune secondhand.
Never tell me the odds.

LittleWheelsandBig

  • Whimsy Rider
Re: 531 versus 725
« Reply #12 on: February 03, 2019, 09:52:39 pm »
Same reason Bruce Gordon stopped brazing. Towards the end, he hooked up a breathing air supply.
Wheel meet again, don't know where, don't know when...

Re: 531 versus 725
« Reply #13 on: February 03, 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. 

Cudzoziemiec

  • Solar powered, tea fuelled cycle-wol
Re: 531 versus 725
« Reply #14 on: February 04, 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?
The earth is vast and beautiful and contains many miraculous places. (Chekhov)

Re: 531 versus 725
« Reply #15 on: February 04, 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  :)
We are making a New World (Paul Nash, 1918)

Re: 531 versus 725
« Reply #16 on: February 04, 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



Never tell me the odds.

Re: 531 versus 725
« Reply #17 on: February 04, 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.

Re: 531 versus 725
« Reply #18 on: February 04, 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! 
We are making a New World (Paul Nash, 1918)

LittleWheelsandBig

  • Whimsy Rider
Re: 531 versus 725
« Reply #19 on: February 04, 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.
Wheel meet again, don't know where, don't know when...

Re: 531 versus 725
« Reply #20 on: February 04, 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.
Never tell me the odds.

Re: 531 versus 725
« Reply #21 on: February 04, 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.

Re: 531 versus 725
« Reply #22 on: February 04, 2019, 08:56:56 pm »
The scales would show it was about a pound heavier, though.
Never tell me the odds.

LittleWheelsandBig

  • Whimsy Rider
Re: 531 versus 725
« Reply #23 on: February 04, 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.
Wheel meet again, don't know where, don't know when...

Cudzoziemiec

  • Solar powered, tea fuelled cycle-wol
Re: 531 versus 725
« Reply #24 on: February 04, 2019, 09:45:03 pm »
oilcanning?
The earth is vast and beautiful and contains many miraculous places. (Chekhov)