6/4 vs 3/2.5

[ericmurphy]

I guess this question is directed mostly at Serotta_James, since he once implied he'd address the issue, but I'd be interested in hearing from anyone who's got an opinion on the subject. My understanding is that for years, those bikes (like the Litespeed Vortex) that were 6/4 were made from seamed tubing, but now you can get actual drawn 6/4 pipes from suppliers like Reynolds.

But it seems like very few builders are using 6/4 yet. I know Moots and Litespeed do, but Seven and Serotta haven't. Are there disadvantages to 6/4 other than cost and difficulty in working with it? Does it make for a harsher ride? Is it just not worth the money or worthy of the hype?

[JohnS]

I've read that it's slightly lighter but alot stiffer (in a bad way).

[Litespeeder]

Here's what Moots has to say about Reynolds 6/4 seamless Ti. It's part marketing hype but so is whatever answer you get from Serotta.

:confused:

The following are comparisons made using the same diameters and gauges. Here are the numbers.
Strength: The 6/4 tubing tests out to be 15-18% greater than 3/2.5
Stiffness: The 6/4 tubing tests out to be 7-8% greater than 3/2.5
Density: The 6/4 tubing tests out to be 1.5% less dense

Here are the benefits.
Strength: The greater strength means we can build a frame 15-18% lighter than a 3/2.5 frame that will have the same fatigue life. Moots products are built to last and this falls into our design philosophy of building products that last.

Stiffness: The increased stiffness means we have been able to build a frame that is lighter by 7-8% that has the same ride characteristics as a heavier 3/2.5 frame. Again our goal was to build a frame that rides very much like our existing line of bikes, solid and comfortable. By effecting the Young’s modulus through cold working, Reynolds has produced a tube that gives us this characteristic.

Density: Although the number is really insignificant, the fact that the 6/4 tubing is less dense at all yet has the above positive attributes is really remarkable.

Another benefit comes form the butting process. By using an internal mandrel and external die and mechanically butting the tubing, Reynolds controls the wall thickness of the material to a very tight tolerance. Relative to a lot of 3/2.5 tubing used on bikes the tolerances kept are many times higher in the 6/4 butted tubes.

[Sandy]

I thought that 6/4 tubing is more difficult to work with than 3/2.5. Is that not true?

Old, fat, and tough simultaneously,


Soft Sandy

[Kevan]

so you can relate, it's sorta like working with copper as opposed to bronze. :D

[Sandy]

I ride an Ottrott, young man. Hence, I have no use for copper or bronze. :)

Snobish Serotta Somebody

[Tom Kellogg]

A bit dated in places, but this might be helpful.

http://spectrum-cycles.com/624.htm

[Serotta PETE]

THankyou, that was a very good description of ti tubing. PETE

[Big Dan]

Great stuff, thanks for the information..just the reason I come to this board..to learn... :)

[Kane]

We are lucky to have such great contributors on our forum as Tom Kellogg.
As always a thoughtful presentation.

Cheers,

Kane

[ericmurphy]

A bit dated in places, but this might be helpful.

http://spectrum-cycles.com/624.htm

Definitely helpful. So it sounds, from this article, that 6/4 is really only of benefit to weight weenies. Same overall modulus, greater strength (which presumably allows for slightly lower weight, since Ti bikes don't seem to be strength-challenged the way Al tubes are); lower hardness, more expensive and harder to work with. Also, since 3/2.5 has higher modulus in torsion, that seems a better choice for larger riders who really torque the top and down tubes.

Would anyone care to estimate the weight savings if, say, a 58 cm Legened Ti OS were to be made of the same tubes Ben uses except using thinner-walled 6/4 tubes? If it's less than eight ounces, it seems hardly worth the effort to me.

[rnhood]

Very good work Tom Kellogg. An excellent dissertation on Ti, especially for us bikers.

[Serotta_James]

Tom's article certainly did our point justice. So I don't need to delve into the minutia of the topic.

We have looked into 6/4 Ti in the past and we chose not to use it for three reasons:

1) 6/4 provides no discernable advantage to ride quality or durability. 3/2.5 Ti is more than strong enough for frame applications. Using 6/4 alloy itself does nothing to benefit the ride quality so far as we have observed.

2) Currently, 6/4 is more difficult to work and shape into performance enhancing shapes such as Colorado Concept. While the advent of seamless 6/4 is certainly a step forward in advancement and workability, it is still very difficult - impossible even - to swage and taper 6/4 tubes into shapes that result in proven rider benefits.

3) 6/4 is more difficult to work with from a manufacturing standpoint. The fact that 6/4 is harder and somewhat stronger means that getting a 6/4 frame to our extremely tight alignment standards is next to impossible, for example.


6/4 is certainly cutting-edge, and has a real place in the world of engineering and bicycles specifically. But after all our research and testing we have to ask ourselves "Is the rider gaining any advantage by us using 6/4 Ti?" The answer is invariably "No."
In a cost/benefit analysis, 6/4 offers no real-world advantage over the highly worked shaped and butted 3/2.5 tubes we currently use.

[ericmurphy]

Tom's article certainly did our point justice. So I don't need to delve into the minutia of the topic.

We have looked into 6/4 Ti in the past and we chose not to use it for three reasons:

* * *
In a cost/benefit analysis, 6/4 offers no real-world advantage over the highly worked shaped and butted 3/2.5 tubes we currently use.

This is as I expected. Obviously, Serotta owners are relatively insensitive to price (else they wouldn't be buying $5,000 Ottrott frames), so Serotta haven't stayed away from 6/4 merely for cost concerns (I doubt the use of 6/4 would increase the price of an Ottrott by more than 10%, would it?). But it's good to know that Ben and his engineers have decided to put the money where it's most useful (e.g., swaging CC tubes, using carbon fiber where it contributes most to frame performance), and not where it's sexiest.

[Butch]

I’d like to offer another opinion about the Reynolds 6/4 butted tubing we use at Moots.

Moots took the same stance as both Tom K. and Serotta just a couple of years ago. When we first received samples of the 6/4 butted tubes we approached it thinking there maybe no advantage to the rider, especially considering the cost. Then we built some frames, and rode them. Unlike Tom and James we love the ride. We felt we had a good thing, a bike that is lighter (1/3 lb.) and stiffer than our 3/2.5 model. Scott Moninger raced one in the US and Australia and loved it. We see an advantage in ride quality.

We, like Serotta and Merlin, come up with designs that we love to ride and that we can stand behind for life. We like round tubes at Moots. The seamless 6/4 tubing is difficult to shape and to work with, there is no doubt. We only slightly ovalize the ends as a manipulation. Since 1991 Moots has focused on manufacturing with ti only and we think we do a pretty good job at it. Combining the main frame tubes from Reynolds with the many gages of 3/2.5 rear triangle we get the ride we want, stiff, light and comfortable.

It works because the yield strength is higher than 3/2.5. As was stated by Tom,”…yield strength comes into play as tubing walls get thinner and tube diameters increase. Thinner tubing tends to “beer can” more easily.” The Reynolds 6/4 tubing is at least 15% stronger so we can use thinner tubes and not have the “beer can” effect. Pretty straight forward, stronger material for the weight means we can build a lighter bike. The 6/4 is even 1.5% less dense. The numbers listed above by Lightspeeder are on our website and they were obtained by Reynolds from testing done by the University of Birmingham.

The bottom line is that Moots builds frames from this material because we feel there is a distinct advantage to the rider, otherwise we wouldn’t do it. In the 2 years we have sold these frames the consistent comment is of total satisfaction.
Thanks for the forum.
Butch@moots

[Sandy]

It is very well accepted that Serotta, Moots, Spectrum, and Serotta (had to put in an extra Serotta, since I ride one) produce some of the very finest and well received bikes. I do have a couple of questions.

You state that your 6/4 tubing produces a bike that is "...lighter (1/3 lb.) and stiffer than our 3/2.5 model", and that "we see an advantage in ride quality".

1. 1/3 of a pound seems so miniscule, relative to overall bicycle, rider and accessories weight that to me it would be almost meaningless. Am I missing something here?

2. When you say stiffer, what do you mean precisely? Efficiency in transmitting pedal effort into forward motion ? Resistance of torsional forces? Stiffer where? BB area?

3. How could 6/4 tubing possibly give an improvement in ride quality? Are you refering to vertical compliance? Vibration damping? I can see how the bike might be "stiffer", whatever that is, and certainly lighter, but how would it have a better ride quality?


1/3 titanium 1/3 carbon 1/3 confused,


Serotta Sandy

PS- You could give me a 6/4 Moots, and I would be Moots Mirman.

[alembical]

These forums are amazing. A serotta rep, a moots rep and Tom all throwing their 2 cents in regarding a question posed by a forumite about Ti tubing. All three have their own point of view (with lots of overlap) and all three expressed their point well enough for us to understand that all three points have merit.

Thanks Serotta for the forum,
Alembical

[Sandy]

And you get to communicate with so many interesting and helpful individuals, and make lifelong profoundly meaningful friendships.

Don't worry Ben, I won't jump the ship!! :D

Moots Mirman, Oops, I mean Serotta Sandy

[Big Dan]

Surprised that there is no outrage..I guess is only when talking LUGS... :eek:

[ericmurphy]

I’d like to offer another opinion about the Reynolds 6/4 butted tubing we use at Moots.

Butch@moots

I think Butch's post illustrates a point I made in another thread on high-end ti bikes. I think everyone can agree that, when you're talking about $3,000+ ti frames, they're all fabulous bikes; no one is ever credibly going to accuse Moots, Spectrum, Seven, or Serotta of making crappy frames. When you get into this stratospheric region of the frame-building art, the differences between any two frames, even when they're marked, are still going to be largely a matter of personal preference. I don't think anyone can say unequivocally that, e.g., a Seven Odonata "blows away" a Spectrum Custom, or that a Serotta Legend "just crushes" a Vamoots. Because someone out there is going to have exactly the opposite opinion.

These are all great bikes, guys, and no one is going to be unhappy with one (assuming it's properly fitted, etc.). Hell, I chose my Legend largely because I could get it with the hottest paint job on the planet! (in my opinion, anyway). But let's not scream at each other and try to change each other's minds. No one riding to a club event on any of these bikes is ever going to feel inadequate (at least about his or her bike!).

[Sandy]

So very well said!


Serotta Sandy aka Seven Sandy aka Spectrum Sandy aka Moots Mirman

[93legendti]

I've read that it's slightly lighter but alot stiffer (in a bad way).

If you owned the bikes I own, your guess would be wrong.

[Litespeeder]

I’d like to offer another opinion about the Reynolds 6/4 butted tubing we use at Moots.

Moots took the same stance as both Tom K. and Serotta just a couple of years ago. When we first received samples of the 6/4 butted tubes we approached it thinking there maybe no advantage to the rider, especially considering the cost. Then we built some frames, and rode them. Unlike Tom and James we love the ride. We felt we had a good thing, a bike that is lighter (1/3 lb.) and stiffer than our 3/2.5 model. Scott Moninger raced one in the US and Australia and loved it. We see an advantage in ride quality.

We, like Serotta and Merlin, come up with designs that we love to ride and that we can stand behind for life. We like round tubes at Moots. The seamless 6/4 tubing is difficult to shape and to work with, there is no doubt. We only slightly ovalize the ends as a manipulation. Since 1991 Moots has focused on manufacturing with ti only and we think we do a pretty good job at it. Combining the main frame tubes from Reynolds with the many gages of 3/2.5 rear triangle we get the ride we want, stiff, light and comfortable.

It works because the yield strength is higher than 3/2.5. As was stated by Tom,”…yield strength comes into play as tubing walls get thinner and tube diameters increase. Thinner tubing tends to “beer can” more easily.” The Reynolds 6/4 tubing is at least 15% stronger so we can use thinner tubes and not have the “beer can” effect. Pretty straight forward, stronger material for the weight means we can build a lighter bike. The 6/4 is even 1.5% less dense. The numbers listed above by Lightspeeder are on our website and they were obtained by Reynolds from testing done by the University of Birmingham.

The bottom line is that Moots builds frames from this material because we feel there is a distinct advantage to the rider, otherwise we wouldn’t do it. In the 2 years we have sold these frames the consistent comment is of total satisfaction.
Thanks for the forum.
Butch@moots


I have a Vamoots 6/4 SL and IMO it just doesn't get any better when it comes to Ti frames. We can talk about double butted vs triple butted vs geometrically enhanced tubing vs cold forged.... But in the end it comes down to the ride characteristics. The Vamoots SL accelerates and climbs like a rocketship yet it still gives you the feel and vertical compliance of a Ti frame. It does everything well and the ride quality and build quality are unsurpassed. And my compact frame came in at 2.5 lbs.

IMO, 6/4 seamless Ti tubes will allow frame builders to push the envelope by bringing the frame weight down to 2 lbs or less while still maintaining the ride characteristics of a 3/2.5 frame. Now, should the industry continue with it's obsession with frame weight savings? Well that's another question for another thread. But, now that seamless 6/4 Ti tubes are available to frame builders and with the increasing number of diameters and gauges becoming available for 6/4 Ti tubes, you are going to see a lot more 6/4 Ti frames out there. Why? Stiffness and weight savings.

I agree with most of Tom Kellog's views on 6/4 Ti but remember that it was written before seamless 6/4 Ti tubes were available. The article accurately describes the weaknesses of seamed Ti. But, everything changes with the introduction of readily available seamless 6/4 Ti tubes. No matter what serotta's current position on 6/4 Ti is, I can bet that within a few years they will be using 6/4 Tubes. Imagine, a Legend coming in at less than 2 lbs.


:bike:

[93legendti]

...Moots took the same stance as both Tom K. and Serotta just a couple of years ago. When we first received samples of the 6/4 butted tubes we approached it thinking there maybe no advantage to the rider, especially considering the cost. Then we built some frames, and rode them. Unlike Tom and James we love the ride. We felt we had a good thing, a bike that is lighter (1/3 lb.) and stiffer than our 3/2.5 model. Scott Moninger raced one in the US and Australia and loved it. We see an advantage in ride quality...Thanks for the forum.
Butch@moots

My real world experience corroborates his post.