Materials (specifically steel), ride feel, and build details

[rustychisel]

Interesting question, OP. Awaiting the informed responses.

[Mark McM]

Originally Posted by Peter P.

Titanium has a different spring rate than steel, which is why it has a different feel than a steel frame with equivalent tube diameters, and why titanium frames typically have larger diameter tubes than "comparable" steel frames.

The difference in tubes of the the same diameter and different materials is less than you might imagine from the differences in modulus. The measure of a material's "springiness" (stiffness) is referfed to as its modulus. Titanium has about 1/2 the modulus of steel, and aluminum has about 1/3 the modulus of steel. But at the same time, titanium has about the 1/2 the mass density of steel, and aluminum has about 1/3 the mass density of steel. So the 3 materials have roughly the same specific modulus (stiffness per unit mass). This means that tubes of the 3 materials that have the same weight and diameter will have roughly the same stiffness. Because of the different densities, the 3 equal weight and diameter tubes will have different wall thicknesses - the titanium tube will have about 2 times the wall thickness of the steel tube, and the alumum tube will have about 3 times the wall thickness as the steel tube.

As a tube's diameter increases, the tube get stiffer and stronger; but to maintain low weight, the tube wall thickness has to decrease. Problems come as tube walls become too thin - thin wall tubing is prone to denting and buckling ("beer canning"). Being able to use thicker tube walls makes it easier to make large diameter lightweight tubing out of low density materials (aluminum and titanium) than out of high density materials (steel). The ability to use larger diameter tubes is what often allows aluminum and titanium frames to be made lighter than steel.

[slowpoke]

Originally Posted by jasonification

Namely, I wonder now if my lower weight/power output is perhaps not enough to elicit the same level of "springiness" that I enjoyed on the Serotta.

Without being pedantic about math, you're saying your power-to-weight (w/kg) ratio has decreased with the weight loss? If that's the case, maybe pick up a used SL/SLX bike in the right size and see if it actually elicits the same feeling as you remembered. It'd be quicker and cheaper than experimenting with any custom builders.

[Peter P.]

Originally Posted by Mark McM

As a tube's diameter increases, the tube get stiffer and stronger; but to maintain low weight, the tube wall thickness has to decrease.

It's obvious that tube diameter is the dominant factor in constructing an adequately stiff frame. That's why the old Teledyne Titan frames were a failure; not just because they used commercially pure titanium but because they used standard tube diameters of the day, in order to accommodate commonly available components.

Once it became acceptable to use larger diameter tubes, the industry solved the stiffness problem. At that point they realized they could reduce weight without a sacrifice in tube strength. Less material meant more profit and lighter weight, without costing a lot of warranty claims.

But the difference in spring rate between steel and titanium remains. Steel has what is described as a "progressive" or linear spring rate; the more you flex it the more it applies a return force whereas titanium is more like a door; initially it is flexible but more suddenly reaches resistance. These qualities result in the ride characteristics of titanium. They can't completely be tuned out, only mitigated. That accounts for the differences in ride qualities between titanium and steel.

I don't think the OP is going to find a titanium frame with the ride qualities he experienced with his old steel Serotta. I don't think he'll find it in the new standard diameter steel. It will take too much guesswork. He can stick with 1" standard steel tubing with the only probable concession being a 1.125" head tube just so he can fit commonly available forks and stems.

[rain dogs]

Columbus still makes SL tubing, and it is easily available. I think it is ever so slightly improved (Omnicrom) from the SL of old old days, but pretty similar. I'm hardly an expert.

If you want the same lightness and feel of an old slx frame, but made today, that'd likely be your best bet in Columbus. You can get 2,54cm top tubes, and 28,6 down tubes in 0,8/0,5/0,8

Everything else that is really thin wall - Spirit, Life etc. is oversize, no?

Zona is not so different and could be built with small diameter tubing. 0.8/0.6/0.8

[Mark McM]

Originally Posted by Peter P.

It's obvious that tube diameter is the dominant factor in constructing an adequately stiff frame. That's why the old Teledyne Titan frames were a failure; not just because they used commercially pure titanium but because they used standard tube diameters of the day, in order to accommodate commonly available components.

Had the Teledyne Titan used thicker tube walls, it would have been just as stiff as the steel frames of the day - but it would have been just as heavy also.

Originally Posted by Peter P.

But the difference in spring rate between steel and titanium remains. Steel has what is described as a "progressive" or linear spring rate; the more you flex it the more it applies a return force whereas titanium is more like a door; initially it is flexible but more suddenly reaches resistance. These qualities result in the ride characteristics of titanium. They can't completely be tuned out, only mitigated. That accounts for the differences in ride qualities between titanium and steel.

I'm sorry, but this description is inaccurate. Steel and titanium are both linearly elastic below their yield points. The graph below shows the stress-strain curves of a variety of titanium alloys. Notice that below the yield point (where the metal starts becoming permanently deformed) they all behave linearly elastic (just like steel). There is nothing "magic" about the stress/strain properties of titanium in the normal working domain.

[jasonification]

Originally Posted by slowpoke

Without being pedantic about math, you're saying your power-to-weight (w/kg) ratio has decreased with the weight loss? If that's the case, maybe pick up a used SL/SLX bike in the right size and see if it actually elicits the same feeling as you remembered. It'd be quicker and cheaper than experimenting with any custom builders.

I see what you're saying. I think that my w/kg ratio has increased, however I mean that typically when I'm mashing on my pedals, the force going through my bottom bracket would be my weight and power. Now that I've lost weight, the overall force has decreased (power is probably the same)

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[jasonification]

Originally Posted by rain dogs

Columbus still makes SL tubing, and it is easily available. I think it is ever so slightly improved (Omnicrom) from the SL of old old days, but pretty similar. I'm hardly an expert.

If you want the same lightness and feel of an old slx frame, but made today, that'd likely be your best bet in Columbus. You can get 2,54cm top tubes, and 28,6 down tubes in 0,8/0,5/0,8

Everything else that is really thin wall - Spirit, Life etc. is oversize, no?

Zona is not so different and could be built with small diameter tubing. 0.8/0.6/0.8

Good to know they still make SL! yeah, from what I've seen it seems that Spirit, Life, etc come in OS only..

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[reuben]

I currently ride an '80s steel bike and love it. I also have an '10s aluminum bike and don't love it.

I'm contemplating a new titanium bike (probably Mosaic), and an updated steel bike (Ciocc San Cristobal 202x).

So I find this discussion quite interesting.

I'm must posting to say "Thanks" to all for the knowledgeable posts.

[bigbill]

My two favorite steel road bikes are my BLE and Merckx MX Leader. The Leader is heavy, even for steel, but it is so nice on a climb and descent. The BLE is very close to the Merckx in riding characteristics while being considerably lighter. The only "springy" steel bike I have is a 1997 vintage Nobilette GT which was a Team Shaklee bike. It is fillet brazed 853 with a steel fork that Cheakas made.

My MTB is springy, it is a Coconino fillet brazed steel with segmented seat stays.

[Peter P.]

Originally Posted by Mark McM

...

That comparison is inaccurate. You should compare the commonly used titanium alloy in bicycle frames (3.2Al/5V) to commonly used steel alloys in bicycle frames.

[charliedid]

Originally Posted by jasonification

Prior to my current bike, I rode a Serotta made with Columbus SLX, which I've noted to be particularly springy (totally got me hooked on the steel bike train!). Ended up selling it because it was a little large for me.

Since then, I've been riding my Bob Jackson with 853 OS steel for close to 5 years now, so this bike has seen my varying levels of fitness/weight. For the most part I've enjoyed the bike as a very smooth ride.

With my recent weight loss (close to 50lbs), I've dropped from 210lbs to 160lbs or thereabouts. Climbing has definitely been more enjoyable. However on my most recent ride, I really started thinking about tubing and design. Namely, I wonder now if my lower weight/power output is perhaps not enough to elicit the same level of "springiness" that I enjoyed on the Serotta.

Previous threads on the forum have often cited builder's ability to elicit certain ride characteristics supercede build material (ie. an aluminium/carbon bike can be made to "feel compliant").

Given the trend for OS steel tubing in modern bikes, I am wondering if the forum can enlighten me:
Can a builder's touch elicit the "springiness" of old, thin diameter steel tubing (Columbus SLX, Reynolds 531) using modern day OS tubing? Would it require perhaps using different steel for different segments of the bike?

Thanks for entertaining my convoluted question!

I have nothing to add other than a link to this article which has always stuck with me over the years.

http://www.bgcycles.com/new-page-1

[Mark McM]

Originally Posted by Peter P.

That comparison is inaccurate. You should compare the commonly used titanium alloy in bicycle frames (3.2Al/5V) to commonly used steel alloys in bicycle frames.

It is hardly inaccurate, since except in the extremely rare case, metals obey Hooke's Law, which states that deformation (stretch) of a body is proportional to load on the body. All common metals used bicycles (steel, aluminum, and yes, titanium) obey Hooke's law when operating below their yield points.

If you want to get technical, Hooke's law is actually a 1st approximation for stress-strain relationship of metals, and if anything, the modulus (stiffness) of metals actually decreases with load, not increases. This can be seen as the stress-strain curve bows over as the metal approaches and exceeds the yield point.

But if insist, here are some stress-strain curves for the two most common titanium alloys used in bicycle frames (3Al/2.5V & 6Al/4V):




As can be seen, the stress-strain curve is quite linear below the yield point If you looked at the stress-strain curves of steel and aluminum, you'd see they are quite linear as well.

[unterhausen]

Teledyne titans used oversized tubes that were crimped in 2 spots to be standard dimension. It certainly was a failure of imagination to do that, but I think they were nearly as stiff as if they had the oversize tube dimension for the full length of the tube. The chainstays might have been the biggest source of flex.

They failed because they broke a lot. I broke 2

Yes, I still have a negative feeling about Ti because they used CP titanium, which is a lot like chewing gum.

[Peter P.]

Originally Posted by Mark McM

It is hardly inaccurate,...

Yet titanium DOES have a different spring rate. One spring manufacturer compares a titanium spring and a steel alloy spring with equivalent function. The titanium spring is 3" shorter for the same functional properties. Had they been the same length, their capacities would be considerably different.

Same with bicycle frame tubes; they way titanium and steel respond to flexing are different; like guitar strings of different materials.

The OP is not going to find that "feel" of his old steel Serotta, in a titanium frame.