24 October, 2012

Steel is... steel?

By Casey

Sometimes customers ask us what tubesets we use in our frames. Different tubesets can offer different benefits to the frame builder, but what difference does it make to you, the rider?

First, what isn't different between tubesets (intensive properties):
  • Elasticity of the steel
  • Weight by volume of the steel. (A cubic cm of high-end bike tubing steel weighs the same as a cubic cm of gas-pipe steel.)
Let's say you had two top tubes from two different tubing manufacturers. Assuming those top tubes have the same dimensions (length, diameter, thickness), then they would weigh the same and have the same rigidity.

So what is different between tubesets (intensive properties)?
  • Tensile Strength
  • Hardness
Tubes with a higher tensile strength can be made thinner; this in turn decreases their overall rigidity. It can also be tempting to think of this as meaning weight savings. Let's do a quick comparison of how much weight is saved within in the Tange line of tubing. Taking a top tube from the Infinity line and from the Prestige line, both are 590mm long and have an outer diameter of 28.6mm. The Tange Infinity tube has a thickness of 0.9mm on the ends and 0.6mm in the middle. The Tange Prestige tube has thickness of 0.7mm on the ends and 0.4mm in the middle. The Infinity weighs 287 grams, the Prestige weighs 207 grams. So you've saved a little less than a fifth of a pound in the top tube. You'll probably end up saving less than that between the down tube and the seat tube. That's not horribly insignificant but it is important to consider the trade off. 

One of my friends used to commute on a nice steel track bike. About a year ago he unlocked his bike from a bike rack. He left it leaning against the rack while he bent over to roll up his pant leg (should have had one of these). A substantial gust of wind blew his bike over and it hit the bike rack next to it dead center on the top tube, that 0.4mm thick section. This gave the top tube a nice dent, which eventually turned into a nice crack. The moral of the story (besides that track bikes might not be the best for commuting) is that different tubing sets offer different advantages. It can be tempting to look at them from an entirely monetary sense, but more expensive doesn't necessarily mean better.

Thin-wall tubing is very easy to dent. That's why we wouldn't recommend it for a commuting bike or a touring bike. It's also more likely to be destroyed in a crash, even a mild one. That high end thin-wall tubing may be okay for racing bikes, but you must still be careful with them.

At the end of the day, the best choice is usually to just trust your builder. They generally have specific tube sets that they prefer to work with and they will choose a tube set appropriate for your application (touring, track, racing, etc.). Sure, you may not be able to see everyone swoon when you tell them that your bike is made of 853 Reynolds, but your pockets might not feel as light, either.

By the way, VO uses a high quality 4130 double-butted tubing made in Taiwan (where a lot of "name brand" tubing is now also made). We feel that that the quality is equal to that of tubing from the old line companies, but by using this tubing we can knock $100 to $200 off our frame prices without losing ride quality or gaining weight.

13 comments:

VeloOrange said...

Note the French 531 sticker. Cool.

Clancy Anderson said...

Nice and well though out post. That is also why we see so many 50+ year old Schwinn's around- thick walls.

Jim in Texas said...

I have six bikes that I ride on a regular basis. They are a Soma Stanyan and a mid-level Trek frame and fork built with modern components, two Miyatas, a Nashbar touring bike made by Maruishi, and a Giant hybrid with an aluminum frame. Except for the Giant hybrid, all of them have steel lugged construction using steel of various grades. I have personally concluded that, for my bikes, there is no detectable difference in ride or handling that I can attribute to the material or construction. It seems to me that differences that do exist are due primarily to different geometry and tires.

So, although the 531 sticker may look cool (in whatever language), paying top dollar for really high grade steel is a waste of money.

Anonymous said...

Had 2 aluminum bikes both good top of the range Nishikis. had problems with knees and back/neck. Always started when the bikes where brought out after winter, and lasted 2-3 months and kept me of them more then I would have liked. Some time the problems would go away... some time not.
Then i got a frame made from reynolds 520 steel, aprox same dimentions etc. No more pain, according to people smarter then me, because the steel is softer then aluminium and therefore save my joints/knees and back.

gypsybytrade said...

I am lucky to co-mingle with people who think quite highly of stickers that simply say Cro-Mo and 4130. Even more, it is not vintage Italian racing frames or Nervex lugs that make us swoon, but repurposed old ATBs made out of good old steel. Most of the bikes we like were never made out of fancy branded steel; rather, the era was ripe with house-brand quad-butted tubes and inexpensive, quality steel.

A well reasoned approach and a great article, Casey.

Richard Risemberg said...

My Bottecchia with 0.9/0.6/0.9 tubing is over 45 years old and still going strong I myself have put close to 40,000 miles on it over potholed LA roads in the last six or seven years, and who knows how many owners it had before. Nice handling, very comfy, just the right amount of flex. Can't complain. I've had heavier-framed bikes and did not like them at all.

VeloOrange said...

Richard, Actually 0.9/0.6/0.9 tubing is what we use for most VO frames. It's perfect for all but some smaller frames. We will, however, go to a slightly thinner-wall tubing on the Pass Hunter to save a little weight.

philcycles said...

Interesting topic, one I've been exploring for 35 years.
Everything in this post refers to standard, not oversized, tubes.
The .9/.6/.9 tube is ideal for 90% of frames. The problem with thin wall tubes is, as noted, that they dent. Heat treatment is meant to help this but nothing can help falling against another steel tube-the bike rack.
Which is not to say other tubes don't have their place.
I'm tall-6'3"-and while not heavy I do weigh 205. I get a lot of leverage on the cranks. That's why i like a heavy down tube, ideally a Columbus SP but I'll take a 531 1.0/.7/1.0 as well.
I don't use heavy chainstays because the back of the bike is triangulated in both horizontal and vertical planes.
The downtube is different because it's the only tube with a big torsion load.
With oversize tubes, like a 1 1/4" downtube, the story is different. You can use a thinner wall because of the increases diameter.
I've built frames with many variations of the tubing theme and have arrived at these opinions after a lot of riding. They work for me and my customers.
Phil Brown

philcycles said...

As an aside, the discussed frame developed a crack at the dent because it is likely the tube was heat treated. Heat treating increases the dent resistance at the cost of brittleness, thus the crack.

Anonymous said...

I take this reasoning one step further. I weigh over 200, as do many touring cyclists. There is minimal difference between the 9/6/9 tubing I use and straight wall tubing, including I would note their cost to me.

As Frank the Welder has pointed out, during the early days of MTB racing the national titles were won on bikes made entirely of straight wall tubing. I'm not Ned Overend, and for a variety of uses, I think straight wall 35 thou tubing is better.

I would point out we are talking about only 2 tubes in the bike. The bb and headtubes are standard in all welded bikes, there is a range, but not that much of one. The seat tube is probably going to be externally butted, externally custom turned, or straight wall, in any of these options depending on budget, function and tooling.

The tapered fancy stays are actually reverse butted, the butts are heavier than need be for any purpose due to the fact that the reduction of thickness in the thin parts of the tube is accomplished by thickening the walls. There is no weight savings over straight tubes, though there may be different characteristics. So again the choice of formed of straight wall is a design not quality choice.

I would not encourage VO to go to straight wall, I think the average cyclist is lighter than me, and VO is bucking enough of a headwind. But the whole butted thing is just another of those powerful myths that has grabbed cycling. Good in it's place but not a one size fits all either.

There are thicker butted tubing, like 1.1/9/1.1, but given that a 9 butt can be welded, or even a 6, I see no reason to gross up the whole tube.

531 is basically just a 4130 anyway.

Josh said...

@gypsybytrade - I believe that you mean to say "rife with," rather than "ripe with." Unless your steel frames are rotten and smelly, in which case I apologize.

Justin Pogge said...

i have been building frames for about 9 years, and ive used everything from expensive heat treated thin walled tubing to straight gauge tubing. intended use and rider size and weight are the most important aspect of tubing selection in order to get the right flex characteristics for that rider. using straight gauge or thicker butted tubing would not be good a small light rider because the frame would be too stiff and uncomfortable and feel more like a cannondale frame than a steel frame. as far as seat and chain stay "butting" some companies draw out their tubes and the wall thickness stays the same throughout, some roll the taper in a way that makes the tube thicker at the end, this is one of the specs you need to pay attention to when purchasing tubing.

Bill Kipnis said...

I have a 1980's Gios Torino. I am 5'4, 130 lbs. I am trying to figure out if I gain anything by purchasing a modern steel bike frame. Since I can't lose weight, and ride mountains, I am looking to reduce bike weight without giving up my campy croce d'auna.