[QUOTE=cyccommute;20424596]
You are giving frame manufacturers too much credit. Most of them...especially the ones who are jumping onto a new fad...build touring bikes based on the available materials and they tend to either copy existing designs (if you are lucky) or go way out on a limb and just throw something together that they label as a "touring bike". A few...Cannondale, Trek and Surly...actually have put some effort in the past into design and selection of materials.
I honestly would not put trek into that category. The 520 they make is a neat frame, but almost everything else about it is garbage. The wheels are by far some of the worst I've ever seen with a build quality more akin to department store bikes than a quality tourer. I really need to build whole new wheels for that one soon since I don't think they'll last much longer. So many of the nipples have been rounded off that truing them is becoming difficult. Trek also had this great notion of cutting the steerer really short making the de fact riding position extremely low especially for a person who has long legs. Had to put a steerer extender on there to make the bike fit my wife.
Cannondales current offerings are way expensive for what they are even if they are quality bikes.
As for the choice of which material to use, the vast majority of actual "touring bike" have been steel because that is all that people will buy. The consumer is afraid that aluminum is too delicate and will break on them while completely ignoring roughly 2 decades of mountain bikes being made of the same material and being subjected to more abuse than any touring bike experiences. There are several steel touring bikes offered by a number of different manufacturers but only a few aluminum touring bikes.
And people don't buy aluminum touring bikes because of the "village smithy" myth.
I'm sure you've heard of Koga? The leading premium touring bike manufacturer in Europe. That builds 90% of their bikes out of aluminum. I think they only have one steel bike...
The village smithy thing also isn't that much of a myth as has been shown on these forums multiple times. You just need to find someone who knows how to tig weld thin walled tube, which in today's world isn't all that difficult. You can repair aluminum, but the frame needs to be heat treated afterwards whereas steel does not. Whether one wants to repair a frame is another matter entirely. I'd warranty it and get a new one sent via DHL.
I think you are confused about the diameter of the tubing being used today. It may be slightly larger sized but I haven't seen any touring bikes with "ultra oversized" tubes in steel. Steel bikes still use tubing that is only marginally larger in diameter than bikes from 40 years ago. Aluminum bikes use oversized tubing but not steel.
Stiffness increase is quadruple when diameter increases vs. wall thickness increases. The tubes used today are significantly bigger in diameter when compared to the tiny 25mm tubes used back in the day. The LHT has 32mm tubes and other touring bikes have even larger ultra oversized tubes as enabled by the Z44 headtube standard. When you combine that with the compact geometry frames = significantly shorter tubes you should start seeing again, significant increase in stiffness. Though the LHT is only semi compact since the top tube is pretty level. Still stiff though.
Oversize tubing means that it's bigger than what could be fit into lugs back in the day so larger than 25mm or even 28mm. Though I think 28mm is already in the realm of oversize. Ultra oversize is then larger than 32mm I think.
I don't consider articles manufactured to repeat manufacturer buzzwords and sell products as representative of "everyone"
Tradition can also be borne out of the fact that there's nothing wrong in steel as a touring bike material. It's tough, resists dings and bangs, resilient, repairable (if need be, honestly DHL is your friend), and today more than stiff enough to handle touring loads.
Also it's not like a touring bike needs to have a feel that it's made of solid concrete. Even the biggest loads put on touring bikes are mostly really small when compared to the rider. What has been mentioned in this thread already and what matters a lot in the whole wiggly bike thing is quality racks and how they support the luggage. If a rack sways from side to side there's no amount of frame stiffness that can remedy that. Hence, tubus racks, which are made of steel and are also crazy stiff. Combine that with a good frame and there'll be no unwanted flex.
Yes, it was standard tubing but, again, that's not that much smaller than the tubing you see on modern steel bikes. "A few years back" suggests that Surly's bikes weren't as stiff as you have implied they all are. The last time I road a Surly touring bike was 15 years ago. That's more than a "few years back".
Again, the difference is significant much to the same effect the energy difference required to go 15mph and 20mph is significant even though the actual speed difference is "not that big".
Oh I haven't implied
all surly bikes are stiff. I wonder where you got that from. I've implied that their LHT's after the year 2012 or 2013 (EU regulation, I mentioned that many times) are more than stiff enough for touring since that's around the time they revised the design of the LHT. Not all surly bikes are touring bikes. You knew that right?
Not the ones I see on a regular basis at my local co-op. The mountain bike frame from its inception used larger tubing than road bikes since they want some longevity out of the frame. But, even with those larger tubes, scale's bike is still not as stiff as aluminum touring bikes are.
Could also be because his bike is not a touring bike but a mountain bike... Hint is in the type of the bike