Last week I wrote a post on how 29"ers have seemed to help steel as a building material enjoy a resurgence in local bike shops. Floor space dedicated to steel hard tails is almost "retro", since that type of mountain bike nearly died out in the late 90's. Someone commented on that post and asked what the salient differences between steel and aluminum hard tails are in my view. Well, consider this your answer.
First of all, preconceived notions abound when it comes to what steel and aluminum ride like. This is probably rooted in early 90's/late 80's perceptions that have been passed down until now. (As are several of our perceptions, but I won't get into that now) These perceptions are largely false today because of the new developments in materials and how they are engineered for use in bicycles. Aluminum that rides like steel and steel that's as light or lighter than aluminum. The old ways of thinking about these materials isn't working anymore.
There are a couple of things that still apply though. One is how the frames look. This is probably the one thing that hasn't changed much at all, actually. Steel tubing is typically smaller in diameter, while aluminum is typically larger in diameter. Big deal? Well, some folks think so. Then you have the joinery techniques, which is limited to TIG welding on aluminum for the most part which leaves that now familiar "stack of dimes" weld joint. (Some are "double pass" welds, which are not that way, ala Cannondale) Steel, of course has a wider variety of ways to join the tubing, but TIG welding is usually the most common way to see frames mass produced. So, a wider variety of choices in how you can join steel tubing, again: Not a big deal, but it is a difference.
Failure mode is another way that the two materials differ. We don't often hear about how materials fail, but it is worth considering, because it still happens. Aluminum, while not nearly as prone to failure as it was in mountain bike frames from 20 years ago, still fails catastrophically. Which means it usually breaks without warning. Steel on the other hand, usually will give you a sign that it's about had it, if you inspect your rig often. If you do not, well it would seem that it fails catastrophically too. Inspect those bikes from time to time! (By the way, cleaning your bike is a good way to do that and get something else done at the same time!)
So, how do they differ where it matters? On the trail, what differences are there? Well, that's a harder question to answer than it was 20 years ago. Aluminum can be made and designed to ride very steel-like. Although I would say it still doesn't feel like a really well designed steel frame. That type of frame, a well designed steel one, still gets my vote as being the best feeling ride out there. Smooth, yet stiff where it needs to be. Springy, yet not flexy. It has "trail feel", but doesn't buzz you. These are all subjective things, to be sure. Of course, you can build a steel frame that has none of those traits too, but this is my point, it needs to be smartly designed and executed no matter what it's made from.
In the end, I'll return to my original idea from the first post on this subject. That is that the whole steel resurrection in mountain bikes has come from 29"ers and that because of the custom builders. These custom builders were catering to the clientele that wanted steel frames and 29"ers. It was a demand/necessity thing and it's carried over to production bikes which has shown me one thing. Steel is still a marketable mountain bike frame material, it's just that most companies didn't believe it. (Of course, a lot of companies only do steel in 29"ers too)
Whatever the reasons, I'm glad to see steel back in the shops and out on the trails again. Sign me: A fan of steel mountain bike frames.