I was in a bike shop where I found myself eavesdropping on a conversation. A woman was there in the shop with her boyfriend, and they wanted a new mountain bike for her. Apparently, the boyfriend had convinced her that she really "needed" a 29er mountain bike. I have no doubt that the boyfriend had recently been "converted" to the gospel of 29-inch wheels (same rim diameter as 700c road wheels, but with fat mountain-bike tires) and he was determined to convert her, too. Problem was, this woman could not have been more than 5-ft. tall -- at the most. I mean, in candy bar parlance, she was "fun size."
|Just because they make it doesn't make it a good idea.|
The touted benefits of 29-inch wheels on a mountain bike are supposed to be better rolling over obstacles, better traction, and some even claim better "gyroscopic" effect to help keep the bike and rider upright (29er). Understand, however, that traction is also affected by other factors besides wheel size (choosing the right tread for the terrain, for instance), and the gyroscopic effect is a myth -- at least inasmuch as keeping us upright (see Here, and Here). But my real point here is that whatever benefits 29-inch MTB wheels may offer, whether real or imagined, are pretty worthless if it means that the design of the bike is so compromised that it doesn't fit right or work well for the rider.
Compromised? Definitely -- There are plenty of no-nonsense sources out there to explain why it doesn't make sense to put huge wheels on a tiny frame. The Velo-Orange article I mentioned above touches on it. There is a very informative argument on the subject at the Rodriquez Bicycles page. There is a bit on the Rivendell Bicycles site also. But to state it all pretty concisely, wheel size should not be chosen for fashion. Putting 700c or 29er wheels on a little tiny frame leads to numerous problems -- toe overlap, poor fit, weird handling. Putting small wheels on a huge frame can lead to some problems, too, though those problems tend to be more aesthetic than serious. A tall frame with small wheels can lose some triangulation and stiffness -- but proportionally it can also look weird.
Regarding large wheels/small frames: with steeply sloping top tubes, the standover can be made to work for a short rider -- but being able to straddle the bike is one of the least of their needs. In order to make the effective top tube short enough so the person doesn't have to stretch to reach the bars, the bike will end up having an overly steep seat tube angle, an unreasonably shallow head tube angle (possibly both), and/or massive toe overlap. The small rider, convinced they need to buy the larger-wheeled bike for various "benefits" (whether convinced by friends, the bicycle mags, overeager salesmen, or the industry's marketing machine) ends up on a poorly fitting, poorly handling bike that fails to deliver on the promises. Another sad thing is that even if a well-intentioned, no-nonsense shop salesperson tries to talk them out of it, they'll probably just go get it somewhere else.
So if it's not a good idea to make small frames with large 700c/29er wheels, why do the manufacturers do it? Two reasons: Economy and Marketing. First, it's much easier and cheaper for the manufacturers to make all the bikes in a model line around the same wheel size. That means fewer variations in forks, wheels, and other parts to stock. And the marketing departments can push a wheel size as a trend -- a new market segment -- touting the benefits of a given wheel size, and encouraging consumers to buy into it even if it isn't really right for them. So people who have 26" mountain bikes will be convinced they need to add a 29er to their stable. More recently, those same people are under the impression that they also need a 650b mountain bike.
|Three common wheel sizes today -- remember that 29er|
is essentially the same rim as the road 700c size.
But again, for road bike riders who were very short, sticking rigidly to 700c wheels created all the comfort/fit/design issues already mentioned above. Small-framed road bikes were plagued with steep seat tubes, shallow head tubes, tons of toe overlap, quirky handling, and uncomfortable fit. The answer was to design smaller frames around smaller wheels -- but most companies were (or still are) unwilling to do that. A few small companies, like Terry, offered bikes with smaller wheels for women -- some used 700c for the back wheel to keep the gearing "normal" with a smaller 24-in. wheel on the front (a compromise that I believe was unnecessary). For the majority of the industry, instead of selling shorter riders bikes that fit them, those riders were often sold excuses -- marketing-based responses about 700c being better, or faster, or about smaller wheels being slower, etc.
In recent years, 650b, a size roughly in-between 700c and 26-inch, re-emerged as a viable option. Once popular on French touring bikes and tandems, the size faded away for a number of years. Then, through the efforts of people like Grant Petersen, Kirk Pacenti, and frame builders re-discovering the classic French randonneuring style of bikes, 650b has been making a comeback. This size gives another good option for both road and mountain bikes.
So, is the introduction (or re-introduction) of more wheel/tire sizes a bad thing? It shouldn't be, but it depends. The bad side is when the wheel size is marketed as a fashion or trend -- something we should all be switching to, as if what we have currently is obsolete, regardless of our needs. For example, the term "29er" doesn't just refer to a wheel size -- it's a whole "genre" of bikes -- a marketing segment. But we don't all need a "29er," and below a certain frame size, they probably shouldn't even make them. Remember the guy trying to get his petite girlfriend on one? It doesn't make sense. And 650b is a great size for road bikes because they make it easy to run comfortable, large-volume tires -- but if someone needs a frame larger than about 60 - 61cm, they'd probably be better off with 700c.
There IS some good in what's happening IF one can ignore the marketing hype and popular trends, and approach wheel size as a function of good design and proper bike fit. Having choices in wheel size (and hopefully with the tire choice/availability to go with it) means that one can potentially get bikes that fit them better and that work better for their intended riding. With the right tires and gearing, all three wheel sizes can work for either road or off-road use. Narrower, fine-tread road tires are available for the 26-in. size, but that is a size still dominated by mountain bike offerings. And large-volume 700c road tires (greater than about 35mm) aren't as common as they should be -- so those are situations that could be improved. But ultimately, what can -- and should -- happen is that manufacturers/builders be willing to vary the wheel size for the frame size. Smaller frame - smaller wheels. Bigger frame - bigger wheels.
Varying wheel size with frame size is something a lot of custom builders would have no problem with, but so far, there aren't a lot of bigger manufacturers doing it. Rivendell does it with some of their models -- their Atlantis, for instance, has long been built for 26-in. wheels in the smaller sizes, and 700c in the larger ones. Other models are built for 650b or 700c depending on frame size. Surly offers their Long Haul Trucker in both 26-in. and 700c versions -- with a lot of overlap in the middle range, so many riders actually have a choice depending on the type of riding they do. Soma Fabrications varies wheel size for some of their models, like their Saga touring frame, and their San Marcos sport touring model (designed in conjunction with Rivendell). And the most recent addition to this club is Velo Orange with their new Camargue touring frame.
What about the bigger brands? I searched Trek, Specialized, Giant, and others -- and (unless I was missing something) none of them varies wheel size with frame size. Some of them offer "women specific" versions of their bikes -- yet as far as I could tell, those use the same wheel sizes as the regular versions, and most of them make the same mistakes they've always made in forcing small frames to work with large wheels -- slack head tube angles with steep seat tube angles, and probably more toe overlap than most people would be comfortable with.
Wrapping it up, wheel size makes much more sense when it is used to make properly proportioned bikes for differently sized riders. Bike fit is much more important than bike fashion. It's good to see some of the smaller manufacturers taking the lead on this -- time will tell if the bigger manufacturers and the tire companies will recognize it. If they did, it would be a comfortable change.