Monday, July 18, 2011

Big Wheels, Little Wheels, It Doesn't Matter- Or Does It?

Recently a new issue of Bicycle Quarterly came out. Now some may not think this quaint looking paper rag has much to offer. Maybe you've taken a peek and thought it was some off shoot of the old "retro-grouch" thing. Maybe you think it is just a denizen of 650B freaks and rando nut jobs. Well, it is, but it is a lot more than this.

The publication is pretty much the "bike geeks geek rag". It doesn't get much more "pointy-headed" and "pocket-protector-like" than "Bicycle Quarterly" for North American bicycle enthusiasts. They do experiments and tests that you'll never see in "Velo Ne....." whoops! I mean, "Velo", or in the glossy pages of "Bicycling", no matter how many times they re-do their formats or change editors. Nope. Not even close.

Why Use A 29" Wheel?
So, I got a peek at the latest issue, anyway, and the newest test was one in which the guys there were determining what wheel size was best. Okay. Got my attention! Inside, the article laid out the testing procedure and basically, what it boils down to is this: "Wheel size has no effect on power output over rough paved surfaces." Zip. Nada. (At least according to "Bicycle Quarterly" who stated that the slight differences they did measure were "statistical noise", or otherwise so small as to be insignificant.)

But you might say, "Well okay, but what about off-road?" They thought about that too. While they did not do any off road testing with 29"er wheels vs. other sizes, they did theorize that the "angle of attack" thing was so statistically small it was probably also insignificant off road.

So, why ride a 29"er wheel at all? Good question, and one I think this test inadvertently supports in the affirmative. You see, part of the testing they did was to fit the bicycle they used with an SRM power measuring crankset. According to their findings, it took basically the same amount of power, (within their standard for accounting for "statistical noise"), for any of the wheel sizes to be powered across their rumble strip test road. This tells me that one of the criticisms of 29 inch wheels isn't all that true, and possibly doesn't matter at all- that is the criticism that 29"er wheels take more energy to move than smaller sizes.

Now, at one time, the weight of a 29 inch wheel was a significant difference, and maybe then it was a detriment, but now 29 inch wheels have weights down into what was never dreamed of just several years ago. Powering up a big wheeled bike is not an issue anymore, on the high performance level, at any rate. (Witness full suspension 29"ers weighing in at sub 22lbs and winning World Cup events recently)

Interestingly, the Editor's post to lead off the latest issue of "Bicycling Quarterly" talks about the "subjective feel" versus the "objective findings" that some testing/reviews feature. In the terms of "subjective feel", I think 29 inch wheels have the advantage, but I also think there is a good reason for that. The testing on wheel size did not account for geometry, and did not account for fat tires at lower pressures. On a 29"er, the rider is in a different relationship to the axles than on a smaller wheeled bike. The testers at "Bicycling Quarterly" actually touch on this subject in terms of handling, but do not reference geometry specifically. The differences in handling play a huge role in why I happen to appreciate 29"ers. Then there is the fat tire thing.

Early on, some 29"er folks did some random testing of tire contact patches versus 26 inch wheeled bikes. Using similar tread patterns, and similar pressures, the contact patches were predictably the same area, but not the same shape. Obviously, it wasn't a huge difference, but in the area of how our tires touch and react to the trail, any differences are big, and I posit, can be felt. Traction and cornering is noticeably different on a 29"er versus smaller wheel sizes, and this is another reason to want to use a 29"er for trail riding. At least I think it works better, and so do others.

It also has to be said that designers of 29"ers are finding that the bigger wheel size demands its own, specific design characteristics. Suspension, tires, and wheels are all things that are or have been re-thought and made better due to the emergence of the 29"er. Not to mention the ever changing geometry of big wheelers, which is still being honed to this day. If wheel size didn't make a difference, then one has to wonder "why bother?" Obviously, something is going on beyond power measurement over rough grounds here.

And that is part of the conclusions reached by the "Bicycle Quarterly" piece. Obviously subjective feel on the part of the rider is an important factor. So, I would encourage you to try a 29"er if you haven't. It isn't for everybody, but it might just work for you.

7 comments:

MG said...

I can't wait to read Jan's report now... And you know we're on the same page as far as the benefits of big wheels. The only place I really "prefer" 26 inch wheels anymore is when I'm jumping and trying to throw my bike sideways a bunch. You can feel the gyroscopic force of big wheels when you're really trying to get all crossed-up. But that stability is also what's helping to keep you on-line in really sketchy terrain when you're hauling, so you benefit from those big 'ol gyroscopes as well... But you know that.

You and I both know it matters... And so do most of the folks reading this blog. If big wheels didn't matter, Rocky Mountain bikes wouldn't be ditching 26 inch wheels for their high-end hardtails for 2012. What's Jan have to say about that one?

Herringbone said...

Remember attaching baseball cards to your spokes with clothespins when you were a kid? My 29er is fun.

DJ Dual Core said...

If you think of it like gearing isn't this pretty much what you would expect

Guitar Ted said...

@DJ Dual Core: You could. That is one way to look at this. However; the test was done to determine if there was any advantages to using a certain diameter wheel on pavement/rough pavement. It was thought that larger diameter wheels had a lower angle of attack, (which, in fact they do), and that this would aid the rider by causing him to use less power. What the findings say is that in "real world terms", this advantage is negligible, if indeed it is advantageous at all.

As for gearing, it has always been my position that as long as you are using the correct gear that makes you feel as though you can get over the patch of terrain in front of you, (be that a hill, down hill, flat, or what have you), without causing you to spend an excess amount of energy, while balancing that with a rate of desired forward motion and desired handling, then you are in the correct gear. This is independent of wheel size but wheel size does play a part in gearing range/choice and handling charateristics. (It can be limiting, or not, depending upon chosen drive train)

So, a 29"er wheel would perhaps present a need for different gear choices available on the bicycle, but the size in and of itself doesn't make one worse or better from a gear choice standpoint.

MG said...

So I bought the issue of BQ in question and read the review in its entirety... It's a lot of not much, as far as I'm concerned. He makes a couple of good points about tire pressure, but with respect to diameter and off-road riding, I sincerely question whether Jan knows enough about true off-road riding to speak at a cogent level about the pros and cons of big wheels relative to the conditions actually ridden.

Because as far as I know, the debate over wheel size isn't really playing out on the road, it's happening off-road. So why would Jan conduct his tests on the road, where they have absolutely no relevance to the conditions I ride?

I don't care about how a bike rolls over rough paved surfaces. I care about how a bike rolls on dirt, over rocks and roots, and how it rails through turns.

If Jan actually rode off-road, he'd care about that too. And he probably would have attempted to test it objectively somehow too... But I really don't think he rides mountain bikes. If he did, I'm convinced his perception and opinion would be different.

Don't take this as a "Matt hates Jan Heine" rant, because I don't. I actually buy every issue of Bicycle Quarterly, and read it from cover to cover. I respect Jan and actually agree with a lot of Jan and his reviewers' opinions. But on this important, and clearly subjective topic, I'm afraid I have to take issue with some of his "findings".

Guitar Ted said...

@MG: Thanks for your considered comments MG. I appreciate, (and agree with), what you have said.

I didn't hit Jan too hard on the points you bring up because, as I read it, he/they were theorizing what the situation might be, and had not actually tested for that. Okay. I get that they have a "guesstimate" of how 29"ers ride, but again, you and I know the deal. So, I agree with you, MG, but I also give the BQ guys a bit of latitude until they make some definitive statements regarding 29"ers specifically.

Guitar Ted said...

@MG: And I'm not trying to read into your comments thinking you wouldn't give them the same latitude, because I know you do. Just wanted to make that clear....