26″ vs. 29″er
Many of you wonder what the difference really is between a 26″ mountain bike, and a 29″ wheeled mountain bike. Let me help you realize the differences. First, I need to give you some specifics.
A 29″ wheel has more mass (weight) further from the center of rotation, or further away from the hub of the wheel. When you do the math, and compare the same quality / type of wheel between a 26″ and a 29er, you realize that the 29er wheel takes 15% more energy to slow down, and speed up when compared to a 26″ wheel with less rotational weight.
A 29er wheel also has a greater gyroscopic effect than a 26″ wheel because of it’s mass further from the center of rotation.
A 29er wheel also has a greater side surface area when compared to a 26″ wheel.
So, what does all this mean. I have been riding a 26″ wheeled Yeti ASR 5, (Full suspension with 5″ of travel), and I recently took a Yeti SB-95 (Full suspension 29er with 5″ of travel) out on a trail that I have always ridden my ASR 5 on. This trail has a little bit of everything. Steep technical climbs, loose rocky technical fast sections, flowing rollers and turns, and quick hard switchbacks. The trails were all over Peavine Mountain in Reno, Nevada. (http://app.strava.com/rides/10052847)
Here are my observations. Right out of the gate, I hit a very steep and loose climb. I was suffering up that climb. I usually clear the climb on my 26er, but had to walk the top of it with the 29er. My first realization is that with a larger circumference wheel, you gain gear inches. That means that you end up with easier gears on the 26er, and lose about 2 of your easiest gears on the 29er. So, you either push harder, or walk. The other issue I had is that when it got steep and loose, and my speed dropped, and the bike stalled out on rocks, I could usually trackstand for a second, then start off again with out having to put a foot down when on the 26er. When I hit this section on the 29er, and stalled out, I would still trackstand, but when I tried to start off again, the front end of the bike would rise off the ground. Remember the part where the wheel takes 15% more energy to speed up? Well, that energy would rotate the bike, and not the wheel, and the front end would come up rather than rotating the wheel. But remember, this section was right around 20% grade, and loose and rocky.
The next observation I made was with the wind. Boy was it windy on Peavine Mountain. Just rolling down a connecting jeep road, I found myself being pushed around by the wind because of the larger surface area of the wheel when compared to my 26er. But again, the winds were gusting around 30mph.
The next section of trail was fantastic. No steep climbs or downhills. Nice flowing corners both uphill, and downhill. It was fantastic. Because of the larger 29er wheels, they tended to hold their momentum even over the lightly rocky sections. They held their speed better, and because of the lower radial angle of the wheel, it rolled over these lightly rocky sections magnificently. The oddity here is that I rode this entire section, both uphill and downhill in the saddle. On the downhill section, I actually found the 29er more stable in the saddle than out of the saddle.
Now for a downhill section of flowing turns with some wider downhill switchbacks. Here I found the bike to be a dream. Usually on my 26er, I am looking for the smoothest line down the hill. With the 29er, I was only looking for the straightest way down the hill. Since it just rolls over the lightly rocky sections, I did not care about the smoothest section. But because the gyroscopic effect of the 29er, and that being amplified by speed, I was only looking for the straightest path because as the speed picks up, the 29er gets more stable, and less responsive. But because of the lower radial angel of the wheel, it would roll over rocks that I would normally try to steer around on my 26er. This section made the 29er shine.
The next section of trail is just simply fast and rolling downhill. Not many turns, and those turns were banked. So this section was fast. Again, I would usually be standing on my 26er, but found more stability sitting on the 29er. Every time I have ridden this section on my 26er, I ALWAYS get a pinch flat. Speed is fast, and the embedded rocks just give my 26er a pinch flat. On the 29er. Yes, another stupid pinch flat. I don’t think I have ever been through this section with any bike and not had to change a tube. So, if you are running tubes, and not running tubeless, you are just as prone to pinch flats with either bike.
The last section of trail is fairly fast, but full of baby head rocks. This is where the 26er shined. When ripping down this section, and my front wheel hits the side of a baby head rock, the bike squirts to one side. Because the 26er has less rotational mass, and less of a gyroscopic effect, it is easy to re-track your bike underneath you and keep riding. Quick directional changes on the 26er is simple, and it is easy to hold a fast pace through these cobbles. When on the 29er, I found myself all over the trail. Every time the bike would squirt to the side, I would have to struggle to get the bike back underneath me. So, I ended up slowing down through this section so that I could reduce the gyroscopic effect of the wheel which is amplified by speed. By slowing down, the 29er wheel becomes more maneuverable, but still not as good as it’s 26er cousin.
So, what does this really mean? The answer is really simple. The best bike is the bike that best fits your riding style and where you are going to be riding. If you are a hammer head that is always pushing the limits, riding technical up’s and technical descents, then a 26″ wheeled bike is probably best. If you are riding more controlled, riding in a comfort level, want something more stable, or are riding in areas where the trails are smoother, and faster without any quick and rapid changes in speed, then a 29er would be a fantastic choice.
I hope this helps.