What Is It?

• Fat mountain bike tires mounted on conventional road diameter rims ("700c" or 622mm).

Good and Bad

Advantages of 29" Wheels

• Rolling over obstacles. 29" wheels roll rocks, roots and other obstacles better. When a bigger wheel encounters a trail obstacle, it hits the tire at a lower angle than on a smaller wheel. That means less work lofting the wheel, less deflection, less suspension compression and ultimately less loss of momentum. The difference in diameter is only about 10% but feels like more. Bottom line is it's just easier to ride a 29"er through technical terrain.
  It's important to note that this matters as much in back as it does in front. When you're climbing through ledgy, techical terrain, it's much easier to get your rear wheel up over all those roots and rocks.
• Tracking in loose conditions. I've ranked this #2 in terms of importance, but it's easily #1 in terms of sheer contrast with smaller wheels. Big wheels track much better through deep sand, snow and mud. They stay on top more easily and they track straighter. I can easily ride my 29"er in conditions that are nearly impossible on a 26"er. Beach riding is easy, whether it consists of firm sand, loose wet sand (OK, loose dry sand is still tricky), or rockpiles. Even a skinny 700x45 snow tire is easier to ride on packed snowmobile trails than a full width 26" tire. And, importantly in muddy Northwest conditions, I ran confidently ride through deep Forest Park mudholes on my 29"er that would have me weaving around and likely falling on a 26"er. The difference is huge. If riding in adverse conditions is important to you, here's your reason to go 29".
• Low speed stability. Bigger wheels are much more stable in low speed situations. When I'm riding around tight switchbacks or picking my way through rock gardens, I find the bigger wheels much more stable, and they allow me to more easily ride through these conditions at the low speeds that they often require. Again, the difference in wheelsize may only be 10%, and the stability benefit should theoretically only be 21%, but it feels like more. And it doesn't work the same as simply riding a 26" bike with heavier wheels.
• High speed stability. Bigger wheels hold a line better at high speeds, and it's harder to get pushed off your line.
• Better endo resistance. When you hit an obstacle, the point of rotation is your front axle, and a 29"er raises that point by 1.5". That makes it a lot harder to get pitched over the handlebars. I'm so used to it now that every time I ride a 26" bike, I feel like I'm about to fly over the bars at any moment.
• Lower rolling resistance. In addition to rolling over big stuff more easily, bigger wheels simply roll faster, all else being equal. This is because although the tires' contact patch with the ground is the same size (assuming no changes in air pressure or loading), the 29"er's contact patch is longer and narrower. That results in less deformation of the tire, and less energy lost. In fairness, that's all else being equal: one area of inequality is that UST Tubeless and its rolling resistance benefits are widely available for 26", and as of 2007 is only just beginning to appear in the 29" world.

Drawbacks

• Weight. With 10% longer spokes and rims and rubber, 29" wheels, tires and tubes are going to weigh more. Due to the higher head tube height, 29" frames need more and possibly heavier tubing. The longer fork legs will weigh more and also need to be beefed up. Expect an extra pound of rolling weight, 1/2 pound more in the frame and 1/2 pound more in the fork, relative to a comparable 26" bike. Big deal (note sarcasm), when constrasted with the advantages.
• Slower acceleration. Everyone knows rotating mass matters a lot more than dead weight, and heavier wheels feel sluggish to spin up. And most of the extra mass exists at a greater radius, further adding to the effect. If you're racing in very twisty with lots of acceleration out of tight turns, a 26"er may well be the better choice for you. That said, most of the singletrack I ride west of the Cascades would be described as "tight and twisty." Although the 29" acceleration disadvantage is always there, I still find it to be much smaller than the advantages.
• Different handling. 29ers do handle differently than 26ers though, and it can take a few rides to get used to the difference. Some people don't like it. And if you steer exclusively from the handelbars a 29er may feel slower. 29ers particularly reward steering from the hips -- which you should already be doing if tight singletrack is a concern.
• Fit issues. For riders under 5'4"-5'5" it can be tricky to get a proper fit. If your shortness is more in the legs, you'll have problems getting enough standover clearance over the taller top tube. If your shortness is in the torso, you'll have problems reaching the handlebars unless the top tube is shortened enough to cause problems with your toes buzzing the tire. That, or you'll need to be willing to put up with the slow handling that results from a slack head angle. Riders of my height (5'7") are on the borderline of having such problems, but it's generally workable while still getting quick handling. If you're 5'9"-5'10" or taller, you shouldn't have fit issues unless you have unusually large feet for your size. And if you're over 6' you'd be foolish not to ride 29" wheels: 26"ers are like shopping cart wheels under you.
• Limited equipment selection. This is getting to be MUCH less true than it used to be. Almost every major bike manufacturer offers 29"ers now, with the last two majors (Specialized and Giant) set to join the club for 2008, and it's the bread and butter of nearly every custom builder today. A dozen major manufacturers even offer 29" Full Suspension bikes, and every major FS type is now represented up to 5"x5" travel. All the major fork manufacturers are in, and as of 2008 so will every major tire company. The only significant tire categories not represented are aggressive freeride and downhill, as well as the availability of UST technology, all of which also will change by 2008. In every other category -- including all mountain, aggressive cross country, mud, cross country race, snow/studded, semislick, extreme cyclocross, fast cyclocross, hybrid and outright road slicks, you can easily find good tires to fit your 29" wheels. And wheels have never been an issue because 29"ers use standard 700c rims. If you can't find 29" equipment to suit you, you haven't looked lately.

Myths

• Slower handling. This is simply not the case, especially on a hardtail. 29"ers can easily be as quick-handling as their 26" cousins if they're designed with that goal in mind: my Vulture 29"er and my Karate Monkey are the best (and quickest) handling mountain bikes I've owned. They handle just as quickly as 29" bikes in tight, technical terrain, and they do it without compromising stability. 29"ers have been widely believed to handle more slowly than 26" bikes for three reasons, all of which are erroneous:
  • Heavier wheels "turn slower". While it is true that a bigger, heavier wheel has a stronger gyroscopic effect, it is not true that that makes 29"ers slower to turn. In fact the opposite is true. A bike is (properly) steered not by wrestling with the handlebars, but by leaning the bike in a direction that leverages the wheel onto a different plane, pulling the bike with it. If you steer using body English and not just your arms, you'll find 29"ers turn just as quickly and easily.
  • Fisher first generation "Genesis" geometry. Up through 2006 or 2007, the only fully built 29"ers widely available in bike shops were from Gary Fisher. God bless Gary for promoting 29" as much as he did, but his "Genesis I" geometry (found on his bikes through 2006) resulted in a bike with a long wheelbase and slack angles -- a sure recipe for slow handling. Thousands of riders demoed GF bikes in the mid 2000s, coming away with the false impression that 29"ers handle slowly.
  • Attempts to copy 26" geometry. The perceived quickness of a bike's handling is a direct function of a geometric measurement known as trail. If you simply copy a 26" bike's geometry and put bigger wheels on it, you will increase the trail and thus slow down the handling. This has become known as a classic mistake on the part of early 29" bike designers. In order to preserve the same trail figure, it is necessary to steepen the head angle or increase the fork rake relative to a 29" bike. The former solution can cause fit issues for smaller riders, and bikes with rigid forks have often used the latter solution. Unfortunately, until 2007 no suspension fork manufacturer has offered forks with increased rake, which is a better way to quicken the handling and avoid fit problems. For 2008 several manufacturers will offer 29" suspension forks with rake significantly greater than the 38-39mm that is standard on 26" bikes.
• Slower climbing. This is technically true, in the sense that 29" bikes tend to be a couple pounds heavier. A heavier bike (or any other object) takes more effort to lift a given distance than a lighter object. But this is true regardless of how much of the mass is in the wheels, how fast they are spinning or whether the object in question has wheels at all. Critics frequently cite the 29"er's slower acceleration as indicative of slower climbing, saying they can feel it with every pedal stroke. Well, on a climb it is certainly true that the heavier 29" wheels will accelerate a bit less on each pedal stroke. But it the heavier wheels also decelerate less between pedal strokes. The effect cancels out, and all you're left with is the fact that the bike weighs slightly more.

What about 29"/26"?

• Most riders who've tried 29"/26" ultimately end up going full 29" later. If you're buying a new bike anyway, save yourself the hassle and extra expense and jump right to 29/29.
• A 29" wheel helps immensely in front because it rolls over obstacles so much better, as everyone knows. Most people think about that in terms of the front wheel, especially when it comes to ride quality. But I believe that property is equally useful in back, especially in steep technical terrain where keeping the rear wheel connected allows you to maintain power and stay on the bike.
• Another well-documented major benefit of 29" wheels is lower rolling resistance. But only 25-35 percent of your rolling resistance is coming from the front tire. If you really want to reduce rolling resistance, you're going to get your biggest bang by going big in back.
• Bigger wheels seem to substantially improve the stability of a bike, especially at higher or at very low speeds. I suspect that both wheels contribute to this.

• I know someone who's a very serious rider and has had a GF 29"er for over 3 years, but believes that 29/26 is the way to go for him, because he's very hard on wheels and 29" rear wheels just aren't strong enough for him, even with a beefy build. Personally I have a hard time believing he'd be able to trash a 36 hole Kris Holm rim with straight gauge spokes, but I see his point.
• Where 29"/26" really makes sense is for riders who want to eke a longer life out of a beloved 26" bike they already own. I don't believe it makes sense if you're spending money to buy a new bike, but there are a couple situations where a big front wheel can breathe new life into that beloved old steed:
  • If your existing 26" bike has 5" or more of fork travel, you can convert it to a 29"/26" with 3" fork travel without significantly altering the geometry. All you need is a new fork, new front wheel and tire.
  • If your existing 26" bike has at least 3" travel (i.e., suspension geometry), you can convert it to a 29"/26" with a rigid fork without messing up the handling. This is a very popular option. Don't believe the myth that 29" eliminates the need for suspension. Compared to a 26" bike, it may equate to 1/2 to 1" of suspension, but that's about it. Still a good choice if you only barely need the suspension on your full 26"er.
  • If your existing 26" bike is an older pre-suspension model, forget about it. There is no way to convert it to 29"/26" with workable geometry. Either keep riding it as-is, or get a new bike.

My Story

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