Fat, Fatter, Fattest – Which Bike’s For You?

With the new plus-size models there’s a wheel revolution going on in mountain bikes. What’s the right size wheel and tire and bike for you?

I distinctly remember throwing my leg over the first 29’er that I ever rode. It was ten years ago, and it was revolutionary. Just like the first time I had suspension or disc brakes, it changed mountain biking for me, permanently.

The bike was a Raleigh XXIX, a steel, fully-rigid, single speed. Like everyone else in the early 2000’s, I rekindled my love for my old hardtail by retrofitting it to be a single speed cross-country rig. But, the Raleigh was different: the joy of the big wheels, the playfulness and that roll-over-everything feel were intoxicating. I found myself running out to purchase my own.

I also remember the first time I rode a mountain bike with a 650b, or 27.5-inch diameter wheel. I had known about 650b for the longest time, having spent years working in the cycling industry and fitting numerous women to smaller-framed road and touring bikes. Due to geometry limitations, these often use 650b sized wheels as opposed to the more commonly spec’ed 700c wheels.  Also, I always loved Rivendell Touring Bikes, which used the 650b platform for a more stable on and off road ride.

This time though, it was a Jamis Nemesis that I was able to test ride. I found that the benefit of marrying the better angle of attack of the 29’er with the agility of the smaller 26’er made sense. Plus, you can build much smaller framed bikes using the 27.5” wheel than you can with a 29’er, making it more practical for smaller riders. For those reasons that I decided to pick up a Jamis Nemesis for my son, who at that time was 10 years old.

However, I’m now finding myself at a new crossroads with the advent of the “plus” size rims and tires:  big fat 3-inch wide tires resting upon 40- to 50-mm rims, in either the 29’er or 27.5’ flavor. [Note, there are also a few 26” plus-size wheeled bikes out in the market now too.]

This effectively gives mountain bikers seven different combinations of wheel diameter and tire size that range from the long standing 26” wheel with 2” tires to 27.5” and 29” wheels with plus size (3” inch) tires and to true fat or “snow” bikes with 4-inch tires.

I was quick to adopt the mindset of the 29’er, and slightly less, but still rather quick to love the 27.5”/650b wheel. I also love having a fat bike (especially in a winter like this past one), but I can’t help myself and ask “Why?” Why do we need another size, or sizes of bike wheel/tire combinations?

So that’s the question I’ve been asking bike retailers around Vermont. Here’s our guide to the pros and cons of the fat-, fatter- and fattest bikes and, of course, plus-sized models.

Big and Bigger Wheels

Since the advent of the mountain bike, the 26” wheel with a tire ranging between 2” and 2.5” in diameter has been the prominent combination. Those of us who started mountain biking back the ’80 and ‘90’s started on bikes with 26” wheels and 2” tires. (We also had no suspension and cantilever brakes, but we’re not bitter about it.)

However, over the past few years bike designers discovered that if they increased the wheel diameters by a few inches, it would improve roll-over capabilities.

And so the 29er was born. The first 29ers were met with very mixed reviews. Riders were quick to either love them or hate them due to their distinct pros and cons. Effectively, adding 3” of wheel and tire onto the bike made for very different riding characteristics, depending on the design of the bike.

However, after companies started to dial in the geometries and more parts became available, the 29er found its place in the cycling world and changed it for the better. The taller, 29” platform provides a substantial amount of roll-over capability: technical trails seem to become easier as the wheels want to roll over things rather than get trapped by them. Add in the factor of inertia and once the wheel is moving, it’s harder for it to get bogged down by softer conditions or more difficult terrain.

But due to the larger wheel, the 29er is more challenging to maneuver on tight singletrack trails. Combine that with the additional rolling weight of the bigger wheel and the 29er has its limitations.

Enter into the game the 650b, or 27.5” wheel. This wheel literally splits the difference between the 26” and 29” wheel in both the physical size, but also in the characteristics of the bike. With the benefit of the smaller diameter, the 27.5” is more agile than its 29” big brother. But since it is taller than the classic 26” bike, it rolls over a rock or root more easily than the old standard.

The additional benefit to the 27.5” platform is that manufacturers can build a wider variety of bikes to meet the demands of different disciplines: Small-framed cross country rigs, trail bikes, all-mountain quiver killers, and long-travel enduro bikes are now spec’d with 27.5” wheels on them.

Fat and Fatter Tires

Just as wheels started to get bigger, so did tires. First came the fat bike, spawned in Alaska by riders attempting the Iditabike ride (which follows sections of the world-famous Iditarod dog sled race). The fat bike has really big tires—4” to 5”, which provide ample traction and flotation, making it ideal for snow and sand.

Over the past few years the fat bike has seen a major increase in both popularity and design as more and more people found that the wide tires, just like the early fat powder skis, made everything a lot easier.

Starting off in much the same fashion as the 29er, the fat bike was limited by the amount of frames and parts offered on the market. Now, one can find fat bikes ranging from fully-rigid to front suspension and even full suspension models, all with wide, 4” to 5” tires. With the winters being the way they have been, fat bikes have also given outdoor adventurers a way to ride year-round, regardless of the snow. Pop on some studded tires, and ice becomes manageable too.

As people began to see how much easier it was to ride over rough terrain on these fat or snow bikes, the question arose: why not put bigger tires on other types of bikes? And lo, the plus-size model was born.

Rich Thomas, owner at Paradise Sports in Windsor, VT equates the changes in wheel size in mountain biking to the technological changes and advancements over the past couple of decades seen in alpine skis. “Fat bikes are like powder skis, and the plus size tires specifically, are like going from the old 75mm wide, 210 cm long alpine skis, to our modern all-mountain mid-fat skis.

“If you think about it” Rich points out, “We use these now to head into the backcountry to ski powder or to carve turns on groomers. In the same way, a plus-size bike excels at almost all terrain and obstacles.”

The new plus-size tire is just that: the happy place in the middle that allows a rider to cover almost any terrain on almost style ride, from entry-level bikes for everyday, to all-day cross country machines, to full suspension enduro race bikes.

And why not? The big fat tires offer a plush ride due to the lower pressure and high volume of air in the tire. This looser, softer tire absorbs the terrain like a sponge and provides more grip.

David Robb, shop manager at West Hill Bike Shop in Putney, notes that “due to the larger tire, you gain more traction making it easier to get over rocks and roots. This will make mountain biking more accessible, to more people.” Diny Sweitzer who is co-owner of West Hill with her husband Jim, loves the new plus size bikes. “We are finding that many women want a plus-size tire bike because the wider tire immediately feels more stable and reliable for them. They want to ride trail with their husband or friends and the plus-size bike has allowed them to do so with confidence.”