If you’re in the market for a new mountain bike, it’s likely you’ll be confronted with a choice on wheel size.
29″ wheels (or 29ers) are measured including the tires to be roughly 29 inches in total diameter including tires, whereas 27.5″ wheels are measured to be – you guessed it – 27.5 inches.
Depending on your riding style, there are a number of advantages and disadvantages to each size.
The most popular wheel size on modern mountain bikes these days is 29″, but that’s not to say they’re for everyone. 27.5″ wheels provide a great alternative to try out a different style of riding or to mix up the type of trails you ride on.
But given the difference in size is so small, how much difference will it actually make? And what are the benefits and drawbacks of each wheel size?
To help you get to grips with 27.5″ vs 29″ mountain bikes, we’ll be covering:
- Does Wheel Size Matter?
- Why 27.5″ Wheels?
- Why 29″ Wheels?
- 27.5″ Vs 29″ Mountain Bike Wheels: Which Is Better?
Let’s dive in!
Does Wheel Size Matter?
A difference in the size of a wheel of just 1.5 inches doesn’t sound like a lot, so you might be wondering: how much difference does it actually make?
A lot. When it comes to mountain bike wheels, size does matter.
Even a small difference in wheel size makes a huge difference to the feel of your ride. These differences cover a diverse set of factors, including responsiveness, stability, acceleration, and more!
However, not so long ago, mountain bikers weren’t given the luxury of a choice in wheel size – mountain bikes exclusively came with 26″ wheels.
These changes included greater suspension travel, the introduction of full-suspension mountain bikes, changes to the geometry of the bikes, wider tires, and, bigger wheels.
29ers came into fashion shortly after a period of rejection from the MTB community. However, now they seem to be the most common fixture on modern mountain bikes.
This played into the development towards comfort: some trails are pretty rough, and the bumpiness or instability can be minimized – and the ultimate capabilities of the machine extended – by increasing the wheel size.
27.5s, sometimes called tweeners, were introduced in the late 2000s as a happy medium between the two existing wheel sizes.
Why 27.5″ Wheels?
So, if the bike industry has evolved to larger wheels, then why do some riders prefer to ride on 27.5″ wheels?
It all comes down to personal preference. Although the bike industry developed towards larger wheels, they do come with relative disadvantages when compared to slightly smaller ones.
Depending on your riding style and where you enjoy riding your bike, it may be better for you to choose 27.5s.
The main advantage of 27.5″ vs 29″ wheels is their responsiveness and agility on technical trails. You can avoid obstacles and bounce from one side of the trail to the other more easily with smaller wheels.
A 29″ wheel is likely going to be noticeably heavier and has a larger amount of the tire in contact with the ground, making it more difficult to lift and move in a swift motion.
The smaller wheel results in a more energetic or – some would say – fun ride. The ability to control the bike underneath you more precisely is a huge advantage for riders who prefer a more technical trail and less pure speed.
Another advantage of 27.5s is that, due to the smaller size, there is physically less material in the wheel so a like-for-like wheel will have a lower weight.
A lighter wheel results in – once again – increased agility. This refers both to the handling ability and the acceleration. A lighter wheel requires less force to reach high speeds and, by extension, less force to slow down.
This lends itself to tight, technical trails with plenty of obstacles that need avoiding. The ability to decelerate extremely quickly when confronted with a surprise obstacle or when going into an unexpectedly tight bend is always an advantage here.
And equally, being able to accelerate out of that corner at high speed means that you can reach your previous speed with less effort than if the wheel were larger.
27.5″ wheels are typically significantly stronger than 29″. This is because the spokes are shorter in length and so require a greater force to deform or buckle.
This is a benefit for those who are seeking the toughest terrain or enjoy bunny hopping obstacles or big drops – they have less chance of damaging their expensive wheelset.
However – it has to be said that any mountain bike wheel is likely to be manufactured to be plenty strong to handle fairly gnarly trails and big drops by nature of the sport. So even if 27.5″ wheels are stronger, it might not make so much of a difference in practice.
Another, perhaps minor consideration, is that a 27.5″ wheel will make your gearing easier relative to 29″ wheels.
When you consider that your lowest gear ratio will force the wheel to spin a certain number of times per revolution of the pedals, the distance the bike travels for each such wheel revolution is decreased with a wheel of smaller circumference, making it easier to push.
Why 29″ Wheels?
Given that there are many benefits to 27.5″ wheels, why would the whole MTB industry tend towards larger wheels?
As with anything in cycling, there are always benefits and drawbacks to every setup. 29-inch wheels have a number of serious benefits that have led to their massive increase in popularity over the past couple of decades.
When they were first popularised around 20 years ago, they were seriously misunderstood. They were initially associated with slower speeds and mellow trails. This is likely due to their large, clumsy appearance on an old-school mountain bike.
But fast-forwarding to today’s market, their reputation couldn’t be more different. The majority of modern MTBs tend to come equipped with 29″ wheels. So what’s the benefit?
The most significant advantage is arguably the increased rollover granted by a wheel of larger diameter. This means they more easily absorb larger obstacles, such as roots and rocks on the trail.
The larger diameter of the wheel means that more of the wheel is in contact with the obstacle as it rolls over it, which provides more friction to drive the bike over the obstacle while minimizing the amount of momentum lost.
Although 29″ wheels are more difficult to handle and so more difficult to avoid obstacles, they are significantly better at absorbing them.
Another advantage of 29ers is the increased stability, particularly at higher speeds. This feeling of stability is particularly important for downhill mountain bikers, hitting extremely high speeds, at which a fall would be extremely dangerous.
This can largely be attributed to the increased rollover once again. Smaller obstacles are more likely to be absorbed, taking the bumpiness out of a trail. At higher speeds, that bumpiness generally leads to a feeling of instability.
Minimizing the bumpiness doesn’t just give stability; it also gives comfort. Regardless of your speed, a brain-shaking bumpy sensation is difficult to describe as pleasant. Anything that minimizes that is definitely beneficial if comfort is a priority for you.
The increase in weight for 29ers isn’t all disadvantage, either. Although they aren’t quite as nimble, taking more force to accelerate and decelerate than 27.5″ wheels, they maintain higher speeds more easily and require less effort to keep going over rough terrain.
This means that on long, straight trails, they are typically the faster choice. Additionally, on climbs with minimal switchbacks, they will likely maintain momentum more easily once you’ve built up some speed.
27.5″ Vs 29″ Mountain Bike wheels: Which is better?
As I’m sure you’ve realized by now, there’s no one-size-fits-all answer to this question. It entirely comes down to how you like to ride your mountain bike.
To summarize, 27.5″ wheels have a number of advantages that tend to lend themselves to tighter, more technical trails with avoidable but large obstacles.
29ers, on the other hand, are more comfortable for most riders, faster on less technical trails, more able to absorb uneven terrain, and pass over large obstacles in the trail.
Most downhill mountain bikers, for example, tend to use 29″ wheels.
The speeds reached during downhill mountain biking mean that anything that makes you more stable is pretty necessary. Additionally, you’re going to be faster since downhill trails have fewer tight bends.
On the other hand, for those who like extremely tight or closed circuit trails with lots of technical jumps and obstacles, 27.5s are the clear choice.
There’s certainly a grey area, though, when it comes to almost everything in between.
XC mountain biking, for example, can have a huge variety in technicality and terrain. So in such a case, it largely depends on what your priorities are.
In general, it all comes down to this: if you take greater enjoyment from being agile and nimble, 27.5s are for you. If you prefer to be comfortable and stable, go for 29ers!
It’s important to note that it’s often not possible to use 27.5″ wheels on a frame designed for 29ers and vice-versa, however! If in doubt, check your manufacturer specifications, or take your mountain bike down to your local bike mechanic to have a look.
29-inch wheel size is a suitable choice on flat terrain because of smooth handling and incredible stability at higher speeds.