Guide to Mountain Bike Wheel Size
It used to be so simple. Mountain bikes had 26" wheels whether you were riding in the park or the Pyrenees and they had been that way since the Californian pioneers of the off-road community adapted 700c beach cruisers with wider tyres to bomb down the fire roads of Marin county. But MTB wheels, like any dynamic market, have been redeveloped and redesigned to cater for the ever-evolving landscape of Mountain Biking, incorporating different designs and ideas into various MTB disciplines in order to get a competitive and performance advantages over other the other cycle brands and manufacturers.
Pop in to any modern day bike shop and you'll see bikes with multiple wheel sizes,styles and positions. 27.5",29", 27.5"+ and fat tyre/wheel combinations are all commonly seen sights on the trails and in the showrooms, with each option offering certain pros and cons in terms of where they're best used and for what purpose the bike is intended for. But which MTB wheel size is right for you? The article below will run you through the different options out there, helping you to decide what size wheel is the best size to enable you to reach your goals.
29" wheels have actually been around for longer than you'd think. Initially spearheaded by major industry players such as Trek's Gary Fisher, 29" wheels were seen as they way to bring more speed to the mountain biking table. 29ers roll much faster over the ground than their 27.5/26" counterparts. The development of this wheel size was originally championed by the XC community, using the larger wheel diameter to increase their overall speed, enhance the stability of the bike over changeable terrain whilst also providing more traction to the wheel in tight corners.
29" frames have been intensely refined and developed since the first examples were seen on the market. The original 29" frames sported questionably steep geometry and particularly long stems to aid the steering of the larger sized wheel. This often meant the frames weren't stiff enough and 'flexed' a little to much, meaning that for proper off-road riding, 29ers were sketchy at best. However, as time has gone on, the boffins and brains of the brand's R&D teams have developed methods to refine the frame to be more supportive of 29" wheels, leading to the development of some truly beast-worthy bikes such as the new Specialized StumpJumper and the Trek's Slash. This new breed of 29" wheeled MTB offers a massively capable,versatile and efficient package to riders, especially taller individuals who find the larger bike size more proportional to their own dimensions - though with the improvements in geometry, frame layout and stem size, 29" mountain bikes are certainly not confined to only those over 6 foot.
Technology wise, a lot of work has gone into the improvement and redevelopment of componentry to not only accommodate 29" wheels, but to also ensure that 29er bikes handle, balance and perform almost as well as a 650b in the tighter trail sections whilst still offering the increased speed and rolling qualities on the flats. This has been achieved via the introduction of Boost Hubs, 110mm at the front and 148mm at the rear, to allow for a stiffer and stronger wheel. Boost, combined with the wider,lighter rims and increased volume tyres has permitted 29" bikes to become mainstays in the XC, Trail and Enduro mountain biking markets - with many companies offering models in both a 27.5" and 29" wheel diameter to appeal to the widest customer base.
For 2019/20, the geometry of 29" bikes has come a long way. From tall, unnatural feeling angles to slick root-hungry platforms - many 29" models now feel more akin to 27.5" than ever before. The perception of the 29" wheel is now changing, with enduro and DH professionals fully accepting the benefits of the larger wheel diameter. It is rare to see a podium in either discipline which is not made up of either 29" wheels or a hybrid mix of 29" front and 27.5" rear, commonly known as a "mullet bike" (business in the front, party in the back!). This combo can be found on some bikes such as the Focus Jam2 Drifter, offering the best of both worlds. There is speculation that many of these combination wheel size bikes seen on the race circuits have come about as some manufacturers do not offer a 29" wheeled option, so it will be interesting to see if this trend fully takes off within the commercial market.
The new(ish) kid on the block, 27.5" wheels first came about around 8 years ago and completely redefined the market in terms of geometry and the creation of proper 'all-rounders' capable of doing all the tight technical turns of a 26" whilst still offering the fast rolling, ultra-traction qualities of a 29". The 27.5" wheel has seen the 26" bike consigned to a future away from the showroom - it's rare to see them anywhere these days other than on cheap,mass-produced bikes found in supermarkets or on trials,DH or gravity specific bikes that are designed to put handling,stiffness and strength above all else.
Quick turning, agile, versatile and fast - 27.5" offers the perfect middle ground for many riders and that's why its experienced so much success in a relatively small space of time. The best of both worlds is something synonymous with 27.5" and with the majority of cyclists still more accustomed to 26", a 27.5" wheel provides a natural step-up that is easily adapted too. Riders going from a 26" to a 29" often find it hard to get used to due to the increased speed in which the bike travels affecting braking distance,corner speed and riding position. 27.5" has also quickly become the standard on long travel trail and DH bikes, moving away from the 26" but maintaining the strength and steering accuracy whilst also improving the frames rollover qualities.
So where do 27.5" wheels come unstuck? well for many, they don't. A move from a 26" to a 27.5" offers a load of benefits with no compromises and, if you are sporting 26" then 27.5" is definitely the wheel to go for on your next bike. However, those that are used to riding on 29" wheels may find the smaller wheel diameter sluggish, especially with the advancements in 29" technology leading to some highly capable and high performing models. This has meant that lighter trail bikes under 140mm travel and a lot of XC bikes are more popular in a 29" option due to the enhancement in speed far surpassing the minor losses of reactivity and handling. So if you are riding a shorter travelled bike or XC, it's certainly worth trying both a 27.5" and a 29" to find out which one feels better for you. Lastly, tyre choice is large within this wheel diameter - just make sure to get the correct style for your type of riding!
'Plus' tyres are an interesting concept that are continually growing in popularity as componentry and geometry are redefined to accommodate wider profiles (EG Boost Hubs). 27.5"+ wheels do not lead to the creation of 'fat bikes' (massive tired bikes for snow,sand & fallout zones usually sat on 26" rims), instead, Plus rims(30-40mm) are 27.5" wheels with huge volume tyres(2.7-3") and offer a number of benefits to the rider. These benefits include increased traction,stability and suspension that come from wider tyre profiles. Plus rims also add a lot of height to the wheel making it almost as wide as a standard 29" and creating(in theory) a bike with the stiffness and strength of a 27.5" wheel, the rollover speed of a 29" and the handling,traction and stability of a fat bike.
This combination has caused advances such as boost hubs and specialist forks to accommodate to bigger wheel. Single ring drivetrains have also become common-place on plus bikes , with the technology spreading onto other frame options (27.5/29”) very quickly. It's important for the performance of 27.5"+ wheels to master your tyre pressures, with very low PSI needed to produce vibration-dampening results. Get it too firm and you'll be bouncing about like a kangaroo in moon boots on a trampoline. It's also not a bad idea to get plus tyres/rims converted to tubeless as this will save you weight and reduce punctures - something much more likely with such a large tyre surface area.
The downsides? Plus tyres aren't light and the choice is pretty limited. Tyres take a lot of punishment on a 27.5"+ bike and so developing more durable, tougher and cheaper tyres for this wheel diameter is a must before it's adopted by the majority of riders. Additionally, due to the continual need to adjust tyre pressure,suspension and tyre profile, a plus bike probably isn't the ideal choice for a those who just want to ‘get out and ride’ as you'll have to spend a fair amount of time making adjustments to your components. Lastly, Plus tyres can be a nightmare in really bad weather, getting clogged up with sticky mud and debris from the trail and slowing your progress considerably.
Although mostly confined to memory large-chain store catalogues, the 26" wheel still has its relevance. As mentioned, 26" is still very popular amongst DH and dirt jump riders, and models such as the Scott Voltage show that this standard is unlikely to change too much in the near future. Furthermore, 26" wheel sizes can be a really good choice for the shorter adult rider or 'betweenagers' (taller riders aged 10-14 that are too big for kids' bikes yet not ready for a full on adult bike.)
The only real way to find the right wheel size for you is through trial and error. It's a good idea to try out a 29" and a 27.5" on your local trails before you decide which wheel diameter to go with on your next new bike. Bare in mind that if you're riding a your first 29", you'll find it to be somewhat unruly in the corners before you've become used to the different way the wheels ride - therefore testing it out on a flat carpark probably won't give you a chance to really see if that wheel size is working for you. Luckily, here at Rutland Cycling we have a massive demo fleet available for short/longer term hires, so you can go out and give both wheel sizes a try before making your decision! We also run a number of MTB events including demo days, led rides and skill sessions, a perfect opportunity to experience all the frame options out there en masse!!