A few years ago, there was a real boom in 29” wheels, offering a proper alternative to the traditional 26”. Nowadays, 27.5” is winning over most of the MTB world, as the ideal compromise. We at Lapierre have believed in this new wheel format from very early on, and we have been offering our OST+ platform in 27.5” for our Spicy and Zesty AM models since 2014. It is also making a name for itself on our brand-new X-Control. For 2015, our 27.5” range is expanding even more: for the first time, we are offering this diameter wheel on our DH models! This new standard has proved itself, with podium finishes at the Downhill World Cup for Loic Bruni and his fellow Team Lapierre Gravity Republic members.
Our choices in terms of wheel size and the emergence of new standards like 27.5” are in response to a need to optimise performance. Our goal is to provide you with the best bike for the way you ride, for your favourite terrain and for your build.
How does it work?
It’s well known that the smaller the wheels, the more responsive the bike and its handling. The bigger they are, on the other hand, the better suited the bike is to speed and rolling over obstacles.
What’s more, larger-diameter wheels have significant inertia (because their rotational mass is greater). You need enough inertia to keep the bike stable, but too much inertia will negatively affect its handling, its acceleration and its braking.
Therefore, we can distinguish 4 criteria that vary significantly with wheel diameter: weight, rollover, grip and acceleration.
For different assemblies with the same component types (wheel + tire):
- A 27.5” wheel is 5 % heavier than a 26” wheel
- A 29” wheel is 11 % heavier than a 26” wheel
A bike’s rollover capacity is determined by the wheel’s angle of attack to the obstacle. The bigger the wheel, the smaller the angle of attack, making it easier to roll over.
The bigger the wheel, the more contact surface between tyre and ground (at the same inflation pressure), which therefore improves grip. Better grip means a bike that is easier to ride and has better braking.
It is wheel inertia that influences a bike’s acceleration performance: the bigger the wheels, the greater the rotational mass, the higher the inertia and, therefore, the slower the acceleration. As we can see in the graph below, a bike fitted with 29” wheels will have a higher top speed, but more time and energy will be needed to reach that speed.
The 26” remains suited to long-travel bikes and to smaller builds that are not comfortable on larger wheels.
The 29” is the ultimate weapon for X-country competition and trails, but it is also suited to larger builds and to riders with more limited skills.
Perfectly suited to all-mountain and enduro, the 27.5” represents the perfect compromise between handling, responsiveness and rollover.
Each diameter has its strengths
Lapierre bikes: the right diametre for the right discipline
With all these standards, it is difficult to find your feet. Our engineers, working together with professional riders, have worked out the most appropriate wheel diameter for the intended discipline, and have made the resulting geometry changes.
That’s why you’ll find 29” on our X-country and trail bikes. As for the 27.5”, it is on all segments, from X country to DH. The 26” is not dead yet: the Froggy remains true to its roots, and still has 26”, for all you freeride diehards!
This table sets out the distribution of the various wheel diameters across the 2015 MTB range: