At Redchilli Bikes, crank length is considered as part of the complete build, rather than simply following a standard specification.
The right choice should suit the rider, their position and the way they want to pedal, whether tackling steep Devon lanes or settling into longer rides across the South West.
A 172.5mm crank has long been treated as the default on many performance road bikes. Yet it is not an automatically sensible choice for every rider. So, are shorter cranks better for your road bike? They can be, particularly where they improve your position, comfort and ability to produce power consistently.
For some riders, moving from 172.5mm to 165mm or 170mm cranks can make the bike feel immediately less restrictive. For others, the difference is subtle, or the existing length already works well. The useful question is not whether shorter is always better. It is whether a shorter crank allows you to ride better.
Are shorter cranks better for your road bike?
A shorter crank reduces the size of the pedal circle your feet travel through. At the top of each pedal stroke, your knee comes less close to your chest. At the bottom, your leg does not extend quite as far if saddle height remains unchanged. Those small changes can have a meaningful effect on the position you can hold for hours.
This matters most where a rider is limited by hip angle, lower-back comfort, knee discomfort or a sense of being too folded over at the top of the stroke. With less knee lift required, it may be possible to lower the front end slightly, rotate the pelvis more comfortably or simply breathe and pedal more freely in a low position.
That does not mean shorter cranks make everyone faster. They can, however, remove a restriction that has been quietly compromising comfort or power. A rider who can stay settled in the saddle, maintain their chosen position and turn the pedals smoothly is normally better placed to perform than one who is fighting the bike.
The top of the pedal stroke is usually the key
The greatest positional benefit is at top dead centre, when the crank is vertical and the knee is at its highest. Long cranks ask for more hip and knee flexion at this point. If your hips are tight, your femurs are relatively long, or you favour an aerodynamic position, that extra flexion can be significant.
Road riders often notice this on the drops, while time-triallists and triathletes may notice it even more in an aggressive aero position. Shorter cranks can create a little more room between torso and thigh, reducing the feeling of the knee rising into the chest. That can help a rider maintain a lower, more stable front end without forcing their lower back to compensate.
The same principle can help endurance riders. You do not need to be riding a time-trial bike to benefit from a more open hip angle. If your lower back stiffens late in long rides, or you continually shift on the saddle in search of space, crank length is one detail worth considering alongside saddle position and handlebar reach.
Crank length, cadence and leverage
The case for longer cranks is simple: a longer lever can provide a little more torque for a given pedal force. In isolation, that sounds compelling. On the road, though, riders do not pedal in isolation. They use gears, ride at different cadences and work within the limits of their mobility and position.
A shorter crank slightly reduces leverage, but modern road gearing gives ample scope to account for that. Moving from 172.5mm to 165mm reduces crank length by 7.5mm. It changes the leverage available at the pedal, while the chainring and cassette ratios remain unchanged. Most riders adapt naturally by choosing a gear that suits the terrain and by allowing cadence to rise a little.
Some riders find that shorter cranks encourage a smoother, quicker pedal stroke, especially when climbing seated or riding at higher cadences. Others prefer the more deliberate feel of a longer crank when pushing a big gear. Neither response is wrong. The aim is a crank length that works with your natural pedalling style rather than one that asks you to change it unnecessarily.
It is also worth separating perceived leverage from real riding performance. A rider may feel more powerful on a longer crank during a short test because the pedal feels more substantial beneath them. Over a four-hour sportive, that perceived advantage may be outweighed if the same crank length closes the hip angle, aggravates a knee or makes a low position difficult to sustain.
Who is most likely to benefit from shorter cranks?
Shorter cranks are commonly worth exploring for smaller riders, but height alone is a blunt measurement. Leg length, femur length, torso proportions, flexibility, riding goals and preferred position all matter.
They can be particularly useful for riders who feel cramped at the top of the pedal stroke, have limited hip mobility, or spend considerable time low on the front of the bike. Riders returning from certain hip or knee issues may also find a smaller pedal circle more comfortable, although that should sit alongside guidance from an appropriate clinician where injury is involved.
They are also increasingly relevant for taller riders seeking a more aerodynamic road or time-trial position. It is easy to assume that a tall rider needs the longest available crank, but a longer leg does not automatically mean a longer crank is the best fit. If that rider’s hip angle is the limiting factor, a shorter crank may allow a markedly better position.
Conversely, a rider with good mobility, a relatively upright endurance position and years of comfortable riding on 172.5mm cranks may gain little by changing. There is no prize for fitting a 165mm crank simply because it is fashionable.
A change in crank length needs a fitting adjustment
Cranks cannot be assessed properly as a simple component swap. Changing length alters the relationship between your foot, saddle and bars through the whole pedal stroke.
When moving to a shorter crank, the saddle will usually need to be raised by roughly the reduction in crank length to maintain a similar extension at the bottom of the stroke. If moving from 172.5mm to 165mm, that often means around 7.5mm higher. In practice, saddle fore-and-aft position, cleat position and the rider’s movement on the bike may mean the final adjustment is not exactly that figure.
The front end may then be reassessed. The real value of shorter cranks is often not merely a higher saddle. It is the opportunity to refine the whole position: perhaps a lower bar height, perhaps a different saddle tilt, or perhaps simply a more relaxed and stable posture with the existing cockpit.
Cleat position matters too. A more rearward cleat can reduce demand on the calf and ankle, while the shoe-pedal interface affects effective leg extension. This is why crank length should be considered as part of a complete fit rather than as a standalone cure for every discomfort.
What length should you choose?
There is no chart that can reliably prescribe the right answer from height and inseam alone. As a broad starting point, 165mm, 170mm and 172.5mm cover a wide range of road riders, while 175mm remains appropriate for some. The trouble is that stock bike specifications have made 172.5mm appear more universal than it really is.
If you are comfortable, producing consistent power and able to use the position you want on the bike, there may be no reason to change. If you suspect that crank length is limiting you, a fitting assessment can help establish whether a shorter crank is worth trying. A 5mm or 7.5mm reduction is more likely to create a clearly noticeable positional change.
Pay attention over several rides, not just the first few miles. Notice whether you can hold the drops more naturally, whether your hips remain quieter on the saddle, how your knees feel after climbing, and whether your cadence settles without conscious effort. A change that feels unfamiliar on day one may be the right one once your coordination adapts. Equally, a change that feels quick indoors may not suit your preferred roads or riding style outside.
Build the bike around the rider
Crank length is a small number with a wide influence. It affects saddle height, hip angle, knee movement, cadence, aerodynamics and the way the bike feels beneath you. That is precisely why it deserves more thought than a default specification line.
At Redchilli, it is one of the details considered alongside frame geometry, gearing, cockpit dimensions, wheels and the terrain a rider actually covers. A fast bike should not ask you to work around its compromises. It should give you the space and support to ride with confidence, whether that means turning a quicker pedal stroke through Devon lanes or settling into a long day in the saddle.
If your current position feels cramped, crank length is worth assessing alongside saddle position, handlebar reach and the rest of your set-up. The useful change is the one that helps you pedal comfortably and consistently on the roads you actually ride.
The right crank length for your Redchilli bike
At Redchilli Bikes, every bike is individually specified and hand assembled in Devon, with crank length considered alongside frame size, gearing and cockpit dimensions. Whether your riding takes you through steep local lanes or further across the South West, these details should work together to support a comfortable position and a natural pedal stroke. Shorter is not automatically better. The right specification is the one that suits you.
Redchilli Bikes. Your Bike. Your Way.