asymmetrical beings
Bikes are symmetrical. Humans are not.
To some extent, all humans have differences in bone length, muscle bulk, ligament laxity, joint range, and movement patterns. Most of the time, our bodies are clever enough to compensate (subconsciously leaning to one side, dropping a hip, or favouring one ankle) to a degree.
But when those asymmetries meet the fixed and repetitive nature of cycling, issues can arise.
Differences in sensitivity, the degree of asymmetry, and bike setup all combine to determine whether a rider remains comfortable or starts to notice pain, fatigue, or inefficiency.
Why not everyone feels uncomfortable
Some riders tolerate asymmetry well. Others don’t.
The reality is that:
Anatomical differences vary widely between individuals
some people are naturally more sensitive to changes and observant of how they feel on the bike
Functional asymmetries (strength, control, flexibility, motor patterning) are extremely common
Cycling can magnify even small imbalances due to repetition and load
This is why two riders with similar asymmetries can have very different experiences on the bike.
A simple way to screen leg length differences at home
While the accuracy in assessment by a trained professional can’t be understated, you can perform a basic screen at home to look for obvious asymmetries in leg length:
Lie on your back on a firm surface
Bend both knees so your feet are flat on the floor
Bring your heels together so they are aligned evenly
Observe the height and position of your knees
A knee that sits higher may suggest a difference in tibial (lower leg) length relative to the other leg
A knee that sits further away from you may suggest a difference in femoral (thigh) length
A combination can reflect both segmental differences or pelvic misalignment
This isn’t diagnostic and measurement error needs to be taken into account, but it can highlight patterns worth exploring further in a bike fit or physiotherapy assessment.
Anatomical vs functional leg length differences
Not all perceived leg length discrepancies are structural.
Anatomical discrepancies involve true differences in bone length
Functional discrepancies can arise from pelvic tilt, muscle tightness, joint restrictions, strength imbalances, or movement strategies / technique on the bike.
Even without a true anatomical difference, some cyclists will display apparent leg length differences on the bike - this is termed a functional discrepancy.
What this looks like on the bike
Asymmetries may show up as:
One-sided soreness or recurring pain
Uneven saddle pressure (one-sided saddle issues is very varely due to ‘the wrong saddle’)
Pelvic rocking or hip drop
Asymmetrical bar tape wear
Changes in knee tracking or foot pressure
Patterns matter, not just measurements.
Trialling solutions: cleat shims
One simple and affordable way to explore suspected leg length differences is through cleat shims.
Thin, stackable shims can be placed under the cleat of the shorter or under-reaching leg
This increases effective leg length on the bike
Shims are inexpensive, reversible, and ideal for controlled trialling
cycling is a game where millimeters matter. a 1-2mm shim can yield significant improvements.
When to involve a professional
If things feel like a minefield, that’s because sometimes they are.
A combined approach often works best:
Bike fitting to optimise your interaction with the bike
Physiotherapy assessment to evaluate muscle length, strength, joint range of motion, movement patterns, and foot/ankle mechanics
Some issues are complex and benefit from professional guidance.
The goal
The aim isn’t perfect symmetry.
It’s to respect human asymmetry, understand how your body compensates, and build a position that supports comfort, performance, and longevity on the bike.