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  • Dr. Lee Brotherston

Putting some science into the wheel size debate.

mountain bike wheel size

Everybody has a preferred wheel size that they think is best, and anyone who rides something different does because they aren’t as clever. In the cross-country race world, 29” wheels are by and large the dominant wheel size. The rationale for 29” wheels has been that the larger diameter improves roll-over and small trail bump absorption, improving contact with the ground - leading to an increase in speed. In addition, it has been proposed by the cycling industry that the larger wheel will also reduce trail vibrations observed in mountain biking being transmitted to the rider. Researchers have found that these vibrations lead to increased muscle activity to aid dampening of shocks, resulting in reduced exercise efficiency. Justification for the newer 27.5” wheel standard has been that it provides a balance between the better handling characteristics of the 26” wheel and the improved rolling properties of 29” wheels.

In a study published in the Journal of Sports Sciences, researchers used surface EMG (sEMG) and acceleration to measure the activity of several different muscle groups to determine if wheel size had an impact on muscle activity while they rode around a dedicated cross country mountain bike course. If a muscle is more active, that means it is liable to fatigue sooner and you would ultimately be slower on the bike.

sEMG and acceleration were recorded for the full lap and during ascent and descent phases of the course at the gastrocnemius, vastus lateralis, biceps brachii and triceps brachii. No significant differences were found between wheel sizes for each of the four muscle groups for sEMG or acceleration during the full lap and for the climbing or descending portions in isolation. When data were analysed between muscle groups, significant differences were found between biceps brachii and triceps brachii for all wheel sizes and all phases of the lap with the exception of for the 26“ wheel during the descent. Riders used their biceps muscle more on the descents, possibly due to the increased need to pick up the front tire to avoid obstacles, rather than steam-rolling over everything like I do on my 29er!

mountain bike race

In summary, it’s not the size of the wheel that makes a rider fast or not – there are far greater factors than wheel size which will determine that (fitness, skill, bike geometry, bike weight, etc). So do you what you’ve always done. Pick the wheel size that works for you, and deride your friends and riding buddies who dare to choose differently!

Happy trails,

Dr. Lee Brotherston

Partner and Chiropractor at

Oak Ridges Health Group

58 Brock Street W, Suite 201

Uxbridge ON, L9P 1P3

468 Main Street E

Beaverton ON, L0K 1A0

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