Frog has redesigned its bikes' geometry and components with the help of Dimitris Katsanis, the man behind Team GB's track bikes

Kid’s bikes have often been viewed as scaled down adult bikes, but now Frog Bikes has worked with Dimitris Katsanis of Metron Advanced Equipment to make its designs more child-friendly.

Optimum geometry studied

Frog asked Brunel University researchers to measure a group of 250 children of different ages to determine their optimum bike set-up for comfort and efficient riding. This research highlighted that, due to their pelvis being narrower than an adult’s, conventionally spaced cranks forced them to ride with their legs splayed, resulting in inefficient pedalling and increased lateral forces on the bike – much more so than on an adult’s bike.

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Brunel University measured cycling geometry for 250 children

Brunel University measured cycling geometry for 250 children

Frog then worked with Dimitris Katsanis to translate this research into new design features which enhanced children’s riding experience. Katsanis’s previous projects have included designing Team GB’s track bikes which were ridden to such great Olympic success by the team’s athletes. More recently, Katsanis has worked on the committee advising the UCI on overhauling its technical regulations.

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Kasanis commented, “Although the ultimate aim of the research is to increase the fun that children derive from riding their bicycles it is nevertheless a serious piece of engineering with significant results. This is more than a marginal gain.  I wish we could find something similar for the Olympic bikes too.”

Changes to Frog’s designs

So since June 2015, Frog has been using newly custom-designed cranks. These reduce the bike’s Q-factor by between 27mm and 36mm. Since the optimum crank length for children, as for adults, is around 20% of their inside leg length, their new cranks are also shorter than their predecessors. As the child grows, there’s the option to swap the cranks out for a longer version.

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Frog's cranks are designed to reduce Q-factor

Frog’s cranks are designed to reduce Q-factor

Frog is also altering its bikes’ geometries, incorporating a steeper seat tube of 74 or 75 degrees to create a shorter reach, so that children do not have to bend so much when riding and are more comfortable. Its research found, however, that bar width was not a significant determinant of comfort so its bar width remains unchanged, although there are narrower and wider options available if that suits an individual child better.

Jerry Lawson, the Chief Frog states, “Children are not just scaled-down adults: they have specific bike requirements which are not currently well met.  We are applying the same rigour to the design of kids’ bikes that is usually applied only to adult bikes.”