Frog Bikes Track Crank Length: 114mm, 127mm and 140mm

Frog Bikes Track crank length changes across the documented range. The three Podium entries list 114mm, 127mm and 140mm arms, alongside different chainrings and handlebars. For a parent arranging a fitting or investigating a replacement, the first task is to identify the installed crank rather than treating the model's age band as a prescription.

Frog Bikes Track crank length: Keep millimetres and teeth apart

Track 58 is listed with 114mm aluminium straight-arm cranks and a 36T chainring. Track 67 pairs 127mm arms with 40T, while Track 70 pairs 140mm arms with 44T. The source calls these Frog Bikes patented cranks. It does not establish that a longer arm will improve a particular child's performance.

Write “crank length” beside the millimetre measurement in your notes and “chainring teeth” beside the tooth count. A seller may put both in one chainset description. Keeping them separate makes it easier to explain whether the concern is riding position, an unreadable component marking or a damaged assembly.

Check the actual arms before comparing

Look for readable identification without removing components or turning an uncertain marking into a guess. Have a mechanic confirm the arm length if the bike's history is unclear. A replacement crank on a second-hand Track bicycle can make the original catalogue figure a poor description of the equipment the child will use.

Use the fitting appointment to assess the whole position

Bring the child's current height and inside-leg measurement, usual shoes and bicycle to the appointment. Explain any discomfort or difficulty managing the bike in plain terms. Ask the fitter and coach to assess the actual movement and position rather than requesting a particular crank length because it belongs to a larger model.

The older Frog owner's manual warns that component changes can compromise compatibility and directs owners to their stockist. Its pedal section also asks the stockist to check the relationship between frame, crank, pedals and shoes where toe overlap is a concern. This is a reason to obtain an assessment, not to prescribe a generic cornering technique for a fixed-wheel track session.

Request a checked replacement specification

Podium's bottom-bracket description identifies a square-taper assembly, but its combined dimensions are insufficient here to approve an alternative crank. Give the mechanic the complete component description and the installed parts. Ask for the suitable replacement and applicable installation instructions to be recorded together.

If a different crank is proposed, have the completed bicycle checked before the child rides it. Preserve what changed and why, including any related adjustments identified during the fitting. That record is more useful at the next growth check than a note saying only that the bicycle was “upgraded”.

Background on child-specific design appears in the Frog Bikes introduction. Other questions are collected under the Frog Bikes topic. A careful Frog Bikes Track crank length enquiry identifies the part and the child's need without inventing a universal ideal measurement.

FAQ

Which crank length is listed for Track 67?

Podium specifies 127mm aluminium straight-arm cranks in its Track 67 entry.

Is 40T another way of describing a 127mm crank?

No. The first figure counts chainring teeth; the second describes crank length.

Should a larger model's crank be fitted automatically as a child grows?

No. Have fit, component compatibility and the complete bicycle assessed before making changes.

Sources

Podium records the three crank lengths alongside their chainrings. The older Frog manual, pages 13–16 and 31, addresses component compatibility and the need for fitting advice; its generic cornering instructions are not applied to a fixed-wheel session. Podium Frog Track 58 (https://www.podium.co.jp/lineup/12779); Podium Frog Track 67 (https://www.podium.co.jp/lineup/12782); Podium Frog Track 70 (https://www.podium.co.jp/lineup/12783); Frog owner manual, manufacturer-branded older copy hosted by North Bikes (https://cdn.shopify.com/s/files/1/0224/5142/1256/files/Frog_Owners_Manual.pdf?v=1765670500). Actual saved sources retrieved and read 27 October 2026. Distributor specifications can change; no model year is inferred.

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