Frog Bikes Mountain Bikes

Decoding the Frog MTB Lineup

The range is refreshingly straightforward. Frog sizes their mountain bikes by inside leg measurement, which is a far more reliable guide than age - two ten-year-olds can have wildly different leg lengths, and the wrong frame size will kill a child's confidence faster than a wet root. The MTB 62 runs 24-inch wheels and suits riders with a minimum inside leg of 62cm. The MTB 69 steps up to 26-inch wheels for a minimum 69cm inside leg. The MTB 72 shares that 26-inch wheel size but sits on a larger frame, bridging the gap before a rider moves to a full adult bike.

All three are dedicated trail bikes - air suspension forks, dropper-post-compatible frames on the larger models, and proper MTB gearing. None of them are hybrid-MTB crossovers hedging their bets. If you're comparing Frog against something like a Carrera mountain bike, the key distinction is how seriously each brand sweats the weight and the child-specific fit details. Frog sweats them considerably.

Riders who aren't ready for suspension trails yet, or who need a rigid-fork option for mixed-use riding, are better served by the Frog Kids Bikes category. And if you've got a younger sibling who's still on two fat wheels, the Frog Balance Bikes page is worth a look.

The Tech That Actually Makes a Difference

Frog's proprietary engineering is where these bikes earn their reputation. Start with the cranks. Frog's patented design uses a reduced Q-factor - the lateral distance between the pedal faces - which is narrower than almost everything else in the kids' market. On a standard junior bike, children end up pedalling with their knees splayed out, wasting energy and putting odd stress on developing joints. Frog's cranks bring the feet closer to the centreline of the bike, matching a child's natural hip width. The result is more efficient pedalling and less fatigue on longer climbs, which is the sort of thing you notice after an hour at Coed y Brenin.

The air suspension forks are the other headline feature - and the distinction between air and coil matters enormously for kids. A coil spring has a fixed rate; you can't tune it without swapping the spring. An air suspension fork can be inflated or deflated with a shock pump in seconds, meaning the fork stays correctly set up as your child gains weight and strength over a riding season. Frog's custom-tuned junior air forks also include lockout and rebound control, so on fire-road climbs the fork can be locked solid, and on descents you can dial in how quickly it recovers after a hit. That level of adjustability on a kids' bike is genuinely unusual.

Then there are the brake levers. Frog fits short-reach hydraulic disc brake levers across the MTB range - the lever blade is positioned close to the bar so small hands can actually reach it without fully extending their fingers. Hydraulic actuation means consistent, progressive feel regardless of cable stretch or wet conditions. It's the kind of detail that stops a child grabbing a fistful of nothing on a steep descent.

Running a Frog MTB Through a UK Winter

Most kids' trail riding in the UK happens in conditions that would send a fair-weather cyclist indoors - autumn Sundays at Swinley Forest, damp half-term weeks in the Brecon Beacons, the kind of mud that seems to have ambitions. The hydraulic disc brakes handle wet and gritty conditions well; unlike cable-disc setups, the hydraulic system doesn't degrade noticeably when the rotors are plastered with clay.

The lightweight aluminium frame has generous mud clearance around the tyres, which means you're not stopping every ten minutes to dig packed mud out from between the fork legs. That said, after a proper winter session, it's worth pulling the air fork seals and reapplying suspension oil - grit works into the stanchions over time, and keeping them clean extends the fork's life significantly. A quick rinse with a hose after each muddy ride goes a long way.

For UK winters specifically, a set of Frog mudguards is worth adding - they keep the worst of the trail spray off a child's back and face on longer days out. Swapping to chunkier Frog grips with more texture also helps on cold, damp mornings when little hands lose feeling quickly. If your child is doing longer trail days, a Frog water bottle sized for the frame is a neater solution than a hydration pack at this age.

From a parent's perspective, it's also worth knowing that Frog MTBs hold their resale value better than almost anything else in the junior market. The combination of durable components, a recognisable brand, and genuine performance means second-hand Frogs move quickly. Buying one isn't just spending money on a bike - it's more like a loan to your child's trail progression, with a reasonable chunk coming back when they outgrow it. If you're weighing alternatives, Cube mountain bikes offer a strong junior range, but Frog's child-specific geometry details are harder to match at equivalent weights.