Is My Child Ready for an Adult Bike? Moving Up from a Kids Bike to an XS or Small Frame

Somewhere between the ages of about 10 and 14, most children outgrow the biggest kids bikes. The saddle is up at its limit, their knees come close to the handlebars, and they start asking to borrow a parent's bike. The next step isn't another kids bike: it's an adult bike in the smallest frame size. Here's how we help families tell when a child is ready to move up, and how to pick a first adult bike that actually fits.

Signs your child has outgrown their kids bike

Wheel size isn't the whole story. A child can still be fine on a 24" or 26" bike for a year or two after friends have moved on, or they can stretch it to the limit early. These are the signs we look for in the shop:

• The seatpost is at its maximum mark. Every seatpost has a minimum-insertion line. If it's showing, or the saddle still feels low with their legs bent at the bottom of each pedal stroke, they've run out of adjustment.
• Their knees come close to the bars when they turn or stand on the pedals.
• They look hunched or cramped, with straight arms and their back rounded over a short top tube.
• They're riding further and faster and want more gears, or are keeping up with adults on family rides and trails.

If two or three of these sound familiar, it's worth trying an adult frame. If you're not sure whether they're still on the right kids wheel size, our kids bike size guide covers the wheel sizes up to 26".

How XS and Small adult frames are different

Many adult bikes now change wheel size with frame size, so the smallest riders aren't stuck on wheels that are too big for them. Cube's Size Split system, for example, puts the Cube Aim Pro on 27.5" wheels in XS and S and on 29" wheels from Medium upwards. Ghost does the same with the Kato. That's only a small step up from a 26" junior bike, so the jump feels natural.

The other differences are less obvious but matter just as much:

• Standover height. Your child should be able to stand over the top tube with both feet flat and a little clearance. A low top tube or a midstep frame makes this easier.
• Brake reach. Adult levers are designed for adult hands. Most hydraulic levers can be adjusted closer to the bar, and we'll set them up before the bike leaves.
• Crank length and bar width. Adult bikes often have 170mm cranks and bars 680mm wide or more. A smaller rider might be happier with the bars trimmed or a shorter stem, which is a quick workshop job.
• Weight. An adult hardtail mountain bike is typically 14–15kg. Scott lists the Scott Contrail 30 at about 14.3kg without pedals, and Cube quotes 15.1kg for the Aim Pro in Large. That's heavier than most junior bikes, so make sure they can lift and wheel it comfortably.

Is buying a bigger size to grow into a good idea?

This is the question we're asked most. It's tempting to buy a Medium so it lasts longer, but a bike that's too big is harder to control, harder to stop safely and much less fun. Teenagers can grow quickly, so we'd always size for the rider they are today, with a little room in the seatpost. An XS or Small that fits now will usually last a couple of years, and a well-kept bike keeps some resale value when it's time to move up again.

Brands publish height ranges for each size, and they're a good starting point. Trek's chart for the Trek FX 2 Midstep, for example, lists the Small for riders from 155 to 165cm with a 72–78cm inside leg. Charts vary between brands and models, though, so a test sit in the shop is the best check.

Mountain bike or hybrid for a first adult bike?

Think about where they'll ride most, rather than what their friends have.

• A hardtail mountain bike suits teenagers who ride woods, trails and sea-wall tracks, or just want a tough bike that handles kerbs and rough paths. A front suspension fork and wide tyres make it forgiving.
• A hybrid is lighter and quicker on the road, with rack and mudguard mounts. It's the better pick for cycling to school or college, or longer road rides with the family.

First adult bikes we'd look at for teens

These are good options in the smaller sizes. Stock in XS and Small changes quickly, so call ahead to check your size before you visit.

• Cube Aim Pro Greige Titan: 27.5" wheels in XS and S, a 100mm SR Suntour fork, Shimano Cues 10-speed gears with an 11-48T cassette and hydraulic disc brakes. The frame takes a dropper post later, so it can grow with their riding.
• Scott Contrail 30 Luminary Green: a 100mm Suntour fork, Shimano CUES 9-speed, Tektro hydraulic discs and grippy 2.4" Maxxis Rekon tyres. A great trail all-rounder.
• Ghost Kato Ink Blue: 27.5" wheels in XS, a 100mm fork, 21 gears and Tektro hydraulic disc brakes. A simple, sturdy, affordable first adult hardtail.
• Raleigh Strada X Grey (Small, 18" frame): 650b wheels, an 80mm fork, 21-speed Shimano gears and disc brakes. It sits between a hybrid and a mountain bike, so it's ideal for teens who mix roads and paths.
• Trek FX 2 Midstep Crystal White (Small): an easy-to-mount midstep frame, Shimano CUES 9-speed and hydraulic disc brakes, with rack and mudguard mounts for school or college.

Moving up to an adult helmet

A growing head often needs a new helmet at the same time as the bike. Measure around the head just above the eyebrows. Many teenagers fit an adult Small/Medium, such as the Oxford Hoxton (S/M 54–58cm, dial fit and reflective detailing) or the Kali Pace (S/M 54–58cm, with a break-away visor and Kali's lifetime crash replacement). The helmet should sit level, just above the eyebrows, and stay put when they shake their head. You'll find more in our helmets range.

Bring them in for a test sit

The easiest way to get it right is to have your child sit on an XS and a Small back to back. We'll check standover, reach and saddle height, adjust the brake levers for their hands and talk you through the gears. Browse our mountain bikes and hybrid bikes online, or have a look at our kids bikes if they still have some growing to do first.

Find us at Les’s Cycles, 365 Long Road, Canvey Island, Essex SS8 0JQ, call 01268 695877 or email sales@lescycles.co.uk.