Adult vs kid's bicycle for a tall kid?

Question

My daughter is 11 years old. She is growing fast and for her age, she is quite tall (154cm). Her bicycle is too small for her now so I'd like to get her a new one.

The question is: should I look for a kid's bicycle for her or would it make more sense to get a normal bicycle; maybe something like a XS size? My guess is a frame size of 48 ~ 50 cm should be right for her. Do kid's bicycles have anything especial besides being maybe simpler when it comes to using gears, etc? Would an adult bicycle be too complicated for her?

Her old bicycle is an Islabike which is around 9 kg and comes with SRAM X4 Gripshift (32 tooth chainring with 12-32 wide range rear cassette). It was simple enough for her at age 7, when bought it.

Answer 1

You are correct that there isn't anything intrinsically different between bikes designed for preteens and adult bikes. Kids bikes tend to have lower end, inexpensive components and drivetrains with a single front chainring only.

A adult bike will come with multiple front chainrings and front derailleur and shifter, so your daughter will have to learn to use those as well as the rear gears, but that isn't particularly difficult. Less expensive mountain or hybrid bikes will come with a triple front crank, if you want to simplify gear shifting to start with put the chain in the middle ring just shift the rear gears.

One concern would be the wheels may have quick releases instead of nuts on threaded axles, which might become unsecured with obvious bad consequences. The quick releases would have to be tightened enough so they couldn't be undone easily, and your daughter would have to know to not ride the bike if one or both come loose.

Answer 2

I would go for the adult version of the bike you would buy for her if you were buying a new kids bike.

There is a whole range of bicycles for small adults which are basically not that different from kid bikes, just bigger.

If your bike shop does not have something you find fitting (for a girl her age) search on.

I live in the Netherlands where a lot of children are tall but we still have smaller adults who are in the same size range. Bikes fitting adults also fit children who are the same size.

It may well be that in a few years you will buy her a new bike again, fitting her adult size. So consider her 'new bike' as a further kids bike which happens to be an adult size frame.

If in your area gears are needed, get a bike with enough gears for her, at 11 she is old enough for two sets of gears, but do teach her how to use them.

In the Netherlands most kids get new bikes before going to secondary school, that is around 11 or 12 years old, and most of those bikes are very sturdy, as school bike sheds are hard on bikes.
Most of those bikes are adult frames in the smaller ends of the range (although some of those kids are already as tall as the average adult.)
If your child will not cycle to school, only for fun or only with you, you can select the bike based on that, and keep an eye on it as well.

An other thing the average teen in the Netherlands has to face is lessons in bike repair and maintenance. I have been patching my own tubes (and replaced the tyres) since I was not yet 12 and I was certainly not the only one in school who did.

Answer 3

Check your child's proportions, that is leg and arm length compared to overall length. They are often distinctly different to adults. Legs, in particular, tend to be very long.

In the case of a rather tall ten-year old I had them try a XS sized road bike. I took photos of several riding positions (drops, hoods, etc) from the side.

We found the height was adequate. The reach of the rider was too short however.

Later I compared the geometry of different bikes (with CAD) and selected a S sized gravel bike and fitted a shorter stem. In this case the bigger size had only 1 cm longer reach. Mostly stack was taller than in an XS bike. Higher stack helped to have higher bars (by less exposed seatpost) to get a more upright position.

While the teen' s flexibility is extremely good their lower back strength is not. I also try to open the thigh-torso angle to prevent undue compression of the lower abdomen. (Which Isla Bikes recommended.) This also gives room to tilt the saddle slightly forward to help pelvic tilt (for less lower back curvature).

A grown up bike is possible but needs some fitting. The advantage is, in a year you have an easier time to fit the adult bike than a youth bike.

Answer 4

I would see 3 reasons to avoid considering adult's bikes (compared to bikes from kids-focused brands — for entry level bikes the differences are less obvious): weight, bike fit and marketing.

• Weight: A point against buying an adult bike is that they are more than probably overbuilt, and hence heavier. In most cases, the XS version of a bike is just a smaller frame and uses the same components as the bigger versions, and are often rated for the same total weight of 130kg. This is especially true for bikes with suspension forks (coil-based), that weight 2.5kg. Entry-level bikes also use heavy wheels, and the list goes on.
• Bike fit: kids-focused brands know that their user's height will vary over time, and they may offer more possibilities to adjust position of the saddle and handle bars. For example, they may have shorter head tubes (the part of the frame that holds the handle bar and fork), and leave enough space for spacers around the handle bar, so that the handle bar can be raised as the kid grows. Or they can propose adjustable stems.
• Marketing: it depends a bit on the brands and retailers, and I haven't done extensive research, so I take Woom as an example, but this answer may not be limited to them. Woom is among the expensive kids brands (and kid-only), they know that it's difficult to sell quality products given that their lifespan is limited anyway. So they offer trade-in programs. That won't probably apply to the last bike of the series, but it's worth asking to the retailer.