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I was looking at the Early Rirder Belter 16" child's bike and noticed that the rear wheel has radial spokes on both sides.

In wheels built for adult bikes this is considered bad practice. From Sheldon Brown's site:-

Wheels with hub brakes and drive wheels should never be radially spoked. Due to the near-perpendicular angle of the spoke to the hub's tangent, any torque applied at the hub of a radial-spoked wheel will result in a very great increase in spoke tension, almost certainly causing hub or spoke failure.

These bikes seem to be popular and get good reviews, so it seems that this isn't an issue in practice. Is this because of the small wheels and the fact that children don't produce so much torque?

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  • You said it -- small wheel and not much torque. And the bikes aren't really expected to last that long, since they're outgrown so quickly and kids' bikes are far more likely to come to a dismal end being run over in the garage or some such.
    – Daniel R Hicks
    Dec 14, 2015 at 13:46
  • Its probably going to depend on the child's weight, and what they do with the bike.
    – PeteH
    Dec 14, 2015 at 18:05
  • Radial spokes on the drive side of a rear wheel and on any side of a disk-brake wheel come under heavy stress. On an adult bike they will certainly fail. On a child's bike they might survive (lower weight, lower pedal power, lower brake force) They have probably been used because radial spoked wheels are quicker to build an therefore cheaper.
    – Carel
    Dec 14, 2015 at 18:41
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    It looks like the spokes aren't completely radial and that there is a single crossing very close to the hub.
    – Kibbee
    Dec 14, 2015 at 20:56
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    Actually, they are diagonally laced, to a degree, just not crossed. The mere fact that the hubs are drilled with holes aligned vs offset produces a diagonal lacing. What you don't have is lacing that balances the "diagonality" on both sides -- the spokes are tugging forwards on one side and backwards on the other. (On a wheel so small, with spokes maybe 5" long, there's simply no room for "crossing".)
    – Daniel R Hicks
    Apr 9, 2016 at 12:20

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For a kids bike where the rider weight is under 25 kilograms / 50 pounds a radial spoked wheel is fine.

I've been trying to clean up and true an old 12" steel wheel with radial spokes and I'm truly astonished how strong it is. The spokes themselves are identical to normal bike spokes, just the length that is different. The cross sectional area is the same.

The rim is normally the same profile as a bigger wheel too, just with more curve on it. This also contributes to the smaller wheel's overall strength.

I'd say a 16" would be fine, but a 20" and above should be properly laced. If the rider is... over 25 kilos then perhaps a cheap wheel is inappropriate. The rider will probably outgrow the bike frame in height before they get too heavy for it.

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