Bicycle Mechanics - Turning a 12" Specialized Kid's bike into a fixed gear: need a 12" rim, other parts

My daughter has a Specialized 12" kids bike with a coaster brake that I can't stop myself from re-imagining. It's been a long winter and I've done all the stuff on my bikes I can think of.

Her bike has a 16 spoke rear rim. I have a 32 hole freewheel hub on my bench. I was thinking about relacing the rim on the hub and threading a cog and a lockring on that hub.

Why would I do this? I have heard that fixed gears, like the pedals on tricycles, make a lot more sense to kids and make it much easier for them to learn to ride. Braking is more natural, and I'm also going to add a high end caliper brake with an Avid single digit lever so it'll actually be functional and get her used to hand brakes right away.

It might be kind of nice, though, to not disassemble that existing coaster brake wheel. Anyone know where to get a 12" alloy rim drilled with 16 holes?

Will the new hub fit the dropout spacing?

Will the new hub fit the dropout spacing?

Yeah, with heavy modifications. The over lock nut diameter was 126 mm for the 32 hole hub, and the kid's frame has BMX 110 mm O.L.D. But the shell itself is probably like 80 mm or something like that. So I'll have to do some spacing and adjusting to the hub and axel.

.. and threading a cog and a lockring on that hub. ..

you have a freewheel hub, it lacks the second threading
that is left hand threaded and smaller than the RH cog thread..
it's there, just for the lockring,..

.. but 110 is the overlocknut width of legit Track rear hubs. so there you go..
look for a small flange rear track hub..


Machine shop? could make the front wheel like a unicycle,
bearings on the end of the fork,
crank thru .. as if a tricycle.. .. same thing .. front wheel drive..
then the back wheel can be a modified front wheel.
no chain at all..

I disagree that a fixed gear makes it easier to teach a child to ride. Getting the concept of "balance" is enough to do without being forced to pedal at the same time. In fact, one popular teaching technique is to remove the pedals entirely to allow the child to use their feet as "outriggers"while coasting.

I taught both of my granddaughters to ride using suitable size bikes with freewheels and can see no benefit to a fixie under these circumstances. I do agree with providing a caliper handbrake on the front wheel as a coaster brake is both counterintutive and inefficient for a learning rider.

the first thing would be a drivetrain less balance bike ,
a throwback to the first 2 wheel in the early 17th century..


I can't stop myself from re-imagining.

this is more about dad, than the girl, I think..

Yeah, my son learn to ride just fine with a regular freewheel. And I don't want to listen to my daughter talk about how learning to ride her bike was Zen and made her feel like one with the road. Still, these ideas are hard to shake. And I admit part of it is my compulsive need to lighten any bike.

Coaster brakes really suck. The first instinct most kids have when trouble arises is to take their feet off the pedal to prepare to bail. Then there's no means of braking.

Coaster brakes really suck. The first instinct most kids have when trouble arises is to take their feet off the pedal to prepare to bail. Then there's no means of braking.
Right, which is why I said they are counterintuitive and a hand operated brake is a good addition.

heck the older kids around here take the brakes off their BMX bikes ,
and think it's cool to have none , their shoes are their brakes.

Right, which is why I said they are counterintuitive and a hand operated brake is a good addition.

True, I was ending out my post by emphasizing our common ground and trying to solidify our friendship: Down with coaster brakes!

Fixed gear for three year old? Debatable!

Coaster brakes really suck. The first instinct most kids have when trouble arises is to take their feet off the pedal to prepare to bail. Then there's no means of braking.

If that's the case, then they'd have even more fun on a fixed gear with the pedals spinning wildly when the feet are removed. Per Sheldon Brown:

"Sometimes, novice fixed-gear riders will try to use plain pedals with no form of retention system. I strongly advise against this. Riding fixed with plain pedals is an advanced fixed-gear skill, only recommended for experienced fixed-gear riders."

Do you plan on putting toe straps or clipless pedals on this thing too? Personally I would not give a fixed gear to a child unless the intention was to injure them. Tricycles are an exception because they move so slowly.

Coaster brake + hand brakes is a perfectly effective way to learn.

My boys learned on coaster brake bikes and had no problems with the concept of pedal forward to go forward and pedal backward to slow/stop. When they had that down, hand brakes were added in addition to the coaster brake. When those were mastered, gears came into the picture. Seems an easy progression that has worked for a lot of kids.

It may not be a terrible idea, but there's not a lot of reason to do it. Riding a bike is a skill. Break it down a bit, and it's a set of skills. Eventually, your kid has to learn a handful of skills, and she'll have to learn a few simultaneously. This is hard, and you cannot and should not change that. Good thing she's young and can bounce with the falls.

I've taught many kids and adults to ride a bike. I usually remove the pedals for the first lesson so the student can learn handling before pedaling.

I don't think handbrakes or "foot brakes" are inherently better. They are both OK.

If that's the case, then they'd have even more fun on a fixed gear with the pedals spinning wildly when the feet are removed. Per Sheldon Brown:

"Sometimes, novice fixed-gear riders will try to use plain pedals with no form of retention system. I strongly advise against this. Riding fixed with plain pedals is an advanced fixed-gear skill, only recommended for experienced fixed-gear riders."

Do you plan on putting toe straps or clipless pedals on this thing too? Personally I would not give a fixed gear to a child unless the intention was to injure them. Tricycles are an exception because they move so slowly.

Coaster brake + hand brakes is a perfectly effective way to learn.

Sheldon Brown is talking to adult fixed gear riders. A 2 1/2 year old riding a bike geared 24/17 with a 12" rear wheel on a flat surface is not going to develop a lot of speed and have the pedals go spinning around madly.

I'm looking for someone who might know where to find a 12" alloy rim, not sources for conjecture.

My boys learned on coaster brake bikes and had no problems with the concept of pedal forward to go forward and pedal backward to slow/stop. When they had that down, hand brakes were added in addition to the coaster brake. When those were mastered, gears came into the picture. Seems an easy progression that has worked for a lot of kids.

Yeah, I know that's how most everyone has learned. But there's no reason not to question it. How old were your kids when they learned to ride?

Turning a coaster brake kid's bike into a fixie? Easy. Weld the inner and outer parts of the freewheel to one another. Weld the freewheel to the hub. Remove the brake arm and retaining strap. Buy her some skinny jeans and Vans. There you go- instant fixie.

Yeah, I know that's how most everyone has learned. But there's no reason not to question it. How old were your kids when they learned to ride?

I doubt you're the first to question it. My kids were 3 when they learned to ride. First bike was a Diamond Back Mini Viper.

At one point in history, freewheels and coaster brakes hadn't been invented yet, so everyone had to learn on fixed...

It's probably healthier for growing knees to use coaster brakes for those mad skidz, though. ;)

- Scott