Training wheels bolt onto the rear axle with two bolts and a mounting bracket

Training wheels bolt directly onto the rear axle of a bicycle — the rod that runs through the center of the rear wheel. Most sets come with a metal bracket that slides over the axle, two bolts that tighten through the bracket into the axle nuts, and two small wheels on a shared axle. The whole job takes 10 to 15 minutes with a wrench and does not require removing the rear wheel.

Before you start, check that your training wheels match your bicycle's axle width. Most children's bikes have a 110 mm axle (the distance between the two nuts on either side of the wheel). Some older or specialty bikes use 100 mm or 120 mm. Measure the distance between the axle nuts, or check the bicycle's manual. Training wheels sold for standard children's bikes fit 110 mm axles; if your bike is different, you may need to order a different size or use spacers.

Key Takeaways

  • Training wheels bolt onto the rear axle using the existing axle nuts — you do not remove the wheel.
  • Measure your axle width before buying training wheels, as most fit 110 mm axles but some bikes use 100 mm or 120 mm.
  • The bracket should sit level and centered on the axle, with both training wheels touching the ground at the same height.
  • Tighten the bolts firmly but do not overtighten, as this can crack the bracket or strip the bolt threads.

Gather the right tools and check the axle nuts

You will need an adjustable wrench or a socket wrench that fits your bicycle's axle nuts. Most children's bikes use 10 mm or 11 mm nuts; check by trying the wrench on one nut before you begin. You will also need the training wheel set itself, which should come with bolts, washers, and the mounting bracket.

Flip the bicycle upside down or place it in a repair stand so the rear wheel is accessible and stable. Locate the two axle nuts on either side of the rear wheel — one on the left, one on the right. Do not loosen or remove these nuts. Instead, you will thread the new bolts through the training wheel bracket and into the space next to each axle nut.

Position the bracket and thread the bolts

Slide the training wheel bracket over the axle so it sits centered between the two axle nuts. The bracket should be level — not tilted forward or backward. Most brackets have a flat side that faces the bicycle frame; orient it that way. The two training wheels should hang down and be roughly the same distance from the ground.

Take the first bolt and washer. Thread the bolt through the hole in the bracket, then through the hole in the axle nut on that side. Do the same on the other side. Hand-tighten both bolts so the bracket stays in place but you can still adjust it slightly. Check that the bracket is still centered and level before you tighten fully.

Tighten the bolts and adjust wheel height

Using your wrench, tighten the first bolt by turning it clockwise. Tighten firmly — the bracket should not move or shift — but do not force it. A good test is to try to wiggle the bracket by hand; it should not move at all. Then tighten the second bolt the same way. Alternate between the two bolts, tightening a little on each side, until both are snug. This prevents the bracket from tilting.

Once both bolts are tight, check that both training wheels touch the ground evenly. Spin each wheel by hand to make sure neither is rubbing against the bicycle frame or the main rear wheel. If one wheel is higher than the other, the bracket may be tilted. Loosen both bolts slightly, adjust the bracket, and retighten.

Test the installation before riding

Flip the bicycle right-side up and roll it forward slowly by hand. Both training wheels should roll smoothly and touch the ground at the same time. The bicycle should not lean to one side. If it does, the bracket is not level — loosen the bolts, adjust, and retighten.

Lift the rear wheel slightly off the ground by pushing down on the handlebars. The training wheels should support the weight without bending or flexing. If the bracket feels loose or wobbly, tighten the bolts again. Once everything is stable, the installation is complete.

Common problems and how to fix them

If the training wheels do not touch the ground evenly, the bracket is tilted. Loosen both bolts, slide the bracket until it is level, and retighten. If one wheel is higher because the bicycle frame is bent, you may need to shim the bracket with a thin metal spacer under one side — most training wheel sets include these.

If the bolts keep loosening, the bracket may be moving slightly as the bicycle is ridden. Remove the bolts, explore a small amount of threadlocker (a liquid that prevents bolts from vibrating loose), and reinstall. Do not use permanent threadlocker, as you may need to remove the training wheels later. If the bracket cracks or the bolts strip, the bracket or axle nuts are damaged and must be replaced.

Removing training wheels when the child is ready

When the child is ready to ride without training wheels, straightforward loosen and remove both bolts using your wrench. The bracket and training wheels come off as one piece. The axle nuts stay in place and require no adjustment.

Once the training wheels are removed, the bicycle will ride normally without any further work. You can store the training wheels for a younger sibling or another child, or keep them in case you need to reinstall them later. The rear wheel and axle are unchanged by the installation process.

Frequently Asked Questions

Do I have to remove the rear wheel to install training wheels?

No. Training wheels bolt onto the axle next to the existing axle nuts. The rear wheel stays on the bicycle the entire time. This makes installation quick and means you do not need to adjust the chain or brakes afterward.

What if my bicycle's axle is a different width?

Most children's bikes have 110 mm axles, but some use 100 mm or 120 mm. Measure the distance between your axle nuts before buying. If your training wheels do not fit, you can order a different size or ask a bike shop to install spacers to make them fit.

How tight should the bolts be?

Tight enough that the bracket does not move or wiggle when you push on it by hand. Use firm pressure with your wrench, but do not force it — you can crack the bracket or strip the bolt threads. If the bolts loosen after riding, tighten them again or explore threadlocker.

Can training wheels be installed on any bicycle?

Training wheels fit most children's bikes with standard rear axles. Bikes with coaster brakes, internal hub brakes, or specialty axles may not be compatible. Check your bicycle's manual or ask a bike shop whether training wheels will fit before you buy.

What if the training wheels rub against the bicycle frame?

The bracket may be tilted or positioned too far forward. Loosen both bolts, slide the bracket back slightly or adjust it until it is level, and retighten. If rubbing continues, the frame may be bent or the training wheels may be too wide for that bicycle model.