My daughter's back wheel bolts on her bicycle just don't seem to be long enough to fit her stabilizers (training wheels). (There's no room left to screw the stabilizer wheel nuts on). I've tried two sets and both have the same problem. So I purchased "stabilizer extender bolts" but after a while of peddling one side loosens and is therefore dangerous and non-functional.
From the description of the problem, I agree with the solution Wiewen suggested in taking the bike to a local hardware store or bike shop and get longer bolts. In my experience, the bolts on stabilizers (training wheels) are standard and one should be able to find a longer bolt with the same thread.
Pictures of the bike and training wheels would certainly help. From the description of the issue after the "extender bolts" were installed, it may simply be a problem of needing a lock washer installed under the nut.
The issue also could be due to the stabilizer sliding and as it slides the bolts loosen because the tube diameter or something else changes and allows the bolt to loosen. If this is the case then the lock washer would not help.
Based on the description the problem is that the axle is too short to attach training wheels / stabilizers and the axle extenders won't stay tight.
Axle extenders are the only solution I know of when the axle is too short. The suffer from some challenges.
- The axle extenders are sometimes difficult to keep tight
- The axle extender moves the training wheel too far from the frame for the frame support portion of the training wheel to connect requiring some bending
- Axle extenders tend to be cheaply made and don't hold up.
If the axle is too short for the training wheels / stabilizers I can think of three solutions.
- You may be able to find rig an axle extender to work (requires mechanical ability and trial and error).
- Find a bike with training wheels / stabilizers installed
- Use a different method of learning to ride a bike (see suggestions in comments)