I spent the last month or so investigating the options for extending family bike trips with our four year old son. He's riding his own bike at this point, but riding unaided anywhere other than our driveway is beyond his skills as of yet. We looked into trail-a-bike type bicycles, but they were well out of our price range. We then came across the Trail Gator. This bar that connects adult and kid bikes was more reasonably priced, and looked like it would fit our needs well. It arrived from Nashbar today and was installed in about an hour by my wife. Here's some thoughts after a (brief) test ride:
* The four year old LOVES IT. He feels very secure and comfortable being towed, and now wants to ride all over town.
* Dad loves it too. Having my son in tow behind my mountain bike makes little difference in how the bike handles. I had no issues turning or braking.
* Mom loves it because we all can go riding together. We already had a bike seat for our other child, who is 17 months old. We needed a way to make sure our older child could keep up and stay safe, and the Trail Gator works well for us in those respects.
If you're looking in this product market, this might work for you.