BMX top tubes are the most important measurement to consider when buying a BMX frame. The ideal top tube length depends on your height: longer top tubes are best for taller riders, while shorter tubes suit shorter riders. Our handy frame buyer's guide can help you determine the right size. Your riding style also influences the top tube length you need. Shorter top tubes offer better manoeuvrability, making them ideal for park or street riding, while longer top tubes provide greater stability, which is better for trail riding.