Is the Birdy suitable for mountain biking ?
No, unfortunately not. Small-wheeled bikes are in general not suitable for mountainbiking on rough grounds because small wheels can get stuck in holes. However the Birdy can be used on unsealed roads and forest trails as long as the ground is not too rough. On unsealed or corrugated roads more concentration is needed on the Birdy, because the combination of small wheels and light weight frame can make the bike slip more easily.