Well I live in Illinois, so I don't have many "grades" to discuss. So my speed is mostly on flats or flats with maybe some rolling hills. My first season I kept track I averaged about 17 mph. Last summer I averaged 21 mph. That's overall, including riding with some boys who are pretty fast, which boosts that average.
I'd say I'm comfortable riding 18-21 mph, and can sprint to 30-32 mph if I have to, but not for very far.
