HTupolev

Depends on the circumstances. On quality road with good visibility for all plausible sorts of oncoming hazards, I'm not sure that there's much of a limit: I got up to 57mph once, and it wasn't especially scary. But something is hindering visibility of the road surface, or if there's a chance of stuff like unseen cross-traffic blundering into the road, I might limit myself to slower speeds. Similarly, sometimes a road just can't be descended very fast for handling reasons. On the double-track gravel roads in the foothills, the fastest I've ever gone is a bit over 40mph, and I only occasionally even exceed 30mph; on yesterday's mixed-surface ride, the fastest I reached off the pavement was only about 27mph.