In reply to balmybaldwin:
Does your Garmin tell you the max gradient ? I looked for that on my Edge 800, but all it has is current gradient. Likewise Strava will show the average gradient of a segment, but not the max.
Veloviewer.com does to show the max gradient, but it doesn't seem too reliable - it was showing 360% on one segment. Though if you play around you seem to get better results, but could easily lose an afternoon !