August 8, 2018
I would call Knob Hills "one of the hardest easy trails in DFW", because it's a deceptively hard trail if you attempt all 13 miles. While it may not have gnarly climbs and descents, it has a lot of unique qualities that make it harder than it seems. First off, it's an "out-and-back" style trail, so you can only bail out at the halfway point. Second, its right on the edge of a big creek, so the humidity can make you feel much hotter than it actually is. Third, the terrain is very soft dirt or gravel for most of the trail, and it can really make it hard to keep your speed up. The real challenge of this trail is having the stamina to do the entire thing, and keeping a smooth pace that doesn't gas you out halfway.
As you start from the main trailhead, the loops are numbered 1-6, and at the turn around point, they count back from 6 to 1 (but you ride different terrain on the way back). Loops 1-3 are very flat, which can fool you into thinking the rest of the trail will be easy. Loop 4 has a lot of short rollings climbs and descents that can wear you out very quickly (think EKG at River Legacy). At this point you can continue onto loop 6 which has the most challenging climbs (and therefore, you'll ride the entire trail), or if you're tired, you can choose to turn around after loop 4, but you've still got another five (demanding) miles back to the trailhead. Another thing that makes this trail hard is that most of the rollers in loop 4 have sharp turns built into them at the bottoms, and therefore you can't really use your momentum to keep yourself going like you could at Northshore (for example), because you're always trying not to go over a ledge.
The toughest parts of the trail are loops 4 and 6 (eastbound) and then loops 6, 4, and 1 going back (westbound). I'd like this trail more if it had more downhill flow and opportunity to go fast, but personally, i'd rather ride it's neighbors Northshore and Horseshoe because I just feel they are more fun.
River Legacy is similar in most parts.