≡ Menu

In Search of the Perfect Turn

After my (very) brief initial rides on my first section of trail, it was obvious that I needed to modify several, if not even most, of the turns that I’d tentatively created (basically “drawn” with a garden rake). Mind you, other than the rake, I haven’t taken any tools to the ground yet. So it was fair to blame some of the problems on an unconstructed trail tread, but it was still pretty obvious that even after actual construction some of the turns would just be too tight or too steep, or both.

I was starting to wonder if many of the turns I’d drawn would need to be built into switchbacks, which I really wanted to avoid due to the reasons mentioned in my previous post (Grading On a Curve). I hadn’t made the turns so tight that switchbacks would be necessary but unfortunately I’d made many of them too tight for climbing turns. That pretty much leaves insloped (bermed) turns. While insloped turns can certainly be relatively tight, the tighter the turn the higher the berm needs to be if any significant speed is to be maintained. Building high berms also doesn’t appeal to me because of both the amount of work involved and I just don’t love the aesthetic of high berms. To me they don’t look “natural.”

I was pretty puzzled as to what to do. Actually, that’s an understatement. I was friggin’ stumped. I just hated the idea of lots of switchbacks, didn’t really like the idea of high berms, and knew that climbing turns wouldn’t really work on my 20% grade. WTF am I supposed to do?! Eventually, after rereading about all of the types of turns in IMBA’s Trail Solutions book and racking my own brain, I decided to take my conundrum to my fellow mountain bikers and trail builders in the mtbr trail building forum.

As is the case with virtually any forum post, there were lots of responses that didn’t really help. A couple of people mentioned “omega” turns, which is essentially an insloped turn with grade reversals before and after to provide drainage and therefore minimize erosion damage. This approach is very well illustrated in IMBA’s Trail Solutions book, as is shown here.


insloped turn

 


 

However, since I’d already read the book, that by itself didn’t seem particularly revelatory. But there were two responses that were brilliantly insightful:

“The Omega shape leads riders into a more correct riding form of counter-steering before the turn to make a more consistent radius. … Keep in mind these berms don’t have to be steep-walled BMX/Dual slalom type berms. Think of something more like the tilt of roulette wheel. All you really need is reverse the standard outslope of the tread into an inslope to make the turn more effective in both directions.”

“You can mitigate the shortcomings/limits of bermed turns to a degree by flattening them out. Dig the upper leg back into the hillside and use the spoils to build up the lower leg.”

For the life of me, whenever I thought of bermed turns I thought of high berms, and they don’t need to be high (of course, in hindsight). I like the term insloped term better than bermed turn since it doesn’t cause the the same mental block for me. Likewise, the second quote was equally helpful. Even though the turns may seem too steep right now, when it comes time to bench the trail tread I can always go a little deeper on the uphill side and build up the downhill side to reduce the grade in the center of the turn.

Gotta love an epiphany. Multiple brains really are better than one. At least my one. 🙂

{ 0 comments… add one }

Leave a Comment