Thursday, May 30, 2013

Science of Flow (non-Newtonian)

I love to complain about trail flow.

In fact, it's one of my favorite things to talk about, especially while riding.  If you ever went riding with me, by the third time I yelled" Ughhh decreasing radius blind corner what the fuck!", you'd have already turned around to ride it uphill instead, figuring that would be much more pleasant.

As an amateur trail builder and enthusiast, I feel like I have a small right to complain.  I've built a small bit of good trail, a fair amount of mediocre trail, and some trail so bad that we had to fix it before anyone else saw what we had done.  I guess I've never been able to learn any other way, but it sure works quickly.  So in other words, I'm an expert in what bad trail looks like.

All mountain bikers can feel the difference between good and bad trail.  But is a slightly awkward corner really worth complaining about?  You're still out in the fresh air, on your bike, and no one's telling you what to do.  You have to appreciate the time someone took to build it.  The weeks that someone took to build it.  It's because we stand on the shoulders of inventive, motivated giants, that we can see the finer points of trail building so well now- both in the negative examples, and the plethora of beautiful, so subtly-executed trails.  The real problem with bad trails is not a rider's enjoyment but the durability of the tread.  Anytime you have hard braking, cornering, and descending at the same time, the tread will blow out quickly.  That's my motto: It sucks to brake hard, corner, and descend at the same time.  Now Keith Bontrager will be quoted on the Internet for the 7-billionth time: "Pick two." (Since less than half of the world has Internet access this is probably at least the second time I've done so)

But the magic of a great trail is worth striving for.  And for the record, I'm not talking about the pump-track type of trail in which no corner goes un-burmed.  There's a place for that kind of trail, and I'm always impressed by the ambition and engineering cred of the builders and the skill of the riders.  But for most mountain bikers, where shared use is a reality and maintaining a wilderness feel and a safer appearance keeps the trails open, this isn't realistic.  A simpler trail doesn't have to come at the expense of flow and challenge.  It's those very trails that use nothing more than a ribbon of singletrack, with just enough grade reversal before the corners, crossing over roots and rocks that are just barely rideable, corners just tight enough that it's very hard to ride fast but doesn't suck to ride slow that are truly great trails.  These are the trails that I'm in love with.

Like everything else, I learned the hard way about tread width- at first it feels right to dig that nice deep backslope, make absolutely sure there's no false toe, and to inslope all the corners.  But wide trails are fast trails and managing speed is the hardest thing about trail building. They're also ugly trails-not only is there a lot of dirt showing, but twice as much (or more) left over dirt to be dispersed.  A high-use trail that crosses or turns on a very steep hillside needs some width.  But for every other situation, let's have narrow. Turns out it takes half the time to build them, too.

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Lately I find myself much less critical of trails.  In fact it's been at least 4 rides since the last time I cursed a corner halfway through.  I would like to believe that it's an indication that I'm much more at peace with the world (I mean, this world, Earth), or my existence in it, or even that the anti-anxiety herbs are working and sleep makes me that much more pleasant of a person.  But I've looked over the evidence again and again and there's only one answer:

I put real tires and a well-damped 120mm fork on my bike.

When I started mountain biking I realized immediately that a five inch fork and some knobby-ass 2.3's turned awkward or sketchy into just fun.  I used to tease my dad (who to my knowledge never has used an index shifter) that not only did my bike have index shifting but also indexed-rolling tires.  I proudly rocked (as opposed to ran) a 200 dollar fork on a bike I paid $380 for, new. Later I developed this road racing problem and all my mtb tires got lighter and faster, and my forks got shorter, even to the point of riding a '99 SID (which that they never should have put disc tabs on, that was just scary). I went tubeless and kept dropping my pressure to try to squeeze a little actual traction out of the fast rolling tires (Michelin Dry2 was the rockbottom equivalent of the SID).

Anyways, a few weeks ago I put 2.4 Conti Mountain King black chili Protections on front and rear.  They fit great on my 26" Anthem.  They actually hook up better at 30-35 psi because the knobs bite so much they need support.  I ride in loose country--Missoula, MT--and an open tread pattern with real knobs is the only thing that hooks up.  Sure, better riders can milk a lot of speed out of some startlingly bald tires, and I'm probably not night-and-day faster than I used to be, but there is a massive difference in the level of control at high speed and the ability to use your brakes.  Magnum rubber = more fun, more control, less trail damage.  Plus, it's a great excuse to be the last up the hill! 

Soon: can you guess what this means?


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