Friday, August 27, 2010

Descending, time to get serious.

I wrote this article for a friend of mine who can climb way faster than me, but keeps getting dropped on descents.  That's a crappy way to lose a race.

Overview:  The entire outcome of a turn will be decided before the turn is initiated.  Your entry point and entry speed into the corner determine if you'll make it through, and how fast that will happen.  Everything depends on setting up the turn correctly.  The second half of a perfect turn is bliss, because all the work has been done, and you just get to ride it out in triumph.

Brake Adjustment:  Make sure that your brakes are centered so that both pads hit the rim at the same time.  Also make sure that the cable tension is such that you can almost make the brake lever touch the handlebar when you're squeezing as hard as you can.  Your hands can apply less force when they're extended, and more force when they're almost closed.  This ensures that you have the most braking power available.  Lots of people (and bike shops) like to make brakes super tight, but then all of the braking action happens when your fingers are extended, and relatively weaker than if they were closed a bit.

Braking:  Try to do 95% of your braking before the turn even starts, and use mainly your front brake.  Always be in the drops, stay low, and shift your weight  as far back as you can while braking.  When you hit your brakes, your center of gravity shifts forward, putting much more weight on the front wheel than on the back.  The extreme of this is the endo, when your back wheel lifts up and you go flying over the handlebars.  If you're low in the drops and have your weight shifted backwards, this will never happen on a road bike unless you hit something like a curb or another cyclist, or are going down a VERY steep hill.  What this weight shift DOES do, however, is take a lot of weight off your rear wheel, giving it significantly less traction.  This will cause it to skid with much less applied brake than it would take to lose traction on the front.  The fastest possible stop that could happen is when you hit the front brake so hard that your rear wheel is just about to lift off the ground.  In this scenario your rear brake is completely useless.  In real life, we don't do this, but mentally know that your front brake is doing almost all of the work, and squeeze it accordingly.  Just feather the rear brake as necessary.

If your rear wheel starts to skid, it your bike will try to swing around you, sometimes called fishtailing.  If this happens, you need to let go of the rear brake completely, and the front brake partially, until you regain control.  Then fully squeeze the front again and be cautious with the rear.  Your momentum wants you to keep going forward.  Since your front wheel is providing most of the stopping power, all of the mass behind the front wheel (you) will have a tendency to want to pivot around so that it can keep moving forward.  Your rear wheel keeps this from happening, but not when it's skidding.

The first thing we're going to practice is hitting the brakes SUPER hard while riding down the hill in a straight line.  The goal of this is to understand what maximum braking feels like.  The goal again is to apply as much front brake as possible, and some rear brake, but not enough to make it skid out.  While practicing, you may lock up your rear wheel to get the feel for what it takes, and how to control the bike while it’s happening, but that’s not the goal when actually descending.

Brake sharply before the turn, then apply minimal brakes through the turn to keep from accelerating due to the hill.  Your speed should be slowest at the beginning of the turn, and you should accelerate or maintain that speed throughout.   If you find your self needing to decrease your speed during the turn, you entered too fast.  There is a concept in auto racing called the Traction Circle.  A tire can only apply so much force to the road before it starts to skid.   A tire is just smooth rubber, so it doesn't know which direction the force is being applied.  The end result is that a tire can apply maximum traction in the forward direction while braking in a straight line, or maximum traction in a sideways direction while turning, or some non-maximal combination of the two.  As a result, the theoretically quickest way through a turn is to apply maximum brakes in a straight line, then turn as sharp as possible without braking through the turn, and coast or accelerate out of it.  Our task is complicated just a bit if the turn is on a downhill section, so what we'll do is slightly different.  You can continue to brake through the turn, but only enough to maintain the proper speed.  You should do all your slowing down before you turn in.

Again, momentum wants us to keep moving forward in a straight line.  If you apply too much brake during a turn, you may lose traction, but more likely is that your bike is going to want to straighten out, and push you into a wider turn than you had anticipated.  This can cause you to cross the yellow line, or even ride off the road.  It's a really weird feeling, and it sucks.  Don't brake hard while turning.

Choosing a Line:  If making a right turn, you should start on the left side of the road, dive in and just brush the white line in the very center of the turn, and drift out to the yellow line on the left side as you exit the turn.  The sideways force required to change direction is directly related to how sharp of a turn you're trying to make.  The purpose of choosing a good line is to make the turn as wide as possible, this requiring the least amount of force and allowing you to get through it as fast as possible.  The point on the inside of the turn, halfway through, is called the apex.  You should aim for this point when turning in to a corner.  If the turn gets progressively sharper, you need to do something called a "late apex,"  where you choose your target point deeper into the turn.  Conversely, if it starts sharp, and then gets wider, you can apex earlier for maximum speed.  Not really important right now, but worth thinking about.

This is the best line through  a 90 degree turn

Learn when to initiate a turn:  Practice diving into corners at different points.  If you turn in too early you’ll reach the inside of the road before the apex.  If you turn in too late, you’ll never reach the apex and you’ll be forced to the outside.  Both of these will result in you having to take the turn slower than you could.  Knowing when to turn in is very specific to the conditions of the turn, but knowing the consequences of turning in too early or late will allow you to learn as you go.  If done correctly, just as you reach the apex of the turn, the road will open up in front of you, allowing you room to drift back to the outside edge without any abrupt braking or turning.

Look Ahead, where you want to go.  Don’t look at your front wheel or directly in front of it.  Your balance and the balance of your bike are important to cornering smoothly.  Your head controls your balance, so point it where you want to go.  Staring at your front wheel will make you very twitchy, and can lead to dizziness and vertigo.  Not good things when you’re trying to control your line at speed.

Weight Balance:  During the turn, keep your weight low and a bit forward compared to normal riding. Stay in the drops, and sit near the front of your saddle, or hover just over it.  Keep your pedals horizontal, and your knees bent.   Our bikes are designed to put more weight on the rear wheel than the front. This makes them more stable for normal riding, but for descending, you want to weight both wheels as evenly as possible.  This means you need to shift your weight forward a bit.  I've heard that you're supposed to drop the outside pedal, and put all of your weight on it, but keeping the pedals even allows you to use your legs to absorb bumps in the road, which I'm a big fan of.

Countersteering:  Know that it exists but don’t worry about it.  Countersteering is the subject of much debate on the internet and otherwise.  It is a physical truth but you don’t really have to think much about it.  The idea is that in order to make a right turn, for example, you must first turn to the left a bit.  Try this:  As you’re riding down a wide, straight, safe road, push your palm forward against the right handlebar.  The bike will twitch to the left, but you’ll end up turning right to keep your balance.  That’s all you need to understand.  While cornering at speed, don’t think about your handlebars turning at all, just look where you want to go, lean, and your bike will follow.

Flat Cornering:   A lot of this stuff isn't applicable to crits.  With crits, I think it's more about pedaling as much as possible than it is about coasting through turns with the right line.  I'm not good at crit cornering, so I'll stop here.

What we're going to do is this:  Once you find out how hard you can slam on the brakes while going straight, we'll start cornering.  You'll approach the corner, hit the brakes, glance at your speed, follow the correct line through the corner, and glance at your speed on the way out.  You will then progressively build speed by repeating the corner over and over.  As you get more familiar, you can brake harder and later, and also carry more speed through the corner.  Lookout has 12 corners that require braking:  Starting from the top:  2 right hand turns that can be taken at 30mph.  The first set of switchbacks can be taken at 25, as can the second set of switchbacks.   There are 2 left turns near the bottom that can be taken at 30 and 35 mph respectively, and then the final left which you can take at 25 or so.  Obviously you can't memorize every turn in every race, but you can get a feel for how fast you can take a corner by looking at it.  By training yourself to eek every bit of speed out of the corners that you’re familiar with, you’ll gain confidence to solidly descend on corners you’re less familiar with.  If a race has many laps like the one at steamboat, you should get progressively faster on each descent as you learn where to turn in to each corner, and how fast you can afford to take it.