Longitudinal tining of portland cement paving surfaces reduces (auto) tire-surface noise. The grooves that lie parallel to the direction of travel provide a space to absorb some of the sound waves that tires produce. Different depths and widths of grooved pavement depend on the engineering goals and application techniques. Regardless of the condition of the new road surface, erosional forces over time cause some grooves to degrade and widen.
Erosional products, remnants of winter ice removal operations, and an endless array of glass and other large sharp-edged debris wash across the grooved pavement and collect at the sides of the roadways.
Where cyclists ride.
No bike tire is immune to large rocks, chunks of broken glass, storm drains, and what-have-you at the edges of the roadway. It's not just flatting that's dangerous, it's also hitting something big and going over the bars. Or skidding out on gravel. Anything that forcefully impacts the direction and momentum of the bike is potentially very dangerous.
My road bike tires are 25mm wide, and I typically run them at 100 psi. My tires are wider than most pavement grooves, but narrower than many expansion cracks and badly eroded grooves. Local cycling folklore is filled with grisly tales of cyclists whose front tire got caught in a crack at high speed. Outcomes usually involve emergency medical care.
I regularly ride a descent that features grooved pavement on the roadway, a generous layer of loose gravel in the bike lane, and strong crosswinds. I'm light enough that strong crosswinds can make my bike skitter around. The descent is neither long nor terrifying, but it is fast, and it makes me extremely uncomfortable. I am afraid of it.
And I'm never sure how to ride it.
Do I ride on the grooves in the roadway and count on their structural integrity and the patience of infrequent drivers?
Do I ride in the bike lane and risk losing control of the bike on the copious gravel?
Do I thread the narrow strip of roadway where the grooves end and the layer of gravel is thinner?
It's been over a year since the last time I flung myself to the ground, and I'm still recovering. Physically and emotionally. And that was actually a pretty minor crash at relatively low speed. No amount physical therapy has managed to purge my fear of crashing. None of the bleeding washed it completely away.
It lives on inside my head. It's what makes me tense up and protect my drops when riders I don't trust get too close. It's why I work and work and work on bike handling skills even though I'm fairly competent. It's what braces me to hold my line and take the hit when objects like water bottles and rocks hurl towards me. It's why descents make me afraid. This one in particular. The cornering on gravel reminds me of that crash, except much, much faster.
So I ride down it differently each time in an effort to figure out how to ride it well and to purge this fear.
The very first time, my goal was just to get to the bottom alive. Slow and calm. Feather the brakes. Check the speed. Breathe... Breathe... Shit! Gravel everywhere! Too fast! Brake gently...gently... Breathe... Fucking sand all over the corner! Glass shards! Jesus.... Don't start crying... Whatever you do, do not cry...
In the six months since then, I've probably descended it fifteen, maybe twenty times. I've been working on figuring out the lines, adjusting for the winds, and above all, relaxing. I know in my head that it's actually safer if I just relax and let the bike go.
So I've tried. Over and over. And over.
I deliberately kept my fingers off my brake levers for increasing distances. I've forced myself to look out farther ahead of the bike and ignore the small debris under my wheels. I've watched larger friends fly down at 50+ miles per hour and then slow politely for me on the other side. I mention this because I am afraid of speed and I marvel at their courage/insanity.
One ride a few weeks ago, I stayed off the brakes for most of the descent. I lightly slowed when I emerged from a sheltering hillside into winds that made my bike wobble. And again before that gravel on the corner by the bridge.
When I caught back up, I bragged about almost making it without brakes. For me, this was huge.
Last week I finally did it. My line was surgically precise right between the thickest gravel and the grooves. My body perched perfectly to both weight the rear tire and weight the front just enough for good control. My hands were in the drops. I was totally steady. My fingers stayed off the levers. And I relaxed! When the wind hit me, I stayed still. Utterly calm at nearly 40 miles per hour. I looked far out ahead and let the bike flow where my eyes took it.
It felt like flying. It felt like peace. It felt like I really could do ALL the things I fear.
It felt so good that I nearly wept when it was over.
But I'm afraid of crying in public.