Wednesday, May 26, 2010

Like the Daring Young Man on the Flying Trapeze

I love my new mountain bike. A 29’er with 4-5 inches of travel rides like a combination hot rod, monster truck and barcalounger. I did things on it tonight at Patapsco I have never done before, like getting dropped on uphills (done *that* before) but then catching back onto the train on medium technical downhills (*that* is the thing I’ve never done before).

She – the Salsa Big Momma with my special heavy duty fatboy Clydesdale build – is a sweet sweet ride. But I just don’t know her ways yet and it's scary sometimes.

That fact was in the back of my mind the whole ride but it really hit me as I was levitating about 4 feet up in the air over the bike. As I sailed along Superman-style, hands on the bars, full layout and parallel to the ground (but perpendicular to my direction of travel), I noticed that some things were flapping in the breeze. Those things were my legs, my testicles, and possibly my ass hairs. How they got there and what is says about how to ride a fully sprung bike is sort of interesting, in an 'at least interesting to me and maybe three other people' sort of way.

I arrived late and was supposed to meet Sven & crew down by the creek crossing below the field coming off Landing Road. They were going to hit Not Your Momma, which is my favorite technical trail *in the world,* not that I know many other than a few around here and a few in upstate NY, but I love it because it has about 45 logs that trouble a rider in the space of 10 minutes. So I missed Yo Momma but hustled to meet the crew, and bombed down the rutted path through the field north of Yo Momma, amazed to be floating along. It was frickin’ sweet not to have to worry about hidden 2"-3” dropoffs that would cause major instability on the hardtail. I just picked any semi-reasonable line and bombed along, not a care in the world. Picking a line was more about tire traction, and less about worrying whether a bump would throw me into the weeds. Sooo awesome.

I carried speed, and confidence, into the woods toward the creek crossing. It’s an interesting crossing because the rider has a choice between a 4’ drop, and a more gradual rutted 18” drop. Just for the hell of it, I chose the big one I've never ridden before.

Baaaaad mistake.

I was going sort of slow and made it off the drop pretty level, so when I landed it was square, in a downward direction. (Full boinger riders, you can skip the next part since you know what happens next).

We hit the ground pretty smoothly, and the suspension did its work, stopping the jolt. I did my work too, bending my knees as if on the hardtail, to absorb the jolt. Together, we weathered the drop.

That’s when things got absolutely bugshit crazy. The suspension – front and rear air units pumped up to “hard riding Clydesdale pressure” was not bottomed out (no “clack”) but it was fully loaded at this point. The rear shock linkage ratio – a Clydesdale friendly 2.2 or so which worked to my advantage on the downward motion because it allows the shock to be set in its midrange rather than jacked up to 400 PSI – the sweet linkage all of a sudden decided to work against me in an equal and opposite direction. Not cool.

Right as my legs bottomed out, the machine started upward. *Hard*.

Now I’ve never ridden a rodeo bull, but a couple buddies of mine were pro bull riders, and I don’t think I ever saw one of their bulls shoot upwards quite as fast as this bike ascended toward the heavens. Why, it acted as if I wasn’t even there – which I wasn’t, after about a tenth of a second.

The bike threw me skyward so hard that I didn’t have a chance to react. In fact, I was still clipped in when it happened, so 29 pounds of scandium love imitated a moon shot and rocketed upwards, with the astronaut hanging on for dear life.

Somewhere near the apex of our journey, my legs came unattached from the bike. I don’t know if it was mountain biking reflex, or if the bike threw me, or if some component or piece of apparel like my nice shorts or cruddy mountain shoes decided that it didn’t want to be a part of the landing of this historic flight. Whatever happened, I was quickly in the air, holding onto the handlebars.

Holding onto the handlebars perhaps 4 feet off the ground, unclipped, perpendicular to the bike, in a layout position.

As the bike and I traveled through an arc, we determined that one of us needed to make a decision and take action to help the two of us land. The bike decided that I would be the one to do that so I started flailing my legs a bit.

Somewhere along the downward trajectory, I managed to bash my left thigh on something, giving me a bad Charlie horse that lasted the remainder of the ride.

But then suddenly, I was standing on the ground dismounted, to the left of the bike, and only slightly hurt and slightly bent over the top tube. It was a pretty hard landing but I didn’t crash, so at least I have that going for me, which is nice.

After that I stood there for about two minutes wondering what in the holy hell just happened to me.

I figured out that there must be something about landing a jump on these springy bikes that you have to do differently from landing a hardtail, but I wasn’t sure what it was.

Most of the rest of the ride was spent cramping, and trying to keep up with Sven and the crew. Sven and Mel hosted, the Northern Contingent of the Family Bikes Shop Ride was present and accounted for, and another one or two of the Ellicott City / Elkridge locals joined us. It was pretty sweet.

Considering that I’m fat, unfit, and my technical skills need work, the ride was awesome. Your May was my January so this is right where I’d expect to be after the long layoff and the slow ramp back to vigorous riding. So all is well in the world and if things work to plan and the back holds, I’ll be half fit about midway through cross season. The main thing was I was riding with some friends and cramps and fat and tired be damned, it was fun. More fun than I can say.

After the ride, it took a couple hours to figure out what had happened to me and the rig at the creek crossing. The rig… It seems the rig is trying to teach me some things. Moving from hardtail to full suspension is a big, big change if you haven’t ridden a boinger before – and I haven’t. A 4” travel 29’er is an especially huge leap; it feels like a long travel motocross bike, except this one steers a bit slower.

It’s hard to articulate exactly what the boinger does differently from a hardtail, which isn’t a surprise. I’ve known many skillful riders but comparatively few who can articulate what a bike is doing under them and how to handle it in different ways. (Sven is one of those people who can articulate it, BTW).

So I’ll try and hope you forgive me if I fail here.

On a hardtail, when you go off a drop, your legs have to provide 100% of the suspension. You get in the habit of riding it as soft as possible. You go off the drop, and your legs compress to the maximum point, because the more flex you do, the more of the shock is dampened because you're dissipating it more gradually, over say 12" of leg flex versus 3". That's pretty easy to understand - you're dissipating the same total force over greater distance, so the force you're exerting at any one point in the landing is reduced.

On a boinger, the bike does a lot of the work. You still want to use your legs though because it’s easier on you and the bike to cushion the force of impact still further. The boinger, *however,* is going to bounce back some at the bottom of the suspension stroke. If you have just taken a huge hit – and you do the math on 280 lbs dropping 4 feet – the suspension has to rebound hard. The problem is that no suspension can completely eat up the force of that impact; you’d need to have sick, sick rebound damping to slow the bounce from that, and if your rebound damping was that heavy the shock would be useless for general trail riding, since it couldn’t bounce back fast enough between little bumps. (I’ll spare you the talk about high and low speed rebound damping, and various valving setups that that I know about from motorcycling that can improve but not eradicate this).

The bottom line is that you’d better not use all your legs’ spring when you hit the ground on a boinger, because that shock is going to bite you back, and while you can easily absorb the kick if you’re prepared, you’ll get thrown if you aren’t.

So I think what happened to me was that I did the usual hardtail thing and had no spring left in my legs when the rig kicked back; I was too low to have any “travel” left in my legs. My leg-based suspension system was bottomed out. Since I couldn’t absorb the bike-moving-upward momentum, both the bike and I took a big, big hop straight up into the air.

How or why I got off and landed safely is beyond me and basically irrelevant; what matters is the lesson learned. And the lesson is to keep the legs flexed but stiffer on the downstroke with a boinger, because what bike goes down must come up, often with vengeance.

You know, I think I like her more because she's a little bit nutty sometimes.

9 comments:

Anonymous said...

Being that you have stated this as an equation you could dial back the 280 lbs of mass and probably solve the whole issue. Crying laughing by the way - good post.

Jim said...

Yeah, true, but being who I am - an endomorphic contact sports athlete mismatched to a fairly high natural VO2 & hematocrit - I will only be able to dial it back so far. Working on the lardass portion of it, that's coming along better, y'know, now that my back is letting me ride 5 times a week. We'll hopefully find out what the weight floor is sometime this year but I'm pretty certain it'll be in the 210-215 range. In the past - the somewhat distant past now - I've been there and I look like a chihuahua, and shiver like one too if the temp drops below 70.

So that'll help, but it's not going to solve the problem on a system that is optimized for a 160 pound rider.

Chuck Wagon said...

You're in the zone. Must feel great after the sh*t you had to shovel all winter. Enjoy

TerribleTerry said...

Yes, I certainly love reading about you crashing more than about you hobbling around. If I were you I'd stay healthy more often.

See....crashing is good for your health.

Jim said...

Hell boys, I didn't crash. That's the weird and wonderful thing about this. I just... dismounted in an unusual and slightly bruising manner, landing on my feet. I that's called a "getoff."

Seems to me I need to do a blog post discussing all the different ways to crash.

shea said...

Made my morning.

Anonymous said...

dude,

hot tip for you. its called rebound damping. when you add mass air pressure to hold your porcine carcass up, it turns your shock into a pogo stick. go to a slower rebound setting.

i probably just saved your life.

Jim said...

I'm not unaware of rebound damping. It's set fine for the small stuff but obviously needs to be cranked up a little to handle the bigger stuff.

The real lesson though is that I need to stop riding like a moron.

Michael Bauman said...

"I’m fat, unfit, and my technical skills need work"

At last, after all these years of searching, my twin!