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-   -   The science of going downhill? (https://www.bikeforums.net/singlespeed-fixed-gear/326907-science-going-downhill.html)

cc700 07-30-07 12:28 PM

yeah. i use brakes. that doesn't mean it's easy to spin though.

the point of oh **** is the point at which the momentum of the bike combined with gravity are exherting more of a force than your backpeddling muscles can with fine motor function and you have to use power to slow your spin.

it's not really a physics thing it's a psycological/chemistry/biology thing. and it all goes away with a nice brake.

peabodypride 07-30-07 12:50 PM


Originally Posted by teddycarfolite (Post 4963505)
Shaloming... is this an anti-semtic spin on the word Slalom. Poor Einstein escaped the Nazis but couldn't escape BFSSFG

Facking LOLD. I knew I spelled "slaloming" wrong... got that show "Shalom in the home" stuck in my head.

:D:D:D

filtersweep 07-30-07 12:55 PM

You can only stop in 20ft if you creep downhill--- even on a roadbike with two brakes, it is impossible to stop in 20ft at 50+ km/h. You cannot stop in a car in 20ft. You probably cannot stop in a run in 20ft.... unless, in all cases, you are moving at very slow speeds.

akaio 07-30-07 01:01 PM


Originally Posted by 9Rings (Post 4963527)
Oh Sh** moment= (Grade of incline x effective gear inches / strength of rider's quads)^amount of cross traffic at next intersection

Haha. Sounds about right. Though it hard to put a mathematical figure for the strength of the riders legs and the amount of cross traffic :)

Another factor you must take into consideration is traction. Not all tires are the same, and if the road is wet you prolly need to multiply your stopping distance. The only 'oh sh*t' moment I can recall with hills was due to me screwing around on a hill that was wet and skidding farther than I anticipated.

How does slaloming help in all reality? The only thing I can see it adding is the fact that you are no longer taking a straight path with your skid therefore and acttually sliding your tire over a longer path.

PS: I can only assume the technique being referred to above derives from slalmon skiiing. So to clear up any spelling issues heres the wiki entry: http://en.wikipedia.org/wiki/Slalom_skiing

teddycarfolite 07-30-07 02:23 PM


Originally Posted by Dumpsterlife (Post 4964156)
...you my friend are responsible for my new sig!

It's an honor.

powers2b 07-30-07 02:39 PM

My first and only moment came a couple weeks ago while descending a very long hill.
The speed didn't phase me as I just let my legs go 'gumby'.
What got me was the rather large "ramp", for lack of a better term, about 3/4 the way down that was formed by a buckle in the road.
By the time i noticed the buckle I had no time to decelerate and found myself airborn for what felt like several seconds.
With a frewheel this would not have been an issue but there is something unnerving about flying through the air with your legs spinning out of control. For starters unless you are spinning in a balanced fashion the subtle torque differences actually cause the bike to tilt (think gyroscope) while in mid-air.
I hit the ground at an angle with a small chirp of the rear tire and managed to regain composure without messing my pants.
I held the front brake as hard as possible the rest of the way down and managed to stop for the intersection at the bottom (50 meters).
Once the ticker migrated out of my throat I actually considered trying it again.

xsdg 07-30-07 06:53 PM


Originally Posted by powers2b (Post 4965345)
By the time i noticed the buckle I had no time to decelerate and found myself airborn for what felt like several seconds.
With a frewheel this would not have been an issue but there is something unnerving about flying through the air with your legs spinning out of control. For starters unless you are spinning in a balanced fashion the subtle torque differences actually cause the bike to tilt (think gyroscope) while in mid-air.
I hit the ground at an angle with a small chirp of the rear tire and managed to regain composure without messing my pants.

Yeah, I pretty much always stop my back wheel when it's airborne (including when bunny-hopping, generally). It's in part a mountain biking habit/reflex, but I like to have my pedals level so I can control the bike when I'm in the air.

bonechilling 07-30-07 07:24 PM

Can some please explain to me why some people continually insist that fixed gear riders should strive to NOT use a brake when one is available?

thequickfix 07-30-07 09:30 PM

Everyone knows that the size of one's genitalia is directly proportional to the gear inches of the bike, divided by the average number of times a braking device is used per mile.

This is why brakeless=indefinite balls.

levity 07-30-07 09:41 PM

indefinite? like "omg where are they"?

chinotex 07-30-07 09:47 PM


Originally Posted by abeabe (Post 4960969)
i guess its pretty important to know bail techniques too. learning how to safely drop a bike is pretty crucial especially for hill bombing.

My dad and I were fly fishing in the Guadalupe River one day, in the Texas Hill country. It was springtime, and there were cyclists everywhere. We are downstream of one of the river crossings (bridges), which was situated at the base of a big hill. We see some cyclists go over the crossing, VERY fast. Then we see a guy come down the hill, disappear out of our sight, and his bike flies over the guard rail into the river right in front of us. An ambulance arrived a few minutes later to gather him from the pavement.

He was hurt pretty bad, but if he had still been attached to his bike as it flew off the bridge, he would have been much worse off.

thequickfix 07-30-07 09:56 PM


Originally Posted by levity
indefinite? like "omg where are they"?

no, indefinite like "a value approaching infinity"


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