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Old 09-13-07, 05:06 AM   #1
joe99
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Is it possible to ride up 45 deg slope?

Is it theoretically possible to ride up a 45 degree slope (without relying on momentum)?

Assuming a coefficient of friction of 1.0, it would require virtually all the weight to be on the driven wheel so that the front wheel would be on the verge of lifting off the ground. Does this mean it would be impossible to apply any torque to the back wheel to actually move the bike without back flipping?

Regardless of what any theories might suggest, has anybody actually done it?

I recall many years ago a car show where a Land Rover was driven up a 45 degree ramp to demonstrate its hill climbing ability so maybe it is possible. (The ramp was probably made of expanded metal or something similar so the coefficient of friction could have been greater than 1)
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Old 09-13-07, 05:43 AM   #2
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As long as the CG of the bike and rider is ahead of the rear axle, yes. Just be careful when you are starting. It's the acceleration of the bike that will impart an additional torque adequate to flip it over backwards.
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Old 09-13-07, 11:32 AM   #3
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Possible, yes...but at 45 degrees, it'll be faster if I carry my bike than have my bike carry me.
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Old 09-13-07, 11:50 AM   #4
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Would you count this. . .?

http://vids.myspace.com/index.cfm?fu...deoid=15272932

(Not my video, sorry about the quality. . .)

I went 'round three times on a single rider version at the Tech Museum in Silicon Valley. That was quite enough. As I told the folks operating it, "This like a bicyclist's bad dream . . . !"
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Old 09-13-07, 04:20 PM   #5
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you mean like these, only with pedal power?





They're stock dirtbikes with super-long custom made rears (duh) so they don't tip over 45+ degree inclines. I think some of them go 60+ degrees
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Old 09-13-07, 09:06 PM   #6
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Originally Posted by Zumba View Post
I've gone up 90 degree slopes. 45 is nothing.
Un huh.
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Old 09-13-07, 09:34 PM   #7
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yes i have before there is a hill near my house that is rated at somewhere around 40-60 degrees, I have done it before on a road bike no less.

you have to lean most of your weight over your handle bars and pray your rear doesnt break loose if you are clipped in. most sane people either zig zag back and forth up that kind of incline or hop off and walk.
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Old 09-13-07, 09:39 PM   #8
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That franken-motorbike is the right idea. As one poster said, center of mass ahead of center of rotation. And the COR is the point where the rear tire touches the ground; the point you rotate around as you flip over backwards. At 90 degrees you would need a trike and a built-in winch. Thats' hoisting, not riding.
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Old 09-13-07, 09:49 PM   #9
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Originally Posted by joe99 View Post
Is it theoretically possible to ride up a 45 degree slope (without relying on momentum)?

Assuming a coefficient of friction of 1.0, it would require virtually all the weight to be on the driven wheel so that the front wheel would be on the verge of lifting off the ground. Does this mean it would be impossible to apply any torque to the back wheel to actually move the bike without back flipping?
I suggest you do a calculation like the one in another thread in this forum to see what kind of power that would require at a reasonable speed, say 5 mph ~= 2 m/s.

Of course, it doesn't really address your question of tipping over versus staying upright, but I figure it would take the typical 75 kg (165 pound) rider about 1000 W on top of what he usually puts out while riding at that speed.

So I think the answer is that to sustain that rate of ascent, you have to really dial it up.

Last edited by njm; 09-13-07 at 09:55 PM. Reason: remove RyanF homage
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Old 09-16-07, 03:27 PM   #10
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yes i have before there is a hill near my house that is rated at somewhere around 40-60 degrees, I have done it before on a road bike no less.
Are you sure it isn't 40%-60% grade instead? That would make a lot more sense. 60% grade is just over 30 degrees.
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Old 09-16-07, 03:52 PM   #11
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You need a bike like this one used on the Fargo Street Hill Climb. Of course, that's "only" a 33% grade (45 degrees would be a 100% grade). Check out the 60+ tooth cog in the back, and tiny chainring. Gotta spin up the hill with this one!

Other riders used a tandem with one rider to get the long wheelbase.

It would be hard to balance on a 100% slope, since you would have to ride very slowly.

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Old 09-16-07, 05:35 PM   #12
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Un huh.
With the slope rotated 90 degrees.
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Old 09-16-07, 06:34 PM   #13
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It's obviously a joke. 90 degrees FROM THE VERTICAL.
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Old 09-16-07, 07:06 PM   #14
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I think many of you are confusing percent-grade with degrees of slope. A 45-degree slope is a 100% grade, which is almost ridiculously steep - even the most steeply pitched roofs are seldom 45 degrees. A 45-degree slope is one in which you would probably not be able to arrest yourself if you fell off the bike - you'd simply tumble down the grade. 100% grade slopes are for mountain climbers with ropes and carbiners.

At about 20% grade, most riders start to have serious difficulty on anything but the briefest grades. I don't know about theoretical issues of CG and traction, but riding up a 100% grade for any length of time is out of the question.

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Old 09-17-07, 06:43 AM   #15
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I know of a road that goes up a hill into a developement,and if it's not 45deg,it's pretty darn close. Not fun to climb,but doable.
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Old 09-17-07, 02:57 PM   #16
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Are you sure it isn't 40%-60% grade instead? That would make a lot more sense. 60% grade is just over 30 degrees.
Considering the steepest street in the world is at a 35% grade (19 degrees), I think it's safe to say that there is no paved road that's anywhere close to 30 degrees.
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Old 09-17-07, 03:07 PM   #17
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I think many of you are confusing percent-grade with degrees of slope. A 45-degree slope is a 100% grade, which is almost ridiculously steep - even the most steeply pitched roofs are seldom 45 degrees. A 45-degree slope is one in which you would probably not be able to arrest yourself if you fell off the bike - you'd simply tumble down the grade. 100% grade slopes are for mountain climbers with ropes and carbiners.
I'll agree that a 45-degree slope is heart-stopping steep... I've skied a couple pitches like that, and trust me, it is frightening to look down an extended grade like that. Falling is definitely a really, really bad idea, as you won't stop.

Hiking up a steep grade like that... It would depend on what's underfoot. Tuckerman and Huntingon Ravine (on Mt. Washington in New Hampshire) are that steep, and people hike them all the time without protection. Then again, both have thousands of big footholds. If there are lots of trees and vegetation to hold onto -- you're fairly safe. If it's an exposed granite boulder that you're trying to walk up -- get a rope.
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Old 09-17-07, 06:10 PM   #18
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i realy want to mesure some hills in columbia

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Old 09-17-07, 06:12 PM   #19
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I dont see how everyone is freaking out about WALKING up 45 degree slopes, thats crazy, maybe you are all a bunch of old fogies
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Old 09-18-07, 07:24 PM   #20
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I dont see how everyone is freaking out about WALKING up 45 degree slopes, thats crazy, maybe you are all a bunch of old fogies
45 degree is like... triple black diamond in terms of difficulty for a ski slope... Black diamond goes up to 40 degrees. Now if you go over 40 degrees that falls in the category of extreme skiing.

45 slope, probably I'd tie a safety rope to myself when walking down or up it.
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Old 09-19-07, 06:08 AM   #21
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Im not a skier. But i mean there is equal vertical and horizontal movement in a 45 degree slope. Its not that huge a deal.
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Old 09-19-07, 07:16 AM   #22
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Im not a skier. But i mean there is equal vertical and horizontal movement in a 45 degree slope. Its not that huge a deal.
Cool, so you can show us where that 45 degree slope that you climb is, using Google Maps?
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Old 09-19-07, 07:22 AM   #23
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You made my knees hurt.

That's pretty cool though. I wanna do it!

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Old 09-22-07, 04:45 PM   #24
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For practical purposes, the force you can exert on a pedal is not too much over your weight, which limits the amount of torgue you can generate in the pedals. Depending on your gearing, you could simply not have enough force in the pedals to move forward. (Envision doing this on a coaster-style bike). This could be overcome by by using different gearing from the norm. So you get into the question of "could it be done" versus "could I do it on my bike".

Similarly, with the problems with angles and weight shift- you COULD build or modify a frame specifically for this purpose, but whether an off-the-shelf bike would work is a different issue.

I was looking at some videos of the world's steepest roads that I found on here. I noticed on one, that when the guy went up it, he had to zigzag back and forth to do so.

As to the 45 degree slope in general... Any slope looks a lot steeper after you get on it than before. If you have a fairly smooth surface at a 45 degree slope, you could quite likely walk up it. But, one slip, and you're into an uncontrolled fall. You hear about mountain climbers and hikers "falling" and never "sliding/tumbling down a steep slope". That's because when they slide and tumble down a steep slope, it's simply counted as a fall. They do make special sticky climbing shoes that would help walk up this kind of slope.

One other point. A bicycle increases efficiency over walking by letting you go farther with the same amount of effort. On a very steep slope, practically all of that effort just goes into raising the weight, and that's true whether riding or walking. So even if you can ride up, it's not necessarily any faster than walking up (plus, you have to move your bike up the slope, too). Of course, coming back down is a good bit faster. I used to hike up a very steep access road near my house in Colorado, and on occasion, I have walked past mountain bikers who were pedaling up.
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Old 09-22-07, 07:25 PM   #25
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Im not saying that i ride any 45 degree roads, im saying i would like some perspective.
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