Forum
Buying gear? Please use these links to help 14ers.com:

More info...

Other ways to help...

Please stay on the trail.

FAQ and threads for those just starting to hike the Colorado 14ers.
User avatar
Posts: 2042
Joined: Thu Apr 12, 2007 11:57 am
Location: Here, Now

Re: Please stay on the trail.

Postby Dex » Mon Oct 01, 2012 7:57 am

Bean wrote:1. Only the case when a person is standing perfectly still, and their weight is being equally distributed across the surface of their soles evenly. Bike tires are inflated to roughly 30psi, in general. Just a SWAG based on looking at a pair of shoes next to me is that there's ~50 square inches of surface area (smooth bottomed running shoes). A hiking boot (as tends to be worn by anti-bike troglodytes) with a raised heel will be less, but close enough (I'll make up the difference in average hiker weight incl. gear). At 200lb all geared up, that's 2psi standing perfectly still, 4psi on one foot, and 50-100+ psi when stepping forward. Meanwhile, 30psi in a bike tire is 30psi. A fatbike can go as low as single-digit air pressure. Lesson learned from all this? We need the metric system because pascals are so much more intuitive to work with.



In your math aren't you missing a couple of points?

Surface area on the ground when in motion - bike tires constantly on the ground - feet no

Surface area affected - when going straight - bike tires in the same line - feet not

PSI - While the tires might be inflated to 30PSI - the PSI for bikes should be a factor of the weight of the bike, rider, equipment etc and the surface area of the tire track?

Interesting math problem, that.
Montani Semper Liberi
"Please use the comments to demonstrate your own ignorance, unfamiliarity with empirical data and lack of respect for scientific knowledge. Be sure to create straw men and argue against things I have neither said nor implied. If you could repeat previously discredited memes or steer the conversation into irrelevant, off topic discussions, it would be appreciated. Lastly, kindly forgo all civility in your discourse . . . you are, after all, anonymous." Barry Ritholtz

Re: Please stay on the trail.

Postby Bean » Mon Oct 01, 2012 8:13 am

Dex wrote:In your math aren't you missing a couple of points?

Surface area on the ground when in motion - bike tires constantly on the ground - feet no

Surface area affected - when going straight - bike tires in the same line - feet not

PSI - While the tires might be inflated to 30PSI - the PSI for bikes should be a factor of the weight of the bike, rider, equipment etc and the surface area of the tire track?

Interesting math problem, that.


I'm not sure what you're trying to say here. 30psi is 30psi is 30psi. The tire conforms to the surface. 30psi is a general number, some run mid-20s, some run mid-30s.
gdthomas wrote:Bean, you're an idiot.

http://throughpolarizedeyes.com

Re: Please stay on the trail.

Postby Bean » Mon Oct 01, 2012 8:17 am

tlongpine wrote:Looking at the trail on Elbert the real problem appears to poor trail engineering that encourages (and in many case probably forces) riders...

The trail exists without any consideration for mountain bikes - and rightly so, because of how few bikes are taken up there. Anyone thinking that bikes are the cause of that braiding isn't thinking about the numbers of bikes vs. hikers reasonably.
gdthomas wrote:Bean, you're an idiot.

http://throughpolarizedeyes.com

User avatar
Posts: 696
Joined: Mon Jan 10, 2011 8:47 pm
Location: Denver, Frisco, KC

Re: Please stay on the trail.

Postby tlongpine » Mon Oct 01, 2012 8:57 am

Bean wrote:
tlongpine wrote:Looking at the trail on Elbert the real problem appears to poor trail engineering that encourages (and in many case probably forces) riders...

The trail exists without any consideration for mountain bikes - and rightly so, because of how few bikes are taken up there. Anyone thinking that bikes are the cause of that braiding isn't thinking about the numbers of bikes vs. hikers reasonably.


Not rightly so. If the land managers are going to permit bikes in the area the most responsible thing to do is maintain trails that encourage the lowest impact usage possible. That only a few bikes are present on the trail is indeed a happy coincidence, but it doesn't resolve irresponsible land management and it doesn't address a latent harm in the status quo. Under the current trail conditions and usage permissions if biking usage levels were to change then the trail would deteriorate very quickly. Because, again, this trail is simply unsustainable given the current usages allowed.

But I agree with you that bikes probably aren't causing the current damage. This trail is engineered poorly for hikers too. Just by looking at the photos it's clear this is the kind of trail that collects and channels water and accelerates the kind of erosion that causes all types of users to break new trail.
I am unable to walk away from the mountain without climbing it. An unclimbed mountain tugs at my consciousness with the eternal weight of time itself. Until I've pressed my face into it's alpine winds, hugged it's ancient granite walls, and put it's weathered summit beneath my heal I'm unable to resist it's attraction.Knowing nature gives the mountain more time than she gives us adds urgency to the obsession. As has been said before; the mountain doesn't care.

It can wait forever. I cannot.

Re: Please stay on the trail.

Postby mtnfiend » Mon Oct 01, 2012 11:26 am

Bean wrote:
Dex wrote:In your math aren't you missing a couple of points?
Surface area on the ground when in motion - bike tires constantly on the ground - feet no
Surface area affected - when going straight - bike tires in the same line - feet not
PSI - While the tires might be inflated to 30PSI - the PSI for bikes should be a factor of the weight of the bike, rider, equipment etc and the surface area of the tire track?
Interesting math problem, that.


I'm not sure what you're trying to say here. 30psi is 30psi is 30psi. The tire conforms to the surface. 30psi is a general number, some run mid-20s, some run mid-30s.


I think what Dex is saying is that your math is incorrect. :-"

The force to the ground is the mass of the bike+rider times acceleration (no tire pressure effect in a static scenario there). The pressure of the bike+rider on the ground is that force previously calculated divided by the tire surface area in contact with the ground (only thing tire pressure effects here is surface area contact). You can make what ever assumption you want about how the force is distributed between the 2 tires to get pressure on each tire (equally distributed, or 60/40 front/rear, or whatever).

Bottom line - just because you have 30 psi in the tires does not mean you exert 30 psi to the ground.

Oh, and fat/larger tires need less pressure because the volume of air in the tire is what supports your weight!! The pressure in the tire is only the byproduct.

I'm not sure pascals are more intuitive, but english units definitely suck because you have the whole pound-force and pound-mass confusion.

Back on track - that section of trail is poorly designed for any/all use.
Didn't I ever tell you.....Bumble's bounce!!!

Posts: 310
Joined: Sun Jul 09, 2006 11:47 pm
Location: Denver

Re: Please stay on the trail.

Postby pw » Mon Oct 01, 2012 11:36 am

inthemtns wrote:It seems like some of these new trails form when rocks settle into the existing trail and people don't want to step on them or modify their step to avoid them. It would probably be too much to ask people to remove rocks on the trail as they hike. It's more of a CFI function, and a pretty easy one at that -- hike the trail to remove rocks so that people aren't tempted to start a new trail.


I think this stuff also happens in spring when water from snow melt flows down the trail and people walk next to the trail to avoid getting wet. I try not to do that unless I'm really going to get dunked.

Online
User avatar
Posts: 763
Joined: Tue Dec 12, 2006 2:17 pm
Location: crested butte

Re: Please stay on the trail.

Postby gb » Mon Oct 01, 2012 12:14 pm

Scott P wrote:Anyway, the suggestion of climbing on snow is a good one. It certainly does lessen impact.


Exactly. No harm, no foul by me on this day a few years back on Elbert:
Image

BTW, since we're doing math, let's say that the "bike" season on Elbert goes from July- September on average. 12 weeks. Very few mountain bikers have any interest in riding Elbert- either they don't have the technical skills to ride it, or they hate hike-a-bike, or they fall into the "ride lifts all day" crowd that wouldn't have the legs and lungs to want to climb Elbert. If I estimate 10 riders/week, I'm actually being generous, IMO. So, at 12 weeks x 10 rides a week, you're only left with 120 rides total in a whole season (and probably fewer than that). Compared to thousands of hiking ascents every summer. All it takes is one muddy day when someone walks next to the trail for a parallel trail to form. And so on. It's just a bad section of trail with poor drainage and a steep slope.

User avatar
Posts: 782
Joined: Fri Jun 29, 2012 3:25 pm

Re: Please stay on the trail.

Postby TallGrass » Mon Oct 01, 2012 1:20 pm

Bean wrote:Only the case when a person is standing perfectly still,
...
Your use of "dV" suggests that you're trying to sound smart by throwing out variable names without knowing what they actually mean
...
Meanwhile, 30psi in a bike tire is 30psi. A fatbike can go as low as single-digit air pressure.
...
But why are we (you) talking about outliers rather than the vast majority of trail users? I'm not bringing up equestrians going out in to muddy areas and doing more trail damage than a bulldozer could, or hikers substantially widening sections of trail in an effort to avoid a little bit of mud (whoops).


Simple test would be ride a bike across a flat stretch of sand or snow at a steady speed and also hike it on a parallel path a few feet off, then compare. The deeper the depression, the greater the PSI exerted on the terrain.

Delta v is at the basic level of even a Physics I high school class as it's used to calculate a (Dv/Dt) then multiplied through m to yield F (N's 2nd).

Regarding tire pressure versus ground force (P.S.I.), I would be interested to see your free body diagram of the two, especially as your line of logic regarding "30psi" and single digit fatbike tire pressures leads to interesting conclusions of the weightless nature of a bike+rider if he drops his tire pressure to 0psi, much less if you created a relative vacuum by dropping it below 1atm (or its 14k' equivalent). :) The ripples do illustrate the force exerted in a highly detectable way unlike loose surfaces where the top layer is redistributed in a more even fashion obfuscating the detection of soil/terrain displacement by keeping it below the JND on a pass-by-pass basis.

I think you're confusing "outlier" with "negligible" as even outliers can be impactful to the overall data set, i.e. a component. I could point out the rhetorical and or logical fallacies of the other part but do not think you would be interested nor that it would have any lasting benefit here.

You seem to want to rely solely on (your) experience, but when accounts of experience on an objective matter differ, do you prefer to settle it with rhetorical devices or a synthesis of rationalism and empiricism (i.e. science; physics)?


pw wrote:I think this stuff also happens in spring when water from snow melt flows down the trail and people walk next to the trail to avoid getting wet.


Yes, but not just snow melt, but any precip'. On Uncompahgre, there were several muddy low points (which the monsoons would highlight) that we rocked in to stabilize the trail and make it possible to keep your feet dry by staying in-trail (removing the impetus to blaze a new one). Our main project was breaking up a straight downhill section into steps (with backfill and crush) which it seems is what that section on Elbert needs as well as rocking in the extra six trails (either to slow erosion, dissuade use, or help return to nature). Switchbacks would help too, but I can see folks cutting them and re-establishing a straight line just as I've seen others hiking over log barricades to take switchback cutoffs. :(
Not sure if I'll do more 14ers. The trip reports are too tiring. :wink:

User avatar
Posts: 626
Joined: Mon Sep 12, 2011 5:41 pm
Location: waiting to see if my doom is impending

Re: Please stay on the trail.

Postby DeucesWild » Mon Oct 01, 2012 1:33 pm

TallGrass wrote:You seem to want to rely solely on (your) experience, but when accounts of experience on an objective matter differ, do you prefer to settle it with rhetorical devices or a synthesis of rationalism and empiricism (i.e. science; physics)?


Man, you're like Beano, shuttin the Bean down with all that Mensa physics action!

We should have a hiking date...
Snowflakes, Uber Alles!

www.deuceIRA.com. Put the Douche in your FiDeuceiary needs today!!

User avatar
Posts: 696
Joined: Mon Jan 10, 2011 8:47 pm
Location: Denver, Frisco, KC

Re: Please stay on the trail.

Postby tlongpine » Mon Oct 01, 2012 1:59 pm

TallGrass wrote:
Bean wrote:Only the case when a person is standing perfectly still,
...
Your use of "dV" suggests that you're trying to sound smart by throwing out variable names without knowing what they actually mean
...
Meanwhile, 30psi in a bike tire is 30psi. A fatbike can go as low as single-digit air pressure.
...
But why are we (you) talking about outliers rather than the vast majority of trail users? I'm not bringing up equestrians going out in to muddy areas and doing more trail damage than a bulldozer could, or hikers substantially widening sections of trail in an effort to avoid a little bit of mud (whoops).


Simple test would be ride a bike across a flat stretch of sand or snow at a steady speed and also hike it on a parallel path a few feet off, then compare. The deeper the depression, the greater the PSI exerted on the terrain.

Delta v is at the basic level of even a Physics I high school class as it's used to calculate a (Dv/Dt) then multiplied through m to yield F (N's 2nd).

Regarding tire pressure versus ground force (P.S.I.), I would be interested to see your free body diagram of the two, especially as your line of logic regarding "30psi" and single digit fatbike tire pressures leads to interesting conclusions of the weightless nature of a bike+rider if he drops his tire pressure to 0psi, much less if you created a relative vacuum by dropping it below 1atm (or its 14k' equivalent). :) The ripples do illustrate the force exerted in a highly detectable way unlike loose surfaces where the top layer is redistributed in a more even fashion obfuscating the detection of soil/terrain displacement by keeping it below the JND on a pass-by-pass basis.

I think you're confusing "outlier" with "negligible" as even outliers can be impactful to the overall data set, i.e. a component. I could point out the rhetorical and or logical fallacies of the other part but do not think you would be interested nor that it would have any lasting benefit here.

You seem to want to rely solely on (your) experience, but when accounts of experience on an objective matter differ, do you prefer to settle it with rhetorical devices or a synthesis of rationalism and empiricism (i.e. science; physics)?


pw wrote:I think this stuff also happens in spring when water from snow melt flows down the trail and people walk next to the trail to avoid getting wet.


Yes, but not just snow melt, but any precip'. On Uncompahgre, there were several muddy low points (which the monsoons would highlight) that we rocked in to stabilize the trail and make it possible to keep your feet dry by staying in-trail (removing the impetus to blaze a new one). Our main project was breaking up a straight downhill section into steps (with backfill and crush) which it seems is what that section on Elbert needs as well as rocking in the extra six trails (either to slow erosion, dissuade use, or help return to nature). Switchbacks would help too, but I can see folks cutting them and re-establishing a straight line just as I've seen others hiking over log barricades to take switchback cutoffs. :(


First, Bean is talking about the PSI within the tire while you are talking about PSI upon the ground.

Second, the forces exerted upon the ground by tires and feet, while both measurable, are red herrings in this discussion. The discussion isn't a question about what is causing the erosion, the question is how to mitigate it. The OP has suggested we simply "stay on the trail". Others have pointed out that the trail needs re-engineered because "It's just a bad section of trail with poor drainage and a steep slope."

Three, unless hikers suddenly begin descending by running then stopping by dragging their feet across the surface, rather than simply not taking another step, you're comparing apples to oranges. This point is key to understanding how feet and tires differently interact with the surface. Measuring PSI alone is gross oversimplification.
I am unable to walk away from the mountain without climbing it. An unclimbed mountain tugs at my consciousness with the eternal weight of time itself. Until I've pressed my face into it's alpine winds, hugged it's ancient granite walls, and put it's weathered summit beneath my heal I'm unable to resist it's attraction.Knowing nature gives the mountain more time than she gives us adds urgency to the obsession. As has been said before; the mountain doesn't care.

It can wait forever. I cannot.

Re: Please stay on the trail.

Postby Bean » Mon Oct 01, 2012 3:32 pm

mtnfiend wrote:Bottom line - just because you have 30 psi in the tires does not mean you exert 30 psi to the ground.

Unless you're talking shear forces (I don't think you are), that's incorrect - unless you're concerned about small parts of the tread pattern exerting higher pressures than other parts of the tire - but it all averages out over the surface. But like tlongpine said, that's not particularly relevant if we're talking about practical trail management. Also, I was kidding about the pascals thing.

TallGrass wrote:Regarding tire pressure versus ground force (P.S.I.), I would be interested to see your free body diagram of the two, especially as your line of logic regarding "30psi" and single digit fatbike tire pressures leads to interesting conclusions of the weightless nature of a bike+rider if he drops his tire pressure to 0psi, much less if you created a relative vacuum by dropping it below 1atm (or its 14k' equivalent).


Given a an ideally smooth surface and round tread, the contact patch for a normally inflated tire will go to zero if you assume a weightless bike/rider (theoretically of course). The contact patch increases in size when you have a heavier bike/rider. When you go over imperfections or have a G-out or similar, the contact patch increases in size. We must have a disconnect here and might be talking about different things - we both seem to know what we're talking about but just don't seem to be on the same page.

DeucesWild wrote:Man, you're like Beano, shuttin the Bean down with all that Mensa physics action!

Actually I was out the door right after my last post, going mountain biking with my off-leash dog.

Also, I mentioned Cory Hart earlier - I meant Danny Hart, the DH mountain biker with balls so big it's surprising that he can sit down - not guys who wear sunglasses at night. I wasn't quite awake and had my attention pulled in a few other directions at the same time.
gdthomas wrote:Bean, you're an idiot.

http://throughpolarizedeyes.com

Posts: 375
Joined: Sun May 25, 2008 11:54 am

Re: Please stay on the trail.

Postby uwe » Mon Oct 01, 2012 3:53 pm

Hi,

Let's get back to the original theme.
STAY ON THE FRIGGIN' TRAIL! Pretty simple.
Need to muddy the boots anyway to show that you're doing something.
I am always amazed by folks who are afraid to get a little dirt and mud on the boot.

PreviousNext

Who is online

Users browsing this forum: No registered users and 1 guest