Forum

## Please stay on the trail.

FAQ and threads for those just starting to hike the Colorado 14ers.
Posts: 120
Joined: Mon Jan 09, 2012 4:45 pm

### Re: Please stay on the trail.

madbuck wrote:But the support of a properly inflated tire is precisely the dominant mechanism for supporting the weight of the bike and rider (with a much lesser, but nonzero, influence of the tire's rigidity.

Agreed, but I would say the psi in the tire (while under loading from the bike and rider) is a pretty close value to the force exerted on the ground. It had been stated above as a "simple law of physics" that internal psi always equals force on the ground, that's not entirely accurate.

Here is a quote from a study by Penn State (about tractor tires which are much stiffer, but you get my point):

"Contact pressure is the pressure that is exerted by a tire or track on the soil surface, expressed in pounds per square inch (psi). Reducing contact pressures will cause less topsoil compaction (Figure 5). In completely flexible tires, surface contact pressure is similar to tire pressure. With most farm tires, surface contact pressure is about 1 to 2 psi higher than tire pressure due to stiffness in the tire." The entire study can be read here: http://pubs.cas.psu.edu/freepubs/pdfs/uc186.pdf

Posts: 120
Joined: Mon Jan 09, 2012 4:45 pm

### Re: Please stay on the trail.

Greenhouseguy wrote:
tlongpine wrote:Now that this matter has been resolved...

What ground force (expressed as PSI) is required to damage tundra?

Wet tundra, dry tundra, frozen tundra, or snow-covered tundra? It makes a difference.

This one is even more complicated......not even going to begin to contemplate this. Depends on velocity of tire, friction factor between ground and tire, root structure of tundra grasses, moisture content of soil, etc.......

Posts: 1437
Joined: Wed Jun 16, 2010 2:33 pm
Location: Crestone, CO and/or Chapel Hill, NC

### Re: Please stay on the trail.

crossfitter wrote:The internal pressure really won't change very much. It will change a little as the tire deforms, sure, but that deformation is a small fraction of the total volume of the tire. In your balloon example, what really changes is the contact area between the balloon and plate. In the 0 psi case, the entire load is carried by the frame and the ground pressure is extremely high due to the thin edges and rigidity of the rims.

Makes sense. I think that's a function of the tire's rigidity though. If you put a plate on a balloon the balloon will deform a lot and the pressure will rise (leading to it popping). Tires don't deform nearly so much so the volume of air is not compacted.

ajkagy wrote:weather and water effect poorly designed and built trails more than any hiker/biker could ever effect it. All it takes is 1 big deluge to do some pretty serious damage.

I think that pretty much sums things up.
-Jason Dorje Short

Posts: 7438
Joined: Sun Jul 25, 2004 7:34 pm
Location: Breckenridge, CO

### Re: Please stay on the trail.

True. Additionally, terrain and natural materials on our peaks don't always provide for "bomber" trail construction.

Posts: 1437
Joined: Wed Jun 16, 2010 2:33 pm
Location: Crestone, CO and/or Chapel Hill, NC

### Re: Please stay on the trail.

I have no idea what you could possibly be talking about. They should just get a backhoe and a bulldozer up there and stop the tundra damage once and for all.
-Jason Dorje Short

Posts: 7438
Joined: Sun Jul 25, 2004 7:34 pm
Location: Breckenridge, CO

### Re: Please stay on the trail.

lol

At least a friggin' rope line!

Posts: 1437
Joined: Wed Jun 16, 2010 2:33 pm
Location: Crestone, CO and/or Chapel Hill, NC

### Re: Please stay on the trail.

Do you need 3000' of gain on your escalator ascent?
-Jason Dorje Short

Posts: 7438
Joined: Sun Jul 25, 2004 7:34 pm
Location: Breckenridge, CO

### Re: Please stay on the trail.

And who's paying for the power? We'll have to revisit the TH collection boxes topic.

Posts: 351
Joined: Wed Oct 14, 2009 9:32 pm
Location: Montrose, CO

### Re: Please stay on the trail.

Now that this thread is safely off-topic.

DeucesWild wrote:Didn't mean to get your Mensa up, Bill. I've only been a member for a short time and sometimes forget the rules. Sorry.

A wasted troll is a shameful thing, but take solace that some among us Lol'ed.

Posts: 1610
Joined: Fri Jun 29, 2012 3:25 pm

### Re: Please stay on the trail. ACTION?

Seriously ON-topic, given the low difficulty rating and #1 elevation status making it popular, what about making some sustainable trail? Yes, rocks (steps, fill) and or logs (breaks) would have to be hauled up, but I think it would 1. help define the "proper" trail and 2. abate erosion. If you wanted to be spiffy, you could even add some "turn outs" for downhillers to use in order to yield to uphill traffic (don't you hate it when slow-moving RVs with 20 vehicles behind them pass up those opportunities?).

Who's willing to commit time and sweat beyond keystrokes and pics? I for one would be willing to schedule my next trip out there around it!

Can you add this to the "possible projects" list at CFI, Bill? Given the traffic, it'd be some great exposure for CFI (and any other co-working groups like VOC, CMC, RMYC, etc.) as well as an opportunity to share knowledge with the general hiking public who may not venture onto more difficult 14ers.

Sweat talks, keystrokes walk?
Not sure if I'll do more 14ers. The trip reports are too tiring.

Posts: 945
Joined: Tue Jul 31, 2007 1:39 pm
Location: Fremont County, CO

### Re: Please stay on the trail. ACTION?

TallGrass wrote:Seriously ON-topic, given the low difficulty rating and #1 elevation status making it popular, what about making some sustainable trail? Yes, rocks (steps, fill) and or logs (breaks) would have to be hauled up, but I think it would 1. help define the "proper" trail and 2. abate erosion. If you wanted to be spiffy, you could even add some "turn outs" for downhillers to use in order to yield to uphill traffic (don't you hate it when slow-moving RVs with 20 vehicles behind them pass up those opportunities?).

Who's willing to commit time and sweat beyond keystrokes and pics? I for one would be willing to schedule my next trip out there around it!

Can you add this to the "possible projects" list at CFI, Bill? Given the traffic, it'd be some great exposure for CFI (and any other co-working groups like VOC, CMC, RMYC, etc.) as well as an opportunity to share knowledge with the general hiking public who may not venture onto more difficult 14ers.

Sweat talks, keystrokes walk?

I just spent my weekend working on a trail project for VOC. That does not make me an expert on the subject, but judging from the pictures in the original post, there is not a lot of large rocks anywhere near the amount that would be necessary to fix one trail, let alone fill in the other 6. The best thing for the hill would be for a trail that zig zagged up, but it's not steep enough to keep people from cutting switchbacks, so I don't have an answer for that. But several thousand rocks in the 2 foot x 1 foot x 3 foot size to be hauled UP? LOL. ---okay, if you haul them up, we'll put them into position. Generally, rocks are moved from an upper location, if possible. I hiked Elbert from another trail, so I don't know how far those upper rocks might be.
"It is not the critic who counts, not the man who points out how the strong man stumbled, or where the doer of deeds could have done better. The credit belongs to the man who is actually in the arena; whose face is marred by the dust and sweat and blood; who strives valiantly; who errs and comes short again and again; who knows the great enthusiasms, the great devotions and spends himself in a worthy course; who at the best, knows in the end the triumph of high achievement, and who, at worst, if he fails, at least fails while daring greatly; so that his place shall never be with those cold and timid souls who know neither victory or defeat." (Theodore Roosevelt)

"Wilderness is not a luxury but a necessity of the human spirit." (Edward Abbey)

Posts: 117
Joined: Sun Oct 10, 2010 10:59 pm

### Re: Please stay on the trail.

Beans is correct. F=ma yes but PV=nrT where P=pressure, V=volume, n=number of moles of the gas, r=ideal gas constant and T=temperature in kelvins or PV=NkT for you physics people. For a mountain bike tire the only variables that can be changed are pressure, volume, and temperature but temperature is not important in this situation given the relatively small pressure and volume changes for our constant number of moles of gas. So where the only two variables that can really be changed are pressure and volume and because they are inversely proportional or always equal to nRT we really only care about the volume of the tire. The volume of the tire is directly related to the deformation from equilibrium so for this application it is related to the surface area change of what ever the tire is being deformed by, which is generally the ground. So because the tire has an internal pressure of 30psi is can only push back against the ground with 30psi but it compensates by pushing back with more surface area. This is why a bike tire has a more uniform pressure. Whether or not this practically translates to trail damage who knows. Also bike tires are way more flexible than a tractor tire so the 1-2psi change would not exist here but even if they did that is less than a 3% change in psi. I personally am an avid mountain biker and hiker and am well aware of the fact that most of the damage that can be caused by bikes are due to the way you ride them and it is also part of being a responsible mountain biker. It also so happens that because static friction is greater than kinetic friction its aids me to not skid my tires but to keep my tires from locking up at all which is also the best way keep the trail form eroding.
They forget that some crisis is necessary to hone skill. "Near misses," those brief encounters with the reality of mortality, are great learning tools if properly approached. -Denali Climbers Guidebook

### Who is online

Users browsing this forum: No registered users and 10 guests