A rainy day question....

[applecrew]

 

I rode to work in the rain this morning, and more is forecast for the rest of the day, and probably tomorrow as well.  So, as I'm riding in and I'm being careful with my speed, I start to wonder as the road surface changes from asphalt to concrete slab and back again.... all things being equal, which surface offers better traction in the wet, asphalt or concrete?

[bobthebiker]

I think texture and oil content has a lot to do with the level of traction attainable when wet.   so does tire condition. 

when I say oil content, I mean how much oil and slippery $h!t soaked into the road from leakin vehicles?

[utgunslinger13]

tires have a huge part, as well as what additives are in the roadway. In Okinawa Japan they add crushed sea shells into their asphalt mix which causes it to be VERY slippery for the first hour after starting to rain.  So while taking the class to get my Japanese drivers license we were told to avoid driving during the first hour after a rainstorm if possible.

[wladziu]

crushed sea shells into their asphalt mix which causes it to be VERY slippery

Not true.  The calcium carbonate in sea shells is polar and has very good ion-dipole interaction with water.  Were it for the rain itself, sea shell component mixtures would allow pretty good traction.  Dipole-dipole electromagnetism is exactly how geckos walk up walls, after all (high coefficient of friction). 

The crappy part is just the layer of non-polar fluids between the tires and the road surface.  The vinylic carbon-carbon bonds in synthetic rubber is only semi-polar and would rather bond to volatile oils when available, than water.  Hence, traction loss. 

The oil on the shells washes off with water, causing initial duration of rainfall to be hazardous.  But, the same thing happens with asphalt alone. 
Without oil on the road, a seashell road would be much, much less slippery than asphalt.  Kind of like talc for a weight lifter.



As far as the original topic, there's really nothing you can do, except pick the "road less traveled".  Both tarmac and asphalt will both have a layer of oil that becomes dangerous in a light rain.  Tarmac or concrete roads store the oil in the cracks and grooves of the surface texture.  Asphalt has the added bonus of releasing lighter hydrocarbons when exposed to the sun, which acts as a distillation mechanism (meaning it generates it's own oil-slick, depending on the breakdown of the particular tar that was used). 

Just thank the ghetto-cruiser in front of you.

[wladziu]

I should clarify (I thought over it a little):

A concrete road depends mostly on mechanical leverage between the tires and tiny little nubs of quartz for it's grip.  These nubs start out sharp, but the edges are very quickly worn off (silicon dioxide is very brittle, though not as much as the pure stuff).  SiO2 is nonpolar as well, meaning no h-bonds between it and water.  This makes water, basically, a lubricant. 
The water does bond well to the mortar in the concrete, which is a decent base.  That's mostly why it takes so long for concrete roads to dry, besides just the surface area.  For your tires, that means the water is pulled off/runs off the quartz ridges and down into the mortar "valleys".  It's held there, decreasing the lubrication effect.  But, in a downpour, I don't think that would matter.

So, in light of this, I believe asphalt roads would be the better choice. 


I remembered this when I was thinking about the tire tracks that cars leave while driving on an asphalt road, in the rain.  Those tracks are proof of the hydrophilic tendencies of both asphalt and rubber. 

These things get sketchy, so my apologies for lapses in judgment. 

I was wrong about the "semi-polarity" of rubber.  I've been taking too much organic chemistry, with water acting as a solvent on hydrocarbon chains.  Kinda got confused.  I was thinking something about a temporary H-bond effect, like in SN1 nucleophilic addition.  So, utgunslinger was partially correct.  The seashells attract water which can decrease traction, but this also acts to repel surface oils. 
Wettability and traction gets sketchy pretty quickly. 
Correct me if I'm wrong, of course.  I've been up all night, so I may be mistaken. 

Stick with new asphalt and wait 15-30 minutes for the rain to wash off the initial oil slicks.  The newer the better, because the gravel will still have it's sharp corners and the tar isn't yet acted upon by volatile aprotic solvents. 

[Roadstergal]

Drainage has a lot to do with it, as does how long it's been raining (the first water brings the oil to the top; more rain eventually washes it away).  Paint is mega-slick.  Metal gratings are pretty slick when wet.

None of these are a reason to crash.  You can ride on concrete, asphalt, oil slicks, metal gratings, etc. without crashing if you are relaxed, deliberate, and smooth in your inputs.  Dirt riding helps, as it gets you the sensitivity to feel slight slips and adapt before they become a problem.

[wladziu]

Ultra-fine powders have an effect (I forget what it's called) where basically they act as liquids.  They've gotta be really dry and in excess.  Not something you'd run into on a city street, but I've been thinking about practicing in something like that with street tires. 

I've gotta get off of this forum.  I think I'm addicted. 

[sblack]

Ultra-fine powders have an effect (I forget what it's called) where basically they act as liquids.  They've gotta be really dry and in excess.  Not something you'd run into on a city street, but I've been thinking about practicing in something like that with street tires. 

I've gotta get off of this forum.  I think I'm addicted. 

Brickies sand is good for that. For some reason they think it's a good way of cleaning up oils spills round where I live but don't bother cleaning the sand up. Very slippery indeed.

[wladziu]

I guess it could be argued that it's simply a matter of mechanical traction:  conformation of the tire rubber against ridges in the road. 

But, bear in mind that electromagnetic force is somewhere in the magnitude of 10 to the 40th times greater than the force of gravity.  Understanding that mechanical traction depends purely on the effect of gravity holding something to the ground...  that arguement loses merit very quickly.

Because of electromagnetic interaction, if your tires provided a large enough patch - your GS could easily travel up walls and upside down.  They would have to be very, very large tires, however. That's exactly how a gecko walks up walls, for example.  It's just glorified static cling.
You can't feel it (like holding two magnets together) but it's there. 

When given two asphalt roads in similar conditions: one with large gravel and one with very small gravel - the small gravel would win.  More interaction between the tire patch and the road.  Plus, the tar covering the rocks rubs off quicker in a large-gravel mix.  So, you get the effect of skiing across the top of the ridges, and those ridges don't adhere very well to your tire patch because of reverse polarities. 

There is a point of diminishing returns, however.  As was said earlier, drainage has to occur.  So, the gravel can't be too small.  If you ever slipped on a wet floor, that's the problem.  Civil engineers have apparently found the happy medium (at least to their standards). 

[Roadstergal]

You're overthinking this.  Ride more.     I'm a scientist by training and profession, and found that I have an inclination to overthinking - which is counterproductive.

Wet is slippery.  Early wet is more slippery than later wet.  Painted wet and metal wet tend to be more slippery than regular road-wet.  Road-wet surfaces vary.

Dirt riding gives you a better feel than any amount of internet discussion for how to ride on traction-compromised surfaces.

[wladziu]

Sorry.  Finals.  Overactive brain.  I'm done now, I promise!

[chipster]

My head hurts just reading all that...I think I've been scare out of riding in the rain...to much involved

[applecrew]

 

Ask a simple question....

and all hell breaks loose!!!

Thanks for all your replies... I think I'll take the simple advice... Ride More!  Although the roads were wet, I felt pretty secure all day.  Something to look forward to, gonna have more of the same tomorrow!

Now, If I could only find a home remedy for my foggy visor...

[Roadstergal]

Now, If I could only find a home remedy for my foggy visor...

A little spit, rubbed onto the back of a clean, dry visor and buffed off.

A little liquid dish soap, rubbed onto the back of a clean, dry visor and buffed off.

I used to have a Scorpion and enjoyed the anti-fog, but after I found out Scorpion was Made In China and ditched it for a Shoei, I'm back to home remedies.