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Thread: Treachery!

  1. #1
    coitus non circum. Mars's Avatar
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    Treachery!

    Is there anything more treacherous (besides my ex-wife) than a sideways sloping surface covered in ice? Maybe a sideways sloping surface covered in ice with a strong crosswind blowing

    Or slippery: how about a polished frozen puddle with a light dusting fresh fluffy snow. Just enough to mask that it is there.

    Or getting hit from the side with a wave of frozen slush from a passing semi? Man, that stuff is HEAVY.

    What are your most treacherous riding conditions?

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    Retrogrouch in Training bostontrevor's Avatar
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    There's a bridge on my commute that's on a high traffic highway with traffic feeding from downtown, an I-93 off-ramp, and the terminus of another expressway. Meanwhile, I gots to be in the left lane because work is at this same corner (Museum of Science for the locals) and it's an unsignalled left. All that's no big deal though if it weren't for the fact that the deck of said bridge is well worn steel traction. When it gets wet--or god forbid, snowy--lookout!

    I can also cross on the sidewalk which connects up to a bike path that I take sometimes when the weather's bad (fewer joggers for me to mow down), but that's also steel. Consequently, last night when it was covered with 1/2" of wet snow, I just got off and walked the bike across. Some dude walking in front of me just about split his head open on the railing, so I didn't stand a chance on 700x23 slicks.

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    Formerly Known as Newbie Juha's Avatar
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    Sideways sloping surface covered in ice with a strong crosswind blowing, a gentle rain that makes the surface of the ice wet, and an urgent need to change direction or reduce speed.

    I find that sheer cold ice (at -15C or so) has a lot more traction than wet ice at around 0C. I feel nervous on wet ice even with studded tyres.

    --J
    To err is human. To moo is bovine.

    Who is this General Failure anyway, and why is he reading my drive?


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    The 'net ruined cycling ajkloss42's Avatar
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    There is a spot on the Greenway (a local commuter path) where you do an S-turn to cross the railroad tracks that are parallel to the path. Heading East, the second half of the S (the part after you've crossed the tracks) is banked the wrong way (meaning the outside of the turn is downhill from the inside) and gets very icy. One of my best crashes last year was on it; it was a long walk to the bike because it kept sliding for so long.

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    Huachuca Rider webist's Avatar
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    Nasty stuff. I've only seen black ice once in Southern AZ in 21 years.
    Just Peddlin' Around

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    Burn-em Upus Icephaltus Gojohnnygo.'s Avatar
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    Anything that has big ruts in it and frozen solid. Scares the hell out of me.
    Sick BubbleGum

  7. #7
    clevernamehere
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    For me, one that so far has been ok, but has potential to be really nasty:
    I cross a freeway bridge over a river (cyclists must use the sidewalk on this bridge according to the city bylaws).
    The problem is that the railing is quite low. I'm 6'1" with an appropriately sized bike, so the railing is at about my seat height. I'm always very aware of the wind situation. A good cross wind gust & I could end up in the river (especially when the sidewalk is icey)
    Right now I'd have about a 50/50 chance of hitting floating ice or simply splashing into the fridgid river... If it's really windy, I'll walk across.

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    Burn-em Upus Icephaltus Gojohnnygo.'s Avatar
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    Quote Originally Posted by Juha

    I find that sheer cold ice (at -15C or so) has a lot more traction than wet ice at around 0C.

    --J
    Same here.

    I have noticed that riding in colder temps that it seems to be more brittle and your studs have more bite. Throw some water on that ice and it becomes nasty slick.
    Sick BubbleGum

  9. #9
    The 'net ruined cycling ajkloss42's Avatar
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    Quote Originally Posted by clevernamehere
    For me, one that so far has been ok, but has potential to be really nasty:
    I cross a freeway bridge over a river (cyclists must use the sidewalk on this bridge according to the city bylaws).
    The problem is that the railing is quite low. I'm 6'1" with an appropriately sized bike, so the railing is at about my seat height. I'm always very aware of the wind situation. A good cross wind gust & I could end up in the river (especially when the sidewalk is icey)
    Right now I'd have about a 50/50 chance of hitting floating ice or simply splashing into the fridgid river... If it's really windy, I'll walk across.

    I've heard there have been several people blown off the 10th Ave. Bridge and killed in Minneapolis, including a woman on a tall bike. Be careful, and stay away from that railing.

    On another note, those deeply frozen ruts are nasty too, especially when people making the ruts couldn't/didn't keep a straight line through it. That crash last winter also resulting in a long walk to catch up to the bike, that was happy to keep going without me. I broke one of those damn little caps that say "Ultegra" off a shifter in that one. Everytime I saw it missing, my hip hurt, so I finally paid the $8 or whatever to replace it. Grr.

  10. #10
    Senior Member jerrryhazard's Avatar
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    The alleyway that used to be the first leg of my old commute to work:

    Old, weathered uneven cobblestone mixed with patches of ashpalt to patch potholes. The surface undulated and buckeled in spots due to long term parking/abondonment, and general wear and tear. When dry, it's fun to try to jump from one depression/pit to the next. But the treacherous part comes in when those freezing rains hit, and the whole alley is encased in ice. It's also downhill, so you build up momentum and have to deal because you cannot brake. Also, at two spots there are intersecting alleys that often provide a nice gush of cross winds just to keep you on your toes, or rear as the case may be. Strange thing was that I could not ignore the alley, and search for a path around. It pulled me in every time....

  11. #11
    coitus non circum. Mars's Avatar
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    Clever,
    Man oh man. That description of the bridge gave me the sweats just reading about it. That sounds just so intimidating. Hats off to you, dude, for braving such a monster.

  12. #12
    clevernamehere
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    Quote Originally Posted by Mars
    Clever,
    Man oh man. That description of the bridge gave me the sweats just reading about it. That sounds just so intimidating. Hats off to you, dude, for braving such a monster.
    It's not really as bad as it sounds 99% of the time... just something that's always in the back of my mind to be aware of if the conditions are just right (or just wrong?)

    I have to say though that reading ajkloss42's post that some people have actually been "blown off" a simmilar bridge makes me a little more nervous.

  13. #13
    The 'net ruined cycling ajkloss42's Avatar
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    Quote Originally Posted by clevernamehere
    I have to say though that reading ajkloss42's post that some people have actually been "blown off" a simmilar bridge makes me a little more nervous.
    That's why I mentioned it. Bridges with low railings are not to be t*****d with. I believe that same bridge also took the only copy of my uncle's dissertation back in the 70s (under the railing, not over it though).

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    All this scary bridge talk is making me nervous . . . I have a short pavement/sidewalk to cross, above train tracks, and if tomorrow at 06:15 hrs I loose my nerves just because I see a touch of frost then I'll be coming after you guys! . . . I was perfectly OK . . . UNTIL I joined this forum . . .

    . . . Next you're going to tell me you encountered a crazy DOG rushing towards you in the dark and nowhere to escape to . . . Oh boy!

  15. #15
    Look out! Vision-'s Avatar
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    Any Winnipeg street after the first couple of snowfalls ice things up. It's not the condition of the streets that you have to worry about, but the drivers. It takes them a couple of weeks to adjust their driving habits, and until then it's open season. Twice this winter I've had to bunny hop up on to the curb to avoid being hit by some idiot who didn't realize that 4 wheel drive won't help him stop his 6 ton SUV in less than 20 feet when he's doing 80 km/h.

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    coitus non circum. Mars's Avatar
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    Yeah yeah, Vision. I saw a statistic once that the most common type of cager crash is rear ending someone. That got me thinking, what if I'm standing with my bike at a red light on an icy day? Which way should I really be looking, up at the light, or behind me for cars unable to stop on time because of the ice and snow????

    I've been rear ended twice in a car while stopped at an intersection. It occurs to me if I had been at the same place on my bike I would have been killed - both times. Wow. Paranoia while destroy ya!

  17. #17
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by Gojohnnygo.
    Same here.

    I have noticed that riding in colder temps that it seems to be more brittle and your studs have more bite. Throw some water on that ice and it becomes nasty slick.
    Ice at the triple point (0C, in equilibrium between solid, liquid and gas) is almost an ideal non-friction surface. In other words, as my pappy would say, as slick as greased owl snot on a doorknob!

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    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by Juha
    Sideways sloping surface covered in ice with a strong crosswind blowing, a gentle rain that makes the surface of the ice wet, and an urgent need to change direction or reduce speed.

    I find that sheer cold ice (at -15C or so) has a lot more traction than wet ice at around 0C. I feel nervous on wet ice even with studded tyres.

    --J
    Sideways sloping surface covered in ice with a strong crosswind blowing, a gentle rain that makes the surface of the ice wet, in the dark with bunnies. (They really aren't as cute as they look. They're evil I tell you! Evil!)

  19. #19
    bici accumulatori pinerider's Avatar
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    I have 2 bad spots close together on my commute. A stop sign, then right turn onto a superelevated left curve. This means I'm turning right onto a road sloping from right to left. Any snow on the right curb melts, runs across the road and freezes. It's almost as treacherous as #2 spot, the lift bridge open metal grated deck. I find it's ok when it's dry, and not too bad on a MTB when it's wet, but on a bike with skinny tires the back wheel doesn't necessarily follow the front wheel, makes for some scary moments!
    ...!

  20. #20
    Listen to me powers2b's Avatar
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    To get to the bike co-op from my house I have to cross a steel draw bridge. The surface consists of open squares 2 inches across. The builders were thoughtfull enough to scallop the edges of the steel squares to add traction. The only cool part is riding across and being able to look down to the river below. On dry days you can ride across and feel the bike shimmy side to side as the tires try to follow the steel squares. On wet or snowy days the steel bridge becomes the largest human cheese grater in the world. The scalloped edges of the steel make nice parallel lines in even the toughest muscle tissue. There have been so many bike accidents that the co-op has instructed its members to walk across or ride on the sidewalk (illegal in Cleveland) when crossing. (hope you are not eating lunch when you read this)
    Enjoy

  21. #21
    Burn-em Upus Icephaltus Gojohnnygo.'s Avatar
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    Quote Originally Posted by cyccommute
    Ice at the triple point (0C, in equilibrium between solid, liquid and gas) is almost an ideal non-friction surface. In other words, as my pappy would say, as slick as greased owl snot on a doorknob!
    Only if your on a lake or pond where the ice is thick and stays frozen solid for long periods of time. I'm talking about thin ice that goes thur a freeze and thaw cycle. Like on the street or path. It becomes very hard in cold temps, but do to the freeze and thaw it becomes brittle. Creating air pockets that collapse under pressure. Therefor giving you more bite.

    If you got more to add please do. info is good.

    Peace John,
    Sick BubbleGum

  22. #22
    Mad bike riding scientist cyccommute's Avatar
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    Quote Originally Posted by Gojohnnygo.
    Only if your on a lake or pond where the ice is thick and stays frozen solid for long periods of time. I'm talking about thin ice that goes thur a freeze and thaw cycle. Like on the street or path. It becomes very hard in cold temps, but do to the freeze and thaw it becomes brittle. Creating air pockets that collapse under pressure. Therefor giving you more bite.

    If you got more to add please do. info is good.

    Peace John,
    Okay. To get hypertechnical:

    "The force of friction depends on two values, the force pushing the surfaces together (FN) and the coefficient of friction (). Thus,

    Ff = FN

    The coefficient of friction is a constant that depends on the two surfaces in contact. This constant changes when motion begins. Since fs > fk, and the normal force (FN) remains constant, the coefficient of friction of static friction is more than that of kinetic friction. Thus, s > k.

    The coefficient of ice is relatively low and much less than one. A system with a low coefficient of friction has a low resistance to the surfaces sliding across one another. The fact that ice has a low coefficient of friction can be seen easily by pushing someone across an ice-skating rink. In order for the person to move the push must exceed the frictional force. The slightest nudge will cause the person to slide across the ice, therefore the frictional force is low and through inference the coefficient of friction for ice is minimal as well."

    From http://hypertextbook.com/facts/2004/GennaAbleman.shtml

    But, for those of us who are mear mortals, what this means is that ice is slick. Adding water to ice - as occurs when ice is near the melting point (32F, 0C) - adds a layer of lubricant to something that is already slick, like putting grease on teflon. Along comes a cyclist, already unstable, hits the ice and water mixture and down he goes! This is independant of the size of the ice patch or how long it has been at temperature.

    Now if you remove one of the components of the triple point by lowering the temperature, you decrease the "lubricity" or slickness of the ice patch and increase the coefficient of friction. (Only the solid ice and liquid water are important for our purposes. The gaseous part is only put in there to confuse chemistry students and, when they think they understand it, to allow them to feel smuggly superior to engineering students.) The ice becomes more sticky which keeps the cyclist from bruising his ego. It's not the air pockets that give bite but the ice is less slick.

    Overall what we all observe is true - wet warm(ish) ice is slick while dry cold ice isn't.

    Boring father/teacher/scientist mode off now.

    Stuart Black

  23. #23
    Senior Member MrCjolsen's Avatar
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    I know what you all mean about the winter conditions.

    Out here in California, it gets really cold. Sometimes down into the 40's!
    And windy too. Unless there's fog, but then it's warmer.

    And one day this month I couldn't ride cause it was raining.
    :-)

  24. #24
    coitus non circum. Mars's Avatar
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    cyccommute:

    You're just the kind of guy I've been wanting to talk to! Here is a friction/traction question for you. A number of winter cyclists advocate letting some air out of tires in slippery conditions in order to increase the area of the contact patch with the ground. They feel, in part, that this will increse traction. However, I have some kind of foggy memory that the amount of friction also depends on the amount of force pushing down on the surface. this is illustrated by imagining sanding a surface and pushing down hard on the sandpaper. If you really want to get a pesky part out, you will use a tiny part of the sandpaper to focus your efforts. So, increasing the size of the surface area will not help increase traction because it is offset by a decrease in the amount of downward force per square inch. At least, that is my theory. What do you think?

  25. #25
    The 'net ruined cycling ajkloss42's Avatar
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    Quote Originally Posted by Mars
    So, increasing the size of the surface area will not help increase traction because it is offset by a decrease in the amount of downward force per square inch. At least, that is my theory. What do you think?
    The interactions between a rolling pneumatic tire and the road surface are much more complicated that basic static and sliding friction formulas describe. Your sandpaper analogy is about sliding friction between surfaces. Until your tires actually begin to slide, that's not much like what's happening between your tires and the ice. It really depends a lot of the temperature and purity of the ice, the composition of the tire tread, and the deflection properties of the tire, and probably a ton of other stuff. By fiddling with tire pressure, you can change the deflection properties of the tire. Performance car tires have the same issues: why would race cars have these super-wide tires with all their extra weight and aerodynamic drag if they didn't get better traction out of them? It's essentially the same deal with bicycle tires (although not so much with width), but racing tires are usually made out of a softer rubber that your typical commuter oriented tire. Even though the softer rubber is a bit more prone to puncture and wears out a lot faster, it bites into the road surface it was designed for better than a harder rubber does (I suspect punctures in racing tires have a lot more to do with the material used for the tire than the tread though). Are there any tire industry insiders lurking around to explain with more detail?

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