Is it easier to ride on wet roads aka rainy

Discussion in 'Cycling Equipment' started by hurricane, May 15, 2005.

  1. hurricane

    hurricane New Member

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    Assuming that there is no wind, and the road is wet, it it easier to move than on a dry road? I do not know why, but I seem to think that the answer is yes for some strange reason.
     
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  2. Jaguar27

    Jaguar27 New Member

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    Well, it's certainly easier to move sideways, especially during turns on painted lines etc...:eek:
     
  3. mattt

    mattt New Member

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    supposedly there is less resistance on your tires because they are riding somewhat on water, as opposed to hard, rough asphalt, so there's less friction. there's got to be somebody else out there who is better equipped to elaborate.
     
  4. wilmar13

    wilmar13 New Member

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    Did you pull this out of your ass? If anything there is more rolling resistance with wet roads.

    You ride faster, not because of the road being wet, but because the atmospheric pressure is lower (because it is or has rained).
     
  5. Conniebiker

    Conniebiker New Member

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    To the contrary. A rubber tire on asphalt(or virtually any surface) will have friction by nature of it rolling with a pressure on it. This friction is lessened by the water on the surface. It is the same effect that allows traction to decrease in rain as well.
    The barometric pressure has little to do with the aspect we are referring to. The difference in density from dry to wet would be negligible by most accounts unless there was a gage present. The moisture in the air can however effect the feel of the air. Moist air in most cases would have a cooling effect which makes it easier to put out power, so that may feel faster.
     
  6. dhk

    dhk New Member

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    That just doesn't sound right to me. When I ride in rain, my front wheel kicks up spray onto my shoes, and the back wheel sprays the back of my jersey. Haven't tried to calculate the volume or weight of water displaced per second here, but I'll bet it takes a measureable amount of additional work to throw this heavy stuff around.
     
  7. peterlip

    peterlip New Member

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    I agree, the act of the tyre cutting through the water to the road surface must cost some energy. Plus (although this is probably a lesser factor) wind resistance through rain would have to be greater than through dry air.
    However, having said that, being wet probably gives the body a better heat exchange to help cool, allowing you to work harder (just a theory).
     
  8. Stjtoday

    Stjtoday New Member

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    I never notice much difference until the rain is heavy enough to cause rooster tails. At that point the bike rides like its stuck to the dang road. Very resistant, like biking up a mild incline on flat ground.
     
  9. wilmar13

    wilmar13 New Member

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    Rolling resistance of a tire comes almost entirely from flexural rubber losses in the tire and tube. Traction and rolling resistance are not the same thing. In automotive applications it is well documented that rolling resistance is increased dramatically on wet roads because of the energy required to displace the water between the tire and the surface... in bikes you have a much smaller contact area, but it is still the same case. If you try arguing that the water helps "smooth out the road" you are forgetting about the fact that the tire has to diplace water to find this "balance". Rolling resistance is increased with wet roads as well as traction with all other variables equal.
    If the temperature changes 3 degrees and you don't have a thermometer are you saying the tempurature never changed? Most of the energy required to ride a bike on level ground is used to overcome air resistance. When the ambient air pressure drops the air resistance is reduced. It is a small difference, but has a much greater effect on speed than rolling resistance (even if you "believe" rolling resistance is reduced on wet roads).
    The moisture in the air gives it a greater thermal conductivity which is why it feels different (humidity makes hot feel hotter and cold feel colder). In terms of cooling, yes it can give you "free sweat" if you will and you can create the same power with greater comfort or more power with equal comfort.
     
  10. 886014

    886014 New Member

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    Wilmar, your theory about air density is correct however air pressure has absolutely no relationship to whether it's raining or not.
     
  11. meehs

    meehs New Member

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    No scientific data to back this up but from my own experience the opposite seems to be true. Wet roads seem to add a bit of drag and slow you down a little. That and obviously you have to ride more carefully (i.e slower) around turns in order to keep from sliding out, which also slows you down.
     
  12. RC2

    RC2 New Member

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    I find it a lot more stressful riding on wet roads -- constantly worrying about loosing it on a turn over an oil slick or on a highway stripe. Over the course of 10-20 miles I actually feel physically more tired.

    Also - on the steepest hill I ride on my normal route, I'll loose a bit of traction if I don't stay on the cleanest oil-free area during the peak power output of my pedal strokes...like you have to pedal twice as fast to make the hill...yucky. My observation is: no, it's harder to ride in the wet stuff.
     
  13. wilmar13

    wilmar13 New Member

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    Yeah, I wasn't clear on that... what I meant to say was that if the road was wet it is likely the atmospheric pressure is lower, I did not mean to imply that it necessarily is. However this is still saying there is a relationship, which I thought there was... Are you sure there is no relationship, not even a weak one? It was the only reason you would ride faster I could think of since it sure isn't because of reduced rolling resistance.
     
  14. 886014

    886014 New Member

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    There is a relationship between air density and moisture content of the air, however note that air may be 100% saturated and yet not be raining. Likewise it may be raining yet the air not 100% saturated. You will probably find this site interesting http://wahiduddin.net/calc/density_altitude.htm

    I'll leave you to do the math, but suggest the density difference is in the order of 1-2%

    Regarding changes in pressure, the greatest variation is very unlikely to be more than 80 Hpa, and here I am taking extremes. This equates to an effective altitude difference of approximately 2,400 ft ie the difference between riding at sea level at the maximum extreme pressure of 1040 Hpa and riding at 2,400 ft at the minimum extreme pressure of 960 Hpa. Again I would suggest the difference is insignificant considering all the other variables a cyclist faces.

    Hope that helps.
     
  15. wilmar13

    wilmar13 New Member

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    Sorry I wasn't clear with my second post either. I didn't mean to say there is a relationship between air density and moisture content... I was thinking that if the road is wet it has or is storming... when it storms the barometric pressure drops. The air pressure does (or at least can) drop when it storms right? Please say my 5th grade science teacher is correct on this one or I will need to question my entire belief system :D .
     
  16. 886014

    886014 New Member

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    Sack your teacher :D

    Storms are often associated with Low Pressure systems however there is no direct correlation between rain (storms) and pressure. For example in Sydney, Australia as I type this the pressure is 1021 Hpa (the mean sea level pressure is 1013 Hpa ... well 1013.2 to be precise) in other words the pressure is higher than the mean. The temperature is 14.8 C, almost exactly the standard temperature of 15 C. Guess why I'm sitting at my computer and not riding? As I look outside my window it's pouring with rain!
     
  17. wilmar13

    wilmar13 New Member

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    Yeah but if it storms doesn't the pressure drop from where it was prior to the storm?
     
  18. 886014

    886014 New Member

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    If you're talking about the passage of a single "storm", for example a Cumulus, and all other factors are constant then no, the pressure will not drop. However your teacher was probably referring to storms associated with frontal and low pressure systems in which case the pressure may be falling at that time. It is the rationale behind the barometers some people hang on their wall that indicate falling pressure as an indication of a change and "bad" weather.

    Whilst this theory is all very interesting, the bottom line is that it is purely that; theory. As far as it relates to the original question it is of no significance.
     
  19. wilmar13

    wilmar13 New Member

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    Hmmm OK well then I rescind my initial stretch of an excuse to the original poster...there is no reason that you would be faster on a wet road other than psychology.
     
  20. meehs

    meehs New Member

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    Yeah, exactly. The discussion of atmospheric pressure variations and the moisture content of the air is pretty much completely irrelevant when all of the other variables are factored in. So what's the point? Look at the TT times of pro cyclists on dry roads vs. wet roads if you want to know the real effect of wet roads on a cyclist's speed. I'd say that would be more accurate.
     
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