How much does rain slow a bike down

rolf_f
rolf_f Posts: 16,015
edited March 2010 in Commuting chat
Felt like the first dry day of the year on my commute today. Also seemed so much easier due to the lack of surface water. True, I've given my colleagues much amusement turning up at the office in what looks like Maori war paint but all that water sprayed up and into my face is energy being sapped from forward momentum; effectively my bike has been lifting buckets of water as I've moved along. Anyone know how big an impact it is in quantifiable terms?
Faster than a tent.......

Comments

  • cjcp
    cjcp Posts: 13,345
    There's some stat about rain water reducing the amount of friction in the drivetrain (11%?), but the rain slows me down because I just cycle slower. Definitely felt faster today.
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  • cougie
    cougie Posts: 22,512
    I did my best time trial for a 10 in the rain - so I think it makes no difference or minimal at best. Maybe if you are wearing a lot of kit then rain would slow you down ?
  • solsurf
    solsurf Posts: 489
    It only makes a difference to me if there is standing water.

    I think temperature makes the most difference, too cold and its hard to breath too hot and your body puts a lot into cooling it down.
  • ...plus you (or maybe it's just me) tend to brake earlier and less strongly - just another factor to weigh in that adds to the sensation of "slow".
    "Consider the grebe..."
  • ...plus you (or maybe it's just me) tend to brake earlier and less strongly - just another factor to weigh in that adds to the sensation of "slow".
    "Consider the grebe..."
  • Oddjob62
    Oddjob62 Posts: 1,056
    When i'm doing laps round the park, i'm definitely quicker in the wet, but there are few turns or stops. If i'm on the main road i'm slower (more careful at corners/lights/etc).
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  • rjsterry
    rjsterry Posts: 28,226
    If you know the road and don't need to brake too much (like laps around RP or a TT), I think the drop in rolling resistance and lower friction will make you move faster, but on a commute, the extra stopping distance, and keeping an eye on raised ironwork makes you much more cautious and hence slower.
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  • rolf_f
    rolf_f Posts: 16,015
    Dunno - much of my commute is long, slow, endless climbs and, besides, I commute on an mtb with discs so braking distance is not quite such a worry. Generally, I have found the dry run most obviously easier on the climbs. It isn't so much a sensation of slowness in the wet but of harder work to move the bike.
    Faster than a tent.......
  • rolf_f
    rolf_f Posts: 16,015
    Snow melt again today and it was definitely harder work! Conditions more or less the same otherwise (temp, lack of wind, cloud cover etc)
    Faster than a tent.......
  • surreyxc
    surreyxc Posts: 293
    I think with the right surface rain actually makes the ride quicker, as it acts like a surface lubricant. To my mind the real difference is in the braking, and how strong the wind is that is bringing the rain. After that I reckon a lot is pyschological, and the other big factor is wearing another half kilo of clothing, not much wieght but restricting and surface area for wind resistance. And the rain tends to be more in the winter so you also have a set of lights so add another 500g
  • rolf_f
    rolf_f Posts: 16,015
    surreyxc wrote:
    I think with the right surface rain actually makes the ride quicker, as it acts like a surface lubricant. To my mind the real difference is in the braking, and how strong the wind is that is bringing the rain. After that I reckon a lot is pyschological, and the other big factor is wearing another half kilo of clothing, not much wieght but restricting and surface area for wind resistance. And the rain tends to be more in the winter so you also have a set of lights so add another 500g

    That's the thing though - no wind today or yesterday, rain not falling - just on the ground. Wearing the exactly the same clothes, bike lights still mounted, backpack similarly weighted, brakes not an issue as it is ease of pedalling I noticed; I'm not actually logging overall travel time at the moment.

    In terms of the rain acting as a lubricant on the drive chain - that must make a difference but, that said, in wet weather the chain has never been more than 2 round trips between a degrease and re-oil so it is generally pretty silky smooth. I still think all that water being lifted up by the tyres (rather fat mtb slicks in my case) is costing more energy than any lubricational benefits the water brings to the cogs and chain. Certainly feels that way.
    Faster than a tent.......
  • RedGT
    RedGT Posts: 238
    And of course if you're soaked you weigh more, surely?