Hi, Rob,
I definitely think that cold weather slows me down. But not by as
much as your Minnesota Theory (1.5 mph for every ten degrees below
50F), because at my overall average speed of 11.2 mph on 200Km's, then
I'd never finish in time at 20F! If I had to use studded tires on a
ride, then I know that I'd get slowed down another two or three mph,
so timely completion would be in serious doubt. My hat is off to your
riders who finished a 200Km on studded tires
Anyway, I was curious just how much I get slowed down by the cold, so
I ran a test of your theory against my own data, and found a slowdown
of about 1/4 mph of average speed for every ten degree temperature
drop below 50F. Moving speed actually slows down by about 0.4 mph for
every ten degree temperature drop. But I think I compensate for
riding more slowly by controlling faster. Plus, whenever you are
stopped, you are getting cold, so the best way to stay warm is to keep
moving.
Data source: I have GPS data and (approximate) temperature records for
each 5 mile leg for all my rides since 2006. The temperature records
for each leg are interpolated from knowing the high and low for the
ride, but I know that it's moderately accurate since I can compare the
interpolation to my recollection of the day. For rides of around
200Km, I have a total of about 16000 miles of data, of which about
5110 miles are at temperatures below 50, and 1200 miles at
temperatures below freezing (but so far, no rides below zero). The
regression also controls for rider weight, bike weight, rate of climb,
rate of descent, cumulative climbing on the ride, cumulative distance
on the ride, whether I'm drafting, whether it's night, and whether I'm
sick.
If I restrict attention to solo brevets that I know I was riding as
hard as I could, and only look at the effect of "extreme" temperatures
(below freezing or above 90) then I find that extreme temperatures
slow my moving average speed from 13.3 mph to 12.6 mph. Night-riding
has about the same effect, as does carrying 10 pounds more weight (ten
pounds extra on the bike is not as bad as ten pounds extra on the
rider).
Nick
> Despite my best efforts, I have been dragged into riding winter permanents
> again this year*. * There is nothing wrong with having good friends insist
> you ride with them, but once the temperature starts dropping, I try to find
> polite ways to stay busy indoors or head south for a while to miss the
> worst of our Minnesota winters. However, aside from my winter wussiness,
> we have a good contingent of hardy winter randonneurs who enjoy getting out
> whenever they can to card winter perms to earn Minnesota Natural R-12s, or
> just because they love to ride.
>
> Over the course of the past two winters in particular we have had a wide
> range of mild to pretty extreme winter riding experiences and have evolved
> a theory about how to predict how fast a given rider can expect do a
> typical permanent route in the winter, based on how long it would take them
> to do the route in the summer (at 60-80 above) under average conditions,
> compared to progressively colder weather, starting at 50 above down to zero
> degrees Fahrenheit.
>
> We don't admit to a high level of scientific rigor in the process of
> developing this theorum but we have a lot of anecdotal experience and a
> good number of examples to work with from a range of randonneurs, faster
> and slower.
>
> Here is our theorum, open for comments and enhancement by others who may
> have similar experiences riding in winter months.
>
> BTW - my apologies to the southern belt of the country who may not have as
> much concrete data or experience to contribute to this topic, not that this
> would hold anyone with an opinion back from expressing it, but our
> suggestion to the warm weather folks would be to conduct a similar set of
> tests on riding speed and time at temps > 80 and report back.
>
> *The Minnesota Randonneur Theory of Speed vs Temperature for Winter
> Permanent Rides*
>
> *Starting at 50 above, for every 10 degrees colder, your net average speed
> will drop by 1.5 mph*