High-40s/Low50's riding: more or less efficient than 70s/80s?

[Dennis Ferguson]

[email protected] wrote:
> Dear Pete,
>
> It's not your imagination. Riders usually go slower as the
> temperature drops for several reasons.
>
> A) Temperature comfort--going slower reduces wind chill
> B) Breathing comfort--cold air is denser, but much less fun
> C) Clothing aerodynamics--winter clothes = wind drag
> D) Raw wind drag--density affects drag more than breathing
>
> The wind drag of the denser cold air is probably the biggest
> factor.

This is probably true. Drag force is proportional to air density,
which (using the ideal gas law) increases by 1% for each 3C
decrease in temperature.

The list is missing rolling resistance of the tires, though.
The new edition of Bicycling Science suggests that rolling
resistance increases by 1% for each 1C decrease in temperature.

Not that these are huge effects, but they do reinforce my own
biases. I like to ride when it is hot.

Dennis Ferguson

 

[Dennis Ferguson]

[email protected] wrote:
> Dear Pete,
>
> It's not your imagination. Riders usually go slower as the
> temperature drops for several reasons.
>
> A) Temperature comfort--going slower reduces wind chill
> B) Breathing comfort--cold air is denser, but much less fun
> C) Clothing aerodynamics--winter clothes = wind drag
> D) Raw wind drag--density affects drag more than breathing
>
> The wind drag of the denser cold air is probably the biggest
> factor.

This is probably true. Drag force is proportional to air density,
which (using the ideal gas law) increases by 1% for each 3C
decrease in temperature.

The list is missing rolling resistance of the tires, though.
The new edition of Bicycling Science suggests that rolling
resistance increases by 1% for each 1C decrease in temperature.

Not that these are huge effects, but they do reinforce my own
biases. I like to ride when it is hot.

Dennis Ferguson

 

[Dennis Ferguson]

[email protected] wrote:
> Dear Pete,
>
> It's not your imagination. Riders usually go slower as the
> temperature drops for several reasons.
>
> A) Temperature comfort--going slower reduces wind chill
> B) Breathing comfort--cold air is denser, but much less fun
> C) Clothing aerodynamics--winter clothes = wind drag
> D) Raw wind drag--density affects drag more than breathing
>
> The wind drag of the denser cold air is probably the biggest
> factor.

This is probably true. Drag force is proportional to air density,
which (using the ideal gas law) increases by 1% for each 3C
decrease in temperature.

The list is missing rolling resistance of the tires, though.
The new edition of Bicycling Science suggests that rolling
resistance increases by 1% for each 1C decrease in temperature.

Not that these are huge effects, but they do reinforce my own
biases. I like to ride when it is hot.

Dennis Ferguson

 

[Mark Hickey]

"Dennis Ferguson" <[email protected]> wrote:

>The list is missing rolling resistance of the tires, though.
>The new edition of Bicycling Science suggests that rolling
>resistance increases by 1% for each 1C decrease in temperature.
>
>Not that these are huge effects, but they do reinforce my own
>biases. I like to ride when it is hot.

Hmmmm, taking into account my current winter speed at about 5 degrees
C, come the next Arizona summer I should be passing all the cars on
the interstate! ;-)

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $695 ti frame