Cold and speed

"Robert Siegel" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

For the last couple of weeks of chilly weather I've been averaging 15+ mph for my 10 and 13 mile
daily rides. Today the temp hit 75 mid afternoon

and

Quoted message said:

I averaged 15+ mph for 10 miles --- BUT BUT BUT -- today I rode without

the

Quoted message said:

fairing on tires that had not been pumped up for the last 5 days. (Tires are usually kept at
120/120 psi front and rear.) It was late in the day

so

Quoted message said:

I did not take the time to pump the tires or put the fairing back on

after

Quoted message said:

a cleaning.

I am slower if my muscles feel cold.

Welcome to the winter penalty. Below about 40 degrees F, I slow down. Heavy air or heavy clothing,
the colder it gets, the slower I go.

I take some comfort in the fact that usually in very cold conditions, I am the only sorry gump out
on a bike...

Rode the Linear to work today, 16 degree, snow. Enjoyed the ride, though.

Brad

Robert Siegel said:

For the last couple of weeks of chilly weather I've been averaging 15+ mph for my 10 and 13 mile
daily rides. Today the temp hit 75 mid afternoon and I averaged 15+ mph for 10 miles --- BUT BUT
BUT -- today I rode without the fairing on tires that had not been pumped up for the last 5 days.
(Tires are usually kept at 120/120 psi front and rear.) It was late in the day so I did not take
the time to pump the tires or put the fairing back on after a cleaning.

Robert,

The pressure in your tires will increase with the ambient temperature, which could account for some
of your speed increase.

Tom Sherman - Quad Cities USA (Illinois side) Various HPV's

Yes ... but to counter that I find that the Stelvios do go down considerably after 3 days. And the
actual high this pm was only 72.5...I just checked. Felt warmer. ;-)) Midday temps hereabouts have
stayed (mostly) in the low 50s for the last 10 days or so.

Also, I usually pump my tires before riding to 120/140 front and rear.

--
Gator Bob Siegel EasyRacers Ti Rush "Tom Sherman" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Robert Siegel said:

For the last couple of weeks of chilly weather I've been averaging 15+

mph

Quoted message said:

Quoted message said:

for my 10 and 13 mile daily rides. Today the temp hit 75 mid afternoon

and

Quoted message said:

Quoted message said:

I averaged 15+ mph for 10 miles --- BUT BUT BUT -- today I rode without

the

Quoted message said:

Quoted message said:

fairing on tires that had not been pumped up for the last 5 days.

(Tires

Quoted message said:

Quoted message said:

are usually kept at 120/120 psi front and rear.) It was late in the day

so

Quoted message said:

Quoted message said:

I did not take the time to pump the tires or put the fairing back on

after

Quoted message said:

Quoted message said:

a cleaning.

Robert,

The pressure in your tires will increase with the ambient temperature, which could account for
some of your speed increase.

Tom Sherman - Quad Cities USA (Illinois side) Various HPV's

Under contributing factors, think about this... Density altitude is the height above mean sea level
adjusted for deviations from standard temperature and pressure (humidity has an impact too, but it
is harder to measure in flight and usually not counted). Cool temps, high pressure, and low humidity
all conspire to decrease density altitude. Consider a person at 6000 feet MSL (per surveyor's
claim). On a cool, high pressure, low humidity (and these things do run together) day, the density
altitude might be as low as 3000 feet or less. On a hot sticky day, with lots of haze, the density
altitude might be closer to 10000 ft. That is, the cooler, dryer day with low humidity gives you the
same thickness of air to push through as you would find at or below sea level (think cold butter).
The warmer day, especially with low pressure, gives you air "thickness" normally found far above
your normal station in life (think warm butter on a pancake). Bottom line is you have less aero drag
on warm days - several percent less. There's a nifty circular slide rule for calculating this sort
of thing (an E6-B).

For this reason there is a well known time-trial course between Moriarty and Estancia NM. Autos are
affected by this phenomenon as well; fuel economy goes down with cold air - both for combustion and
drag reasons, but increases during the summer.

FYI 2

Thanks! That is very interesting. That would partially explain why I am considerably faster in warm
air with the same effort. Warm muscles and ease of breathing pre-warmed air also might contribute.

--
Gator Bob Siegel Easy Ti Rush "Howard Bishop" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Under contributing factors, think about this... Density altitude is the height above mean sea
level adjusted for deviations from standard temperature and pressure (humidity has an impact too,
but it is harder to measure in flight and usually not counted). Cool temps, high pressure, and low
humidity all conspire to decrease density altitude. Consider a person at 6000 feet MSL (per
surveyor's claim). On a cool, high pressure, low humidity (and these things do run together) day,
the density altitude might be as low as 3000 feet or less. On a hot sticky day, with lots of haze,
the density altitude might be closer to 10000 ft. That is, the cooler, dryer day with low humidity
gives you the same thickness of air to push through as you would find at or below sea level (think
cold butter). The warmer day, especially with low pressure, gives you air "thickness" normally
found far above your normal station in life (think warm butter on a pancake). Bottom line is you
have less aero drag on warm days - several percent less. There's a nifty circular slide rule for
calculating this sort of thing (an E6-B).

For this reason there is a well known time-trial course between Moriarty and Estancia NM. Autos
are affected by this phenomenon as well; fuel economy goes down with cold air - both for
combustion and drag reasons, but increases during the summer.