Optimal temperature for a Time Trial

big D wrote:

Your statement is absolutely correct and quite insightful. Air density
is, indeed, inversely proportional to temperature. In other words, on a
hot day, air around you will be less dense, hence offer less
resistance.

I don't know where you live, but I live in Texas. I suggest that, if at
all possible, you come down here for your time trial in July or August
when it's 100+ F (95 at least) and you should be really happy with the
results. Or, better yet, do it in Arizona where it's even hotter (might
get lucky and get to do it when it's 115 F) and dry (Texas humidity
might add to the air resistance.)

No, water vapor (molecular weight 18) reduces the density of the air
(average molecular weight about 29) and therefore creates less air
resistance than you would have with completely dry air. This assumes
you don't have condensation (fog).

Oh, my, I almost forgot about Death
Valley! Do they do time trials there?

The relatively low elevation in much of that area would not be
favorable for reduced air resistance.

Best o'luck!

Of course physiological factors may result in your power output
not being at its peak on particularly hot and humid days.

Art M wrote:

2 questions:

1. I suppose there's an optimal temperature for power output on a bicycle in
a 40K TT. Does the effect of temperature being inversely proportional to air
density substantially raise the optimum (for speed) such that a little power
lost is more than offset by the decrease in drag? (Based solely on air
density calculations at 45 and 60 deg. F. I'm coming up with a 55 sec.
improvement at the hotter temperature given 250W using analyticcycling.com.)

2. Does anyone know of a formula for predicting air Density given only
Temperature and Elevation?

The hotter the better for me. Some riders seem to do less well in the
heat; they say there's less oxygen.

Philip Holman wrote:

"MagillaGorilla" wrote in message
...

Philip Holman wrote:


"Art M" wrote in message
news:%CZPd.62364$jn.55595@lakeread06...


2 questions:

1. I suppose there's an optimal temperature for power output on a
bicycle in a 40K TT. Does the effect of temperature being inversely
proportional to air density substantially raise the optimum (for
speed) such that a little power lost is more than offset by the
decrease in drag? (Based solely on air density calculations at 45 and
60 deg. F. I'm coming up with a 55 sec. improvement at the hotter
temperature given 250W using analyticcycling.com.)

2. Does anyone know of a formula for predicting air Density given
only Temperature and Elevation?



http://www.digitaldutch.com/atmoscalc/

Phil H

Manhole,

Sounds like the domain of a website that has photos of van Poppel
fingering Mirjam Melchers and Leontien van Moorsel.


Very funny. If the hole fits............

A few years ago I did work out pursuit speeds (mph) for a range of
temperatures and pressures at a given power output.

T(F) P(in Hg) 29 30 31
50 30 29.5 29
60 30.3 29.8 29.3
70 30.6 30.1 29.6
80 30.8 30.3 29.8
90 31.1 30.6 30.1
100 31.4 30.9 30.4


You forgot to factor in the effects of dehydration and the increased
stress on the body caused at higher temperatures. Those numbers would
have to come down some.


Magilla

"Philip Holman" wrote in message
...

"MagillaGorilla" wrote in message
...
Philip Holman wrote:

"Art M" wrote in message
news:%CZPd.62364$jn.55595@lakeread06...

2 questions:

1. I suppose there's an optimal temperature for power output on a
bicycle in a 40K TT. Does the effect of temperature being inversely
proportional to air density substantially raise the optimum (for
speed) such that a little power lost is more than offset by the
decrease in drag? (Based solely on air density calculations at 45 and
60 deg. F. I'm coming up with a 55 sec. improvement at the hotter
temperature given 250W using analyticcycling.com.)

2. Does anyone know of a formula for predicting air Density given
only Temperature and Elevation?



http://www.digitaldutch.com/atmoscalc/

Phil H

Manhole,

Sounds like the domain of a website that has photos of van Poppel
fingering Mirjam Melchers and Leontien van Moorsel.

Very funny. If the hole fits............

A few years ago I did work out pursuit speeds (mph) for a range of
temperatures and pressures at a given power output.

T(F) P(in Hg) 29 30 31
50 30 29.5 29
60 30.3 29.8 29.3
70 30.6 30.1 29.6
80 30.8 30.3 29.8
90 31.1 30.6 30.1
100 31.4 30.9 30.4

I know. The effect of air density was larger than I expected. I just signed
up rather early for a TT in March where you start based on the order of
registration. I figured I would prefer to go when it was a little cooler,
but it's very unlikely that the temp will be above 70F on that day.
Obviously you don't want go when it's 100 F. I know that because I started
cramping on the last kms of a 40 K last August at that temperature.

--Art

"MagillaGorilla" wrote in message
...
Philip Holman wrote:

"MagillaGorilla" wrote in message
...

Philip Holman wrote:


"Art M" wrote in message
news:%CZPd.62364$jn.55595@lakeread06...


2 questions:

1. I suppose there's an optimal temperature for power output on a
bicycle in a 40K TT. Does the effect of temperature being inversely
proportional to air density substantially raise the optimum (for
speed) such that a little power lost is more than offset by the
decrease in drag? (Based solely on air density calculations at 45 and
60 deg. F. I'm coming up with a 55 sec. improvement at the hotter
temperature given 250W using analyticcycling.com.)

2. Does anyone know of a formula for predicting air Density given
only Temperature and Elevation?



http://www.digitaldutch.com/atmoscalc/

Phil H

Manhole,

Sounds like the domain of a website that has photos of van Poppel
fingering Mirjam Melchers and Leontien van Moorsel.


Very funny. If the hole fits............

A few years ago I did work out pursuit speeds (mph) for a range of
temperatures and pressures at a given power output.

T(F) P(in Hg) 29 30 31
50 30 29.5 29
60 30.3 29.8 29.3
70 30.6 30.1 29.6
80 30.8 30.3 29.8
90 31.1 30.6 30.1
100 31.4 30.9 30.4


You forgot to factor in the effects of dehydration and the increased
stress on the body caused at higher temperatures. Those numbers would have
to come down some.


Magilla

Magilla gets serious?

Anyway, that's the whole point of the question. Where's the crossover? You'd
think someone would have written their thesis on this.

--Art

Art M wrote:
2 questions:

1. I suppose there's an optimal temperature for power output on a bicycle in
a 40K TT.

Whatever temperature it is, is optimal.

No other answer gets you anywhere.