Wheel drag

Quoted message said:

Hi,

A while ago I remember using an online calculator that had lots of
different wheel combinations to test. In particular I am trying to
figure out how many watts a set of Zipp 404's will "save" at 45 kmh (28
mph) over a set of conventional 28 or 32 spoke wheels.

Anyone have any pointers?

Thanks!

Joseph

Se below for a objective look at such things. Remember tho, it assumes
all things being equal, one wheelset to the other, rider output wise
and that rarely is.

A.Lee said:

I used to worry about such things, but now I realise, as others point
out regularly, that the time spent comparing different wheels/equipment
is better spent training, and reducing your times, without spending a
fortune.

Unless you are actually in danger of winning a competition, it makes
sense to me to just ride what you have and calculate what the fancy
stuff might have done for you. If it looks like you might have won if
you'd had an upgrade, then spending the money would make more sense. If
it is just a matter of finishing 20th instead of 30th in a TT, then it
doesn't really matter to me.

On that note, you can build (or have built) a decent set of aero wheels
for much less than what the boutique models cost. A 30mm deep aluminum
rim (Velocity Deep, Sun TA1, Speedcific Niobium), with oval spokes
(Wheelsmith AE15 or XE14, DT Aerolites, Sapim Cxray), should be quite
fast, durable, and serviceable.

Quoted message said:

I use a .35 CdA for simulating being in the drops. Is that reasonable?
I'm working on a way to measure frontal area using a bitmapped b/w
photo with a histogram, but until then I use .65 sq meters.

That is probably a good guess for the GL330 case (CdA is the thing that
actually changes when you swap wheels)... as I recall, you are larger
than the average cyclist. I've been using .32 to model myself (6ft,
160lbs). Of course it will vary quite a bit depending on how
aerodynamic your body is, and how low you get in the drops.

It amazes me that elite cyclists can get CdA values of less than .20
with the best equipment.

You can get a good estimate of your sustainable power if you have a
good climb with a known grade... aero effects will be small. Then you
can translate that power number to riding on the flat and get a guess
at CdA. Or, you could also estimate CdA by taking measurements while
coasting down the hill. IHPVA has info on how to do this.

http://www.ihpva.org/

Ron Ruff said:

It amazes me that elite cyclists can get CdA values of less than .20
with the best equipment.

That *is* amazing! Unless you're talking about faired HPVs, of course.
But 0.20 on a diamond frame setup?

--
Dave
dvt at psu dot edu

Ron Ruff said:

A.Lee said:

I used to worry about such things, but now I realise, as others point
out regularly, that the time spent comparing different wheels/equipment
is better spent training, and reducing your times, without spending a
fortune.

Unless you are actually in danger of winning a competition, it makes
sense to me to just ride what you have and calculate what the fancy
stuff might have done for you. If it looks like you might have won if
you'd had an upgrade, then spending the money would make more sense. If
it is just a matter of finishing 20th instead of 30th in a TT, then it
doesn't really matter to me.

On that note, you can build (or have built) a decent set of aero wheels
for much less than what the boutique models cost. A 30mm deep aluminum
rim (Velocity Deep, Sun TA1, Speedcific Niobium), with oval spokes
(Wheelsmith AE15 or XE14, DT Aerolites, Sapim Cxray), should be quite
fast, durable, and serviceable.

There is no danger of me winning my main event, but the 4 events I am
going to concentrate on next season are all over 250km. These are more
or less big team time trials (without aero bars) where up to 30 riders
start per team, and the best 10 riders' times count toward the team
competition. Folks get "used up" along the way, but I'd like to be one
of those who finish with the lead group. In the 540km event, the 404's
theoretically could save me 1 hour. I won't finish an hour sooner, but
I might be able to stick it out the whole distance at speed.

Many months ahead to find some money for these wheels...

Joseph

Quoted message said:

There is no danger of me winning my main event, but the 4 events I am
going to concentrate on next season are all over 250km. These are more
or less big team time trials (without aero bars) where up to 30 riders
start per team, and the best 10 riders' times count toward the team
competition. Folks get "used up" along the way, but I'd like to be one
of those who finish with the lead group. In the 540km event, the 404's
theoretically could save me 1 hour. I won't finish an hour sooner, but
I might be able to stick it out the whole distance at speed.

Many months ahead to find some money for these wheels...

Joseph

Well, now that we know you're not talking about differences between
wheels during a TT-style event, the differences become even less
important. The benefits of aero wheels are greatly reduced when riding
in a pack. If your team of riders isn't riding 'on the rivet' as they
say, in full team time trial mode, you'll probably recognize no
appreciable benefit whatsoever.

Scott said:

Quoted message said:

There is no danger of me winning my main event, but the 4 events I am
going to concentrate on next season are all over 250km. These are more
or less big team time trials (without aero bars) where up to 30 riders
start per team, and the best 10 riders' times count toward the team
competition. Folks get "used up" along the way, but I'd like to be one
of those who finish with the lead group. In the 540km event, the 404's
theoretically could save me 1 hour. I won't finish an hour sooner, but
I might be able to stick it out the whole distance at speed.

Many months ahead to find some money for these wheels...

Joseph

Well, now that we know you're not talking about differences between
wheels during a TT-style event, the differences become even less
important. The benefits of aero wheels are greatly reduced when riding
in a pack. If your team of riders isn't riding 'on the rivet' as they
say, in full team time trial mode, you'll probably recognize no
appreciable benefit whatsoever.

We will be in rows of 2. The road is open to traffic so we can only
spread across one lane for crosswinds. There is always wind. On the
flat sections it will be expected of me to be one of the riders in the
pull rotation. I get to daft on climbs. I expect to have as much as 2
hours total (of 15) spent at the very front. Perhaps I will not get too
much benefit further back while "resting" but out front it will
certainly help. And if I can limit the amount of my reserves I burn up
while at the front, I increase my chances of being able to have some
juice left over to stick with the group for some of the last hills.

Not "on the rivet," but a lot more structured than a pack. I wonder
what that means.

Joseph

dvt said:

Ron Ruff said:

It amazes me that elite cyclists can get CdA values of less than .20
with the best equipment.

That *is* amazing! Unless you're talking about faired HPVs, of course.
But 0.20 on a diamond frame setup?

Yup... that's how those guys can go so fast! The forums at
BikeTechReview have a lot of discussions about aero position and CdA.
0.20 is very good but not impossible these days...

Quoted message said:

We will be in rows of 2. The road is open to traffic so we can only
spread across one lane for crosswinds. There is always wind.

If you have a strong cross wind you should be in a series of double
echelons, then.

Quoted message said:

On the
flat sections it will be expected of me to be one of the riders in the
pull rotation. I get to daft on climbs. I expect to have as much as 2
hours total (of 15) spent at the very front. Perhaps I will not get too
much benefit further back while "resting" but out front it will
certainly help. And if I can limit the amount of my reserves I burn up
while at the front, I increase my chances of being able to have some
juice left over to stick with the group for some of the last hills.

Your thinking seems pretty sound. One problem with deep rims though, is
that they will be harder to control in a crosswind... make sure you
have plenty of experience on them before the race.

What do you estimate the average speed to be?

I'd consider going with deep aluminum rims and oval spokes if you want
to save money... maybe upgrade later if it seems warranted. Also make
sure your clothing and helmet is the best it can be.

Quoted message said:

Scott said:

Quoted message said:

There is no danger of me winning my main event, but the 4 events I am
going to concentrate on next season are all over 250km. These are more
or less big team time trials (without aero bars) where up to 30 riders
start per team, and the best 10 riders' times count toward the team
competition. Folks get "used up" along the way, but I'd like to be one
of those who finish with the lead group. In the 540km event, the 404's
theoretically could save me 1 hour. I won't finish an hour sooner, but
I might be able to stick it out the whole distance at speed.

Many months ahead to find some money for these wheels...

Joseph

Well, now that we know you're not talking about differences between
wheels during a TT-style event, the differences become even less
important. The benefits of aero wheels are greatly reduced when riding
in a pack. If your team of riders isn't riding 'on the rivet' as they
say, in full team time trial mode, you'll probably recognize no
appreciable benefit whatsoever.

We will be in rows of 2. The road is open to traffic so we can only
spread across one lane for crosswinds. There is always wind. On the
flat sections it will be expected of me to be one of the riders in the
pull rotation. I get to daft on climbs. I expect to have as much as 2
hours total (of 15) spent at the very front. Perhaps I will not get too
much benefit further back while "resting" but out front it will
certainly help. And if I can limit the amount of my reserves I burn up
while at the front, I increase my chances of being able to have some
juice left over to stick with the group for some of the last hills.

Not "on the rivet," but a lot more structured than a pack. I wonder
what that means.

Joseph

Are you saying you're not familiar with the term 'on the rivet'? It's
a slang term implying that you're going all out, max effort, suffering
so badly you find yourself sliding up to the nose of the saddle (where
they used to have rivets, back in the day) trying to squeeze every last
bit of power out of your pedalstroke.

If my hunch is correct, considering that you're talking about a very
long event, you're likely to be pacing yourself to such a relatively
low power output (relative to your max) that what little aero benefit
you receive will be negligible toward your desired outcome of saving
your reserves.

But, hey, you apparently have your mind made up and you're looking for
validation of your decision to buy new wheels. Who needs validation,
anyway. Just buy your new wheels and be happy. I can hook you up with
a set of Reynolds DV tubular wheels, very lightly used (3 crits), for
waaay less than current retail. Email me directly if you're
interested.

Scott

Scott said:

Quoted message said:

Scott said:

[email hidden] wrote:

> There is no danger of me winning my main event, but the 4 events I am
> going to concentrate on next season are all over 250km. These are more
> or less big team time trials (without aero bars) where up to 30 riders
> start per team, and the best 10 riders' times count toward the team
> competition. Folks get "used up" along the way, but I'd like to be one
> of those who finish with the lead group. In the 540km event, the 404's
> theoretically could save me 1 hour. I won't finish an hour sooner, but
> I might be able to stick it out the whole distance at speed.
>
> Many months ahead to find some money for these wheels...
>
> Joseph

Well, now that we know you're not talking about differences between
wheels during a TT-style event, the differences become even less
important. The benefits of aero wheels are greatly reduced when riding
in a pack. If your team of riders isn't riding 'on the rivet' as they
say, in full team time trial mode, you'll probably recognize no
appreciable benefit whatsoever.

We will be in rows of 2. The road is open to traffic so we can only
spread across one lane for crosswinds. There is always wind. On the
flat sections it will be expected of me to be one of the riders in the
pull rotation. I get to daft on climbs. I expect to have as much as 2
hours total (of 15) spent at the very front. Perhaps I will not get too
much benefit further back while "resting" but out front it will
certainly help. And if I can limit the amount of my reserves I burn up
while at the front, I increase my chances of being able to have some
juice left over to stick with the group for some of the last hills.

Not "on the rivet," but a lot more structured than a pack. I wonder
what that means.

Joseph

Are you saying you're not familiar with the term 'on the rivet'? It's
a slang term implying that you're going all out, max effort, suffering
so badly you find yourself sliding up to the nose of the saddle (where
they used to have rivets, back in the day) trying to squeeze every last
bit of power out of your pedalstroke.

If my hunch is correct, considering that you're talking about a very
long event, you're likely to be pacing yourself to such a relatively
low power output (relative to your max) that what little aero benefit
you receive will be negligible toward your desired outcome of saving
your reserves.

But, hey, you apparently have your mind made up and you're looking for
validation of your decision to buy new wheels. Who needs validation,
anyway. Just buy your new wheels and be happy. I can hook you up with
a set of Reynolds DV tubular wheels, very lightly used (3 crits), for
waaay less than current retail. Email me directly if you're
interested.

Scott

I figured out the term from the context of your post. I was wondering
what the effects of the deep dish wheels in the group would be.

One of the reasons I am considering the 404's or perhaps Mavic is I
need something with a metal rim. It rains and is so gritty around here,
pure carbon would get worn out real fast. And since they are so
expensive, I plan to use them alot.

A few other I know may be interested in some Reynolds DV's. I'll see.

Joseph

Ron Ruff said:

Quoted message said:

We will be in rows of 2. The road is open to traffic so we can only
spread across one lane for crosswinds. There is always wind.

If you have a strong cross wind you should be in a series of double
echelons, then.

One of the problems is that our group is from a wide geographic area
which makes practicing as a complete group difficult to arrange. So
things that can be logistically complicated on the road may be avoided
due to lack of sufficient practice. This is one of the topics under
discussion. The whole tactical side has not been decided yet. One of
the ideas is to have 3 groups. The first group pulls the first 1/3
which is uphill, the next group pulls the next 1/3 which is flat, and
then last group "the finishers" pull the last 1/3 which is rolling with
some short steep climbs.

Quoted message said:

Quoted message said:

On the
flat sections it will be expected of me to be one of the riders in the
pull rotation. I get to daft on climbs. I expect to have as much as 2
hours total (of 15) spent at the very front. Perhaps I will not get too
much benefit further back while "resting" but out front it will
certainly help. And if I can limit the amount of my reserves I burn up
while at the front, I increase my chances of being able to have some
juice left over to stick with the group for some of the last hills.

Your thinking seems pretty sound. One problem with deep rims though, is
that they will be harder to control in a crosswind... make sure you
have plenty of experience on them before the race.

I plan to get my money's worth out of whatver wheel I end up with. I'll
make sure I have plenty of practice. Since I am pretty heavy, that
should make me a little less susceptible to getting blown around that
much.

Quoted message said:

What do you estimate the average speed to be?

The goal is 38.5 kmh for the 540km ride and 40+ for the 250km rides. On
the flats when I am to be helping with the pulling will be about
40-45kmh.

Quoted message said:

I'd consider going with deep aluminum rims and oval spokes if you want
to save money... maybe upgrade later if it seems warranted. Also make
sure your clothing and helmet is the best it can be.

Clothes is pretty straight forward. Tight with no flapping. Helmets is
a more difficult propoosition. Any suggestions? It has to be something
that can be worn for 20 hours and not be a waste when I'm fried and
keep looking down, unable to look straight ahead the whole time. I'll
probably stick with my normal LAS.

Joseph

Quoted message said:

[...]

Clothes is pretty straight forward. Tight with no flapping. Helmets is
a more difficult propoosition. Any suggestions? It has to be something
that can be worn for 20 hours and not be a waste when I'm fried and
keep looking down, unable to look straight ahead the whole time. I'll
probably stick with my normal LAS.

Joseph

From http://www.pezcyclingnews.com/?pg=fullstory&id=3574

"Most think that the frame matters the most, wheels next, and helmet
last. Some even think that the components come before the helmet. In
reality, a well designed aero-helmet will save you more time (power)
than anything else. The drag difference between a vented road helmet and
an aero-helmet is 2-4 times larger than the difference between a good
aero-wheelset and a 32-spoked wheelset."

Maybe looking for a more aero helmet could be worth it in your case.

Francesco

Quoted message said:

One of the problems is that our group is from a wide geographic area
which makes practicing as a complete group difficult to arrange. So
things that can be logistically complicated on the road may be avoided
due to lack of sufficient practice. This is one of the topics under
discussion. The whole tactical side has not been decided yet. One of
the ideas is to have 3 groups. The first group pulls the first 1/3
which is uphill, the next group pulls the next 1/3 which is flat, and
then last group "the finishers" pull the last 1/3 which is rolling with
some short steep climbs.

What event is this? Is it in Scandanavia?

JT

****************************
Remove "remove" to reply
Visit http://www.jt10000.com
****************************

Francesco Devittori said:

Quoted message said:

[...]

Clothes is pretty straight forward. Tight with no flapping. Helmets is
a more difficult propoosition. Any suggestions? It has to be something
that can be worn for 20 hours and not be a waste when I'm fried and
keep looking down, unable to look straight ahead the whole time. I'll
probably stick with my normal LAS.

Joseph

From http://www.pezcyclingnews.com/?pg=fullstory&id=3574

"Most think that the frame matters the most, wheels next, and helmet
last. Some even think that the components come before the helmet. In
reality, a well designed aero-helmet will save you more time (power)
than anything else. The drag difference between a vented road helmet and
an aero-helmet is 2-4 times larger than the difference between a good
aero-wheelset and a 32-spoked wheelset."

Maybe looking for a more aero helmet could be worth it in your case.

Francesco

That article doesn't really apply to the typical rider. They're talking
about minimizing drag on a pro cyclist that has the benefit of wind
tunnel testing and R&D to design a helmet to fit the specific rider's
profile.

Any 'off the shelf' aero helmet will have almost no appreciable gain
for the typical rider not riding in his optimal aero position, and will
likely be very poorly ventilated as well.

John Forrest Tomlinson said:

Quoted message said:

One of the problems is that our group is from a wide geographic area
which makes practicing as a complete group difficult to arrange. So
things that can be logistically complicated on the road may be avoided
due to lack of sufficient practice. This is one of the topics under
discussion. The whole tactical side has not been decided yet. One of
the ideas is to have 3 groups. The first group pulls the first 1/3
which is uphill, the next group pulls the next 1/3 which is flat, and
then last group "the finishers" pull the last 1/3 which is rolling with
some short steep climbs.

What event is this? Is it in Scandanavia?

JT

Yes, it is in Norway:

http://www.styrkeproven.no/styrk2003/index_en.shtml

Come join the fun! We could use another ex-messenger, NYC rider on the
squad!

The racing scene isn't very well developed in Norway, so lots of folk
concentrate on these "tour" rides. Quite a bit different from pack
racing where folks attack on climbs to drop people. These rides are all
about consistency and team work. There are regular bike races too, but
since the fields are so small, it isn't divided up into cat II,III, etc
so often. This means only the best show up because other folks don't
want to get punished so bad. Which means even fewer show up next time.
Vicious circle. So the rest of us do these tour rides.

Joseph

Scott said:

Francesco Devittori said:

Quoted message said:

[...]

Clothes is pretty straight forward. Tight with no flapping. Helmets is
a more difficult propoosition. Any suggestions? It has to be something
that can be worn for 20 hours and not be a waste when I'm fried and
keep looking down, unable to look straight ahead the whole time. I'll
probably stick with my normal LAS.

Joseph

From http://www.pezcyclingnews.com/?pg=fullstory&id=3574

"Most think that the frame matters the most, wheels next, and helmet
last. Some even think that the components come before the helmet. In
reality, a well designed aero-helmet will save you more time (power)
than anything else. The drag difference between a vented road helmet and
an aero-helmet is 2-4 times larger than the difference between a good
aero-wheelset and a 32-spoked wheelset."

Maybe looking for a more aero helmet could be worth it in your case.

Francesco

That article doesn't really apply to the typical rider. They're talking
about minimizing drag on a pro cyclist that has the benefit of wind
tunnel testing and R&D to design a helmet to fit the specific rider's
profile.

Any 'off the shelf' aero helmet will have almost no appreciable gain
for the typical rider not riding in his optimal aero position, and will
likely be very poorly ventilated as well.

That's what I'm worried about. Gain 2 seconds while sitting just right,
then lose 5 seconds when I look down from exhaustion. Since it is
usually pretty cold, ventilation isn't too big an issue. Looking like
an idiot getting passed by hundreds of people at the end while wearing
an aero helmet wouldn't be too satisfying either...

Joseph

Quoted message said:

Ron Ruff wrote:

Quoted message said:

Quoted message said:

If you have a strong cross wind you should be in a series of double
echelons, then.

One of the problems is that our group is from a wide geographic area
which makes practicing as a complete group difficult to arrange.

You can all practice the basic technique if you can get a couple of
other guys together. The speed difference is huge... if you expect any
crosswinds it would be a bad idea to avoid this. Heck, with 20-30 guys
you don't need much of a side wind before you'd be stretched out across
the lane. Teamwork is key if you desire a good result.

Quoted message said:

Clothes is pretty straight forward. Tight with no flapping.

Skinsuit, arm and shoe covers.

Quoted message said:

Helmets is
a more difficult propoosition. Any suggestions? It has to be something
that can be worn for 20 hours and not be a waste when I'm fried and
keep looking down, unable to look straight ahead the whole time. I'll
probably stick with my normal LAS.

One like this might be helpful:
http://www.performancebike.com/shop/profile.cfm?SKU=20002&subcategory_ID=4210

Also... if you are too big to be blown around... lose some weight! That
will help more than anything on the climbs.

BTW... how can the first 3rd of a 250km+ race be a climb?... and then
the next 3rd is flat? Is that a half percent grade or something?

Ron Ruff said:

Quoted message said:

Ron Ruff wrote:

Quoted message said:

Quoted message said:

If you have a strong cross wind you should be in a series of double
echelons, then.

One of the problems is that our group is from a wide geographic area
which makes practicing as a complete group difficult to arrange.

You can all practice the basic technique if you can get a couple of
other guys together. The speed difference is huge... if you expect any
crosswinds it would be a bad idea to avoid this. Heck, with 20-30 guys
you don't need much of a side wind before you'd be stretched out across
the lane. Teamwork is key if you desire a good result.

This is one of those things that can be practiced in theory, but when
the time comes could backfire bigtime, with lots of wasted effort,
shouting, etc. It will be dicussed at some of the winter meetings, and
if we can do it successfully in one of the warm-up rides, it may be an
option during the real event.

Quoted message said:

Quoted message said:

Clothes is pretty straight forward. Tight with no flapping.

Skinsuit, arm and shoe covers.

The weather is often cold, so arm and shoe covers are there anyway.
Most folks will have long pants too, at least for aprt of the ride.
Rain gear too. I'm amazed at how much ill-fitting rain gear you see
people using.

Quoted message said:

Quoted message said:

Helmets is
a more difficult propoosition. Any suggestions? It has to be something
that can be worn for 20 hours and not be a waste when I'm fried and
keep looking down, unable to look straight ahead the whole time. I'll
probably stick with my normal LAS.

One like this might be helpful:
http://www.performancebike.com/shop/profile.cfm?SKU=20002&subcategory_ID=4210

That looks pretty good. Not too agressive.

Quoted message said:

Also... if you are too big to be blown around... lose some weight! That
will help more than anything on the climbs.

Losing weight is on the program! But I'll never be under 95kg which
will keep we well anchored (in more ways than one!)

Quoted message said:

BTW... how can the first 3rd of a 250km+ race be a climb?... and then
the next 3rd is flat? Is that a half percent grade or something?

The first 1/3 isn't a climb, but it is "mostly up". The 540km has
4,400m of total ascent. The high point is about 1,000 meters 150km into
the ride, by which time at least half of the 4,400m has been climbed.
It is on a major road that is well graded with no significant sections
more than say 3-4%, usually less. All the 250km races are more or less
flat with at most a few 5 km climbs. One of the shorter prep rides has
a climb about 10km of 6% which kills me. I will be very surprised if I
hang with the group on that ride.

Joseph