Advice on Carbon wheels

"Arthur Clune" <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

Deep section rims with low spoke counts do make you go faster. That's a
very vague statement, but about as good as it gets I fear.

http://damonrinard.com/aero/aerodynamics.htm

is interesting on this.

Surprising how much time can be saved by cheap and easy solutions,
especially acquiring a pair of aero shoe covers and temporarily
dispensing with bottle & cage. I always used to carry a water bottle
in TTs, which explains why I never did all that well. Or at least
that's my excuse, and I'm sticking to it ;-)

David E. Belcher

In article <[email hidden]>, [email hidden] says...

Quoted message said:

http://damonrinard.com/aero/aerodynamics.htm

I was doing OK until I reached the following line:

"So far no measurements have been published concerning the influence of
beards."

at which point I began to suspect a spoof.

A quick question for the recumbenteers. When descending rapidly (And not
pedalling), knees together or apart for greatest aero effect?

Eddie demonstrated the "recumbent-super-aero-position" which involved
unclipping one foot and resting the back of the calf on the pedal thus
having both legs fully extended. I guess the next step would be an aero
chin guard so as to decrease air resistance under / around the neck!

<Hmm. Note to self - get out more!>

Jon

in message <[email hidden]>, Paul Rudin

(') said:

Clive George said:

The only time it does matter is when accelerating - it takes more
energy to accelerate mass on the wheel rims than it does to that
which is fixed to the bike/you. But since we're not talking about
fitting dumbbells to the rims, it still isn't that much difference.

I'm a bit confused about this. Even when the bike isn't accelerating
the rims must, surely be accelerating all the time - after all they're
stationary at the point of contact with the road and moving at twice
the speed of the bike at the opposite point.

No, if they're rotating at constant speed they're neither accelerating
or decelerating.

Quoted message said:

In the absence of friction, air resistance and so forth it wouldn't
matter, but given that we do have these things it's necessary to keep
added a bit of energy to keeps the wheels going round, and doesn't
this acceleration mean that weight is more signiifcant on the rims
than on (e.g.) the frame of the bike - even at constant bike speed?

No, Clive (and by extension James) is perfectly right - the point about
extra mass on the rims is only really significant during acceleration
and deceleration.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

;; not so much a refugee from reality, more a bogus
;; asylum seeker

in message <[email hidden]>, Clive George

(') said:

Jon Senior said:

In article <[email hidden]>, [email hidden]
says...

Quoted message said:

For (non-mountainous) TTing, certainly not - since you're pretty
much maintaining a constant speed, weight differences of the orders
being discussed don't matter.

For hill climbing, weight on rims counts exactly the same as weight
elsewhere.

The only time it does matter is when accelerating - it takes more
energy to accelerate mass on the wheel rims than it does to that
which is fixed to the bike/you. But since we're not talking about
fitting dumbbells to the rims, it still isn't that much difference.

And if your predominant riding style involves rapid sprints from set
of lights to another, or road racing where sprinting may be a
significant part of the competition?

Then you get a light bike/light wheels. But you still need to
consider the aero advantages - if these outweigh your acceleration
advantage, then it's worth getting the heavier wheelset. Eg in road
racing, if you want to make a break, having aero wheels would be
useful while trying to keep in front.

OK, but again can we quantify that? What is the aerodynamic benefit of
such rims as a percentage of the overall air drag of bike and rider?

I mean, I understand putting carbon rims on your bike if you think they
look pretty. I can understand putting carbon rims on your bike if you
think it will help you psych out the opposition. But I would assume
that most people buying carbon wheels do so in the belief that it will
make the bike faster, and so the question I'm asking is, will it? And
if so, under what conditions, and why?

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

Wise man with foot in mouth use opportunity to clean toes.
;; the Worlock

in message <[email hidden]>, David E.

Belcher (') said:

Back to the wheels topic - conventional spoked wheels are generally
reckoned to be better than Cosmics or Ksyriums on cost and maintenance
grounds

Quoted message said:

Oldham Cycle Centre is one shop worth contacting for
well-priced builds of such wheels.

Oddly enough, they're the people who sold me my Ksyriums - on the basis
that they were cheaper than Centaur hubbed wheels (admittedly due to a
special offer). I was impressed with the service I had from them - very
knowledgeable.

I am thinking about building myself a pair of Centaur hubbed wheels this
winter but the budget may not run to it.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

;; I'd rather live in sybar-space

On 11/10/04 5:05 pm, in article
[email hidden], "Simon Brooke"
<[email hidden]> wrote:

But I would assume

Quoted message said:

that most people buying carbon wheels do so in the belief that it will
make the bike faster, and so the question I'm asking is, will it?

Yes

Quoted message said:

And if so, under what conditions?

When you are faster than me.

Quoted message said:

and why?

To give me an excuse for not being so quick..

I'd expect them to make a difference as soon as you get into air resistance
territory, ie when it starts to become hard work [1] on the flat. For me
that would be about 20mph.

How much? the figures on the page linked elsewhere suggest as much as 5%. Or
in SFB [2] terms, a good handful of seconds over a ten TT.

The hillier the course, the less they will help.

...d

"Simon Brooke" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

OK, but again can we quantify that? What is the aerodynamic benefit of
such rims as a percentage of the overall air drag of bike and rider?

Ah well, at this point I duck out :-)

I can well believe it's significant for top level riders, but I don't know
how good you need to be to justify them. And on my bike, the
mudguards/SON/rack all almost certainly outweigh anything I could do with
the rims..

cheers,
clive

On Mon, 11 Oct 2004 16:37:21 +0100, Jon Senior

jon@restlesslemon_DOT_co_DOT_uk.remove said:

I was doing OK until I reached the following line:
"So far no measurements have been published concerning the influence of
beards."
at which point I began to suspect a spoof.

I think that might have been Rinard's sense of humour asserting itself
rather than part of the original Kyle study, which is, as far as I am
aware, genuine.

Guy
--
May contain traces of irony. Contents liable to settle after posting.
http://www.chapmancentral.co.uk

88% of helmet statistics are made up, 65% of them at Washington University

On 11/10/04 5:19 pm, in article [email hidden], "Clive

George said:

"Simon Brooke" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

OK, but again can we quantify that? What is the aerodynamic benefit of
such rims as a percentage of the overall air drag of bike and rider?

Ah well, at this point I duck out :-)

I can well believe it's significant for top level riders, but I don't know
how good you need to be to justify them. And on my bike, the
mudguards/SON/rack all almost certainly outweigh anything I could do with
the rims..

If you are not racing I don't suppose it makes much difference. If you are
racing then it would be significant enough to swing decisions if you are
replacing wheels.

...d

"Just zis Guy, you know?" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

On Mon, 11 Oct 2004 16:37:21 +0100, Jon Senior

jon@restlesslemon_DOT_co_DOT_uk.remove said:

I was doing OK until I reached the following line:
"So far no measurements have been published concerning the influence of
beards."
at which point I began to suspect a spoof.

I think that might have been Rinard's sense of humour asserting itself
rather than part of the original Kyle study, which is, as far as I am
aware, genuine.

The only properly bearded rider I can think of is one of the Aussie track
riders. But aero isn't so important for sprinting.

cheers,
clive

Jamie Smith said:

I am looking at buying myself some carbon wheels and would like some
advice from the group.

Firstly I am not the lightest of cyclists at 13 stone (82 Kg), I will
be using them for time trialling and also road racing.

So I would be looking for a reliable set of wheels which will take the
abuse of my weight.

I have been looking at a set of Mavic Cosmic Carbons and before
spending my cash want to be sure I am getting the right set.

Any advice would be great.

whatever you get, if you are using them for both RR & TT, then make sure
they comply with UCI rules for wheels, even domestic races count for RR.
http://www.uci.ch/modello.asp?1stlevelid=W&level1=1&level2=0&idnews=1628

Simon Brooke said:

No, if they're rotating at constant speed they're neither accelerating
or decelerating.

Relavative to the ground they're stationary at the bottom and moving
at twice bike speed at the top, they must accelerate to get from one
to the other, Shirley?

Just zis Guy said:

Quoted message said:

I was doing OK until I reached the following line:
"So far no measurements have been published concerning the influence of
beards."
at which point I began to suspect a spoof.

I think that might have been Rinard's sense of humour asserting itself

the Rinard pages are now hosted by Sheldon Brown....

---
Marten

"Paul Rudin" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Simon Brooke said:

No, if they're rotating at constant speed they're neither accelerating
or decelerating.

Relavative to the ground they're stationary at the bottom and moving
at twice bike speed at the top, they must accelerate to get from one
to the other, Shirley?

'tis true. But an entirely unhelpful view of it.

Better to think of it if you must as the sum of two constant speeds : one
linear (with the bike) and one spinning. WRT the ground, at the top, these
add up, at the bottom, they cancel out.
There's no acceleration for the linear bits. There is acceleration for the
rotational bits - there's a pull inwards causing them to stay as a circle
rather than fly apart into lots of little pieces.
But that acceleration involves no work, since it is perpendicular to the
direction of motion.

Alternatively, just remember that all the accelerations are cancelled out by
equivalent decelerations so they don't matter.

cheers,
clive

Simon Brooke said:

in message <[email hidden]>, Clive George
([email hidden]'😉 wrote:

Quoted message said:

OK, but again can we quantify that? What is the aerodynamic benefit of
such rims as a percentage of the overall air drag of bike and rider?

All the figures are on the Damon Rinard site, and here:
http://www.analyticcycling.com/
where you can input various variables to see how they would work.

From memory:All things being equal, and you changed your Mavic MA3 rims
with 32 spokes for a pair of good aero wheels, then you can expect a 30
second advantage over a 25mile flattish TT course.
Larger savings can be had, but you need to be good - the faster you go,
the better these wheels are - from 15-20mph, they make virtually no
difference, over 25mph they do make a difference.
Alan.
--
To reply by e-mail, change the ' + ' to 'plus'.
http://www.dvatc.co.uk - Off-road cycling in the North Midlands.

Simon Brooke said:

in message <[email hidden]>, Clive George

(') said:

"Simon Brooke" <[email hidden]> wrote in message
news:[email hidden]...

[someone had recommended Mavic Cosmic Carbon wheels]

Quoted message said:

Quoted message said:

885g front, 1090 rear. As against Ksyrium Equipe (which is what I'm
currently riding on) one third of the price, 835g front, 1000g rear,
on apparently the same hubs (all figures from Mavic's website).
Forgive me if I'm being very thick here, but what's the benefit of
the Cosmic Carbons which makes them worth 8% extra weight and 200%
extra money? (OK, the money I can understand, but paying more money
for _more_ weight really hurts).

Don't more aero wheels tend to be heavier?

That's really what I'm asking, I suppose. Clearly there is some benefit
from a more aerodynamic wheel. But at the same time we're forever being
told that weight at the rim of the wheel is the worst place to have it,
and, clearly, a non-structural aero fairing (which is what the Cosmic
Carbon appears to have) is just that - weight in exactly the wrong
place.

So is there a realistic trade off here, and does it make sense?

And if the aero benefit of the carbon fairing is so much as to be worth
8% (or more) extra rotating mass, then what is the (purely aero)
benefit of 20mm tyres as opposed to 23mm? Surely it must be of the same
order?

I mean I know there has always been snake-oil and pseudo-science in kit
for time trial bikes (bent crank-arms, for one example)... Don't get me
wrong, I think the deep aero section carbon rims look extremely cool.
But if one is trying to get a bike to go fast, are they a benefit or a
hindrance?

Dear Simon,

A table in the middle of this somewhat elderly page suggests
a 44 second benefit in a 40 km time trial by switching to an
aero front rim and bladed spokes:

http://damonrinard.com/aero/aerodynamics.htm

Comparing tire-width to aero-rim is trickier.

The tire is a nicely rounded object, so a wider tire is
pretty much just a scaled-up thinner tire.

But a deep aero-rim is a different shape than a normal rim
and works in several ways.

It fills in the turbulence-filled void behind the leading
section of a normally blunt rim, just like the trailing
fairing on a time trial helmet.

It provides a smooth wedge to part the air hitting the
trailing section of a normally blunt rim. Think of a blunt
barge bow versus the prow of a kayak.

It moves the rim-spoke joint inward, slightly reducing the
rotating speed at which the awful structure flails the wind.

It reduces the length of the spokes, slightly reducing the
amount of egg-beater action.

Carl Fogel

Simon Brooke said:

I mean, I understand putting carbon rims on your bike if you think they
look pretty. I can understand putting carbon rims on your bike if you
think it will help you psych out the opposition. But I would assume
that most people buying carbon wheels do so in the belief that it will
make the bike faster, and so the question I'm asking is, will it? And
if so, under what conditions, and why?

I am fairly confident that more aero wheels will help under almost all
circumstances, unless the weight penalty is very severe. A steep
hill-climb is likely to be one of the rare exceptions, but even in that
case, there is no _extra_ penalty relating to the position of the weight
on the rim.

James
--
If I have seen further than others, it is
by treading on the toes of giants.
http://www.ne.jp/asahi/julesandjames/home/

in message <[email hidden]>, Arthur Clune

(') said:

Jon Senior <jon@restlesslemon_dot_co_dot_uk.remove> wrote:

: Back to Simon's question. Does the aero advantage of low-spoke count
: deep section rims outweigh <sniggers> the disadvantage of the
: additional weight?

More helpful reply that has just occured to me: a good rule of thumb
would be the amount of time you spend above 25mph while pedaling
(downhill counts but only if you are putting effort in). Above that
speed you're getting noticable benifts from the aero affect. Below
that and it drops off.

Well, that answers the question as far as I'm concerned then. I'll stick
with my Ksyriums!

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

;; For in much wisdom is much grief; and he that increaseth
;; knowledge increaseth sorrow.." - Ecclesiastes 1:18

On 11/10/04 6:11 pm, in article [email hidden], "Clive

George said:

Better to think of it if you must as the sum of two constant speeds : one
linear (with the bike) and one spinning. WRT the ground, at the top, these
add up, at the bottom, they cancel out.

but going round a banked track, the part of the wheel in contact with the
track is stationary, but the part at the top of the wheel is moving slower
in the bends than in the straights for a given speed of rider...

...d

Simon Brooke <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

Oddly enough, they're the people who sold me my Ksyriums - on the basis
that they were cheaper than Centaur hubbed wheels (admittedly due to a
special offer).

At least I *think* they advertised the advantage of conventional
wheels over factory built ones. Nottingham-based PH Performance
certainly did in their CW ads of a couple of years ago (again,
competitive deals on Campag/Open Pro/Sapim combos).

Quoted message said:

I was impressed with the service I had from them - very
knowledgeable.

Yup, I'd definitely recommend Oldham Cycle Centre for mail order, very
helpful people to deal with.

David E. Belcher