Aero, Tension, and Low Spoke Counts Oh My!!

Breaking spokes, wheels that don't stay true, rubbing brake pads. The bane of those big and tall. You know what I'm talking about. But do we really need beefy aero wheels? Or just well built hoops at the hands of people who know what they're doing?

The following comes from the Framebuilders list. Obviously the topic generally revolves around frame building, but many times it branches out....and these folks know of what they speak.

William

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I'm curious to get everyone's opinion on minimum spoke count wheels such as the Rolfs, Cryseriums (sp?) etc. Some of these wheels have as few as 12 spokes and most are radially laced. All of them require very strong rims to counteract high spoke tensions. Very strong rims also means very heavy rims which puts all the rotating mass at the outside of the wheel. Compare this to a set of tubular rims laced 3x with 28 or 32 15/16 gage double butted spokes and you create a much lighter wheel which according to the laws of physics would take less force to accelerate. So does the wind resistance of 28 or 32 spokes offset the additional mass of these minimum spoke count wheels or are they just another marketing ploy?
Hal Bielstein

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I don't know about others' opinions, but I'm not a big fan - AT ALL. I'm not denying their performance, because they are really light and they typically offset the stiffer/heavier rim by using straight pull spokes with the nipples on the hubs. I think it's just a trade off between how aero you want your rim vs. how light you want your wheels. The Cane Creeks and Ksyrium SSCs spin up really quickly and actually do ride pretty well. They've managed to use a pretty low spoke count with a fairly light non-aero rim.

That said, I think it's all a bunch of marketing hype. My big complaint comes from their durability. Last summer riders in my group were put out of commission on two occasions. The first was a Ksyrium that broke a spoke, and with that low spoke count there was no way to even get the wheel true enough to continue the ride. So he had to call his wife to rescue him on the side of the road. As an added kick in the ass, none of the local bike shops carried that spoke, so he waited a week for one to come in. His wheels had less than 1000 miles on them at the time.

The second occasion was the previous generation (pre 10 speed) Dura-Ace. Same thing happened: A spoke broke and the wheel came out of true so badly there was no way to continue. Those wheels had less than 50 miles on them at the time. She had just bought them two days prior.

I've been running 28 spoke Ritcheys, which admittedly aren't the best wheels, but I've got a good 4000 miles on them and have had 3 broken spokes. In each case, I was able to compensate enough with the neighboring spokes to complete the ride and fix it when I got home. I finally got rid of the black-anodized bladed spokes that came stock and laced it up with some DT competitions and I haven't broken another one since.

Just my 2 cents,
Sean

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I wrench for a Mavic sponsored team and have also worked neutral
support at several rides/races.

For racing the wheels do offer an advantage in stiffness, weight, and
aerodynamics.

For the other 99.9% of the population they pretty much are a marketing
tool. With the exception of top of the line models, most use
considerably heavier rims, are a bear to work on, and have a harsh
ride. For any non-racing application I'd much prefer a more
conventional wheelset. I personally use Mavic Cosmos wheels on my road
and cross bikes and a set of 32 hole Open Pro wheels on my
commuting/light touring bike even though I have a basement full of
Ksyrium and Cosmic wheels.

I've had great success with Mavic wheels. Our team is mostly juniors
and we've used Ksyrium and Cosmic wheels for cross without any
problems (and teenagers are arguably harder on equipment than many
pros!) We have dented a few Kysrium rims from cross - that happens
when you ride half a lap on a flat - but they are pretty easy to
rebuild. Just make sure you take apart the hubs every so often clean
any dirt out of the hub/cassette interface. Fortunately, Mavic hubs
are a snap to take apart so this only takes a few minutes.

Prior to moving over to Mavic I used Campy wheels on my personal bikes
and had great luck with them. Only real difficult part of their wheels
is that some require you to remove the tire and rim strip to true
them. Fortunately, I only had to do that once.

Been less than impressed with Rolf wheels. I wrenched on a 7 day
charity ride and of the 11 broken spokes I repaired 7 were on Rolf
wheels. The Ritchey OEM wheels are also notorious for snapping spokes
though their WCS models seem to be much better. Haven't had enough
hands-on experience with Shimano wheels to fairly comment.

Chris Lowe

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Hal et al,
Perhaps a bigger factor for some riders (especially a Clydesdale like me) is the overall lateral stiffness of the wheel. True, the rim is heavier, and true, the rotating weight is therefore greater, but the stiffness Iin my experience, using Ksyriums) is WAY greater for climbing or sprinting than the hypothetical set of tubulars you mentioned, particularly for bigger folks. To me, that's the greatest benefit of the Ksyriums I ride--along with the fact that, touching wood, I haven't had an issue with them in 3 years, while any standard wheel would have given me at least a broken spoke or two.

In terms of marketing, I'm not sure why they don't focus on the strength and stiffness more than the 'aero' and just sell 'em to crit racers all day long...

John Cully

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Harold wrote
>>>The bottom line still is that if you break a spoke, you're gonna be
thumbing home.>>>

There is a solution! I'm 6'6" and 240 and I got tired of pushing my bike
home with broken spokes.

I bought a Stein tool for removing the cassette (available at Harris) and I
carry 3 spokes in my seat post.

I filled the post with foam and then stuck a cork in the end and pushed the
spokes through the cork. The foam keeps them from rattling on the tube.

I feel much more confident knowing I'm not going to get stuck in the
boonies!
Jim

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I don't really understand though.

Yes, I have had all my wheels custom made. But I weight 230lbs and have
broke a single spoke in all my life, that included Mountain biking. How
are all these spokes breaking all the time?

I also ride normal stuff, 32 hole, Mavic or Campy rims and DB spokes.
Same for MTB.

Dave Bohm

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dave bohm wrote:
How are all these spokes breaking all the time?


making them from aluminium as in Mavic Ksyriums helps a lot ;)
--

Marten Gerritsen

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Sean Ebert:

Both of the incidents I referred to (Dura Ace and Ksyrium) were faulty spokes. Close inspection by the bike shops revealed flaws near the heads. As for the spokes I broke on my Ritcheys, I later found out there was a recall due to a bad batch of the black bladed DTs. Since switching to round double-butted (and building them myself), I've not had a problem.

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Sean Ebert:
I'm not a wheel expert (and only recently acquired a tensiometer), but I'm operating under the impression that tension is determined by the strength of the hubs and rims, not by the weight of the rider you're building for.

From: Jim Blair
To: dave bohm >, framebuilders@phred.org
Subject: Re: [Frame] Minimum Spoke Count Wheels
Date: Wed, 04 May 2005 14:57:23 -0400

Dave wrote
How are all these spokes breaking all the time?

Doers a wheel builder tension the spokes the same for say a 160 lb rider
and a 240 lb rider?
Jim

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Seen a few snap. Most were due to the heads shearing off the nipples
at the rim. High spoke tension and alloy nipples are a less than ideal
combination!

Chris

On 5/4/05, Harold Bielstein wrote:
Thanks Chris- great information - appreciate your input. I guess I've
only seen the lower end of that wheel type spectrum. The bottom line
still is that if you break a spoke, you're gonna be thumbing home. Have
you had any experience with Velomax's wheels?

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Chris Lowe:
Umm that should be tiny fraction of all RIDERS.

On 5/4/05, Chris Lowe wrote:
Simple: the market for crit racers represents a tiny fraction of a
percentage of all racers. The reality is the majority of Ksyrium SL,
Zipp, Campy Bora, etc. wheels sold will never see competition just
like the majority of Ferraris sold will never be driven past 100mph.
Take a look at the number of USCF license holders and compare that to
the number of bikes sold.

Chris Lowe


On 5/4/05, john cully wrote:

In terms of marketing, I'm not sure why they don't focus on the
strength and stiffness more than the 'aero' and just sell 'em to crit
racers all day long...

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I have about 1200 miles on a set of Campy Eurus wheels (21 rear, 16 front
spokes, 28.5mm rim depth). So far I have had no problems, and they seem
to maintain true very well (no adjustments needed). I weigh 175 lb in r
iding gear, and while I avoid obvious road hazards, I do not baby them ei
ther. This is consistent with one test report I have read, and my LBS ag
rees.


I do worry about spoke breakage due to the high spoke tension and uniquen
ess (availability) of the spokes. I think the attachment design has a la
rge influence on this though. Straight-pull spokes (no elbow) are much l
ess likely to fail, since the bend is where most spokes break. Campy’s
design uses threads at both ends of the spoke, with the hub ends secured
by a T-nut that slides into the flange from the side, and has a circular
seating surface. Spoke failure due to impact damage is something else a
gain. If you don’t want to walk home, better have a spare wheel, or sp
are parts, tools, and not be in too much of a hurry.

WARNING: Engineer speak follows!

There are definitely some drag reduction benefits in deeper rims, but mos
t agree that you need more than 30mm rim depth to really get at it. Note
that full aero rims are ~60mm deep, and not suitable for general use due
to wind effects. I can hold a straight line with the Eurus wheels in gu
sty conditions, but it takes effort. Deep rims might exacerbate a shimmy
problem, with unsteady flow providing an excitation force. The Eurus spo
kes are “aero” shaped, but I don’t believe the thickness-to-chord r
atio is much over two (haven’t measured), so they are not much better t
han round spokes of the same thickness. However, they are about half as
thick as round spokes, and there are half as many of them, so the spoke d
rag must be about one fourth. For conventional wheels, the wheel drag is
maybe 10% of total bike + rider drag, so taking a wild guess, maybe ther
e is a few percent total bike + rider drag reduction possible here, less
in an extreme cross-wind (deep rims actually have lower drag in a moderat
e cross-wind).


On the flat at constant speed the power lost due to the extra weight is e
ssentially zero since it only affects rolling resistance. When accelerat
ing, the effective mass increase is doubled due to rotational inertia (as
suming all the weight increase is at the tire radius). For reference, Ca
mpy Eurus vs. Neutron (18.5mm, 22 front 24 rear spokes), both clinchers,
weight difference is 110g per pair. Let’s say I could save as much as
125g per wheel by going to a lighter shallow rim. This would equal 250g
per wheel set in mass, and 500g per wheel set “effective” mass. So f
or accelerating on the flat, I have added about 0.6% to total bike + ride
r mass (which is about 87 kg for me), and about the same in instantaneous
power required at the same acceleration rate. Climbing a significant hi
ll (say 7%) at a steady speed, the effect is only from hauling the increa
sed mass up the slope. I know that 1 kg mass increase is about 1% in pow
er under these conditions, so the heavier rims cost about 0.25% in power.



Adding up the numbers, the aero benefits will far outweigh any weight pen
alty on the flat (where close to 90% of rider power is in overcoming drag
), and probably come close to canceling out the weight penalty on a climb
, where close to 90% of rider power is used for climbing. Acceleration p
ower will always be increased, but maybe the extra lateral stiffness of t
he deeper rim will offset some of this.

Martin Manning

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A long time lurker, but I wanted to comment regarding wheels.

1. Spokes should **NEVER** break unless it is from a manufacturing
defect.
Manufacturing defects are rare and any spoke that is defective will break
either during the initial build or within the first few days of use.
Spokes that
break after this time do so because they are not stress relieved. There
are residual stresses at the elbows of the spokes that are caused by
the manufacturing process. If you don't relieve these stresses, then
eventually the spoke will break. I weigh over 200 pounds, often
commute with as much as 80 pounds on my bike, and have not had
a broken spoke not due to an accident as far back as I can remember,
at least 10-15 years, and I've never heard of a spoke breaking in any
of the 30-50 wheelsets I've built in that time either. Proper stress
relieving
results in a strong wheel which doesn't go out of true nor break spokes.

2. The weight of the wheel is inconsequential. If you take a bike, put
it in the largest gear (say a 53X12), and flip it upside down, you can
likely spin the rear wheel up to 40 MPH with one full crank revolution
from using just your arm. If you ride this bicycle and try to accelerate
it up to 40 MPH, you might never make it. The first example shows
the amount of power necessary to accelerate the wheel. The second
example shows the amount of power necessary to accelerate the
bike/rider combo. In relation to the mass and power necessary to
accelerate the complete bike/rider combo, wheel weight is basically
inconsequential. Aerodynamic effects outweigh weight in all but steady,
steep climbing. As a real life example, look at match sprinters, who
rely on acceleration the most of all bicycle racing events. They will
always use a heavy but aerodynamic wheelset.

3. In general, wheels that don't go out of true when a spoke breaks
aren't
built with enough tension. The amount of tension you can put into the
spokes greatly determines the load carrying and impact handling
capacity of a wheel, so whether you build for a 100 pound cyclist or
a 200 pound cyclist, you should use the same tension.

4. Harshness from certain wheelsets because they are "stiff" is not
backed up by measurement. Radial stiffness of most wheelsets is in
the 5000 lb/inch to 15000 lb/inch range. A 200 pound load on the ends
of this spectrum result in rim deflections of 0.04 inches in the least
stiff wheel to 0.013 inches in the stiffest wheel. Meanwhile, between the
tires and saddle, the amount of deflection is magnitudes greater,
probably on the order of a half inch or so, which is 12.5 times greater
than the least stiff wheel. It is hard to imagine that a rider could feel
something that offers that little contribution. It is likely that
wheelsets
which are described as "stiff" may sound differently or transmit
different frequencies of vibration, and these may be interpreted as
harsh.

Thanks for all the information on your list.

Wayne Lim

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So now the big question. As a frame builder producing a complete bike for a customer, will you stake your rep on a set of minimum spoke count wheels? Or do you spec a set of aftermarket wheels or do you build a set yourself? Whats the general consensus?
Hal Bielstein

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I have thought about this. I have had my fair share of issue with trick
aftermarket wheelsets and customers. They are a great money maker, I
might still offer them, but I have considered doing what e-richie does
and get somebody really good, like Joe Young to provide them for me.

Dave Bohm

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alas. great advice from bohemian-issimo.
e-RICHIE

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I build some frames, But I build waay more wheels. It
definitely belongs in the precision watchmaking
category of jobs, not many people do it well anymore.
Heck if QBP has it's way not only will you pay a lot
for a small order, but oem bike assembly will occur
there too. It's just one more way to remove labor and
services from the stores, that lbs' simply cannot do.


Low spoke count, high spoke count, carbon fiber helium
filled spoke rims welded by pass joints, who cares.
What ever the customer pays for and makes them grin is
the final answer. I have done plenty of low spoke
count wheels,a nd high ones, and properly designed for
an individuals needs, I've had no problems across the
board.

MYLES
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yeah,

custom wheels is my opinion. Why?
because why throw on wheels for 320lb guy on a frame
for a 130 lb woman?

I came into frame building from wheel building. My
favorite wheels are my 260 gr alum fiamme Ergals..

Build a pair of those up and you learn much. It's easy
to over tension those, even using 36 spokes. It's
weird to see a wheel want to buckle in the stand.

If your going to build, or have contract built wheels,
to go with your frame, you better understand how a low
spoke count wheel usually has a greater interia.
((less spokes mean higher tension each, and there is
also much more space between spokes that the rim has
to stabilize it's self. A double wammy. do the math)

For a store the pre-builts make sense, no labor
charge, and much, much more profit.

There is a vendor I'm working with that's about to do
330 gram clinchers.. the question is how to sell my
current customer on two sets of wheels...

Also consider how much drag is by using more, much
smaller spokes that have signifiacntly less drag...




cheers
Ed "a true race wheel is too light for touring or even
daily training, and only last a season anyhow"
westhead
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I build all the wheels for my bicycles. The only exceptions are when
the customer brings his old parts or the customer wants some specific
wheelset that is commercially available. I try to discourage the "wheel
systems" based on performance per dollar analysis. The general
population usually doesn't go fast enough to get anything out of these
fancy wheels, except perhaps bragging rights.
Omar Khiel
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A fun experiment... let the air out of your tires, and check the spoke tension, fill your tires again and check the tension.

Nat"going drink another cup of coffee and watch a movie while building up a pair of track wheels with DT comp, Campy Omega V-profile, Gipiemme Special Hubs, and Linseed Oil"Weller

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The conversation then branched off into spoke tension ....

William

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daniel:

I have yet to make a contribution, so why start now.
When I was in Italy many decades ago, I befriended a bike store owner,
and he taught me how to build wheels. I asked him why not just make each
spoke the same tension? He replied by saying, we are not dealing with
perfect materials. The rim is not a perfect circle. I do not understand
when people say there must be uniform tension. If every spoke had the
same tension, the wheel would be out of true.

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cosmetic trueness is a myth; you must err on the
side of proper and equal tension. furthermore,
rim materials and production tolerances many decades
ago bear no resemblance to current offerings.
e-RICHIE

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Even spoke tension. IT's important to realize that
tension increases and decreases as the wheel turns...
pardon the pun. In my humble opinion, perfect even
tension is relatively impossible. Within 5% or so, is
another story. Huge differences in tension can cause
things like premature spoke break-age, inability of
wheels to stay in true, and possibly low tides in
montauk.

myles

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Gott agree with Richard on that one. I recently built a wheel with an
old GEL 280 rim and couldn't help but notice how much more difficult
it was to build than an Open Pro. The rim simply wasn't round to begin
with.

You can make a wheel that has a deviation of only +/-5% tension and is
laterally and vertically true enough not to be noticed using modern
materials. Forced to compromise, I'll go with even spoke tension over
perfect trueness everytime.

Chris Lowe

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snipped:
"I recently built a wheel with an old GEL 280 rim..."


this example as well as ed's ergal 290 (or was it 260?)
gram rim illustrates the contrast when you use 20-30
year old technology. rims today are quite stout, and
machined sidewalls are a plus too. proper tension over-
rides cosmetic trueness any day of the week but today's
offerings allow that both are a possibility.
e-RICHIE

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Your friend in Italy is absolutely correct!
Omar Khiel

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I agree that today's rims are closer to true out of the box. But, the
example you mentioned, the difference you noticed was from the welded
seam versus the pinned seam. The welded seam rims are much more stable
to build. The machined sidewalls are also done to improve tolerances.
I will bet that the GEL and the Open Pro were rolled on the same or
similar machine at Mavic. They have always been good on tolerances.
They run into trouble when they get too light. A good example of this
was the Open 4CD which just pre-dates the Open Pro.
Omar Khiel

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Having built hundreds of wheels, I have observed that it is possible to
arrive at what Richard calls "cosmetic trueness" with uneven/incorrect
tension. The same wheel can be re-tensioned properly and cosmetic trueness
will follow. Like many things you will find that there are multiple ways to
get the wheel true, but only one way to really do it correctly.

Tony Pereira

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but...
cosmetic trueness must take a backseat to
proper and equal tension if IF the wheel
is to have integrity.
e-RICHIE

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I completely agree. I was trying to emphasize that cosmetic trueness is not
an indicator of correct tension.

Tony Pereira

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Is it just me, or does this thread have a decidedly "eastern" tone? The Yin and Yang of wheelbuilding... The ideals of cosmetic trueness and even tension can never be achieved simultaneously. These are false virtues. One can defeat the other, but the true ideal, integrity, is only possible with a peaceful compromise. Otherwise, self destruction is assured.

MPM