Wheels for 700lb guy?

Chalo wrote:
jim beam wrote:

Chalo wrote:

jim beam wrote:

n3ox.dan wrote:

I've gone through a couple decent sets of rims with fatigue cracks
around the spoke holes (yes, both were eyeletted),

excess spoke tension - pure and simple. use a tensiometer and
build to the manufacturer's spoke tension spec.

Funny that it only seems to be a reliability issue with Mavic rims,
though.

you mean the commonest rims, crack most commonly? go figure!

If you think Mavics are more common than inexpensive rims, you are
fooling yourself. You should get out more.

Most rims in the world may not be Mavics, but Mavic is the single most
common make of rim with those who post to cycling newsgroups and forums -
therefore you will read more problems about Mavic rims than any other single
make.

~PB

On Mon, 17 Nov 2008 23:57:33 -0800, Chalo wrote:

jim beam wrote:

Chalo wrote:

jim beam wrote:

Chalo wrote:

jim beam wrote:

n3ox.dan wrote:

I've gone through a couple decent sets of rims with fatigue
cracks
around the spoke holes (yes, both were eyeletted),

excess spoke tension - pure and simple. use a tensiometer and
build
to the manufacturer's spoke tension spec.

Funny that it only seems to be a reliability issue with Mavic rims,
though.

you mean the commonest rims, crack most commonly? go figure!

If you think Mavics are more common than inexpensive rims, you are
fooling yourself. You should get out more.

i do actually, and round these parts, the only wheels i see that aren't
pre-built or mavic rimmed are the multi-colored velocities the bike
messengers use. but bike messengers are a dying breed.

OEM wheels outnumber handbuilt wheels by an order of magnitude.
Hardly any of them are Mavics. I have never seen one crack at the
drillings (not to say that it never ever happens, of course). OEM
wheels are rarely tensioned as high as handbuilt, but many of them are
repeatedly trued until individual spokes are abnormally tight.

that unfortunately is true - all because some underinformed "engineer",
unclear on the fundamentals, wrote a book dictating the use of spoke
tension "as high as the rim can bear".



In my
time with Austin Bike Zoo and Yellow Bike Project, I come across lots
and lots of wheels on their last stop before the recycler. They
aren't cracked unless they're Mavics.

I've tensioned cheapo rims until the spoke holes puckered, and the
wheels were still reliable and long-lasting. Good rims like Alex
take whatever tension I give them and just work right. I don't
have
to wonder, "is the tension spec high enough that I won't have spoke
loosening?" I just build them and run them. If I use my
tensiometer, it's only to verify that I got them plenty tight
enough
for my liking.

for a guy that spends his days machining to aircraft specs, that's
extraordinarily unbelievably imprecise.

It ain't rocket science, and it never has been.

absolutely fundamentally WRONG.

OK, it was the rocket science of the 1870s. But they weren't using
tensiometers to build wheels then.

and they didn't have wheels that stayed true out of the box then. and
they didn't have spokes that didn't break, so weren't cavalier about
potential damage prior to re-spoking.




dude, let's get the fundamentals absolutely crystal clear - wheel
strength does /not/ increase with increasing spoke tension.

Are you suggesting that a wire wheel's ability to bear weight is not a
function of spoke tension? I feel like such a doofus for adding all
those unnecessary extra steps after lacing them up.

you're simply regurgitating jobstian misconception. there is no magic
here - if a rim yield because of excess poke tension, it yields at
exactly
the same point load as if by excess load. if spoke tension is high,
because total yield stress on any point on the rim remains fixed, then
yes, that spoke tension detracts from the load capacity of the rim.
when
you look at jobst's "f.e.a.", that is a load calculation, not a strength
calculation.

I agree with you that hoop compression on the rim exerted by spokes
subtracts from the rim's net beam strength for riding loads. But
failures caused by exceeding a rim's radial beam strength are
vanishingly few, outside of landing jumps or impacts against obstacles
that bottom the tire.

disagree. the only wheel i've ever had taco was one where the spoke
tension was way above spec. it was a mountain wheel, hit a bump, and
"POW", it's wavy gravy locking against the frame.




Service failures related to spoke breakage or
slackening or inadequate lateral spoke support causing rims to go out
of true are far more common.

spoke breakage is real rare these days - with quality spokes at least.
and with thread lock, even loose spokes wheels last seemingly forever. my
mavic cosmos are crazy loose non-drive side rear, yet that wheel remains
completely true.




you /do/ need spoke tension to mitigate spoke fatigue cycling, keep
the
wheel quiet, stop spoke nipples unscrewing, etc., but that's not the
same thing.

Oh, so the wheel's ability to bear weight _is_ a function of spoke
tension, then.

ah, so you want to have your cake and eat it too? sorry, fatigue is not
static loading. next.

Ability to withstand static load is not reliability either, which is
what I keep trying to bring it back to. That's the OP's issue and the
name of the game for most of us. We have a given amount of weight to
carry, a given set of riding conditions, and we want our rides to be
trouble-free. 100kgf of spoke tension is usually necessary to reach
that goal for me. Not using recent Mavic rims is necessary too.

how can that be chalo? you use a tension higher than the rim
manufacturer's limit, it cracks, yet it's the rim's fault? the fault is
that you're using a rim that's too flexible for the load. unsurprising
unless you're using tandem rims.




Module 3 rims were fine, but a little too light for my use. M261 rims
broke at the sidewalls. T519s and A719s pooched out at the welds.
These are only my own rims I'm talking about-- I've seen more cracked
Mavics on customers' and acquaintances' bikes than I can shake a stick
at.

yeah, and i'll show you 100% failure to recognize manufacturer spoke
tension specs. spoke tension "as high as the rim can bear" is
fundamentally underinformed garbage.



At $80 per, I am through giving them more opportunities to
disappoint. $20 buys me an Alex rim I can live with, and $45 buys me
the strongest 700c rim ever made.

and at $80, i'm going to use the manufacturer spoke tension spec!!!



what else do we need to know? that spokes only go slack due to rim
elasticity distortion.

We also know that low tension spokes go slack long before high tension
spokes do. Or some of us do, anyway.

no, you've discovered that rims are elastic and distort at high load.
regurgitating jobstian misconception doesn't change that.

Higher tension means more elastic range on the spokes, which means
more load before they slacken. You know this.

and higher tension also means less available beam strength or point
loading strength. you know this. if you have elasticity problems, use a
less flexible rim.

again, this is a fundamental jobstian misunderstanding with his "wheel
stands on the spokes" model. the wheel is not all about the spokes - it's
about the spokes /and/ the rim. without the rim, the spokes are nothing.
and with an infinitely stiff rim, you don't see the bottom spokes
significantly slacker than any others. think about that. /all/ your
problems are rim stiffness, not spoke slackness.




if you have built to manufacturer spoke tension spec, and your spokes
are going slack, you have an inappropriately un-stiff rim for the
load.

Or your spokes are too loose, or they are too thick.

question: you believe that thin spokes at high tension are just as stiff
as thick spokes at low tension, yes?

Of course not. But they allow the rim to move a whole lot more before
it goes unsupported.

but it's not the "support" that's the problem.
http://www.flickr.com/photos/38636024@N00/417157612/




conclusion: get a stiffer rim, /don't/ simply increase spoke tension.

I'm sorry, but this is crap. Heavier loads require higher spoke
tension
_and_ rims that can bear higher spoke tension.

no chalo, you're laboring under the yoke of jobstian misinformaton.
elasticity is not a function of load. all you achieve with higher spoke
tension is higher point loading at the spoke nipple junction and less
rim
load capacity [hoop strength].

Why higher tension on M/C spokes, then? Nothing to do with the loads
involved?

who says they're higher??? they're stiffer, but that doesn't mean they're
tighter.



It's the same whether
we're discussing pushbikes, motorbikes, or wire-wheeled cars. Mavic
have
their reasons to recommend the same spoke tension for all their rims
regardless of weight and cross-section, but it gives away half of a
heavy rim's means of carrying a load compared to a light rim. It's
like
using the same spoke tension for a kidbike or a BMW R1150GS.

no. again, it's rim distortion due to elasticity that allows a spoke to
go lack. tightening a spoke doesn't change the modulus of the rim - or
the spoke.

Right, it only gives the spoke more takeup-- which you need if you are
to carry more load.

no, you need a stiffer rim to carry more load. see above.



Anyone who has had the opportunity to observe the difference in what
the
same rim will carry with 32 vs. 36 vs. 48 spokes can attest that gross
spoke tension is a critical component of the equation. And anyone who
has been messing around with bikes for very long can tell you from
experience that tightly strung wheels are categorically more reliable
than loose ones.

except for when the spoke tension causes the rims to crack!

spoke count is not spoke tension. more spokes mean more rim support -
it's spoke count making the difference, not the combined tension.

You were just saying it was all about rim stiffness! I'm pointing out
that a Sun CR18 with 48 spokes in fact carries more load and lasts
longer than one with 32. Same rim, same radial stiffness. More total
spoke tension.

spokes do support the rim. but the /fundamental/ problem is exactly as i
state, not fudging the issue with an infinite number of spokes.




again,
modulus is the same whether near yield or near zero. but near yield,
there is little additional load possible, and that's what you're causing
with excess spoke tension.

I know that there are rims so skinny and feeble that they collapse
before it becomes difficult to tighten the spokes due to windup or the
limitations of the nipple flats. But these are not on the table when
the issue is how to improve reliability for a heavy rider.

but their analysis is /essential/ if the heavy rider is to understand the
principles involved in building a reliable wheel!!!



As a heavy
rider and one who has had the opportunity and inclination to try,
prove, and destroy a lot of wheels, I have been able to correlate
increased spoke tension (over 100kgf but less than 150kgf) with
increased reliability

for undersized rims. and you experience other reliability problems as a
result. this is not a zero sum game.


, _in wheels built with rims that tolerate such
tension_. When a rim can't tolerate that sort of tension, I have to
use especially thin spokes to keep it from being a maintenance hassle,
with predictable side effects on stiffness and ease of building and
truing.

all of which you'd avoid if you weren't laboring under certain fundamental
misunderstandings.




Given that Mavic rims exhibit shortcomings related to spoke tension
(hole cracking, weld buckling) and unrelated to spoke tension (brittle
sidewalls, needlessly high cost), I won't go to the trouble of
accommodating them by using extra-slender spokes. It isn't worth
it.

they're high end, at the limit rims chalo. and they're not stiff enough
for a 300-400lb guy. listening to you complain about mavic is like
listening to you complain about shimano cranks - they're simply not built
for a guy like you. and it's unreasonable for the rest of us to have them
do so - we don't want to lug all that extra weight about!

On Tue, 18 Nov 2008 04:13:12 -0600, Ben C wrote:

On 2008-11-18, jim beam wrote:
On Mon, 17 Nov 2008 21:03:29 +0100, Pete Biggs wrote:
[...]
A lower number of spokes needs higher tension per spoke, not lower.

no, that's a fundamental jobstian misunderstanding - increasing wheel
strength is not a function of increasing spoke tension, so you don't
need to compensate for lower spoke count with higher tension.

With fewer spokes there are longer sections of rim between spokes, so
won't you get a bigger displacement for a given load?

The stiffer the rim is to start with the fewer spokes you need but if
you built an 18 spoke MA-2 (using every other hole) you would need more
tension to support the same load before they went slack than if you used
36 spokes.

like this?
http://www.flickr.com/photos/38636024@N00/417157612/



In practice low spoke-count rims are presumably stiffer (hence the low
spoke count), which is why the recommended tension isn't usually any
higher than for high count rims.

in practice, that is correct. and these days, most rims are much deeper
profile than ma2's.

On Mon, 17 Nov 2008 22:16:41 -0800, Chalo wrote:

Tom Sherman wrote:

Chalo Colina wrote:
[...]
Mavic is a high end product and their success is built on making big
profit margins by selling at a premium without manufacturing at a
premium. Â*One of the things they have to do to make this happen is
consistently put out nicely finished rims that are smooth with crisp
edges and clean surfaces.[...]

Mavic rims also have a high European Heritage & Mystique® content.

That is a very expensive ingredient. Almost as expensive as unobtanium.

Chalo

ridiculous comment. address the facts - don't play schoolyard smear games.

On Mon, 17 Nov 2008 22:14:36 -0800, Chalo wrote:

jim beam wrote:

Chalo wrote:

Pete Biggs wrote:

There must be millions of rims in the world that are weaker than
anything Mavic have made. Â*They'll crack when over-tensioned, and
won't when not.

In most cases, nothing, not even overtensioning to the point of
buckling, causes rims to crack. Â*The difference is that most rims,
but not Mavics, are made with relatively ductile rather than brittle
alloys.
Â*I adequately addressed this in my previous post.

The Vuelta rims you mentioned may be an exception, as are Velocity
rims which are made from the same weak alloy as Mavics (but with
better geometry and thicker spoke beds).

chalo, istr having a chat with you about the difference between mavic
and a campy rim that was causing severe "gritting" with a fellow's
brakes. Â*as i recall, we concluded that the mavic rim offered better
braking because it was closer to a "free machining" alloy.

do you recall?

No, but I do believe that we had such a discussion, and that the topic
is relevant. It brings up a possible reason I hadn't already thought of
for Mavic to overharden their rims during heat treatment-- easier or
faster sidewall machining.

braking trumps machining.




do you not agree that clean linear braking is of higher importance than
whether a rim cracks if the spoke tension is exceeded?

Sure. I don't think one choice precludes the other, but that is a good
order of priorities.

What then justifies Mavic's use of 6106 alloy in their heaviest rims--
the ones that are designed to see the highest loads-- when it is
specifically stipulated that those rims are not to be used with rim
brakes?

Chalo

er, when it's specifically stipulated that you stop being dogmatic and
start paying attention to the fundamentals?

On Tue, 18 Nov 2008 12:24:47 +0100, Pete Biggs wrote:

Chalo wrote:
Pete Biggs wrote:

There must be millions of rims in the world that are weaker than
anything Mavic have made. They'll crack when over-tensioned, and won't
when not.

In most cases, nothing, not even overtensioning to the point of
buckling, causes rims to crack. The difference is that most rims, but
not Mavics, are made with relatively ductile rather than brittle
alloys. I adequately addressed this in my previous post.

You have to tension at least near to the point of buckling for a good
Mavic rim (e.g. A719, Open Pro) to crack, if it does. That is an
unnecessary amount of tension, therefore the fact that some Mavic rims
can crack is irrelevant.

indeed.

this is like a guy bleating that the steel wires used as circumferential
bracing in radial car tires may fatigue. indeed, they can, and ultimately
will. but not before the tire rubber wears out. so such a fear is
completely baseless and irrelevant.




The Vuelta rims you mentioned may be an exception, as are Velocity rims
which are made from the same weak alloy as Mavics (but with better
geometry and thicker spoke beds).

This "excepion" just looks like an average modern cheap rim to me. It
didn't crack immediately after the over-tensioning. The cracks
developed some days and miles later.

The Mavic rims I've used with similar tension to what I used with the
Vuelta have a better design with more material or double eyelets. None
of these have cracked.

~PB

On Nov 18, 6:13*am, jim beam wrote:
On Mon, 17 Nov 2008 22:16:41 -0800, Chalo wrote:
Tom Sherman wrote:

Chalo Colina wrote:
[...]
Mavic is a high end product and their success is built on making big
profit margins by selling at a premium without manufacturing at a
premium. *One of the things they have to do to make this happen is
consistently put out nicely finished rims that are smooth with crisp
edges and clean surfaces.[...]

Mavic rims also have a high European Heritage & Mystique® content.

That is a very expensive ingredient. *Almost as expensive as unobtanium.

Chalo

ridiculous comment. *address the facts - don't play schoolyard smear games.- Hide quoted text -

- Show quoted text -

Says the guy whose idea of the basest insult possible is "jobstian."

Cripes, jim, sometimes you make sense, but you don't need to be a jerk
about it, especially when Tom & Chalo are just having a laugh.

On Sun, 16 Nov 2008 16:42:33 -0800 (PST), may have
said:

Ok, I don't weigh 700 pounds. I weigh a solid 300. I don't care about
the weight of my rims, I care only about strength and fatigue
performance. I have a short, flat, bike ride to work every day.

I bought some Mavic A719 36 hole wheels for my bike

Well, there's your problem. Mavic has become infamous for rim cracks
of late, and it happens even with riders a lot lighter than you.

Presumably I had uneven spoke tension that I should have kept an eye
on, and I got cracks from that, causing the wheel to go out of true.
Does that sound right?

IMO, blame the rims...and get some from a different manufacturer.

I used this subject line because I find plenty of "I'm 250lb and
touring with 50lb of gear and my Mavic A719's are fine" kind of posts
on the internet, but what I want to know is "I'm 300 pounds and want
wheels I can ignore at least a little in the interest of just getting
into work." I'm not saying I'm not going to true the things, I'm just
saying I want to do it on Saturday and I don't want eight miles of out-
of-true ride to be an absolute death knell for my wheels

Is that a ridiculous hope? Is the 300-lb fat-guy wheel **with a
margin of error** a pipe dream, at least in a price range under
several hundred bucks? Hopefully I'm not offending everyone by even
asking ;-)

Any rim rated for use on a tandem *should* be far more than capable of
carrying you around, even on rough surfaces.

I've gone through a couple decent sets of rims with fatigue cracks
around the spoke holes (yes, both were eyeletted), and I suppose it's
just my fault for being cavalier about maintenance but it seems like
cracking rims on an 8 mile round trip, flat, minimally bumpy ride
means I'm right up at the capacity limit for the wheel, and I want
something that will do more. I probably can't have it, but I figured
I'd ask.

Wheels that will do the job are easily possible, and no, you shouldn't
be seeing this kind of failure rate.


--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.

jim beam wrote:

Chalo wrote:

jim beam wrote:

chalo, istr having a chat with you about the difference between mavic
and a campy rim that was causing severe "gritting" with a fellow's
brakes. *as i recall, we concluded that the mavic rim offered better
braking because it was closer to a "free machining" alloy.

do you recall?

No, but I do believe that we had such a discussion, and that the topic
is relevant. *It brings up a possible reason I hadn't already thought of
for Mavic to overharden their rims during heat treatment-- easier or
faster sidewall machining.

braking trumps machining.

Not for the manufacturer, it doesn't. Mavic isn't in the game for
passion, like so many others in the bike biz. They're all about
margin.

do you not agree that clean linear braking is of higher importance than
whether a rim cracks if the spoke tension is exceeded?

Sure. *I don't think one choice precludes the other, but that is a good
order of priorities.

What then justifies Mavic's use of 6106 alloy in their heaviest rims--
the ones that are designed to see the highest loads-- when it is
specifically stipulated that those rims are not to be used with rim
brakes?

er, when it's specifically stipulated that you stop being dogmatic and
start paying attention to the fundamentals?

You didn't answer the question. If, as you suggest, they may be using
a weak alloy partly to provide cleaner sidewall machining and better
rim braking, than why would they use the same weak alloy on disc-
specific rims that are supposed to be as strong as possible?

Chalo

In article
,
Chalo wrote:

jim beam wrote:

Chalo wrote:

jim beam wrote:

Chalo wrote:

jim beam wrote:

n3ox.dan wrote:

I've gone through a couple decent sets of rims with fatigue
cracks around the spoke holes (yes, both were eyeletted),

excess spoke tension - pure and simple. *use a tensiometer
and build to the manufacturer's spoke tension spec.

Funny that it only seems to be a reliability issue with Mavic
rims, though.

you mean the commonest rims, crack most commonly? *go figure!

If you think Mavics are more common than inexpensive rims, you
are fooling yourself. *You should get out more.

i do actually, and round these parts, the only wheels i see that
aren't pre-built or mavic rimmed are the multi-colored velocities
the bike messengers use. *but bike messengers are a dying breed.

OEM wheels outnumber handbuilt wheels by an order of magnitude.
Hardly any of them are Mavics. I have never seen one crack at the
drillings (not to say that it never ever happens, of course). OEM
wheels are rarely tensioned as high as handbuilt, but many of them
are repeatedly trued until individual spokes are abnormally tight.
In my time with Austin Bike Zoo and Yellow Bike Project, I come
across lots and lots of wheels on their last stop before the
recycler. They aren't cracked unless they're Mavics.

I've tensioned cheapo rims until the spoke holes puckered, and
the wheels were still reliable and long-lasting. *Good rims
like Alex take whatever tension I give them and just work
right. *I don't have to wonder, "is the tension spec high
enough that I won't have spoke loosening?" *I just build them
and run them. *If I use my tensiometer, it's only to verify
that I got them plenty tight enough for my liking.

for a guy that spends his days machining to aircraft specs,
that's extraordinarily unbelievably imprecise.

It ain't rocket science, and it never has been.

absolutely fundamentally WRONG.

OK, it was the rocket science of the 1870s. But they weren't using
tensiometers to build wheels then.

And rocket science has moved on, even if jim hasn't.