Wheels for 700lb guy?

On Mon, 17 Nov 2008 00:07:24 -0800, Chalo wrote:

wrote:

landotter wrote:

Alex DM18s are a good choice for a clyde. It's got even more meat
than the Mavic. Less than $20. ERD is close enough to the 604 I found
for the Mavics for you do tape 'em up and do a direct swap. You'll
need to emery paper the joints as they aren't welded, if you want
smooth braking.

Well that sounds like maybe a good combo of cheap solution and an intro
to wheel building. If I mess it up, not such a big deal for $20. It
does look like a pretty hefty cross section too.

After trying a variety of spoke types and gauges we switched to a 48
spoke rim and haven't had any more problems.

That sounds like the correct long term solution for me. I'm going to
take a hard look at tandem wheels. Rebuilding with a cheap rim is
probably better given my grad school budget at the moment, but more
spokes sound like a good idea as soon as I can.

I second landotter's recommendation of the Alex DM18. It's a sane
cross-section, heavy enough for the job, made of good strong 6061-T6
alloy, and cheap to buy. It's what most people should have on their
road bikes if they don't like to repair their wheels and don't want to
spend a lot of money on them.

If you intend to run tires at least 30mm wide (and you should do so),
the Sun Rhyno Lite 700c is another good candidate. It weighs in the
same range as the DM18, but it has a larger cross-section (therefore
more stiffness and better load sharing among spokes).

Both of the above rims are made from much more ductile and less crack-
prone than anything Mavic has made in a long time.

If you want to use narrow tires of less than 28mm width, the Velocity
Deep-V is a more expensive but very strong rim, especially when laced
with 36 or more spokes. It's pretty lightweight, too-- just 520g
claimed, though all rims vary from one specimen to the next.

Most of my bikes have 48 spoke wheels. (I weigh about 350 lbs. at the
moment, but I have weighed as much as 400 lbs. I am 6'8" tall.) But
most of my bikes have rims that are no longer available. To complicate
matters, most of today's strongest rims come only in 32 and 36 hole
versions. So it's no longer the undisputed best idea to use 48 spokes
if you want the strongest possible wheel. You have to weigh your
priorities against the available options. Where 48 spokes may still
offer the best weight bearing and the greatest future serviceability,
some 36 spoke wheels may offer better stiffness and less frequent
maintenance simply because the choice of rims is better.

For the ultimate in strength, but a width that makes it incompatible
with most road bikes, the Kris Holm 29" (700c) mountain unicycle rim is
currently without peer in its rim diameter. It's 38mm wide and weighs
in the neighborhood of 900g. It comes only in 32 and 36 hole variants.

http://www.unicycle.com/shopping/shopexd.asp?id=805

I don't think that will be necessary for you. I think that a good wheel
build with 36 14ga. or 14/15ga. spokes and Alex DM18 rims should do the
trick. If your riding habits or road conditions are particularly harsh
and that does not solve your problems, it is at least the cheapest and
most effective next step along your way. 300 pounds is really not all
that much in the grand scheme of things. 700 pounds, well... that's
another matter. Check back in with me in that case. I have some ideas.

I encourage you to read _The Bicycle Wheel_ by Jobst Brandt,

that book is ONLY usable for lacing instruction. for engineering theory,
it's got a multitude of fundamental mistakes, not least of which being the
recommendation to use spoke tension "as high as the rim can bear". if you
only need lacing instruction, there are other books, or as you say, the
excellent sheldon brown's.


or
http://www.sheldonbrown.com/wheelbuild.html, or b oth, and try your hand
at building your own wheels. If your above average mass, like mine, is
a permanent condition rather than a weight fluctuation, you will do
yourself a service in the long term by building and maintaining your own
wheels.

Chalo

Chalo wrote:
Pete Biggs wrote:

wrote:

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?

Cracks around the spoke holes sounds like excessive spoke tension.

--which is only a chronic issue with Mavic rims from the last ~20
years.

Not in my experience with A719 and Open Pro.

"Excessive" spoke tension therefore can be evaluated
alternatively as "substandard" rim structure.

I can say that recent Mavic rims have failed for me at spoke tensions
where lighter rims from other makers have held up fine.

I built a rear wheel with an A719 - and it has tolerated good tension. I
got to the point where the (lubed) nipples were hard to turn, so that's
pretty high tension. I would expect only an unreasonable degree of tension
to crack it. People do do unreasonable things with their wheels.

~PB

On Nov 17, 2:32*am, Hank wrote:
On Nov 17, 12:09*am, landotter wrote:



On Nov 17, 1:33*am, Hank wrote:

On Nov 16, 10:49*pm, landotter wrote:

On Nov 16, 9:56*pm, wrote:

Alex DM18s are a good choice for a clyde. It's got even more meat than
the Mavic. Less than $20. ERD is close enough to the 604 I found for
the Mavics for you do tape 'em up and do a direct swap. You'll need to
emery paper the joints as they aren't welded, if you want smooth
braking.

Well that sounds like maybe a good combo of cheap solution and an
intro to wheel building. *If I mess it up, not such a big deal for
$20. *It does look like a pretty hefty cross section too.

You'll have to double check the ERD for sure, but if it's within a
couple mms--indeed, just tape the rims together, making sure that the
"handedness" of the spoke holes is correct, and swap the spokes one by
one. Use an electric driver from the inside to do this. A flat head
will do, or a philips bit with most of two fins ground off works as
well. If you don't have a truing stand, like most of us, do remember
to set your brake pads very carefully and closely before you do this--
and you can use your bike as a truing stand.

The Alex is a good strong rim--it's not machined and it's not welded,
so it will take emery paper for a minute or three on the joint. It
should solve your problem if built right and tensioned well. My last
rerimming I did with some has a couple thousand miles on 'em with no
touch ups needed. I've hauled groceries, ice biked--you name it, DM18s
is strong stuff. Don't let the non-Eurosnob price tag fool you.

I'll cast another vote for Alex, but I say spring for another 5 bucks
and get the Adventurer, which has eyeleted spoke holes.

DM18 in 700c *is* eyeleted.* The Adventurer is powder coated and has
machined walls and handsomer for sure, but the ERD ain't right.

ERD for A719 is 600.5 (per Spocalc)
Adventurer is 603.1
DM18 is 606.4 (per alexrims.com)

I'd say you're much more likely to be able to do the swap with the
Adventurer.

Heh, funny how Mavic's so retarded as to not even put ERD on their
site. My search gave figgurs from 600-604. Either will work, I'm sure.
Get the Adventurer if you want black and machined, DM18 if ya want
classic silver.

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.

No it is not. I had cracking around the spoke holes with a Vuelta Tempest.

~PB

Qui si parla Campagnolo wrote:

wrote:

I bought some Mavic A719 36 hole wheels for my bike and kept an eye
(not good enough, apparently) on them to see if they were still
running true. *They ran true for a long time but when did go out, I
already had fatigue cracks around several spokes and I need a new rear
wheel again.

Set of these-

http://www.velocityusa.com/default.asp?contentID=584

Too light for tandems and big men, too expensive for what they are,
too crude to be top-shelf, and made from weaker 6106 alloy like Mavics
instead of stronger 6061-T6 like Alex. I wanted to like them when I
first became aware of them, but they are OEM-grade stuff. They're
fine for touring bikes for light to average riders. Deep-Vs are a
couple of ounces heavier and more structurally optimized/stiffer, so
they make better heavy-duty rims.

36 front, 48 rear. Good enough for a tandem, good enough for you.
shimano tandem hubs modified for your frame or Phil Wood.

Shimano tandem hubs and Phil Wood anything hubs are ridiculously,
comically overpriced for what you get. At least the Phils look nice;
Shimano doesn't even give you that.

The OP said something about being in school. I doubt he would warmly
welcome the idea of spending $350 on a whole wheelset, let alone on
just the hubs.

Chalo

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.

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.

But Mavics don't work like that. They crack. The fact that they are
almost alone in that regard tells me there ain't nothin' wrong with
high spoke tension; there's something wrong with Mavic rims.

Chalo

Chalo wrote:

"Excessive" spoke tension therefore can be evaluated
alternatively as "substandard" rim structure.

I can say that recent Mavic rims have failed for me at spoke
tensions where lighter rims from other makers have held up fine.

I built a rear wheel with an A719 - and it has tolerated good
tension. I got to the point where the (lubed) nipples were hard to
turn, so that's pretty high tension.

How many newtons of tension is "nipples were hard to turn"?

I don't know the number of newtons because I don't have a tensiometer, but
the tension is as high as a good pro builder would use with any wheel with a
good rim and the same number of spokes. It's the same with Mavic Open Pro.
You can build good strong reliable wheels with them. The body of evidence
for that is overwhelming.

And how many spokes are you talking about?

36.

A719s might be OK with 32 taut
spokes, but I have observed firsthand that they are not OK with 48
taut (1200N) spokes.

A lower number of spokes needs higher tension per spoke, not lower.

I wouldn't be interested in running that deep
into my structural safety margin, but if you're not hard on wheels it
might not be a problem.

The wheel is better than one I could build with a more average and cheaper
rim like the Vuelta I mentioned in my other reply - with which I could not
get such high tension. Unlike many cheaper alternatives, some of Mavics
best rims (including A719 and Open Pro) have double eyelets - which help
according to Jobst Brandt's theory and my experience so far.

If you're not hard on wheels, you don't have to spend a lot of time or
money on them. Mavics cost a lot of both, compared to other rims.

I would expect only an unreasonable degree of tension
to crack it. People do do unreasonable things with their wheels.

The body of field evidence is overwhelming

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.
Riders who are much heavier than average need wheels with more spokes, then
they won't need such high spoke tension that the rims will crack.

~PB

Pete Biggs wrote:

Chalo wrote:

Pete Biggs wrote:

wrote:

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?

Cracks around the spoke holes sounds like excessive spoke tension.

--which is only a chronic issue with Mavic rims from the last ~20
years.

Not in my experience with A719 and Open Pro.

I had 48h T519s and A719s and they were both cheese. They didn't even
last long enough to crack at the spoke holes; they squashed in
compression at their heat-affected welded joints. Horrible. Even the
cheapest, corniest rims I have ever used never did that.

"Excessive" spoke tension therefore can be evaluated
alternatively as "substandard" rim structure.

I can say that recent Mavic rims have failed for me at spoke tensions
where lighter rims from other makers have held up fine.

I built a rear wheel with an A719 - and it has tolerated good tension. *I
got to the point where the (lubed) nipples were hard to turn, so that's
pretty high tension. *

How many newtons of tension is "nipples were hard to turn"? And how
many spokes are you talking about? A719s might be OK with 32 taut
spokes, but I have observed firsthand that they are not OK with 48
taut (1200N) spokes. I wouldn't be interested in running that deep
into my structural safety margin, but if you're not hard on wheels it
might not be a problem.

If you're not hard on wheels, you don't have to spend a lot of time or
money on them. Mavics cost a lot of both, compared to other rims.

I would expect only an unreasonable degree of tension
to crack it. *People do do unreasonable things with their wheels.

The body of field evidence is overwhelming-- Mavics are crack-prone.
Here is my personal understanding as to why:

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.

Strong aluminum alloys (most aluminum alloys, actually) don't yield a
particularly fine surface or crisp detail from extrusion, the process
by which rims are made. But 6106 alloy is particularly good for
making pretty extrusions; you don't, as a manufacturer, have to spend
a lot of downtime, labor, and consumables messing around with your
equipment to keep the finish quality good. The catch is that 6106 is
the weakest member of its family of aluminum alloys-- substantially
weaker than all-round standard 6061. Mavic could simply use more of
it, and thus enjoy the benefits of increased stiffness and heat
capacity along with adequate strength, but if they did that their rims
would be heavier, like for like, than rims using plain old 6061. That
would put a crimp in their plans to charge more for less.

So the smart folks at Mavic do two things: Overharden their rims in
heat treatment, so that they are not as conspicuously soft and weak as
they would be with a normal T6 treatment, and spec a spoke tension low
enough to mostly prevent buckling of the (weak) rims or cracking of
the (overhardened and brittle) alloy they use. If you use their
tension spec, and you are not hard on wheels, then you got a "premium"
product that works for you, they got their fat margins, and
everybody's happy.

It doesn't work so well when the rim's performance is seriously
challenged. Big guys and some tandemists do this, but so do racers
and weight weenies (because their rims are so light). Since the racer
and weight weenie crowds are important to Mavic's continued ability to
charge more for less, they use a different, stronger alloy on their
Open Pro and probably some other racy rims, so that those rims don't
blow their reputation for making stuff that does in fact work. They
spend more money making those extrusions pretty, but they get to
charge even more for them as they boast about their fancy Madeupname
alloy that's "20% stronger!" or some such thing, but which might well
just be plain old 6061-T6.

The scheme is good, and it works to provide Mavic with a big stream of
profit that they can use for marketing, so they can continue to charge
more for less into the indefinite future. But cracking around the
spoke holes at spoke tensions that are well tolerated by other,
cheaper rims is one of the ways that those of us who are not privy to
their trade secrets can figure out that what is premium for Mavic
might not be premium for us.

Chalo

landotter wrote:

Hank wrote:

ERD for A719 is 600.5 (per Spocalc)
Adventurer is 603.1
DM18 is 606.4 (per alexrims.com)

I'd say you're much more likely to be able to do the swap with the
Adventurer.

Heh, funny how Mavic's so retarded as to not even put ERD on their
site. My search gave figgurs from 600-604. Either will work, I'm sure.
Get the Adventurer if you want black and machined, DM18 if ya want
classic silver.

I've built with Adventurer too, and it's a nice rim, probably stiffer
than the DM18. It looks a little tawdry by comparison, but that's
what black and machined does to my eyes. It's still a hell of a good
rim for the price.

Chalo

Michael Press wrote:

Not your fault. The Mavic rims cannot sustain sufficient
force at the spoke holes.

Have you used an A719?

~PB