Too many spokes

Hi folks

At what point does a wheel have too many spokes?

If you go above a certain number, I'm speculating that the increase in
number of holes weakens the rim. clearly the spokes are under lower
individual tension.

Also more spokes equates to undesired extra mass and (some) more drag for a
deminishing improvement in reliability.

As a base for conjectu

A front wheel for a road bike (20lbs) with rider of 170lbs
700C box rim such as Mavic Open Pro or something available with lots of
holes. Eyelets or sockets fitted.
No specific front hub, but something large-flanged enough to take lots of
spokes. Drilled for the right number in each case.
Spokes guage to be determined by number used.
Brass nipples.
Laced 3x.
Built by the same guy.

It's common belief that a wheel can have too few spokes, but how about too
many?

Skippy
E&OE
(Hope this won't start another rant-fest, and that it's not FAQ)

Skippy wrote:
Hi folks
snip
If you go above a certain number, I'm speculating that the increase in
number of holes weakens the rim.
snip

All else being equal, this sounds correct..
However, all else isn't equal.
Take the extreme example of 40 hole tandem rims - although the extra
holes nominally weaken the rim, the rim is almost certainly a heavy
duty item, so overall, it comes out stronger.
Likewise, 40 hole tandem hubs generally have larger hubs to keep a
decent amount of material between the spoke hole drillings.
Equally, where the spoke count is low, the rim has been designed to
take that into account.

clearly the spokes are under lower individual tension.

Ummm - dunno if that's right.... you'd need to see the spec sheet for
the hubs to see if they give different max. spoke tensions for the
various drillings of the same rim.

Also more spokes equates to undesired extra mass and (some) more drag for a
deminishing improvement in reliability.

Yep, but those using the higher spoke count wheels (typically
tandemists, heavily laden tourists, those doing long distance
unsupported rides, or the very large rider) see these trade offs as
worthwhile.

The loaded tourist is hauling luggage + extra kit (say 20-30kg) anyway,
and probably at a relatively low average speed, so the weight and
aerodynamic concerns are lower on their list of priorities that they
are for the unladen day rider.


As a base for conjectu

A front wheel for a road bike (20lbs) with rider of 170lbs
700C box rim such as Mavic Open Pro or something available with lots of
holes. Eyelets or sockets fitted.
No specific front hub, but something large-flanged enough to take lots of
spokes. Drilled for the right number in each case.
Spokes guage to be determined by number used.
Brass nipples.
Laced 3x.
Built by the same guy.

snip

Common range for that kind of wheel would be 28, 32 or 36 spoke.
Looking as Sheldon's table at:
http://www.sheldonbrown.com/gloss_sp-ss.html#spoke

..and taking the wheelsmith 2.0DB (2.0/1.8) as an example, the spokes
weigh 193 g. for 32, so each spoke weighs about 6g, plus a nipple, say
1g.
Each four extra spokes weighs an extra 7g x 4 = 28g - say 55g for
eight, two wheels 100g.
That's not nothing, but again, looking at:
http://weightweenies.starbike.com/li...ype=roadwheels

....light end wheelsets seem to come in at 1500g .
100g / 1500g - approx. 7% - not huge.
A more typical wheelset might come in at 2kg, or more - the difference
is proportionally less in that case.

Long experience has shown that conventional wheels with 28 to 36 spokes
are a good reliable balance between longevity and performance for most
riders. That doesn't mean that it can't be improved on,.

As regards aerodynamics, I've no idea, but I would suggest that for the
majority of bikes (my own included), the limiting factor is the engine,
and the biggest gains are available by working on that, rather than
saving 10% on wheel weight or wheel drag ;-)

bookieb

Also realize that 40 gate stuff can be hard to find. 36/32 is a bit
more common.

"bookieb" wrote in message
ups.com...
Skippy wrote:
Hi folks
snip
If you go above a certain number, I'm speculating that the increase in
number of holes weakens the rim.
snip

All else being equal, this sounds correct..
However, all else isn't equal.
Take the extreme example of 40 hole tandem rims - although the extra
holes nominally weaken the rim, the rim is almost certainly a heavy
duty item, so overall, it comes out stronger.
Likewise, 40 hole tandem hubs generally have larger hubs to keep a
decent amount of material between the spoke hole drillings.
Equally, where the spoke count is low, the rim has been designed to
take that into account.

clearly the spokes are under lower individual tension.

Ummm - dunno if that's right.... you'd need to see the spec sheet for
the hubs to see if they give different max. spoke tensions for the
various drillings of the same rim.

Sorry, I thought that generally, when the spoke count went down the tension
went up (that's what the E&OE's for). Is this just that boutique wheels use
deeper/stiffer rims? Does a 32 spoke wheel have similar tension to a 36 for
example?



Also more spokes equates to undesired extra mass and (some) more drag for
a
deminishing improvement in reliability.

Yep, but those using the higher spoke count wheels (typically
tandemists, heavily laden tourists, those doing long distance
unsupported rides, or the very large rider) see these trade offs as
worthwhile.

The loaded tourist is hauling luggage + extra kit (say 20-30kg) anyway,
and probably at a relatively low average speed, so the weight and
aerodynamic concerns are lower on their list of priorities that they
are for the unladen day rider.


As a base for conjectu

A front wheel for a road bike (20lbs) with rider of 170lbs
700C box rim such as Mavic Open Pro or something available with lots of
holes. Eyelets or sockets fitted.
No specific front hub, but something large-flanged enough to take lots of
spokes. Drilled for the right number in each case.
Spokes guage to be determined by number used.
Brass nipples.
Laced 3x.
Built by the same guy.

snip

Common range for that kind of wheel would be 28, 32 or 36 spoke.
Looking as Sheldon's table at:
http://www.sheldonbrown.com/gloss_sp-ss.html#spoke

.and taking the wheelsmith 2.0DB (2.0/1.8) as an example, the spokes
weigh 193 g. for 32, so each spoke weighs about 6g, plus a nipple, say
1g.
Each four extra spokes weighs an extra 7g x 4 = 28g - say 55g for
eight, two wheels 100g.
That's not nothing, but again, looking at:
http://weightweenies.starbike.com/li...ype=roadwheels

...light end wheelsets seem to come in at 1500g .
100g / 1500g - approx. 7% - not huge.
A more typical wheelset might come in at 2kg, or more - the difference
is proportionally less in that case.

Long experience has shown that conventional wheels with 28 to 36 spokes
are a good reliable balance between longevity and performance for most
riders. That doesn't mean that it can't be improved on,.

As regards aerodynamics, I've no idea, but I would suggest that for the
majority of bikes (my own included), the limiting factor is the engine,
and the biggest gains are available by working on that, rather than
saving 10% on wheel weight or wheel drag ;-)

bookieb


Agreed that the increased loads on tandems and tourists may warrant a
tougher rim and more spokes. That's why I proposed the 'roadie' example.

The point I'm trying to get to is that yes 40/48 spoke wheels are in
practical terms no more reliable for the roadie. I'm just pondering whether
36 and then maybe 32 are too. I've got a 28 3x front wheel which seems to
be as durable as the 32 3x wheels I've had before. We're not into
'boutique' silliness here, but is 32 the optimum?

It seems to me that wheel components have got a bit better since it was
common to have 32/36 in a road wheel. A comment from the guy who built my
wheels was that 'well the rims are round to start off with these days. That
helps!'. I'm fairly sure spokes are better too.

So for the example roadie might we be 'over-building his/her wheels? I know
it's not much, but it would be one in the eye for the box wheel enthusiasts
to see a 24 spoker on proper hubs that looks as 'trendy' as theirs, costs
less, but doesn't turn into a Pringle when you look at it funny. Would such
a wheel be noticibly worse than 28, which seems no worse than 32 for me
anyway.

Just food for thought, not a crusade.

Skippy
E&OE

Skippy wrote:
Hi folks

At what point does a wheel have too many spokes?

If you go above a certain number, I'm speculating that the increase in
number of holes weakens the rim. clearly the spokes are under lower
individual tension.

Both points are not correct, I guess unless the rim had say 200 or so
spoke holes.

Also more spokes equates to undesired extra mass and (some) more drag for a
deminishing improvement in reliability.

As a base for conjectu

A front wheel for a road bike (20lbs) with rider of 170lbs
700C box rim such as Mavic Open Pro or something available with lots of
holes. Eyelets or sockets fitted.
No specific front hub, but something large-flanged enough to take lots of
spokes. Drilled for the right number in each case.
Spokes guage to be determined by number used.
Brass nipples.
Laced 3x.
Built by the same guy.

It's common belief that a wheel can have too few spokes, but how about too
many?

Skippy
E&OE
(Hope this won't start another rant-fest, and that it's not FAQ)

Right....nobody will argue about this...kinda of a non argumant-yes?

In the world of what is available hole wise in hubs and rims, worry
about not enough, not too many..36, what is currently available as a
maximum for non tandem stuff, is not too many..

Skippy wrote:
If you go above a certain number, I'm speculating that the increase in
number of holes weakens the rim.

Let's assume a hole in a continuous structure has an influence on (say)
3 times its diameter, ie that at more than 3 times hole radius, stress
is the same with or without the hole. If the above is correct, then
with 8mm holes and 600mm ERD you can put as much as (600*3.14)/3*8=75
spokes on a 622mm rim.
Of course, the "3time radius" hypothesis is rather optimistic, but the
point is that as the stress is not uniform on a wheel, the stress
concentration around the holes are a more weaker link that the general
decrease in supporting matter, ie the wheel will more likely fail
around a hole than elsewhere.



clearly the spokes are under lower
individual tension.

Doesn't seem so clear to me...

Spoke tension should be a compromise between two things:
- on one hand, keep it lower than the weaker of the following limits :
tensile strength of the spoke, or of the rim around spoke hole, or of
the spoke nipple thread (a common problem with the special Mavic FORE
nipples),
- on the other hand, keep it higher than the load exerted on spokes by
the sum of rider weight, shocks and pedaling or braking if any couples.

The first high limit is relatively constant according to the above (at
least around 36 spokes), as the second low limit is clearly linearly
decreasing with spoke count.

So, a higher-spoke-count wheel can be built with the same spoke
tension, it will only make it stronger (or to be more correct, less
prone to spoke slackening, which is the Big Bad Evil in a spoke-laced
wheel, isn't it?) unless holes are close enough to have significant
stress buildup between them.

It can also be built with proportionnally less tension, decreasing
stress arond holes. According to that, it would need the rim to be a
real Emmental-cheese before having the wheel weaker because of too many
spokes!

It reminds me of trial rims sold here in France, that are largely
hollow between spoke holes, made by (or sold by) Try All :
http://www.peppl.com/media/product/i...fdfb02db1d.jpg
Didn't hear complaints about these rims being too weak. Of course, the
upper sectrion of the box is not hollow! That can make a difference,
specially with a non-eyelet or single-eyelet rim.

Practically, very high spoke count could have at least the disavantage
of being difficult to lace, as the cross count shall increase with
spoke count to keep spoke angles constant (ie a 24 spokes wheel built
2X has the same spoke angles as a 36 spokes 3X and as a 48 spokes 4X
and so on) : the 6X needed for a 72-spokes wheel should not be easy to
deal with.

Skippy wrote:
If you go above a certain number, I'm speculating that the increase in
number of holes weakens the rim.

Let's assume a hole in a continuous structure has an influence on (say)
3 times its diameter, ie that at more than 3 times hole radius, stress
is the same with or without the hole. If the above is correct, then
with 8mm holes and 600mm ERD you can put as much as (600*3.14)/3*8=75
spokes on a 622mm rim.
Of course, the "3time radius" hypothesis is rather optimistic, but the
point is that as the stress is not uniform on a wheel, the stress
concentration around the holes are a more weaker link that the general
decrease in supporting matter, ie the wheel will more likely fail
around a hole than elsewhere.



clearly the spokes are under lower
individual tension.

Doesn't seem so clear to me...

Spoke tension should be a compromise between two things:
- on one hand, keep it lower than the weaker of the following limits :
tensile strength of the spoke, or of the rim around spoke hole, or of
the spoke nipple thread (a common problem with the special Mavic FORE
nipples),
- on the other hand, keep it higher than the load exerted on spokes by
the sum of rider weight, shocks and pedaling or braking if any couples.

The first high limit is relatively constant according to the above (at
least around 36 spokes), as the second low limit is clearly linearly
decreasing with spoke count.

So, a higher-spoke-count wheel can be built with the same spoke
tension, it will only make it stronger (or to be more correct, less
prone to spoke slackening, which is the Big Bad Evil in a spoke-laced
wheel, isn't it?) unless holes are close enough to have significant
stress buildup between them.

It can also be built with proportionnally less tension, decreasing
stress arond holes. According to that, it would need the rim to be a
real Emmental-cheese before having the wheel weaker because of too many
spokes!

It reminds me of trial rims sold here in France, that are largely
hollow between spoke holes, made by (or sold by) Try All :
http://www.peppl.com/media/product/i...fdfb02db1d.jpg
Didn't hear complaints about these rims being too weak. Of course, the
upper sectrion of the box is not hollow! That can make a difference,
specially with a non-eyelet or single-eyelet rim.

Practically, very high spoke count could have at least the disavantage
of being difficult to lace, as the cross count shall increase with
spoke count to keep spoke angles constant (ie a 24 spokes wheel built
2X has the same spoke angles as a 36 spokes 3X and as a 48 spokes 4X
and so on) : the 6X needed for a 72-spokes wheel should not be easy to
deal with.

Ok, I was wrong about spoke tension being lower with a larger number of
spokes.

I'd just picked that up from RBT.... Reduced spoke-count wheels using higher
tensions being noted on a number of occasions.

Skippy
E&OE, as ever!

Skippy wrote:
At what point does a wheel have too many spokes?

Here's my take on the subject... it's a practical limit.

In days gone by, a 36 spoke wheel would occasionally break spokes. That
failure rate was deemed acceptable at the time. If you used fewer spokes
of the same size and brought the wheel to the same tension, you would
experience more broken spokes because the stress in the spokes was
higher. One could possibly have used thicker spokes to compensate, but
then you'd need a deeper rim since the unsupported spans were larger. As
far as I can tell, deep section rims were not available in the 70s.

More than 36 spokes of the same diameter would reduce spoke failures,
but increase weight. Nobody wants to do that without good cause. Again,
one could have compensated with thinner spokes, but spoke windup would
be a problem during the build process.

So 36 spokes became a de facto standard.

Fast forward a few years... spoke quality improved, as did the
understanding of the wheel building process. The standard 36 spoke wheel
is now nearly immune to spoke failures. We can now use fewer spokes of
the same diameter (1.8 or 2.0 mm) with a low failure rate. Rim cross
sections have become deeper, allowing the larger unsupported spans
required.

The spoke windup problem has not changed; thin spokes are still a pain
in the butt to build with.

Note that this does not cover all of the pros and cons of different
spoke counts (i.e. failure mode, heavier riders, aerodynamics, and the
list goes on). It's my general opinion of the current state of affairs.

--
Dave
dvt at psu dot edu

Everyone confesses that exertion which brings out all the powers of body
and mind is the best thing for us; but most people do all they can to
get rid of it, and as a general rule nobody does much more than
circumstances drive them to do. -Harriet Beecher Stowe, abolitionist and
novelist (1811-1896)

Skippy Peanut Butter writes:

At what point does a wheel have too many spokes?

If you go above a certain number, I'm speculating that the increase
in number of holes weakens the rim. clearly the spokes are under
lower individual tension.

Can't you just ask without blurting out misinformation to show that
you really don't know much about it? This is a mix of MAS (male
answer syndrome) and wanting to find an answer. MAS: Give an answer
whether you know anything about it or not.

The rim is as weak as its smallest cross section and it doesn't get
worse with more spokes, spokes that give the rim radial rigidity. A
bare rim can be deflected manually more than 100 times what it does in
a wheel under heavy loading.

As for spoke tension, it is only needed to keep spokes from going
slack and the more of them the less individual loading they carry to
become slack. With your argument, taken to the limit, the best wheel
would have no spokes and no holes, not even a valve stem hole.

Also more spokes equates to undesired extra mass and (some) more
drag for a deminishing improvement in reliability.

So get some 10-spoke wheels and use them. You seem to have reasons in
favor of that.

As a base for conjectu

A front wheel for a road bike (20lbs) with rider of 170lbs
700C box rim such as Mavic Open Pro or something available with lots
of holes. Eyelets or sockets fitted.
No specific front hub, but something large-flanged enough to take
lots of spokes. Drilled for the right number in each case.
Spokes guage to be determined by number used.
Brass nipples.
Laced 3x.
Built by the same guy.

Spoke gauge is mainly a wheel building parameter. Too thin a spoke
cannot be tightened without twisting off in the process, so when fewer
spokes (that require higher tension) are used, they must be thicker.
That's how we came to the 1.6mm diameter spoke shaft because 1.5mm
ruptures when tightened for 36-spoke wheels. Causes and effects are
so often misrepresented that repeating them once more only helps
perpetuate these myths. Building with thin spokes is more difficult
than with thick ones.

It's common belief that a wheel can have too few spokes, but how
about too many?

So what's your point? BMX wheels with 72 spokes aren't unusual.
Today, spoke count is fashion!

Don't worry, the best number of spokes for durable 700c wheels was
pragmatically determined a long time ago at 36. As you see, cracking
rims are part of the landscape today (and formerly were not) with most
riders believing that this is to be expected. Today many people with
extra money are erasing the long development of reliable bicycle
wheels. Mavic appears to be pandering to those people.

(Hope this won't start another rant-fest, and that it's not FAQ)

I'm not sure what you had in mind but by its nature this is a troll,
starting as it does.

Jobst Brandt