Proper tension for Rolf Sestriere?

I have some Rolf Sestriere Ti wheels, which are practically brand new. They
aren't even as tight as some conventional wheels I've had. So I'm wondering
what the proper tension should be. I want to make sure they're perfectly tuned
before I ride on 'em and bend 'em up. Any thoughts?

These are spoked 20f, 24r. The rims are similar to other contemporary,
semi-aero designs. The spokes are paired, but round/conventional, not bladed.

Any thoughts?

Matt O.

PS -- I probably *will* unload these in favor of something more reliable, but I
want to bring these up to par while I still have 'em.

I have some Rolf Sestriere Ti wheels, which are practically brand new. They
aren't even as tight as some conventional wheels I've had. So I'm wondering
what the proper tension should be. I want to make sure they're perfectly tuned
before I ride on 'em and bend 'em up. Any thoughts?

matt

if the spokes are ti, they're unlikely to feel as "tight" as steel
spokes, and increased tension is not going to do anything to change it.
ti has about half the modulus of steel, so, very roughly speaking, a
14-gauge ti spoke is going to be twice as elastic as a 14-gauge steel one.

other than that, just make sure they're properly tensioned in the normal
way. sorry!

"Matt O'Toole" wrote in message ...
I have some Rolf Sestriere Ti wheels, which are practically brand new. They
aren't even as tight as some conventional wheels I've had. So I'm wondering
what the proper tension should be.

Those are limited by the use of Revolution spokes on the drive side,
and by the rear hub's high dish. You pretty much tighten the spokes
until the first right side spoke yeilds (combined tension and
torsion), and that's your limit.

They are probably at the limit now. The ones I've seen never get the
spokes very tight. Just ride and enjoy!

jim beam wrote in message om...
I have some Rolf Sestriere Ti wheels, which are practically brand new. They
aren't even as tight as some conventional wheels I've had. So I'm wondering
what the proper tension should be. I want to make sure they're perfectly tuned
before I ride on 'em and bend 'em up. Any thoughts?

matt

if the spokes are ti, they're unlikely to feel as "tight" as steel
spokes, and increased tension is not going to do anything to change it.
ti has about half the modulus of steel, so, very roughly speaking, a
14-gauge ti spoke is going to be twice as elastic as a 14-gauge steel one.

other than that, just make sure they're properly tensioned in the normal
way. sorry!

Dear Jim,

Forgive the anguished cry of the layman, but what
do you mean? I'm not teasing you or being sarcastic,
just trying to understand what you wheel-builders
are saying. It may be like trying to understand
baseball batters.

Titanium spokes won't feel as tight as steel, so
other than that make sure that they're properly
tensioned in the normal way?

I'm guessing that this means that "feel" isn't
what you consider the proper, normal method of
tensioning spokes, but I'm not sure that I'm right.

Still confused,

Carl Fogel

Titanium spokes won't feel as tight as steel, so
other than that make sure that they're properly
tensioned in the normal way?

if you have two springs, one rated at 20lbs & the other at 10lbs, the
20lb spring is going to deflect half that of the 10lb spring for each lb
of load. a ti spoke has roughly half the modulus of an identically
sized steel spoke so is roughly twice as elastic.

I'm guessing that this means that "feel" isn't
what you consider the proper, normal method of
tensioning spokes, but I'm not sure that I'm right.

it's nothing to do with tensioning method. it's purely a function of
the modulus. easy!

jim beam wrote:
Titanium spokes won't feel as tight as steel, so other than that make
sure that they're properly tensioned in the normal way?


if you have two springs, one rated at 20lbs & the other at 10lbs, the
20lb spring is going to deflect half that of the 10lb spring for each lb
of load. a ti spoke has roughly half the modulus of an identically
sized steel spoke so is roughly twice as elastic.

I'm guessing that this means that "feel" isn't
what you consider the proper, normal method of tensioning spokes, but
I'm not sure that I'm right.


it's nothing to do with tensioning method. it's purely a function of
the modulus. easy!


The force you feel when deflecting a tensioned spoke is not
purely or even primarily a function of modulus. It would be
for a spoke with zero initial tension, but not for a tensioned
spoke. At small deflections the additional elongation is
negligible, and the resisting force comes from the sines
of the deflection angles and the initial tension. At high
deflections, additional elongation becomes significant and
modulus does matter.

Dave Lehnen

matt- I have some Rolf Sestriere Ti wheels, which are practically brand new.
They
aren't even as tight as some conventional wheels I've had. So I'm wondering
what the proper tension should be. BRBR

To really be sure, have a tensionometer slapped on them, with a proper look at
the tension conversion chart. Your idea to ensure they are built correctly,
with these and ohhh so many other wheels outta boxes, is a good one before you
ride them.

Peter Chisholm
Vecchio's Bicicletteria
1833 Pearl St.
Boulder, CO, 80302
(303)440-3535
http://www.vecchios.com
"Ruote convenzionali costruite eccezionalmente bene"

Dave Lehnen wrote in message ...
jim beam wrote:
Titanium spokes won't feel as tight as steel, so other than that make
sure that they're properly tensioned in the normal way?


if you have two springs, one rated at 20lbs & the other at 10lbs, the
20lb spring is going to deflect half that of the 10lb spring for each lb
of load. a ti spoke has roughly half the modulus of an identically
sized steel spoke so is roughly twice as elastic.

I'm guessing that this means that "feel" isn't
what you consider the proper, normal method of tensioning spokes, but
I'm not sure that I'm right.


it's nothing to do with tensioning method. it's purely a function of
the modulus. easy!


The force you feel when deflecting a tensioned spoke is not
purely or even primarily a function of modulus. It would be
for a spoke with zero initial tension, but not for a tensioned
spoke. At small deflections the additional elongation is
negligible, and the resisting force comes from the sines
of the deflection angles and the initial tension. At high
deflections, additional elongation becomes significant and
modulus does matter.

Dave Lehnen

Dear Dave,

I suspect that what you're saying is said quite clearly
for the engineering crowd, but I'm so far behind here
that I'm not even certain that I'm on the same page as
you and Jim.

By "deflecting" do you mean plucking or pushing the tensioned
spoke sideways to get a "feel" for the "tightness," a sort
of seat-of-the-pants tension-measurement that a tensiometer
would measure far more slowly and accurately?

If so, are you and Jim discussing whether this sideways "feel"
would be noticeably different between steel and titanium spokes,
given the small sideways movement involved, with Jim suggesting
that the twice-as-elastic titanium spoke would bend or deflect
further, while you suggest that the elastic difference doesn't
actually matter much for a tensioned spoke that moves only
slightly sideways?

Sorry if I've completely missed what's being said.

Carl Fogel

Carl Fogel wrote:

Dave Lehnen wrote in message ...

jim beam wrote:

Titanium spokes won't feel as tight as steel, so other than that make
sure that they're properly tensioned in the normal way?


if you have two springs, one rated at 20lbs & the other at 10lbs, the
20lb spring is going to deflect half that of the 10lb spring for each lb
of load. a ti spoke has roughly half the modulus of an identically
sized steel spoke so is roughly twice as elastic.


I'm guessing that this means that "feel" isn't
what you consider the proper, normal method of tensioning spokes, but
I'm not sure that I'm right.


it's nothing to do with tensioning method. it's purely a function of
the modulus. easy!


The force you feel when deflecting a tensioned spoke is not
purely or even primarily a function of modulus. It would be
for a spoke with zero initial tension, but not for a tensioned
spoke. At small deflections the additional elongation is
negligible, and the resisting force comes from the sines
of the deflection angles and the initial tension. At high
deflections, additional elongation becomes significant and
modulus does matter.

Dave Lehnen


Dear Dave,

I suspect that what you're saying is said quite clearly
for the engineering crowd, but I'm so far behind here
that I'm not even certain that I'm on the same page as
you and Jim.

By "deflecting" do you mean plucking or pushing the tensioned
spoke sideways to get a "feel" for the "tightness," a sort
of seat-of-the-pants tension-measurement that a tensiometer
would measure far more slowly and accurately?

If so, are you and Jim discussing whether this sideways "feel"
would be noticeably different between steel and titanium spokes,
given the small sideways movement involved, with Jim suggesting
that the twice-as-elastic titanium spoke would bend or deflect
further, while you suggest that the elastic difference doesn't
actually matter much for a tensioned spoke that moves only
slightly sideways?

Sorry if I've completely missed what's being said.

Carl Fogel

After re-reading the original post, I'm not sure what he
meant when saying the wheels didn't feel tight. If he meant
the wheels had too much lateral (sideways) flexibility, Jim
was correct in saying tightening the titanium spokes would
not do any good. If he meant that the spokes seemed to be
too loose when pushed sideways by hand, or perhaps plucked
like a guitar string, tension will matter.

The possibly irrelevant point I was trying to make in my last
post was that if you push a tensioned spoke sideways, but only
a small distance, the modulus of elasticity of the material
has very little effect. Modulus of elasticity is a measure of
material stiffness.

As an example, suppose you have two spokes, one stainless, and
one titanium, tensioned to 250 lb each, between two perfectly
rigid supports. Each spoke is 1.8 mm diameter. The titanium
spoke has elongated about 1.074 mm from the tension, but the
stiffer stainless spoke has elongated 0.632 mm. Now push each
spoke 2 mm sideways at mid-span. From triangle geometry, each
spoke elongates an additional 0.028 mm. The tension in the
titanium spoke goes up to about 257 lb, and the tension in
the stainless spoke to about 263 lb. It takes about 7.3 lb
of force to deflect the ti spoke, and about 7.5 lb for the
stainless spoke. For bigger deflections the modulus matters a
lot more. If you push each spoke 10 mm sideways at mid-span
instead of 2 mm, the additional elongation is 0.713 mm.
Tension in the ti spoke goes up to about 416 lb, and in the
stainless spoke to about 532 lb. The deflection forces are now
about 59 lb for the ti spoke and about 76 lb for the stainless
spoke, probably now enough to feel the difference.

The above calculations ignore bending stresses in the thin
wire spokes, and assume neither spoke starts to yield. I mixed
English and metric units only because not many people have much
feel for how much force a Newton is, but spokes are sold in mm.

Dave Lehnen

Dave Lehnen wrote in message ...

[snip]

After re-reading the original post, I'm not sure what he
meant when saying the wheels didn't feel tight. If he meant
the wheels had too much lateral (sideways) flexibility, Jim
was correct in saying tightening the titanium spokes would
not do any good. If he meant that the spokes seemed to be
too loose when pushed sideways by hand, or perhaps plucked
like a guitar string, tension will matter.

The possibly irrelevant point I was trying to make in my last
post was that if you push a tensioned spoke sideways, but only
a small distance, the modulus of elasticity of the material
has very little effect. Modulus of elasticity is a measure of
material stiffness.

As an example, suppose you have two spokes, one stainless, and
one titanium, tensioned to 250 lb each, between two perfectly
rigid supports. Each spoke is 1.8 mm diameter. The titanium
spoke has elongated about 1.074 mm from the tension, but the
stiffer stainless spoke has elongated 0.632 mm. Now push each
spoke 2 mm sideways at mid-span. From triangle geometry, each
spoke elongates an additional 0.028 mm. The tension in the
titanium spoke goes up to about 257 lb, and the tension in
the stainless spoke to about 263 lb. It takes about 7.3 lb
of force to deflect the ti spoke, and about 7.5 lb for the
stainless spoke. For bigger deflections the modulus matters a
lot more. If you push each spoke 10 mm sideways at mid-span
instead of 2 mm, the additional elongation is 0.713 mm.
Tension in the ti spoke goes up to about 416 lb, and in the
stainless spoke to about 532 lb. The deflection forces are now
about 59 lb for the ti spoke and about 76 lb for the stainless
spoke, probably now enough to feel the difference.

The above calculations ignore bending stresses in the thin
wire spokes, and assume neither spoke starts to yield. I mixed
English and metric units only because not many people have much
feel for how much force a Newton is, but spokes are sold in mm.

Dave Lehnen

Dear Dave,

Beware. If you insist on providing such clear, detailed
explanations for the nearly innumerate like me, we may
show no mercy and ask for more--particularly when you
pander to us by providing details in easy-to-follow pounds.

So with spokes of titanium and steel at 250 pounds of tension,
a 7-pound pull, plus or minus 3%, is enough to move the
spokes sideways the same tiny distance, 2mmm, not enough
to be noticeable to most people.

But to pull the same spokes sideways 10mm takes 59 pounds
for the titanium spoke and 76 pounds for the steel spoke, about
25% more and probably noticeable to a spoke-tugger.

The reason is presumably that the greater the sideways
bend, the greater the length of the elongated spoke,
and the greater the difference in force needed to stretch
stubborn steel versus easily stretched titanium?

Thanks again for a wonderful explanation.

Carl Fogel