Large spoke tension drop with inflated tire

[tiborg]

I built a rear wheel using a DT Swiss XR 4.1d rim and tensioned the
drive side to about 120 kgf (measured with a Park Tool TM-1). After
mounting a Marathon Plus tire (47-559) and inflating to 80 psi, the
measured spoke tension dropped about 25 kgf.

I read through a long thread from a couple years ago about whether or
not to build the wheel taking into account this drop and it seemed
like the drop in tension people were seeing was relatively small. What
I'm seeing seems to be larger, so I'd like to re-open this can of
worms and ask if I should be upping the tension to compensate?

The rim's maximum recommended tension is 120kgf and the intended use
is for a full-sus bike that will run over poorly maintained roads at
30-40 km/h.

 

[Peter Cole]

tiborg wrote:
> I built a rear wheel using a DT Swiss XR 4.1d rim and tensioned the
> drive side to about 120 kgf (measured with a Park Tool TM-1). After
> mounting a Marathon Plus tire (47-559) and inflating to 80 psi, the
> measured spoke tension dropped about 25 kgf.
>
> I read through a long thread from a couple years ago about whether or
> not to build the wheel taking into account this drop and it seemed
> like the drop in tension people were seeing was relatively small. What
> I'm seeing seems to be larger, so I'd like to re-open this can of
> worms and ask if I should be upping the tension to compensate?
>
> The rim's maximum recommended tension is 120kgf and the intended use
> is for a full-sus bike that will run over poorly maintained roads at
> 30-40 km/h.
>

The compressive force of the tire will vary with the pressure and the
cross section area. You've got almost the same pressure and 4x the cross
section of a typical road tire, so you'll see a greater spoke tension
drop. You'll also get high hoop force (spreading the rim at the bead),
make sure your rims can take that.

 

[jim beam]

tiborg wrote:
> I built a rear wheel using a DT Swiss XR 4.1d rim and tensioned the
> drive side to about 120 kgf (measured with a Park Tool TM-1). After
> mounting a Marathon Plus tire (47-559) and inflating to 80 psi, the
> measured spoke tension dropped about 25 kgf.
>
> I read through a long thread from a couple years ago about whether or
> not to build the wheel taking into account this drop and it seemed
> like the drop in tension people were seeing was relatively small. What
> I'm seeing seems to be larger, so I'd like to re-open this can of
> worms and ask if I should be upping the tension to compensate?
>
> The rim's maximum recommended tension is 120kgf and the intended use
> is for a full-sus bike that will run over poorly maintained roads at
> 30-40 km/h.
>
write to carl fogel about this - he's done more investigation on this
topic than anyone else that i've seen.

in answer to your question, no, do not "up" the tension to compensate.
rim manufacturers determine spoke tension specs from empirical testing.
that means running a rim as part of a loaded wheel with an inflated
tire on it.

 

[jim beam]

Peter Cole wrote:
> tiborg wrote:
>> I built a rear wheel using a DT Swiss XR 4.1d rim and tensioned the
>> drive side to about 120 kgf (measured with a Park Tool TM-1). After
>> mounting a Marathon Plus tire (47-559) and inflating to 80 psi, the
>> measured spoke tension dropped about 25 kgf.
>>
>> I read through a long thread from a couple years ago about whether or
>> not to build the wheel taking into account this drop and it seemed
>> like the drop in tension people were seeing was relatively small. What
>> I'm seeing seems to be larger, so I'd like to re-open this can of
>> worms and ask if I should be upping the tension to compensate?
>>
>> The rim's maximum recommended tension is 120kgf and the intended use
>> is for a full-sus bike that will run over poorly maintained roads at
>> 30-40 km/h.
>>
>
> The compressive force of the tire will vary with the pressure and the
> cross section area. You've got almost the same pressure and 4x the cross
> section of a typical road tire, so you'll see a greater spoke tension
> drop. You'll also get high hoop force (spreading the rim at the bead),
> make sure your rims can take that.

he said, completely avoiding the op's question...

 

[[email protected]]

On Mon, 01 Oct 2007 06:41:47 -0700, tiborg <[email protected]> wrote:

>I built a rear wheel using a DT Swiss XR 4.1d rim and tensioned the
>drive side to about 120 kgf (measured with a Park Tool TM-1). After
>mounting a Marathon Plus tire (47-559) and inflating to 80 psi, the
>measured spoke tension dropped about 25 kgf.
>
>I read through a long thread from a couple years ago about whether or
>not to build the wheel taking into account this drop and it seemed
>like the drop in tension people were seeing was relatively small. What
>I'm seeing seems to be larger, so I'd like to re-open this can of
>worms and ask if I should be upping the tension to compensate?
>
>The rim's maximum recommended tension is 120kgf and the intended use
>is for a full-sus bike that will run over poorly maintained roads at
>30-40 km/h.

Dear T,

Some reviews of the rim:

http://www.mtbr.com/reviews/Rim/product_122485.shtml

Google suggests that you have a 32 or 36 spoke 26" 425 gram
box-section clincher rim designed for disk brakes only (no rim wear):

http://www.go-ride.com/prod_rims.html

With a wide tire inflated as high as 80 psi, a box-section clincher as
wide as your rim may well drop 25 kg of spoke tension from 120 kgf.

But that 80 psi does sound awfully high. In fact, you're about 14%
over Schwalbe's maximum suggested 70 psi for that tire:

http://www.schwalbetires.com/node/142/ok

I'd think hard about why I needed 80 psi on a 47 mm nominal width tire
when I was running full suspension. If I really needed that much
inflation because of weight or impact flats, I'd try to find a wider
rim, a wider tire, or a rim with more spokes, not over-inflate the
tire and over-tension the spokes.

In any case, I wouldn't try to tension spokes according to how much
the tension drops after the tire is inflated.

I've realized that I have no idea how manufacturers arrive at their
recommended maximum rim tensions, but I suspect that they aim at bare
rims.

Even if you use Jobst's method of raising tension until the rim goes
out of true when spoke pairs are squeezed and then backing off a
little, remember that Jobst doesn't try for higher tension with the
tire inflated--he works on bare rims.

The obvious reason is that a flat tire would make the wheel go boing!
You'd have to re-true the rim on the spot because the spoke tension
would jump past the bare rim's practical limit.

In other words, I wouldn't want to be riding a bike at 25 mph on a bad
road when a flat tire caused my spoke tension to jump 25 kgf past the
rim's 125 kgf recommended tension, particularly when I don't know
whether the manufacturer has already factored in some tire-inflation
tension-drop.

Cheers,

Carl Fogel

 

[tiborg]

On Oct 2, 1:56 pm, [email protected] wrote:
> But that 80 psi does sound awfully high. In fact, you're about 14%
> over Schwalbe's maximum suggested 70 psi for that tire:
>
> http://www.schwalbetires.com/node/142/ok
>
> I'd think hard about why I needed 80 psi on a 47 mm nominal width tire
> when I was running full suspension. If I really needed that much
> inflation because of weight or impact flats, I'd try to find a wider
> rim, a wider tire, or a rim with more spokes, not over-inflate the
> tire and over-tension the spokes.

Thanks for catching this, I did mean to inflate the tire up to the max
rating but in the time between reading the markings on the tire and
setting the indicator ring on my pump, the number may have been
corrupted in my head.

My reasoning for the high pressure is because I have a suspension on
the frame, I shouldn't need to rely on the tire for any buffering.
Therefore, I'm trying to maximize the rolling efficiency (as absurd as
that sounds when talking about a full suspension bike carrying
panniers stuffed with clothing and tools and riding on a tire that has
a 1 cm thick rubber lining).

> In any case, I wouldn't try to tension spokes according to how much
> the tension drops after the tire is inflated.
>
> I've realized that I have no idea how manufacturers arrive at their
> recommended maximum rim tensions, but I suspect that they aim at bare
> rims.
>

This makes sense since there they cannot easily account for the
variety in tires and pressures that will be used on their rims.

> Even if you use Jobst's method of raising tension until the rim goes
> out of true when spoke pairs are squeezed and then backing off a
> little, remember that Jobst doesn't try for higher tension with the
> tire inflated--he works on bare rims.
>
> The obvious reason is that a flat tire would make the wheel go boing!
> You'd have to re-true the rim on the spot because the spoke tension
> would jump past the bare rim's practical limit.
>
> In other words, I wouldn't want to be riding a bike at 25 mph on a bad
> road when a flat tire caused my spoke tension to jump 25 kgf past the
> rim's 125 kgf recommended tension, particularly when I don't know
> whether the manufacturer has already factored in some tire-inflation
> tension-drop.
>

Hmm, a possible experiment for Fogel labs?

> Cheers,
>
> Carl Fogel

 

[[email protected]]

On Tue, 02 Oct 2007 00:11:51 -0700, tiborg <[email protected]> wrote:

>On Oct 2, 1:56 pm, [email protected] wrote:
>> But that 80 psi does sound awfully high. In fact, you're about 14%
>> over Schwalbe's maximum suggested 70 psi for that tire:
>>
>> http://www.schwalbetires.com/node/142/ok
>>
>> I'd think hard about why I needed 80 psi on a 47 mm nominal width tire
>> when I was running full suspension. If I really needed that much
>> inflation because of weight or impact flats, I'd try to find a wider
>> rim, a wider tire, or a rim with more spokes, not over-inflate the
>> tire and over-tension the spokes.
>
>Thanks for catching this, I did mean to inflate the tire up to the max
>rating but in the time between reading the markings on the tire and
>setting the indicator ring on my pump, the number may have been
>corrupted in my head.
>
>My reasoning for the high pressure is because I have a suspension on
>the frame, I shouldn't need to rely on the tire for any buffering.
>Therefore, I'm trying to maximize the rolling efficiency (as absurd as
>that sounds when talking about a full suspension bike carrying
>panniers stuffed with clothing and tools and riding on a tire that has
>a 1 cm thick rubber lining).
>
>> In any case, I wouldn't try to tension spokes according to how much
>> the tension drops after the tire is inflated.
>>
>> I've realized that I have no idea how manufacturers arrive at their
>> recommended maximum rim tensions, but I suspect that they aim at bare
>> rims.
>>
>
>This makes sense since there they cannot easily account for the
>variety in tires and pressures that will be used on their rims.
>
>> Even if you use Jobst's method of raising tension until the rim goes
>> out of true when spoke pairs are squeezed and then backing off a
>> little, remember that Jobst doesn't try for higher tension with the
>> tire inflated--he works on bare rims.
>>
>> The obvious reason is that a flat tire would make the wheel go boing!
>> You'd have to re-true the rim on the spot because the spoke tension
>> would jump past the bare rim's practical limit.
>>
>> In other words, I wouldn't want to be riding a bike at 25 mph on a bad
>> road when a flat tire caused my spoke tension to jump 25 kgf past the
>> rim's 125 kgf recommended tension, particularly when I don't know
>> whether the manufacturer has already factored in some tire-inflation
>> tension-drop.
>>
>
>Hmm, a possible experiment for Fogel labs?
>
>> Cheers,
>>
>> Carl Fogel

Dear T,

I suspect that full suspension losses would overshadow any slight
improvement in rolling resistance gained by high inflation.

I really do wonder how rim makers arrive at their modern maximum
recommended tension. I've never seen anything specific about it. They
may have elaborate road tests, complicated laboratory equipment, or
just some guy with a tension gauge and a well-thumbed copy of "The
Bicycle Wheel" who keeps turning the spoke nipples until the rim tacos
when he squeezes spoke pairs or he notices the spokes turning into
barber poles.

Whatever the method, there's probably a practical fudge factor. Rims
are extruded through dies that wear, so the last rim through the die
may be as much as 10% heavier (and stronger) than the first.

Concerning your hopes for an experiment at 25 mph on what sounds like
a dirt road, Fogel Labs uses about 6 psi with full suspension and
declines to test anything less than a 4x18 trials tread tire on the
rear.

An impromptu test in Baja in 1972 showed that a skinnier 3.50 x 18
tire would last only 180 miles on rough dirt roads when flat. The
spokes were re-tightened and loc-tited at about 90 miles and the wheel
survived for later riding, but the flat tire came apart, snarling
everything with bead wire.

More enthusiastic (or perhaps even less intelligent) testers have run
greater distances on bare rims at much higher speeds in Baja without
even a flat tire for padding, an amazing example of how sturdy
Husqvarna desert race wheels were in those days. I hate to think what
Husqvarna did to show how tough their sewing machines were--maybe they
embroidered their logo on the side of Sherman tank turret?

The RBT wheel-building wars are pretty much unknown in the motorcycle
world, where engine power means that there's no need to build fragile
wheels.

Cheers,

Carl Fogel

 

[Chalo]

tiborg wrote:
>
> Carl Fogel wrote:
> >
> > I'd think hard about why I needed 80 psi on a 47 mm nominal width tire
> > when I was running full suspension. If I really needed that much
> > inflation because of weight or impact flats, I'd try to find a wider
> > rim, a wider tire, or a rim with more spokes, not over-inflate the
> > tire and over-tension the spokes.
>
> Thanks for catching this, I did mean to inflate the tire up to the max
> rating but in the time between reading the markings on the tire and
> setting the indicator ring on my pump, the number may have been
> corrupted in my head.
>
> My reasoning for the high pressure is because I have a suspension on
> the frame, I shouldn't need to rely on the tire for any buffering.
> Therefore, I'm trying to maximize the rolling efficiency (as absurd as
> that sounds when talking about a full suspension bike carrying
> panniers stuffed with clothing and tools and riding on a tire that has
> a 1 cm thick rubber lining).

My experience with the Schwalbe Marathon Plus was problematic. I used
the 40-622 size on my electric-assist bike with a gross weight of just
over 500 pounds. Because of the heavy load, and because of the ride-
softening effect of the elastomer belt, I ran them at higher than
recommended pressure-- about 90psi, but I do not remember precisely.
Two tires suffered casing failures at the bead wires (the fabric
stripped off the wires), resulting in tremendous blowouts. After I
lowered the pressure to within the sidewall rating, a third tire
suffered a major sidewall bulge from an internal casing failure. All
three of these failures occurred after minimal mileage.

I was never able to determine whether the batch I got was faulty, and
because I was loading the bike well beyond the tire's intended
capacity, I did not pursue warranty replacement.

The moral of my story is that, if my experience is any guide, you
probably shouldn't inflate those tires in excess of their rating. I
wouldn't even run them at their maximum pressure rating, because their
traction and wear should be better at a lower pressure, with
negligible added rolling resistance.

My casual experiments with some fat street tires lately seem to
indicate that rolling resistance does not diminish noticeably between
modest and very high pressures. My hypothesis is that a very fat tire
need not deform much even if the pressure is relatively low, and the
reduction of losses as bumps and jolts more or less offsets any
increase in tire losses.

There's certainly no harm in trying your tires for a while at 70psi
and then at 45-50psi to see if you can detect any loss in speed or
increased times over familiar routes.

Chalo

 

[tiborg]

On Oct 2, 5:01 pm, Chalo <[email protected]> wrote:
> tiborg wrote:
>
> > Carl Fogel wrote:
>
> > > I'd think hard about why I needed 80 psi on a 47 mm nominal width tire
> > > when I was running full suspension. If I really needed that much
> > > inflation because of weight or impact flats, I'd try to find a wider
> > > rim, a wider tire, or a rim with more spokes, not over-inflate the
> > > tire and over-tension the spokes.
>
> > Thanks for catching this, I did mean to inflate the tire up to the max
> > rating but in the time between reading the markings on the tire and
> > setting the indicator ring on my pump, the number may have been
> > corrupted in my head.
>
> > My reasoning for the high pressure is because I have a suspension on
> > the frame, I shouldn't need to rely on the tire for any buffering.
> > Therefore, I'm trying to maximize the rolling efficiency (as absurd as
> > that sounds when talking about a full suspension bike carrying
> > panniers stuffed with clothing and tools and riding on a tire that has
> > a 1 cm thick rubber lining).
>
> My experience with the Schwalbe Marathon Plus was problematic. I used
> the 40-622 size on my electric-assist bike with a gross weight of just
> over 500 pounds. Because of the heavy load, and because of the ride-
> softening effect of the elastomer belt, I ran them at higher than
> recommended pressure-- about 90psi, but I do not remember precisely.
> Two tires suffered casing failures at the bead wires (the fabric
> stripped off the wires), resulting in tremendous blowouts. After I
> lowered the pressure to within the sidewall rating, a third tire
> suffered a major sidewall bulge from an internal casing failure. All
> three of these failures occurred after minimal mileage.
>
> I was never able to determine whether the batch I got was faulty, and
> because I was loading the bike well beyond the tire's intended
> capacity, I did not pursue warranty replacement.
>
> The moral of my story is that, if my experience is any guide, you
> probably shouldn't inflate those tires in excess of their rating. I
> wouldn't even run them at their maximum pressure rating, because their
> traction and wear should be better at a lower pressure, with
> negligible added rolling resistance.
>
> My casual experiments with some fat street tires lately seem to
> indicate that rolling resistance does not diminish noticeably between
> modest and very high pressures. My hypothesis is that a very fat tire
> need not deform much even if the pressure is relatively low, and the
> reduction of losses as bumps and jolts more or less offsets any
> increase in tire losses.
>
> There's certainly no harm in trying your tires for a while at 70psi
> and then at 45-50psi to see if you can detect any loss in speed or
> increased times over familiar routes.
>
> Chalo

Well I'm happy to report that I was in error in stating I had the tire
inflated to 80 psi, it is in fact running at 70. When I first tried
this tire out, I was running it 60 psi and boosted it up to 70 about a
month ago. As I stated above, the idea was to see if I could do
without the tire's inherent suspension and only rely on that of the
bike (2005 Giant Reign 3 - Japan export model).

My daily round-trip distance is only 40km, so any gains of the higher
pressure are likely offset by having to stop for one extra feral ninja
cat on any given day. However, in the pursuit of an ever smoother
ride, I will take your suggestion of dropping the pressure
considerably and see how that suits me.

 

[Tim McNamara]

In article <[email protected]>,
Chalo <[email protected]> wrote:

> My casual experiments with some fat street tires lately seem to
> indicate that rolling resistance does not diminish noticeably between
> modest and very high pressures. My hypothesis is that a very fat
> tire need not deform much even if the pressure is relatively low, and
> the reduction of losses as bumps and jolts more or less offsets any
> increase in tire losses.

That's not inconsistent with the rolling resistance tests that compared
inflation pressures. On those curves, there is quite a bit of
flattening of the curve between medium and high pressures compared to
low and medium pressures. Jan Heine found the same thing, that medium
pressures don't seem to result in a large increase in rolling resistance
compared to high pressures.

 

[Peter Cole]

jim beam wrote:
> Peter Cole wrote:
>> tiborg wrote:
>>> I built a rear wheel using a DT Swiss XR 4.1d rim and tensioned the
>>> drive side to about 120 kgf (measured with a Park Tool TM-1). After
>>> mounting a Marathon Plus tire (47-559) and inflating to 80 psi, the
>>> measured spoke tension dropped about 25 kgf.
>>>
>>> I read through a long thread from a couple years ago about whether or
>>> not to build the wheel taking into account this drop and it seemed
>>> like the drop in tension people were seeing was relatively small. What
>>> I'm seeing seems to be larger, so I'd like to re-open this can of
>>> worms and ask if I should be upping the tension to compensate?
>>>
>>> The rim's maximum recommended tension is 120kgf and the intended use
>>> is for a full-sus bike that will run over poorly maintained roads at
>>> 30-40 km/h.
>>>
>>
>> The compressive force of the tire will vary with the pressure and the
>> cross section area. You've got almost the same pressure and 4x the
>> cross section of a typical road tire, so you'll see a greater spoke
>> tension drop. You'll also get high hoop force (spreading the rim at
>> the bead), make sure your rims can take that.
>
> he said, completely avoiding the op's question...

I'm unfamiliar with the rim. If it was a Mavic, I'd say no. Off hand,
I'd say unless you're pushing the load limit of the wheel, I don't see
the point in obsessing about getting the maximum possible spoke tension
-- but others may disagree -- so my answer would only be a personal
preference.

I doubt that it would cause any harm to bump up the spoke tension, but
since he's nominally running a normal size MTB tire at twice typical
pressure, I'd bump it up by half the tension drop he's seeing ~12kg.

There is a real danger in running very large tires at high pressure. I
wouldn't push that limit myself, especially with a lightweight rim.

 

[Peter Cole]

jim beam wrote:
> tiborg wrote:
>> I built a rear wheel using a DT Swiss XR 4.1d rim and tensioned the
>> drive side to about 120 kgf (measured with a Park Tool TM-1). After
>> mounting a Marathon Plus tire (47-559) and inflating to 80 psi, the
>> measured spoke tension dropped about 25 kgf.
>>
>> I read through a long thread from a couple years ago about whether or
>> not to build the wheel taking into account this drop and it seemed
>> like the drop in tension people were seeing was relatively small. What
>> I'm seeing seems to be larger, so I'd like to re-open this can of
>> worms and ask if I should be upping the tension to compensate?
>>
>> The rim's maximum recommended tension is 120kgf and the intended use
>> is for a full-sus bike that will run over poorly maintained roads at
>> 30-40 km/h.
>>
> write to carl fogel about this - he's done more investigation on this
> topic than anyone else that i've seen.
>
> in answer to your question, no, do not "up" the tension to compensate.
> rim manufacturers determine spoke tension specs from empirical testing.
> that means running a rim as part of a loaded wheel with an inflated
> tire on it.

Typical XC tires don't run at 80lb.

 

[Jambo]

"jim beam" <[email protected]> wrote in message
news:[email protected]...
> in answer to your question, no, do not "up" the tension to compensate. rim
> manufacturers determine spoke tension specs from empirical testing. that
> means running a rim as part of a loaded wheel with an inflated tire on it.

Whaddaya know, beamboy borrows from JB's book again...

 

[tiborg]

On Oct 2, 5:01 pm, Chalo <[email protected]> wrote:
> tiborg wrote:
>
> > Carl Fogel wrote:
>
> > > I'd think hard about why I needed 80 psi on a 47 mm nominal width tire
> > > when I was running full suspension. If I really needed that much
> > > inflation because of weight or impact flats, I'd try to find a wider
> > > rim, a wider tire, or a rim with more spokes, not over-inflate the
> > > tire and over-tension the spokes.
>
> > Thanks for catching this, I did mean to inflate the tire up to the max
> > rating but in the time between reading the markings on the tire and
> > setting the indicator ring on my pump, the number may have been
> > corrupted in my head.
>
> > My reasoning for the high pressure is because I have a suspension on
> > the frame, I shouldn't need to rely on the tire for any buffering.
> > Therefore, I'm trying to maximize the rolling efficiency (as absurd as
> > that sounds when talking about a full suspension bike carrying
> > panniers stuffed with clothing and tools and riding on a tire that has
> > a 1 cm thick rubber lining).
>
> My experience with the Schwalbe Marathon Plus was problematic. I used
> the 40-622 size on my electric-assist bike with a gross weight of just
> over 500 pounds. Because of the heavy load, and because of the ride-
> softening effect of the elastomer belt, I ran them at higher than
> recommended pressure-- about 90psi, but I do not remember precisely.
> Two tires suffered casing failures at the bead wires (the fabric
> stripped off the wires), resulting in tremendous blowouts. After I
> lowered the pressure to within the sidewall rating, a third tire
> suffered a major sidewall bulge from an internal casing failure. All
> three of these failures occurred after minimal mileage.
>
> I was never able to determine whether the batch I got was faulty, and
> because I was loading the bike well beyond the tire's intended
> capacity, I did not pursue warranty replacement.
>
> The moral of my story is that, if my experience is any guide, you
> probably shouldn't inflate those tires in excess of their rating. I
> wouldn't even run them at their maximum pressure rating, because their
> traction and wear should be better at a lower pressure, with
> negligible added rolling resistance.
>
> My casual experiments with some fat street tires lately seem to
> indicate that rolling resistance does not diminish noticeably between
> modest and very high pressures. My hypothesis is that a very fat tire
> need not deform much even if the pressure is relatively low, and the
> reduction of losses as bumps and jolts more or less offsets any
> increase in tire losses.
>
> There's certainly no harm in trying your tires for a while at 70psi
> and then at 45-50psi to see if you can detect any loss in speed or
> increased times over familiar routes.
>
> Chalo

50psi worked out great. Didn't notice any extra effort and it almost
completely eliminated the road buzz from an overpass covered in 10cm
tiles. Spoke tension went up about 5kgf with the lower pressure.

 

[Tom \Johnny Sunset\ Sherman]

Peter Cole wrote:
> ...
> There is a real danger in running very large tires at high pressure. I
> wouldn't push that limit myself, especially with a lightweight rim.

I use 53-406 Maxxis Hookworm tires on Velocity Taipan rims at 7.5 bar
(110 psi) for my trike. I will see if the rims eventually split [1].

[1] The front wheels have disc brakes, while the rear wheel lacks a
brake, so there will be no brake track wear.

--
Tom Sherman - Holstein-Friesland Bovinia
A Real Cyclist [TM] keeps at least one bicycle in the bedroom.

--
Posted via a free Usenet account from http://www.teranews.com

 

[Tom \Johnny Sunset\ Sherman]

Peter Cole wrote:
> jim beam wrote:
>> tiborg wrote:
>>> I built a rear wheel using a DT Swiss XR 4.1d rim and tensioned the
>>> drive side to about 120 kgf (measured with a Park Tool TM-1). After
>>> mounting a Marathon Plus tire (47-559) and inflating to 80 psi, the
>>> measured spoke tension dropped about 25 kgf.
>>>
>>> I read through a long thread from a couple years ago about whether or
>>> not to build the wheel taking into account this drop and it seemed
>>> like the drop in tension people were seeing was relatively small. What
>>> I'm seeing seems to be larger, so I'd like to re-open this can of
>>> worms and ask if I should be upping the tension to compensate?
>>>
>>> The rim's maximum recommended tension is 120kgf and the intended use
>>> is for a full-sus bike that will run over poorly maintained roads at
>>> 30-40 km/h.
>>>
>> write to carl fogel about this - he's done more investigation on this
>> topic than anyone else that i've seen.
>>
>> in answer to your question, no, do not "up" the tension to compensate.
>> rim manufacturers determine spoke tension specs from empirical
>> testing. that means running a rim as part of a loaded wheel with an
>> inflated tire on it.
>
> Typical XC tires don't run at 80lb.

However, BMX freestyle tires [1] are typically 44 to 53 mm in nominal
width, with maximum inflation pressures of 6 to 9 bar (90 to 130 psi) [2].

[1] Often the best road tire choice for small wheel recumbents.
[2] The Snafu Rim Job is an example of the latter case.

--
Tom Sherman - Holstein-Friesland Bovinia
A Real Cyclist [TM] keeps at least one bicycle in the bedroom.

--
Posted via a free Usenet account from http://www.teranews.com

 

[Michael Press]

In article
<[email protected]>
,
tiborg <[email protected]> wrote:

> On Oct 2, 1:56 pm, [email protected] wrote:
> > But that 80 psi does sound awfully high. In fact, you're about 14%
> > over Schwalbe's maximum suggested 70 psi for that tire:
> >
> > http://www.schwalbetires.com/node/142/ok
> >
> > I'd think hard about why I needed 80 psi on a 47 mm nominal width tire
> > when I was running full suspension. If I really needed that much
> > inflation because of weight or impact flats, I'd try to find a wider
> > rim, a wider tire, or a rim with more spokes, not over-inflate the
> > tire and over-tension the spokes.
>
> Thanks for catching this, I did mean to inflate the tire up to the max
> rating but in the time between reading the markings on the tire and
> setting the indicator ring on my pump, the number may have been
> corrupted in my head.
>
> My reasoning for the high pressure is because I have a suspension on
> the frame, I shouldn't need to rely on the tire for any buffering.
> Therefore, I'm trying to maximize the rolling efficiency (as absurd as
> that sounds when talking about a full suspension bike carrying
> panniers stuffed with clothing and tools and riding on a tire that has
> a 1 cm thick rubber lining).

Anything worth doing is worth overdoing.

--
Michael Press

 

[jim beam]

Jambo wrote:
> "jim beam" <[email protected]> wrote in message
> news:[email protected]...
>> in answer to your question, no, do not "up" the tension to compensate. rim
>> manufacturers determine spoke tension specs from empirical testing. that
>> means running a rim as part of a loaded wheel with an inflated tire on it.
>
> Whaddaya know, beamboy borrows from JB's book again...
>
>
eh? you're making no sense. moron.

 

[Chalo]

Tom \"Johnny Sunset\" Sherman" wrote:
>
> Peter Cole wrote:
> > ...
> > There is a real danger in running very large tires at high pressure. I
> > wouldn't push that limit myself, especially with a lightweight rim.
>
> I use 53-406 Maxxis Hookworm tires on Velocity Taipan rims at 7.5 bar
> (110 psi) for my trike. I will see if the rims eventually split [1].

I don't know about the Taipan, but many freestyle rims are made for
such pressures.

I doubt that you are benefiting from such high pressure, though.
Freestylers use it to keep from pinching tubes when they land on
square-edged steps, coping, and curbs. I bet that you could let that
tire down 40-50 lbs and not see any difference in speed. A Primo
Comet 20 x 2.1" would probably be faster, even at 60psi.

Chalo

 

[[email protected]]

On Oct 2, 10:56 pm, Chalo <[email protected]> wrote:
> Tom \"Johnny Sunset\" Sherman" wrote:
>
> > I use 53-406 Maxxis Hookworm tires on Velocity Taipan rims at 7.5 bar
> > (110 psi) for my trike. I will see if the rims eventually split [1].
>
> I don't know about the Taipan, but many freestyle rims are made for
> such pressures.
>
> I doubt that you are benefiting from such high pressure, though.
> Freestylers use it to keep from pinching tubes when they land on
> square-edged steps, coping, and curbs. I bet that you could let that
> tire down 40-50 lbs and not see any difference in speed. A Primo
> Comet 20 x 2.1" would probably be faster, even at 60psi.
>

You think so, but you haven't seen the speed at
which Tom rides down steps or curb-hops on his trike.
Freestyling on a machine like that, you can't always
land gently.

Ben