Exploding tires II

Chris Neary writes:

I have, and the tire didn't come off. I have a set of Vredestein
Fortezza Pista tires, which are spec.'ed with a maximum pressure
of 145 psi. When competing in time trials of up to 40 km, I have
been known to inflate them to maximum pressure, or maybe a smidgen
more. I also compete in roller races where I inflate these tires
to 160 psi. They are mounted on a set of Campagnolo Shamal
wheels. They have never even given a hit of coming off.

Rims have blown apart at lower tyre pressures than this. At what
tyre pressure will a rim sustain with what amount of wear? Do rim
manufacturers publish such data? Are they too concerned about
machined surfaces?

FWIW, Mavic specifies maximum recommended pressures for their rims
by tire size. Example:

http://www.mavic.com/servlet/srt/mav...ct.id=55&lg=uk

These numbers seem to arise from tire casing tension which increases
with cross section but is unrelated to blow-off pressure which is
entirely dependent on rim width. A free body diagram of pressure will
reveal that only air pressure, acting at the inside-to-inside width of
the rim, acts on the tire to affect lift-off force. I have no doubt
that casing failures are directly related to tire size (cross section)
but this is not related to lift-off force.

Jobst Brandt

Chris Neary writes:

I have, and the tire didn't come off. I have a set of Vredestein
Fortezza Pista tires, which are spec.'ed with a maximum pressure
of 145 psi. When competing in time trials of up to 40 km, I have
been known to inflate them to maximum pressure, or maybe a smidgen
more. I also compete in roller races where I inflate these tires
to 160 psi. They are mounted on a set of Campagnolo Shamal
wheels. They have never even given a hit of coming off.

Rims have blown apart at lower tyre pressures than this. At what
tyre pressure will a rim sustain with what amount of wear? Do rim
manufacturers publish such data? Are they too concerned about
machined surfaces?

FWIW, Mavic specifies maximum recommended pressures for their rims
by tire size. Example:

http://www.mavic.com/servlet/srt/mav...ct.id=55&lg=uk

These numbers seem to arise from tire casing tension which increases
with cross section but is unrelated to blow-off pressure which is
entirely dependent on rim width. A free body diagram of pressure will
reveal that only air pressure, acting at the inside-to-inside width of
the rim, acts on the tire to affect lift-off force. I have no doubt
that casing failures are directly related to tire size (cross section)
but this is not related to lift-off force.

Jobst Brandt

Frank Krygowski wrote in message ...
Trevor wrote:

Frank Krygowski wrote in message ...

I know that typical blowoffs don't rip the tire this way. Still, I
wonder if this gives further evidence that the problem is related to the
effect of temperature on the materials. I think most of us agree it's
not simply high pressure doing the damage.



Perhaps there are nicks on the hook of the rim, either escaping quality
control or subsequent damage due to mishandling, including the use of hard,
possibly steel, tyre levers. Because the tyre flexes with each rotation, a
small burr on the rim may cut the tyre casing. Eventually it rips a small
amount and when left in the boot the tubes pressure is sufficient to tear
the tyre apart.

Trevor

Frank Krygowski wrote in message ...
Trevor wrote:

Frank Krygowski wrote in message ...

I know that typical blowoffs don't rip the tire this way. Still, I
wonder if this gives further evidence that the problem is related to the
effect of temperature on the materials. I think most of us agree it's
not simply high pressure doing the damage.



Perhaps there are nicks on the hook of the rim, either escaping quality
control or subsequent damage due to mishandling, including the use of hard,
possibly steel, tyre levers. Because the tyre flexes with each rotation, a
small burr on the rim may cut the tyre casing. Eventually it rips a small
amount and when left in the boot the tubes pressure is sufficient to tear
the tyre apart.

Trevor

Why not glue wired on tyres? All the disadvantages of both tub's and wired
ons. Not true. No needle to put through tube.

Trevor
]

DRS wrote in message ...
"Trevor" wrote in message

DRS wrote in message ...

[...]

FWIW, when Anna Meares was interviewed the other night at one point
she said she was running at 220psi, but obviously she was using
tubulars.

That pressure amazes me. Anna Meares, Australian, sprint gold medal?

Yes.

What makes it obvious tubulars were used?

Something she said about gluing the tyres to the rims.

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Q: What is the most annoying thing on Usenet?

Why not glue wired on tyres? All the disadvantages of both tub's and wired
ons. Not true. No needle to put through tube.

Trevor
]

DRS wrote in message ...
"Trevor" wrote in message

DRS wrote in message ...

[...]

FWIW, when Anna Meares was interviewed the other night at one point
she said she was running at 220psi, but obviously she was using
tubulars.

That pressure amazes me. Anna Meares, Australian, sprint gold medal?

Yes.

What makes it obvious tubulars were used?

Something she said about gluing the tyres to the rims.

--

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Q: What is the most annoying thing on Usenet?

Notice subject heading has transferred to split rims. All your supposed
suggestion to calculating forces are irrelevant. Due to inaccuracies in
tolerance of manufacture, ongoing sample testing is really the only way to
go.

Trevor


wrote in message ...
Chris Neary writes:

I have, and the tire didn't come off. I have a set of Vredestein
Fortezza Pista tires, which are spec.'ed with a maximum pressure
of 145 psi. When competing in time trials of up to 40 km, I have
been known to inflate them to maximum pressure, or maybe a smidgen
more. I also compete in roller races where I inflate these tires
to 160 psi. They are mounted on a set of Campagnolo Shamal
wheels. They have never even given a hit of coming off.

Rims have blown apart at lower tyre pressures than this. At what
tyre pressure will a rim sustain with what amount of wear? Do rim
manufacturers publish such data? Are they too concerned about
machined surfaces?

FWIW, Mavic specifies maximum recommended pressures for their rims
by tire size. Example:


http://www.mavic.com/servlet/srt/mav...ct.id=55&lg=uk

These numbers seem to arise from tire casing tension which increases
with cross section but is unrelated to blow-off pressure which is
entirely dependent on rim width. A free body diagram of pressure will
reveal that only air pressure, acting at the inside-to-inside width of
the rim, acts on the tire to affect lift-off force. I have no doubt
that casing failures are directly related to tire size (cross section)
but this is not related to lift-off force.

Jobst Brandt

Notice subject heading has transferred to split rims. All your supposed
suggestion to calculating forces are irrelevant. Due to inaccuracies in
tolerance of manufacture, ongoing sample testing is really the only way to
go.

Trevor


wrote in message ...
Chris Neary writes:

I have, and the tire didn't come off. I have a set of Vredestein
Fortezza Pista tires, which are spec.'ed with a maximum pressure
of 145 psi. When competing in time trials of up to 40 km, I have
been known to inflate them to maximum pressure, or maybe a smidgen
more. I also compete in roller races where I inflate these tires
to 160 psi. They are mounted on a set of Campagnolo Shamal
wheels. They have never even given a hit of coming off.

Rims have blown apart at lower tyre pressures than this. At what
tyre pressure will a rim sustain with what amount of wear? Do rim
manufacturers publish such data? Are they too concerned about
machined surfaces?

FWIW, Mavic specifies maximum recommended pressures for their rims
by tire size. Example:


http://www.mavic.com/servlet/srt/mav...ct.id=55&lg=uk

These numbers seem to arise from tire casing tension which increases
with cross section but is unrelated to blow-off pressure which is
entirely dependent on rim width. A free body diagram of pressure will
reveal that only air pressure, acting at the inside-to-inside width of
the rim, acts on the tire to affect lift-off force. I have no doubt
that casing failures are directly related to tire size (cross section)
but this is not related to lift-off force.

Jobst Brandt

"Trevor" wrote in message

Why not glue wired on tyres? All the disadvantages of both tub's and
wired ons. Not true. No needle to put through tube.

Why are you top-posting all of a sudden?

--

A: Top-posters.
Q: What is the most annoying thing on Usenet?

"Trevor" wrote in message

Why not glue wired on tyres? All the disadvantages of both tub's and
wired ons. Not true. No needle to put through tube.

Why are you top-posting all of a sudden?

--

A: Top-posters.
Q: What is the most annoying thing on Usenet?