Tyre Pressures

[davebee]

The tyres that I am using are Continental Grand Prix road tyres for MTB's, and are rated to 120 psi. I have just inflated these up to 105psi with a track pump and the inner tube has exploded in spectacular style. I was wondering why this might have happened? Possibly the ineers aren't rated as highly as the tyre?

Does anybody have suggestions as to how to prevent this kind of thing happening?

(apart from inflating the tyres to ridiculously high pressures ;-)) looks like I am on "rugged" tyres tomorrow as i don't have any more 1" inner tubes and there is now ay this can be repaired as the hole is massive.

 

[Vincent Wilcox]

davebee wrote:
> The tyres that I am using are Continental Grand Prix road tyres for MTB's, and are rated to 120
> psi. I have just inflated these up to 105psi with a track pump and the inner tube has exploded in
> spectacular style. I was wondering why this might have happened? Possibly the ineers aren't rated
> as highly as the tyre?
>
> Does anybody have suggestions as to how to prevent this kind of thing happening?
>
> (apart from inflating the tyres to ridiculously high pressures ;-)) looks like I am on "rugged"
> tyres tomorrow as i don't have any more 1" inner tubes and there is now ay this can be repaired as
> the hole is massive.

This happens when the tyre isnt seated properly and part of the tube is outside the tyre. When
pumping up check around the tyre to make sure that its seated properly when pumping it up and that
the tube is not pinched between the tyre and rim.

 

[Pete Biggs]

davebee wrote:
> The tyres that I am using are Continental Grand Prix road tyres for MTB's, and are rated to 120
> psi. I have just inflated these up to 105psi with a track pump and the inner tube has exploded in
> spectacular style. I was wondering why this might have happened? Possibly the ineers aren't rated
> as highly as the tyre?

Any inner tube in good condition will take the pressure if all else is well.

Make sure tyre is seated properly (pushing valve up into tyre while fitting helps at that point),
and make sure rim tape is adequate. Don't use rubber tape if the rim has recessed spoke holes. Use
high pressure tape instead like Velox.

Occasionally, faulty tyres or tyres that don't suit the rims can pop off the rim even if you've done
nothing wrong with the fitting. To test for this, over-inflate and leave standing for 36 hours and
supply everyone in the neighbourhood with ear plugs.

~PB

 

[Simon Brooke]

John Hearns <[email protected]> writes:

> On Tue, 10 Feb 2004 19:20:06 +0000, davebee wrote:
>
> > The tyres that I am using are Continental Grand Prix road tyres for MTB's, and are rated to 120
> > psi. I have just inflated these up to 105psi with a track pump and the inner tube has exploded
> > in spectacular style. I was wondering why this might have happened? Possibly the ineers aren't
> > rated as highly as the tyre?
> Are the types quite old? If so, carefully examine them for splits in the sidewalls. This happened
> to me with an old tyre, which had to be binned.

I once had a blow out about three miles into the first run on a brand new tyre. The casing split.
There's no doubt in my mind that it was a manufacturing fault. In davebee's case he was lucky it
blew before he got on the bike.

--
[email protected] (Simon Brooke) http://www.jasmine.org.uk/~simon/

;; 99% of browsers can't run ActiveX controls. Unfortunately ;; 99% of users are using the
1% of browsers that can... [seen on /. 08:04:02]

 

[Dave Kahn]

Vincent Wilcox <[email protected]> wrote in message news:<[email protected]>...
> davebee wrote:

> > Does anybody have suggestions as to how to prevent this kind of thing happening?
>
> This happens when the tyre isnt seated properly and part of the tube is outside the tyre. When
> pumping up check around the tyre to make sure that its seated properly when pumping it up and that
> the tube is not pinched between the tyre and rim.

Agreed. It is axiomatic that if a tube goes explosively part of it was outside the tyre at the time.
Top 3 causes of this are:

- Tube pinched by tyre bead.

- Tyre bead is broken, allowing tube to work its way out.

- Split in tyre.

--
Dave...

 

[Dave Kahn]

"Pete Biggs" <ptangerine{remove_fruit}@biggs.tc> wrote in message news:<[email protected]>...

> Occasionally, faulty tyres or tyres that don't suit the rims can pop off the rim even if you've
> done nothing wrong with the fitting. To test for this, over-inflate and leave standing for 36
> hours and supply everyone in the neighbourhood with ear plugs.

And keep the cat out of the room.

--
Dave...

 

[Dave Larrington]

Dave Kahn wrote:

> Agreed. It is axiomatic that if a tube goes explosively part of it was outside the tyre at the
> time. Top 3 causes of this are:
>
> - Tube pinched by tyre bead.
>
> - Tyre bead is broken, allowing tube to work its way out.
>
> - Split in tyre.

I had #3 yesterday. A small sidewall split, covered with one of Mr. Park's tyre boots, suddenly
decided to let all the air out with utmost despatch, while I was overtaking a bus at V>40 km/h. Note
to self (and anyone else who's interested): Mr. Park's tyre boots do not last for ever...

--

Dave Larrington - http://www.legslarry.beerdrinkers.co.uk/
===========================================================
Editor - British Human Power Club Newsletter
http://www.bhpc.org.uk/
===========================================================

 

[Elyob]

"Dave Larrington" <[email protected]> wrote in message
news:[email protected]...
> Dave Kahn wrote:
>
> > Agreed. It is axiomatic that if a tube goes explosively part of it was outside the tyre at the
> > time. Top 3 causes of this are:
> >
> > - Tube pinched by tyre bead.
> >
> > - Tyre bead is broken, allowing tube to work its way out.
> >
> > - Split in tyre.
>
> I had #3 yesterday. A small sidewall split, covered with one of Mr.
Park's
> tyre boots, suddenly decided to let all the air out with utmost despatch, while I was overtaking a
> bus at V>40 km/h. Note to self (and anyone else who's interested): Mr. Park's tyre boots do not
> last for ever...
>

I was wondering why my back wheel was buckled, checked the spokes, gave a small tighten all
round, carried on. Still buckled, checked it again, and again. Still buckled, cheked the front
(weird theories entering my head). Then noticed that the sidewall was disintegrating badly,
bulging the tyre.

Two new tyres later a perfect ride again

 

[Just Zis Guy]

On 11 Feb 2004 02:52:35 -0800, [email protected] (Dave Kahn) wrote
in message <[email protected]>:

>Agreed. It is axiomatic that if a tube goes explosively part of it was outside the tyre at the
>time. Top 3 causes of this are:

> - Tube pinched by tyre bead.
> - Tyre bead is broken, allowing tube to work its way out.
> - Split in tyre.

- rim tape problem

Among our weapons are...

Guy
===
May contain traces of irony. Contents liable to settle after posting.
http://chapmancentral.demon.co.uk

 

[davebee]

>Agreed. It is axiomatic that if a tube goes explosively part of it was outside the tyre at the
>time. Top 3 causes of this are:

> - Tube pinched by tyre bead.
> - Tyre bead is broken, allowing tube to work its way out.
> - Split in tyre.

- rim tape problem

Among our weapons are...

I think it was probably a rim tape problem then as the tyres are brand new and have barely been used. There were large indents around the inner tube from the spoke eyelets even in the unburst sections, and the rim tape has been pushed down into the spoke eyelets to an extent. New tyres have been ordered along with (hopefully) better rim tape. Am I right in thinking that a kevlar bead would go between the tyre and the tube, because this is another option I am considering.

 

[Just Zis Guy]

On Wed, 11 Feb 2004 21:08:44 GMT, davebee
<[email protected]> wrote in message
<[email protected]>:

>New tyres have been ordered along with (hopefully) better rim tape.

Velox make the One True Tape

>Am I right in thinking that a kevlar bead would go between the tyre a

I guess - I don't use same.

Guy
===
May contain traces of irony. Contents liable to settle after posting.
http://chapmancentral.demon.co.uk

88% of helmet statistics are made up, 65% of them at the University of Washington.

 

[Martin Family]

On 11/2/04 10:30 pm, in article [email protected],
"Just zis Guy, you know?" <[email protected]> wrote:

> On Wed, 11 Feb 2004 21:08:44 GMT, davebee <[email protected]> wrote in message
> <[email protected]>:
>

>> Am I right in thinking that a kevlar bead would go between the tyre a
>
> I guess - I don't use same.

No. If you look at a clincher tyre (standard tyre we mostly use - roadies may be on tubulars which
ara different) then you will see that at the edges of the tyre it forms a little bulge. This is
because it wraps around a steel wire that keeps the tyre round and stops it blowing off the rim by
preventing the rubber from stretching.

Kevlar beaded tyres replace this steel bead with a kevlar one which does exactly the same job but is
foldable so the tyre can be packed smaller.

A cross section through a flattened tyre (ascii art.. use a fixed width font)

(*)----mmmmmmmm----(*)
1 2 3 4 5

1 + 5 beads 2 + 4 sidewalls 3 tread

hope this helps.

..d

 

[davebee]

Two new inner tubes (both tyres blew up within about 5 minutes of each other) and two rolls of velox rim tape later, everything seems to be in order again. The tyres also seem to be a lot harder than they were before I put new rim tape on. Is this because before the tubes could have been sagging into the spoke eyelet "access holes" (my rims are quite deep) and causing a lower tyre pressure, and then exploded on the jagged edge when the pressure got too high??

Anyway, who cares, I have nice rock hard tyres now. Cheers for the rim tape advice guys its worked a treat :-D

 

[Pete Biggs]

davebee wrote:
> Am I right in thinking that a kevlar bead would go between the tyre and the tube, because this is
> another option I am considering.

There are anti-puncture kevlar bands that fit between tube and tyre but these aren't relevant to the
problem mentioned. Beads are the things inside the edges of the tyre that holds it in the rim. These
are steel wires in ordinary tyres but can alternatively be kevlar to make them lightweight and
foldable. Kevlar material can also be used within the tyre tread or casing for some puncture
resistance.

~PB