Fold Up Roll Off Query

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On Fri, 16 Apr 2004 cyci@ric.net wrote:
> Any current views/experiences on this one? I'm a little wary of
> racing through corners at the moment!

I have seen three blow-offs and I avoid kevlar bead tyres as keenly as
possible.
Chances are that, after flatting in the middle of the curve, your bike
sled and friction extracted the tyre.

Sergio
Pisa

I am presently recovering from sundry scrapes and bruises obtained
when my road bike came unstuck while taking a fairly easy corner at
about 25 mph. After the crash I found that my rear tyre, a Continental
Ultra 2000 fold up had rolled off the rim. I cannot be sure whether
the roll off caused the accident or whether it was the result of it (I
may have hit some oil) but I have not had this experience in 20 odd
years of riding (and crashing!) either wire bead clinchers or
tubulars. The local Continental agent tells me there is nothing wrong
with my tire and that roll offs are unheard of.

A Google search of older posts about Kevlar beaded tyres was
inconclusive though there seems to be a view that the fold ups are
more prone to "blow offs". My tyre was inflated to the max of 120psi
and was properly seated (been riding with it for about five months)

Any current views/experiences on this one? I'm a little wary of
racing through corners at the moment!

Thanks

<cyci@ric.net> wrote in message
news:mc5v70l5ccjvk78bogtvh91a536f7aaiie@4ax.com...
> I am presently recovering from sundry scrapes and bruises obtained
> when my road bike came unstuck while taking a fairly easy corner at
> about 25 mph. After the crash I found that my rear tyre, a Continental
> Ultra 2000 fold up had rolled off the rim. I cannot be sure whether
> the roll off caused the accident or whether it was the result of it (I
> may have hit some oil) but I have not had this experience in 20 odd
> years of riding (and crashing!) either wire bead clinchers or
> tubulars. The local Continental agent tells me there is nothing wrong
> with my tire and that roll offs are unheard of.
>
> A Google search of older posts about Kevlar beaded tyres was
> inconclusive though there seems to be a view that the fold ups are
> more prone to "blow offs". My tyre was inflated to the max of 120psi
> and was properly seated (been riding with it for about five months)
>
> Any current views/experiences on this one? I'm a little wary of
> racing through corners at the moment!
>
> Thanks

I use kevlar bead tires pretty much exclusively on all my bikes (5) because
of the ease of mounting (and de-mounting to fix flats). I have Conti's,
Michelin and Vittoria's. I weigh 205#, keep the tires inflated to
100~105lbs, and have had no problems with roll-offs or anything else
regarding the tires. I would suspect that your roll-off was a result of the
accident, not the cause.

cyci@ric.net wrote:

>I am presently recovering from sundry scrapes and bruises obtained
>when my road bike came unstuck while taking a fairly easy corner at
>about 25 mph. After the crash I found that my rear tyre, a Continental
>Ultra 2000 fold up had rolled off the rim. I cannot be sure whether
>the roll off caused the accident or whether it was the result of it (I
>may have hit some oil) but I have not had this experience in 20 odd
>years of riding (and crashing!) either wire bead clinchers or
>tubulars. The local Continental agent tells me there is nothing wrong
>with my tire and that roll offs are unheard of.
>
>A Google search of older posts about Kevlar beaded tyres was
>inconclusive though there seems to be a view that the fold ups are
>more prone to "blow offs". My tyre was inflated to the max of 120psi
>and was properly seated (been riding with it for about five months)
>
>Any current views/experiences on this one? I'm a little wary of
>racing through corners at the moment!

I've had the same thing happen due to a leak I had't noticed (once I
ended up somehow riding the bike to a stop at a 45 degree angle like a
dirt track racer). It is unusual for a fully inflated tire to roll
off a rim - did you hear an explosive sound when the tube went?

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $695 ti frame

On Fri, 16 Apr 2004 06:57:28 -0700, Mark Hickey <mark@habcycles.com>
wrote:


>>Any current views/experiences on this one? I'm a little wary of
>>racing through corners at the moment!
>
>I've had the same thing happen due to a leak I had't noticed (once I
>ended up somehow riding the bike to a stop at a 45 degree angle like a
>dirt track racer). It is unusual for a fully inflated tire to roll
>off a rim - did you hear an explosive sound when the tube went?
>

Yes. Shortly after I fell. I don't think I had an earlier slow
puncture, at least not that I had noticed. Given the loudness of the
bang I assumed the tyre was fully inflated hence my concern that the
problem lay with the Kevlar bead. Another poster has suggested that
roll off was caused by my skid. But I've had a good many and worse
skids in my time without my wire beaded tyre departing from the rim

Ken <cyci@ric.net> wrote:

>On Fri, 16 Apr 2004 06:57:28 -0700, Mark Hickey <mark@habcycles.com>
>wrote:
>
>>>Any current views/experiences on this one? I'm a little wary of
>>>racing through corners at the moment!
>>
>>I've had the same thing happen due to a leak I had't noticed (once I
>>ended up somehow riding the bike to a stop at a 45 degree angle like a
>>dirt track racer). It is unusual for a fully inflated tire to roll
>>off a rim - did you hear an explosive sound when the tube went?
>
>Yes. Shortly after I fell. I don't think I had an earlier slow
>puncture, at least not that I had noticed. Given the loudness of the
>bang I assumed the tyre was fully inflated hence my concern that the
>problem lay with the Kevlar bead. Another poster has suggested that
>roll off was caused by my skid. But I've had a good many and worse
>skids in my time without my wire beaded tyre departing from the rim

A skid will normally produce fairly small lateral forces at the tire
(since after all, if the tire had a lot of traction, you wouldn't be
skidding). The likely cause for actually wrenching the tire off would
be that after the skid initiated the tire "hooked up" somehow
(probably a road surface irregularity).

For a good example of this, review Beloki's tragic crash in last
year's Tour de France. Although the tire was a tubular the effect is
the same - what started out as a normal skid (if you can call getting
significantly sideways at THAT speed "normal) got much, much worse
when for some reason the tire hooked up and simultaneously rolled the
tire off the rim and pitched the back of the bike the other direction.

OTOH, the fact the tube didn't blow until "shortly after you fell"
might support the possibility you had a slow leak that caused the tire
to roll. At 100+ psi (7+ bar) I would expect the tube to fail almost
instantly when released from its kevlar confines.

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $695 ti frame