Fold Up Roll Off Query

16 Apr 2004 said:

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

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Quoted message said:

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.

Quoted message said:

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 habcycles.comhabcycles.comOpen ↗ Home of
the $695 ti frame

On Fri, 16 Apr 2004 06:57:28 -0700, Mark Hickey <[email hidden]>

Quoted message said:

Quoted message said:

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 said:

Mark Hickey said:

Quoted message said:

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 habcycles.comhabcycles.comOpen ↗ Home of
the $695 ti frame