Front blowout

Last week a friend was following me at about 30 mph down a gentle hill on
our road bikes, when I heard the sounds of a blowout and a crashing bike
behind me. When I went back to check, I found him on the ground, out cold,
breathing heavily and bleeding from the mouth. It was evident that he had
hit the asphalt pavement hard with the left rear of his head. His helmet
appears to have taken much of the blow, as there were pieces of foam broken
off. He was taken to the hospital and is still there a week later. The
doctors say he will recover, but it will take a while.

I did not see him fall, and there was nobody else around. When I inspected
his front wheel, I found that his clincher tire was completely separated
from the rim and his tube was wrapped around the hub at one end and caught
on a brake pad at the other. There was a spot on the tire where the tread
had worn almost completely off, otherwise the tire was in good shape. The
rim was scraped all the way around, but there was no spot that was much
worse than the rest. The tube was split where the bead had been and the tire
had no holes in it, so it was evident that the bead had come loose from the
rim, allowing the tube to blow out. I think my friend had fixed a flat on
his front tire a few months ago. He must not have seated the tire correctly.

My question is about the mechanics of the fall. It seems to me that he must
have taken a header over the handlebars. That would only happen if his front
wheel had stopped. His knuckles are scraped, especially on his left hand, as
though his hands were still on the hoods when he hit the ground. I don't see
that the wheel could have stopped with the tire off the rim, as there would
be insufficient friction between a bare rim and the pavement to stop the
wheel. So the tire must have been on the rim when the wheel stopped and it
somehow came loose from the rim during the fall.

When I first started riding some 30 years ago, I had an improperly glued
tubular tire come loose on my front wheel while in a practice sprint. The
wheel stopped when the tire became lodged between the fork blade and the
rim. I took a header and landed on the right side of my head. I was wearing
a hairnet helment and suffered a slight concussion, but nothing as serious
as my friend has. Until his fall, I didn't realize it was possible to suffer
severe injuries to the head from taking a header on pavement.

I have two questions:

If a stopped tire caused my friend's fall, what might have caused the tire
come loose from the rim during the fall?

Also, has anyone else seen such a severe head injury from taking a header
onto pavement?

"Bob Shanteau" wrote in message
om...
Last week a friend was following me at about 30 mph down a gentle hill on
our road bikes, when I heard the sounds of a blowout and a crashing bike
behind me. When I went back to check, I found him on the ground, out cold,
breathing heavily and bleeding from the mouth. It was evident that he had
hit the asphalt pavement hard with the left rear of his head. His helmet
appears to have taken much of the blow, as there were pieces of foam
broken
off. He was taken to the hospital and is still there a week later. The
doctors say he will recover, but it will take a while.

I did not see him fall, and there was nobody else around. When I inspected
his front wheel, I found that his clincher tire was completely separated
from the rim and his tube was wrapped around the hub at one end and caught
on a brake pad at the other. There was a spot on the tire where the tread
had worn almost completely off, otherwise the tire was in good shape. The
rim was scraped all the way around, but there was no spot that was much
worse than the rest. The tube was split where the bead had been and the
tire
had no holes in it, so it was evident that the bead had come loose from
the
rim, allowing the tube to blow out. I think my friend had fixed a flat on
his front tire a few months ago. He must not have seated the tire
correctly.

My question is about the mechanics of the fall. It seems to me that he
must
have taken a header over the handlebars. That would only happen if his
front
wheel had stopped. His knuckles are scraped, especially on his left hand,
as
though his hands were still on the hoods when he hit the ground. I don't
see
that the wheel could have stopped with the tire off the rim, as there
would
be insufficient friction between a bare rim and the pavement to stop the
wheel. So the tire must have been on the rim when the wheel stopped and it
somehow came loose from the rim during the fall.

When I first started riding some 30 years ago, I had an improperly glued
tubular tire come loose on my front wheel while in a practice sprint. The
wheel stopped when the tire became lodged between the fork blade and the
rim. I took a header and landed on the right side of my head. I was
wearing
a hairnet helment and suffered a slight concussion, but nothing as serious
as my friend has. Until his fall, I didn't realize it was possible to
suffer
severe injuries to the head from taking a header on pavement.

I have two questions:

If a stopped tire caused my friend's fall, what might have caused the tire
come loose from the rim during the fall?

Also, has anyone else seen such a severe head injury from taking a header
onto pavement?

His tube/tire may have gotten stuck in the brakes. That'll stop a wheel
quickly.

I don't have any front teeth from a bicycle crash when I was 15. That
count?

Mike

"Bob Shanteau" wrote in message
om...


Also, has anyone else seen such a severe head injury from taking a header
onto pavement?


Sounds like an invitation to another helmet thread - the helmet probably
saved his life, no, it probably caused his injury either through risk
compensation or cranial rotation... etc. etc. Why should it be surprising
that hitting your head on the pavement can cause severe head injury?

Rich

A special feature of front blowouts, at least with wide tires, is that
balance corrections reverse; if you steer right, it steers the loose
tire casing left, and you go over faster than if you hadn't corrected
at all. So if you have a front blowout, at least on wide tires,
stop very fast. I don't recall any similar difficult on narrow
tires. The fall though is to the side, not over the handlebars,
at least not a first. I suppose you could wind up in front of the
bike though.
--
Ron Hardin


On the internet, nobody knows you're a jerk.

"Bob Shanteau" wrote in message
om...

Also, has anyone else seen such a severe head injury from taking a header
onto pavement?

Last year a local (MA) rider (helmeted) died in a similar fall. The theory was
that he threw a chain, causing the rear wheel to skid and eventually crash. As
in your case, there was another cyclist riding with, but not closely, and the
deceased rider was going downhill pretty fast at the time of the crash.

In article vSxtb.3838$6G3.2069@fed1read06,
"Mike S." mikeshaw2@coxDOTnet wrote:

"Bob Shanteau" wrote in message
om...
Last week a friend was following me at about 30 mph down a gentle hill on
our road bikes, when I heard the sounds of a blowout and a crashing bike
behind me. When I went back to check, I found him on the ground, out cold,
breathing heavily and bleeding from the mouth. It was evident that he had
hit the asphalt pavement hard with the left rear of his head. His helmet
appears to have taken much of the blow, as there were pieces of foam
broken
off. He was taken to the hospital and is still there a week later. The
doctors say he will recover, but it will take a while.

I did not see him fall, and there was nobody else around. When I inspected
his front wheel, I found that his clincher tire was completely separated
from the rim and his tube was wrapped around the hub at one end and caught
on a brake pad at the other. There was a spot on the tire where the tread
had worn almost completely off, otherwise the tire was in good shape. The
rim was scraped all the way around, but there was no spot that was much
worse than the rest. The tube was split where the bead had been and the
tire
had no holes in it, so it was evident that the bead had come loose from
the
rim, allowing the tube to blow out. I think my friend had fixed a flat on
his front tire a few months ago. He must not have seated the tire
correctly.

My question is about the mechanics of the fall. It seems to me that he
must
have taken a header over the handlebars. That would only happen if his
front
wheel had stopped. His knuckles are scraped, especially on his left hand,
as
though his hands were still on the hoods when he hit the ground. I don't
see
that the wheel could have stopped with the tire off the rim, as there
would
be insufficient friction between a bare rim and the pavement to stop the
wheel. So the tire must have been on the rim when the wheel stopped and it
somehow came loose from the rim during the fall.

When I first started riding some 30 years ago, I had an improperly glued
tubular tire come loose on my front wheel while in a practice sprint. The
wheel stopped when the tire became lodged between the fork blade and the
rim. I took a header and landed on the right side of my head. I was
wearing
a hairnet helment and suffered a slight concussion, but nothing as serious
as my friend has. Until his fall, I didn't realize it was possible to
suffer
severe injuries to the head from taking a header on pavement.

I have two questions:

If a stopped tire caused my friend's fall, what might have caused the tire
come loose from the rim during the fall?



Well, it sounds like you nailed the fact that the blowout was caused by
a bead separation (Jobst would approve, having previously claimed that
explosive blowouts are almost always caused by bead failures). Once that
happens, the tire is de facto loose from the rim, and can do any number
of things, all bad.

A few guesses, though I am not an accident reconstructionist (Jobst has
done this very job, so he probably knows with fair certainty what did
happen):

the worn spot on the tire means the wheel spent a short time locked in
place, sliding on that part of the tire. I guess at one of two causes:

1) your friend reacted to the blowout by grabbing the front brake. Tire
locked up, and over he went.

His tube/tire may have gotten stuck in the brakes. That'll stop a wheel
quickly.

2) Yeah, your friend's tube separated from the wheel, got caught on the
hub and brake just as you found it, and stopped the bike dead. Er,
near-dead. Tire, already semi-loose, locked up and over he went.

He could well have been on the hoods the whole time, as the accident
probably happened so fast he had no time to react. You just end up on
your face practically before you know there's a problem. Note that in
this kind of accident, you can actually hit the ground with more speed
than mere acceleration due to dropping from the height of your head
(maybe 5 feet or so) to the ground would indicate, because as the wheel
locks up, you effectively get most or all of your forward speed
translated into rotation of the bike around the now-locked wheel,
slamming you into the ground at something very close to the bike's
former speed.

Also, has anyone else seen such a severe head injury from taking a header
onto pavement?

Close. My father got knocked off his bike many years ago, and ended up
landing helmet-first on the pavement. He got away with a broken finger,
shock, and persistent numbness in part of his face, evidence of nerve
damage from the accident. I gather he was fairly weird for the rest of
the day, though my mother sometimes suggest he's been fairly weird for
the whole time she's known him.

Bathtub falls have been known to cause fatal head injuries, and many
drops to pavement are in the same range of forces. Accidents like this
are interesting in their effects on the body and whatnot because you
just don't experience the violent forces of a bike accident or road
accident (especially a car accident) in ordinary life. Weird stuff
happens, and the forces you get can be very unpredictable. I've taken
some headers nearly that violent, though usually at lower speeds than 30
mph, and mostly walked away with minimal trauma (took a mountain-bike
handlebar in the gut one time, which made the rest of the bike race
fairly slow; won "most blood" at another race). OTOH, catch things just
the wrong way and you can break your neck. Racing cyclists can and have
died even with helmets on, just thanks to the bad fortune to crash the
wrong way in the wrong place.

Since this is already close to being a helmets thread, how about a
bent-vs-DF thread instead? Richard Ballantine of "Richard's Bicycle
Book" has gone so far as to claim that recumbents are a bit safer than
upright bikes because you tend to arrive at accidents feet first, low,
and with a bike structure ahead of your head and torso, rather than head
first, high, and with very little in front of you. (I'm paraphrasing and
interpolating his argument, which was framed around an anecdote about a
friend having a very bad crash in a recumbent crit while riding a faired
trike)

--
Ryan Cousineau, http://www.sfu.ca/~rcousine
President, Fabrizio Mazzoleni Fan Club

RE/
Also, has anyone else seen such a severe head injury from taking a header
onto pavement?

A drunk sideswiped me on my Yamaha YDS-6. The bike went endo and I did a sort
of swan dive onto the blacktop. I was doing about 45 when he hit me.

Cracked a perfectly-good Bell helmet, and I saw flashes of light intermittantly
for several days.

Also, I suspect I put my dentist's kid through college....
--
PeteCresswell

Sweeping right turn, gradual descent, going about 25 mph... front tire blew
throught a 4-5 cm gash on its right sidewall cut by a curved piece of
razor-sharp Budweiser bottle I hadn't seen.

I slowed and stopped safely, but with a scare. What surprised me most, and
what I still remember, was the bike's tendency to straighten out when the tire
blew. I actually let it cross the yellow line into the oncoming lane rather
than wrestle with it (luckily no traffic).

This was on a road bike with 23 mm tires on MA-2 rims. The bead stayed on.


Mike Yankee

(Address is munged to thwart spammers.
To reply, delete everything after "com".)

shantes- Last week a friend was following me at about 30 mph down a gentle
hill on
our road bikes, when I heard the sounds of a blowout and a crashing bike
behind me. When I went back to check, I found him on the ground, out cold,
breathing heavily and bleeding from the mouth. It was evident that he had
hit the asphalt pavement hard with the left rear of his head. His helmet
appears to have taken much of the blow, as there were pieces of foam broken
off. He was taken to the hospital and is still there a week later. The
doctors say he will recover, but it will take a while.

I did not see him fall, and there was nobody else around. When I inspected
his front wheel, I found that his clincher tire was completely separated
from the rim and his tube was wrapped around the hub at one end and caught
on a brake pad at the other. There was a spot on the tire where the tread
had worn almost completely off, otherwise the tire was in good shape.
BRBR

another reason to use tubulars...

C'mon, don't get excited, it's nearly winter and it's tiime for this type of
discussion..

BTW-hope your friend finds a good Neuro and a good Clinical Psych if he needs
eval and brain trama retraining, like I did/do..hope he recovers well.

Peter Chisholm
Vecchio's Bicicletteria
1833 Pearl St.
Boulder, CO, 80302
(303)440-3535
http://www.vecchios.com
"Ruote convenzionali costruite eccezionalmente bene"

Ryan Cousineau wrote:
... Note that in
this kind of accident, you can actually hit the ground with more speed
than mere acceleration due to dropping from the height of your head
(maybe 5 feet or so) to the ground would indicate, because as the wheel
locks up, you effectively get most or all of your forward speed
translated into rotation of the bike around the now-locked wheel,
slamming you into the ground at something very close to the bike's
former speed.

I don't think this is true. The vertical component of speed is the same
as in a stationary 5 foot drop.

For your effect to work, the front wheel would have to somehow be tied
to the ground, and the rider tied to the bike. That is, the wheel and
bike frame would have to exert tension on the rider's body, to pull him
into a vertical circular arc.

The horizontal component of your original speed (minus a bit for
whatever braking took place) has to be added vectorially to the "5 foot
drop" speed, but that's not the same thing as what you're describing.

Since this is already close to being a helmets thread, how about a
bent-vs-DF thread instead? Richard Ballantine of "Richard's Bicycle
Book" has gone so far as to claim that recumbents are a bit safer than
upright bikes because you tend to arrive at accidents feet first, low,
and with a bike structure ahead of your head and torso, rather than head
first, high, and with very little in front of you.

Not to mention that the recumbent rider is likely to be going much slower.

There, that should do it! ;-)

--
Frank Krygowski