Wanted: Accident Investigator



On Saturday, I got the bike out of the shed for the first time in a
couple of months, pumped up the tyres, and headed off for a tootle to
Bigton and back. I'd got about 3km up the road, and was at the top of a
slight descent, when a few things happened, seemingly simultaneously. I
heard the pinging sound of spokes hitting something as the front wheel
rotated; the front tyye punctured with a loud pop; the front wheel
suddenly stopped rotating; and I found myself flying over the
handlebars towards freshly-chipped tarmac. To cut a rather unpleasant
story short, I've now got twenty-one stiches in my right ear, a black
eye, road rash on my shoulder, and some unexpected time off work. Th
real problem is, however, that I'm going to be a bit nervous whne I
eventually get back on a bike unless I figure out what went wrong on
Saturday. I've got two main lines of inquiry at the moment:

1) the front type slowly deflated, and the valve got stuck in the
spokes, eventually jamming it,
2) I panicked at what appeared to be imminent mechanical disaster, and
propelled myself over the handlebars by applying the front brake too
hard

I've given the bike a cursory inspection since: the front wheel rotates
freely, and the front tyre is flat.

Ideas, anybody ?
 
I

iakobski

Guest
Front brake way out of alignment?

Whereabouts on the tyre is the puncture? What kind of hole is it? What
happens if you spin the front wheel slowly and apply the brake?
 
R

Richard

Guest
[email protected] wrote:

> slight descent, when a few things happened, seemingly simultaneously. I
> heard the pinging sound of spokes hitting something as the front wheel
> rotated; the front tyye punctured with a loud pop; the front wheel
> suddenly stopped rotating;


> 1) the front type slowly deflated, and the valve got stuck in the
> spokes, eventually jamming it,


Unlikely, I'd have thought, unless it's a particularly big valve and
very close clearances.

> 2) I panicked at what appeared to be imminent mechanical disaster, and
> propelled myself over the handlebars by applying the front brake too
> hard


Possible. :)

Do you have mudguards? is it possible they jammed the wheel? Although
if so, I'd expect the plastic to be visibly distressed [1].

Perhaps your spokes picked up a stick or other piece of road debris,
whipped it round to the top of the forks, pinged a spoke or two, and
then jammed the wheel there? (and subsequently it fell out)?

Hope you recover quick.

R.

[1] sobbing, wailing, etc.
 
M

m-gineering

Guest
"[email protected]" wrote:
>
> On Saturday, I got the bike out of the shed for the first time in a
> couple of months, pumped up the tyres, and headed off for a tootle to
> Bigton and back. I'd got about 3km up the road, and was at the top of a
> slight descent, when a few things happened, seemingly simultaneously. I
> heard the pinging sound of spokes hitting something as the front wheel
> rotated; the front tyye punctured with a loud pop; the front wheel
> suddenly stopped rotating; and I found myself flying over the
> handlebars towards freshly-chipped tarmac. To cut a rather unpleasant
> story short, I've now got twenty-one stiches in my right ear, a black
> eye, road rash on my shoulder, and some unexpected time off work. Th
> real problem is, however, that I'm going to be a bit nervous whne I
> eventually get back on a bike unless I figure out what went wrong on
> Saturday. I've got two main lines of inquiry at the moment:
>
> 1) the front type slowly deflated, and the valve got stuck in the
> spokes, eventually jamming it,


Doesn't make sense, but given the state you're in ... ;)


> 2) I panicked at what appeared to be imminent mechanical disaster, and
> propelled myself over the handlebars by applying the front brake too
> hard
>
> I've given the bike a cursory inspection since: the front wheel rotates
> freely, and the front tyre is flat.
>
> Ideas, anybody ?


you go over the bars if a) the front wheel jams or b if you loose your
balance

a) could be caused by
heavy braking or defective brake
foreign object in spokes or between tyre and forkcrown (beercan, stick,
feedbag, mudguard....
pothole

b)
freewheel slipping or chain jumping
letting go of bar & turning bars 90 degrees


It sounds like your tyre popped a bead and the tube exploded. If the
tyre came of the rim it probably jammed in the forks.
Other scenario (more likely with an mtb with low pressure): you pick up
a stick, the stick jams in the fork, the tyre moves around the rim
tearing the valve out while you're cartwheeling

How is the fit of the tyre, did you do anything to it recently? Are your
forks still straight? bent spoke? scuffmarks

--
---
Marten Gerritsen

INFOapestaartjeM-GINEERINGpuntNL
www.m-gineering.nl
 
H

Helen Deborah Vecht

Guest
If the road was rececently resurfaced/redressed, soft tar could have
stuck to the tyre, taking a chipping with it. This lump could have then
got stuck in a mudguard, bringing OP to painful, unscheduled halt and
dismount.

Is there any evidence to support this wild hypothesis?

Heal fast!

--
Helen D. Vecht: [email protected]
Edgware.
 
S

Simon Brooke

Guest
in message <[email protected]>,
[email protected] ('[email protected]') wrote:

> On Saturday, I got the bike out of the shed for the first time in a
> couple of months, pumped up the tyres, and headed off for a tootle to
> Bigton and back. I'd got about 3km up the road, and was at the top of a
> slight descent, when a few things happened, seemingly simultaneously. I
> heard the pinging sound of spokes hitting something as the front wheel
> rotated; the front tyye punctured with a loud pop; the front wheel
> suddenly stopped rotating; and I found myself flying over the
> handlebars towards freshly-chipped tarmac. To cut a rather unpleasant
> story short, I've now got twenty-one stiches in my right ear, a black
> eye, road rash on my shoulder, and some unexpected time off work. Th
> real problem is, however, that I'm going to be a bit nervous whne I
> eventually get back on a bike unless I figure out what went wrong on
> Saturday. I've got two main lines of inquiry at the moment:
>
> 1) the front type slowly deflated, and the valve got stuck in the
> spokes, eventually jamming it,


Can't happen and wouldn't cause a problem if it did. A stick getting
caught in the front wheel might cause the wheel to suddenly stop as you
describe, but is unlikely to happen on the road, and in any case it
wouldn't puncture the tyre.

Punctures don't normally cause a tyre to go 'pop', but the can do so,
particularly if there is a split in the outer tyre or if the outer tyre
is too loose on the rim. I suggest you carefully inspect your outer tyre
and replace if necessary.

> 2) I panicked at what appeared to be imminent mechanical disaster, and
> propelled myself over the handlebars by applying the front brake too
> hard


I'm fairly sure that's what happened. The bang of the tyre rupturing
caused you to panic and grip the brake levers.

--
[email protected] (Simon Brooke) http://www.jasmine.org.uk/~simon/
"This young man has not the faintest idea how socialists think and does
not begin to understand the mentality of the party he has been elected
to lead. He is quite simply a liberal"
-- Ken Coates MEP (Lab) of Tony Blair
 
R

Richard

Guest
Simon Brooke wrote:

>>2) I panicked at what appeared to be imminent mechanical disaster, and
>>propelled myself over the handlebars by applying the front brake too
>>hard

>
>
> I'm fairly sure that's what happened. The bang of the tyre rupturing
> caused you to panic and grip the brake levers.


Perhaps this is an argument for riding with steel rims and caliper
brakes in the wet, then? Guaranteed no dives over the handlebars. ;-)

R.
 
M

Mark Tranchant

Guest
Richard wrote:

> Perhaps this is an argument for riding with steel rims and caliper
> brakes in the wet, then? Guaranteed no dives over the handlebars. ;-)


....and you could fit an "ABS" badge to the bike... ;-)

--
Mark.
http://tranchant.plus.com/
 
Simon Brooke wrote:

> > On Saturday, I got the bike out of the shed for the first time in a
> > couple of months, pumped up the tyres, [then bang, over the bars]


> Punctures don't normally cause a tyre to go 'pop', but the can do so,
> particularly if there is a split in the outer tyre or if the outer tyre
> is too loose on the rim. I suggest you carefully inspect your outer tyre
> and replace if necessary.


Bearing in mind the newly-pumped-up nature of the tyres, my guess is
that the bead had come away from the hook of the rim and trapped the
tube as it was re-inflated.

Tube creeps out, forming a bubble, then blows the tyre off the rim and
into forks and/or mudguard when it goes bang.

> > 2) I panicked at what appeared to be imminent mechanical disaster, and
> > propelled myself over the handlebars by applying the front brake too
> > hard

>
> I'm fairly sure that's what happened. The bang of the tyre rupturing
> caused you to panic and grip the brake levers.


Maybe - it's certainly possible.

John
 
T

Tony Raven

Guest
[email protected] wrote:
>
> 2) I panicked at what appeared to be imminent mechanical disaster, and
> propelled myself over the handlebars by applying the front brake too
> hard
>


That would be my guess. I've had front tyres blow out at speed and
while they make you wobble a bit while you slow down they do not stop
the front wheel or throw you over the handlebars.

Of course it could be the new tar was super super sticky;-)

Heal soon.

--
Tony

"I did make a mistake once - I thought I'd made a mistake but I hadn't"
Anon
 
T

Tony Raven

Guest
Mark Tranchant wrote:
> Richard wrote:
>
>> Perhaps this is an argument for riding with steel rims and caliper
>> brakes in the wet, then? Guaranteed no dives over the handlebars. ;-)

>
> ....and you could fit an "ABS" badge to the bike... ;-)
>


For Absolutely Bl**dy Sh*te brakes ;-)
--
Tony

"I did make a mistake once - I thought I'd made a mistake but I hadn't"
Anon
 
P

Peter Fox

Guest
Following on from [email protected]'s message. . .
>On Saturday, I got the bike out of the shed for the first time in a
>couple of months, pumped up the tyres, and headed off for a tootle to
>Bigton and back. I'd got about 3km up the road, and was at the top of a
>slight descent, when a few things happened, seemingly simultaneously. I
>heard the pinging sound of spokes hitting something as the front wheel
>rotated; the front tyye punctured with a loud pop; the front wheel
>suddenly stopped rotating; and I found myself flying over the
>handlebars towards freshly-chipped tarmac. To cut a rather unpleasant

[involuntary gymnastics snipped]

"pinging of spokes"
This is curious. Either they were snapping (but that shouldn't be a
'ping') or something was hitting them. Whatever it was wouldn't have
been on the wheel itself so that leaves:
(a) Bit of the bike
(b) Bit of the rider/luggage
(c) Bit of the local environment
It is reasonable to assume /providing your recollection is correct/ that
whatever started as spoke-pinging turned into spoke-jamming or then
became a wedge. (And the puncture was secondary - but see later.)
If there are witness marks on the spokes then that would indicate
something jamming them and in case (a) there would be something
seriously bent on the bike. There is the possibility that the pinging
you heard was loose chippings and these wedged your wheel in a mudguard.

There is another way in which the bike could become uncontrollable and
the puncture is a result rather than the prime cause. If there were
swathes of chippings you may have come across a little 'dune' of
chippings and the front tyre lost grip and at this point you 'did
something' to correct the unpleasant feeling which caused the bars to
turn. When the tyre regains its grip it isn't pointing 'ahead' and then
a puncture-waiting-to-happen occurs as the tyre experienced unusual
stresses. A tube that goes bang is an abused (or inherently defective)
tube. [Psssssss is normal.]

Could a burst tube or bad tyre be the prime cause? In itself it
wouldn't cause spoke-pinging. However if we accept the presence of some
loose chippings then there might be a way. The pings would be from
chippings being fired at the rear wheel from a deflated/locked/turned
front spraying lots of chippings into the rear spokes.

FWIW My guess is that you hit a dune of chippings neatly piled up in the
direction you were going, braked when you felt uncomfortable, lost
control of the front, and then returned to firm road all out of balance.
At this point you were probably in for a painful landing. The tyre may
have punctured due to a combination of distress and inappropriate
fitting etc.


PS Don't give up cycling. Practice emergency stops and looking out for
loose surfaces.

--
PETER FOX Not the same since the deckchair business folded
[email protected]
www.eminent.demon.co.uk - Lots for cyclists
 
Thanks for the replies, everybody. It's given me some ideas of what to
look for when I finally feel well enough the drag the bike out of the
shed again. A quick look over it this morning reveals that the front
wheel is rotating freely again, and the tyre is still on the rim. My
next step will be to have a look at the inner tube, and try to find the
source of the puncture.

The bandages came off today, and I'll be having the stitches out on
Monday, so hopefully I'll be back in the saddle in the not-too-distant
future.