M-gineering said:does the goathead puncture at the firat encounter, or doea it need a few
revolutions to strike home? In the latter case you might want to
investigate a tyre saver. I haven't seen them lately, but you'll
probably find them going back to 1900 😉
Schwalbe Marathon Plus tyres with a very thick thread might be worth a
look too
Dear Marten,
A goathead thorn probably goes in up to the hilt when hit squarely by
a 700c tire at 110 psi under a 220 lb rider and bicycle doing 20 to 40
mph. After all, the thorn is needle-sharp and darned near hardwood:
http://i20.tinypic.com/103tm9v.jpg
That's a sewing pin on the left, and a sharp toothpick on the right.
Here a few goatheads pose around a dime, next to Russian olive thorns:
http://i20.tinypic.com/24mexph.jpg
The tiny yellow flower is a goathead's idea of beauty. That's a seed
pod with four green goatheads on the lower right, not a strange 4-leaf
clover.
If you hit a Russian olive branch just right, the inch-long thorn acts
like a nail sticking up from a board. Luckily, Russian olives rarely
attack tires except when the road crews cut the brush next to roads
and paths.
Usually, the goathead's body breaks off, leaving the broken-off base
of the thorn flush with the tread and the sharp end sticking into the
tube. Sometimes you can pry the thorn out with a fingernail, but often
a paper-clip comes in handy--you push the thorn all the way through to
get it out of the tire.
Some goatheads will stab and then be pulled out, leaving no thorn
behind, but you still have to check the whole tire, feeling the inside
for any tiny thorn tip and peering at the tread for the tiny round
base of a broken-off thorn. This gets harder as your eyes get older.
Here's a large and very easy-to-see example, before and after
extraction:
http://i20.tinypic.com/2rei5v9.jpg
http://i23.tinypic.com/nq5oyf.jpg
It's common to notice a goathead flashing past on the front tire,
stuck in the sidewall. This one probably attacked my rear tire at
least two miles before I reached home:
http://i18.tinypic.com/2gtpxd2.jpg
Still holding air:
http://i24.tinypic.com/nfocvk.jpg
The further up the side of the tire, the less protection from thick
tread, thick tubes, tire liners, and sealants.
With hundreds of goatheads on a single flat vine, you can pick up
several at once. Four of them ganged up on this tube:
http://i23.tinypic.com/x1x6ih.jpg
Riders unfamiliar with goatheads sometimes roll right onto a vine and
pick up a few dozen thorns. They usually don't do this twice, any more
than a dog sticks his face into a porcupine more than once. Here's a
modest example of goathead growth next to a bike path:
http://i23.tinypic.com/jkceu0.jpg
Some posters have used tire-savers and claimed that they reduce
goathead flats. I'm skeptical, since the needle-sharp thorns probably
go in all the way as soon as you hit one. If you walk on goatheads
while wearing rubber-soled shoes, it's hard to maintain much faith in
the theory that goatheads work their way in gradually.
Frank Krygowski was kind enough to send me some old tire savers. They
didn't fit a modern bike, but they gave me a model for making my own.
(I don't think that anyone even makes tire savers any more, which
hints that they aren't as useful as claimed.)
Sadly, I abandoned tire-savers after a single ride, which wasn't much
of a test. The trouble was that they threw a cloud of dust right in my
face when I tucked in for my daily 2-mile descent, so I was coughing
my lungs out. (Jobst points out that dusty, muddy legs show who's
using tire-savers and doubts their effectiveness even more than I do.)
Unfortunately, anti-goathead measures tend to work best where
goatheads aren't really much of a problem. Out where goatheads are a
_real_ problem (as opposed to my daily ride, which is practically
goathead free in comparison), people use knobby MTB tires to get up
and away from the thorns, thick thorn-resistant tubes, tire liners,
and Slime-style sealants--and they still get flats.
If I just rode around my neighborhood, I wouldn't have any trouble
with goatheads, but I wouldn't have much fun. The bright side is that
goatheads discourage bicyclists, so my daily ride is uncrowded.
But not much fun today--still raining and snowing after 86F yesterday.
Cheers,
Carl Fogel
