On Mon, 26 Nov 2007 14:56:22 -0800 (PST), Brad Kliewer
<
[email protected]> wrote:
>On Nov 23, 12:11 pm, Ted Bennett <[email protected]> wrote:
>> Brad Kliewer <[email protected]> wrote:
>> It's most likely your technique, Brad. Steel beads are meant to be
>> tight and they do not stretch. To get the bead up and over the rim's
>> edge you have to create some slack, and that is by ensuring that as much
>> of the bead as possible is down in the well in the middle of the rim.
>
>I'm sure I need to refine my technique a bit more -- flats are fairly
>infrequent, so I don't get a lot of practice. Carl's description of
>holding the tire by the top made me think of a way that would probably
>both save some time and give more reliable results. I usually use one
>hand to hold the (Schrader) valve open while working the other hand
>more or less from the top to bottom trying to get as much air out as
>possible punctures/cuts often aren't big enough to dump air out very
>quickly). Then I squeeze the bead with both hands from bottom to top.
>I probably should loosen the valve first to free up the other hand and
>then grip the top to help keep the bead in place on the bottom (I
>assume by his description that he's using gravity to make sure the
>bead stays in the well once it's seated there).
[snip]
Dear Brad,
Yes, that's the idea. Dangling the tire and squeezing the beads
together with one hand helps you keep the slack that you gain by
pinching the rest of the tire with your other hand and forcing the
bead into the rim well.
Otherwise, when you pinch the bead on one side of the tire, you can
pull it back out a little on the other side of the tire and end up
going round and round without ever getting anywhere.
The same principle causes trouble when people with broken hips are put
in traction.
Unfortunately, people now live long enough to break their hips while
taking blood thinners for severe heart trouble.
When they do, the surgeon may decide to stop the blood thinner, wait a
few days, and then fix the broken hip when the patient has a better
chance of surviving the surgery.
Meanwhile, the patient's foot is strapped into a padded boot attached
to a cable, which runs over a pulley at the end of the bed to a modest
weight, perhaps ten pounds.
The steady gentle pull on the patient's leg relieves some of the pain
of the broken hip and prevents further damage.
(One sign of broken a hip is a shortened leg. Normally, muscles pull
the leg upward, keeping the round head of the femur tight against the
pelvic socket. When the head of the femur breaks off, the muscles pull
the leg up further. Loud screams are another sign that this is
happening.)
After traction is set up, the innocent-looking little weight takes
only a few hours to pull a helpless patient to the foot of the bed.
The padded boot jams against the pulley, the traction is lost, and the
patient is left in even worse agony.
What happens is that the relentless traction pulls the patient a tiny
bit toward the foot of the bed whenever he moves, a hundredth of an
inch at a time. Even unconscious patients creep down the bed--just
breathing provides enough motion, and the traction guarantees that
ground will always be lost.
The patient is helpless. Normally we can wriggle back toward the head
of the bed, but no one tries to pull himself away from the foot of the
bed against a 10-pound pull on a foot connected to a broken hip.
So every few hours, three nurses need to show up to fix things. One
raises the weight at the end of the pulley, while the other two stand
on each side of the bed, grab the patient under the arms, and pull him
back toward the head of the bed. No matter how gentle they are, this
reminds the patient that he has a broken hip.
The nurses aren't likely to let a visitor haul on the patient, but two
of them may trust you to raise the weight. Even if they don't, you can
let them know when the traction weight has pulled the patient to the
end of the bed again. (For some reason, patients themselves may be
reluctant to ask three nurses to come to their bedside and hurt them.)
Of course, tilting the adjustable bed's head slightly downward would
solve the problem, but doctors frown on having patients with severe
heart trouble lying with their heads downhill.
Anyway, it's the same idea as letting gravity help while you work a
tire bead down into the rim well. Any bead that moves into the rim
well stays down there, so you keep all the slack that you gain.
Getting the bead down into the rim well isn't easy, since you're
trying to slide rubber that's touching a metal rim. Even faint
pressure makes the bead act like a huge brake pad, which is why
mechanics often spray water on reluctant tires--wet beads slip down
into the well more easily, just as wet brake pads fail to grab wet
rims.
Cheers,
Carl Fogel
