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Your thumb is probably more accurate



 
 
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  #1  
Old January 30th 08, 08:45 PM posted to rec.bicycles.tech
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Default Your thumb is probably more accurate

The basic idea of this spring-loaded tire pressure gauge is okay, but
the scale is a bit off.

You'd need a dial indicator micrometer to measure the change in tire
compression with the spring and plunger head shown:

http://www.google.com/patents?id=ZBB...660445#PPP1,M1

Cheers,

Carl Fogel
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  #2  
Old January 30th 08, 09:40 PM posted to rec.bicycles.tech
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Posts: 1,611
Default Your thumb is probably more accurate



wrote:
The basic idea of this spring-loaded tire pressure gauge is okay, but
the scale is a bit off.

You'd need a dial indicator micrometer to measure the change in tire
compression with the spring and plunger head shown:

http://www.google.com/patents?id=ZBB...660445#PPP1,M1

Cheers,

Carl Fogel


I like the gentleman's name.

Joseph
  #3  
Old January 30th 08, 09:44 PM posted to rec.bicycles.tech
Tom Nakashima
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Posts: 497
Default Your thumb is probably more accurate


wrote in message
...
The basic idea of this spring-loaded tire pressure gauge is okay, but
the scale is a bit off.

You'd need a dial indicator micrometer to measure the change in tire
compression with the spring and plunger head shown:

http://www.google.com/patents?id=ZBB...660445#PPP1,M1

Cheers,

Carl Fogel


Looks like it does have a built-in indicator.
I'm afraid a dial indicator wouldn't work well, unless you're on top-dead-
center of the radius. If you had a micrometer, you wouldn't need the spring
plunger head shown.
And glad you're finally convinced about using your thumb as a gauge...
for awhile there thought you were calling us a liar. ;-)
JB's bounce method also works well.
-tom


  #4  
Old January 30th 08, 10:01 PM posted to rec.bicycles.tech
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Default Your thumb is probably more accurate

On Wed, 30 Jan 2008 12:44:26 -0800, "Tom Nakashima"
wrote:


wrote in message
.. .
The basic idea of this spring-loaded tire pressure gauge is okay, but
the scale is a bit off.

You'd need a dial indicator micrometer to measure the change in tire
compression with the spring and plunger head shown:

http://www.google.com/patents?id=ZBB...660445#PPP1,M1

Cheers,

Carl Fogel


Looks like it does have a built-in indicator.
I'm afraid a dial indicator wouldn't work well, unless you're on top-dead-
center of the radius. If you had a micrometer, you wouldn't need the spring
plunger head shown.
And glad you're finally convinced about using your thumb as a gauge...
for awhile there thought you were calling us a liar. ;-)
JB's bounce method also works well.
-tom


Dear Tom,

I'm not convinced that a thumb is all that accurate, despite
anecdotes, but I think that it would be better than that contraption.

The bounce test sounds even less accurate.

Cheers,

Carl Fogel

  #5  
Old January 30th 08, 10:13 PM posted to rec.bicycles.tech
Tom Nakashima
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Posts: 497
Default Your thumb is probably more accurate


wrote in message
...
On Wed, 30 Jan 2008 12:44:26 -0800, "Tom Nakashima"
wrote:


wrote in message
. ..
The basic idea of this spring-loaded tire pressure gauge is okay, but
the scale is a bit off.

You'd need a dial indicator micrometer to measure the change in tire
compression with the spring and plunger head shown:

http://www.google.com/patents?id=ZBB...660445#PPP1,M1

Cheers,

Carl Fogel


Looks like it does have a built-in indicator.
I'm afraid a dial indicator wouldn't work well, unless you're on top-dead-
center of the radius. If you had a micrometer, you wouldn't need the
spring
plunger head shown.
And glad you're finally convinced about using your thumb as a gauge...
for awhile there thought you were calling us a liar. ;-)
JB's bounce method also works well.
-tom


Dear Tom,

I'm not convinced that a thumb is all that accurate, despite
anecdotes, but I think that it would be better than that contraption.

The bounce test sounds even less accurate.
Cheers,
Carl Fogel


I can see where Andre got a little fired up.
I believe I said you can use your thumb to gauge tire pressure.
I think the bounce test was more of the same.
Accuracy....perhaps at 60 mph?
-tom


  #6  
Old January 30th 08, 11:34 PM posted to rec.bicycles.tech
Ben C
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Posts: 3,084
Default Your thumb is probably more accurate

On 2008-01-30, wrote:
On Wed, 30 Jan 2008 12:44:26 -0800, "Tom Nakashima"
wrote:


wrote in message
. ..
The basic idea of this spring-loaded tire pressure gauge is okay, but
the scale is a bit off.

You'd need a dial indicator micrometer to measure the change in tire
compression with the spring and plunger head shown:

http://www.google.com/patents?id=ZBB...660445#PPP1,M1

Cheers,

Carl Fogel


Looks like it does have a built-in indicator.
I'm afraid a dial indicator wouldn't work well, unless you're on top-dead-
center of the radius. If you had a micrometer, you wouldn't need the spring
plunger head shown.
And glad you're finally convinced about using your thumb as a gauge...
for awhile there thought you were calling us a liar. ;-)
JB's bounce method also works well.
-tom


Dear Tom,

I'm not convinced that a thumb is all that accurate, despite
anecdotes, but I think that it would be better than that contraption.

The bounce test sounds even less accurate.


Another pressure test you have mentioned before is to use a
3-decimal-place odometer to measure apparent mileage over exactly the
same route.

Someone has since explained to me that that's how some cars with
low-tyre-pressure warning lights do it. You have an individual odometer
on each wheel and look for discrepancies, averaged out over reasonable
mileages to filter out the effects of steering.

http://en.wikipedia.org/wiki/Tire_pr...itoring_system

I made some estimates for how 15 miles would look on the odometer
against percentage tyre drop:

0% 15.000
1% 15.006
2% 15.011
3% 15.017
4% 15.022
5% 15.028
6% 15.033
7% 15.039
8% 15.045
9% 15.050
10% 15.056
11% 15.061
12% 15.067
13% 15.073
14% 15.078
15% 15.084
16% 15.089
17% 15.095
18% 15.101
19% 15.106
20% 15.112
21% 15.118
22% 15.123
23% 15.129
24% 15.135
25% 15.140
  #7  
Old January 30th 08, 11:44 PM posted to rec.bicycles.tech
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Posts: 3,751
Default Your thumb is probably more accurate

Tom Nakashima writes:

The basic idea of this spring-loaded tire pressure gauge is okay, but
the scale is a bit off.


You'd need a dial indicator micrometer to measure the change in tire
compression with the spring and plunger head shown:


http://www.google.com/patents?id=ZBB...660445#PPP1,M1


Looks like it does have a built-in indicator. I'm afraid a dial
indicator wouldn't work well, unless you're on top-dead- center of
the radius. If you had a micrometer, you wouldn't need the spring
plunger head shown. And glad you're finally convinced about using
your thumb as a gauge... for awhile there thought you were
calling us a liar. ;-) JB's bounce method also works well.


I'm not convinced that a thumb is all that accurate, despite
anecdotes, but I think that it would be better than that
contraption.


The bounce test sounds even less accurate.


I can see where Andre got a little fired up. I believe I said you
can use your thumb to gauge tire pressure. I think the bounce test
was more of the same. Accuracy... perhaps at 60 mph?


These tests need to be viewed in context. First comes inflation with
pump having and easily readable and accurate gauge. Then comes the
ride on which that pressure is assessed. The next day, assuming a
reasonable inner tube is used, the tire should again be ridable unless
there is a leak. A thumb or bounce test will reveal whether one of
the tires got a leak on last use, not the precise pressure... that
doesn't matter anyway.

Riding the bicycle on successive days without topping off pressure
will reveal what a 85psi tire does in comparison to a 100psi one.
That it was 85psi will be revealed when topping off a tire that was at
the lower end of acceptable pressure. Again, the pump has a gauge.

Cutting all this a laboratory analysis is misplaced as I see it. I'm
only being practical with my daily ride. The sound of the bounce
tells me whether I need more precise scrutiny. It doesn't tell me
what the pressure is unless it is "hard".

Jobst Brandt
  #8  
Old January 31st 08, 03:57 AM posted to rec.bicycles.tech
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Posts: 2,673
Default Your thumb is probably more accurate

On Jan 30, 5:44 pm, wrote:


These tests need to be viewed in context. First comes inflation with
pump having and easily readable and accurate gauge. Then comes the
ride on which that pressure is assessed. The next day, assuming a
reasonable inner tube is used, the tire should again be ridable unless
there is a leak. A thumb or bounce test will reveal whether one of
the tires got a leak on last use, not the precise pressure... that
doesn't matter anyway.

Riding the bicycle on successive days without topping off pressure
will reveal what a 85psi tire does in comparison to a 100psi one.
That it was 85psi will be revealed when topping off a tire that was at
the lower end of acceptable pressure. Again, the pump has a gauge.

Cutting all this a laboratory analysis is misplaced as I see it. I'm
only being practical with my daily ride. The sound of the bounce
tells me whether I need more precise scrutiny. It doesn't tell me
what the pressure is unless it is "hard".


Regarding accuracy: I recently used a dead weight pressure gage
calibrator to test three pencil-style gages, one plastic Zefal dial-
type gage (presta & shraeder head), and the dial-type gage built into
my floor pump (Nashbar brand). The pencil gages varied in
construction, from nice heavy-feeling metal to flimsy-feeling plastic.

Unfortunately, I was able to test only the floor pump at 90 true psi.
All gages were tested at 30 true psi.

Results? I was surprised to find that all the pencil gages were much
better than the dials. At true 30, they read 31, 31 and 32. The
Zefal read 39, and the Nashbar read 36. At 90.5 true psi, the Nashbar
read 95.

I assume the Nashbar is a true bourdon tube gage. If so, it's pretty
easy to calibrate - but it's easier to just remember to add about 5
extra psi. The Zefal is a disappointment, and it's not obvious how to
take it apart to improve it.

Second point: Of course, "when topping off" a tire, the unpressurized
volume in the pump normally reduces the tire's pressure. A gage on a
floor pump like mine gives an initial reading lower than what the tire
actually was.

- Frank Krygowski
  #10  
Old January 31st 08, 03:51 PM posted to rec.bicycles.tech
Tom Nakashima
external usenet poster
 
Posts: 497
Default Your thumb is probably more accurate


wrote in message
...

These tests need to be viewed in context. First comes inflation with
pump having and easily readable and accurate gauge. Then comes the
ride on which that pressure is assessed. The next day, assuming a
reasonable inner tube is used, the tire should again be ridable unless
there is a leak. A thumb or bounce test will reveal whether one of
the tires got a leak on last use, not the precise pressure... that
doesn't matter anyway.
Jobst Brandt


I actually rely on my thumb to check tire pressure when I repair a flat on
the road, since I don't carry a mechanical pressure gauge when I ride. My
thumb gauging technique is accurate enough.

We ran a recent test on the road when I had flattened on my rear tire. One
of the riders had a tire pressure gauge. I told him I didn't need one, I
use my thumb. He said; "Let's see how accurate you are?" After I repaired
and pumped up the flatten tube/tire, I used my thumb to feel the
"non-flatten front" tire, then thumbed my rear tire and felt I was a little
low. I pumped it up a little more until the rear tire pressure felt like
the front tire pressure, by using my thumb as a gauge. We then put the
mechanical tire pressure gauge to both tires and they were within a pound of
eachother.
-tom




 




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