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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
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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
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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
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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
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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 |
#7
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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
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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 |
#9
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Your thumb is probably more accurate
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#10
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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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