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  #11  
Old October 19th 04, 08:03 PM
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Badger South writes:

When inflating tires the psi reading on my floor pump (it's a
Blackburn) goes up and down and up and down, while pumping.


Which is the correct pressure reading? The high or the low
reading?


The high reading is the pressure required to free the conical
Presta valve from its seat. The low reading, if the pump head
grommet does not leak, is the pressure in the inner tube and the
pressure at which the valve settled back into its seat.


I've been assuming the high reading is correct, so my tires are
either inflated to the correct pressure, or they're underinflated.


The tires are underinflated, the amount depending on how sticky the
valve is. If the valve is not popped open manually before pumping,
pressure can exceed 200psi (damaging the gauge), before the valve
will open.


Isn't the gauge in the pump at least as reliable as putting a
hand-held tire pressure gauge on it?


The gauge may be but it can't engaged without letting air out, so the
pump gauge, if it is any good, gives a more accurate reading.

A sure test, but one which will probably make you want to add more
air again, would be to measure it with one and you'll surely find
that the existing pressure shares one of the readings, high or
low. (most likely low).


As I said, that will let out air.

I routinely give mine about 5-10 lbs more air than it calls for
anyway. Since you're not a heavy rider, km, why not over inflate a
bit? Of course I'm not running skinny tires, so YMMV.


That may work if you don't make any steep descents, but after you have
blown a tire off the rim, you may think differently about that. If
you don't ride in mountains then it's probably safe.

I like to descend and corner fast, and for that rock hard tire is not
ideal.

Jobst Brandt

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  #12  
Old October 19th 04, 08:14 PM
maxo
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On Tue, 19 Oct 2004 19:03:31 +0000, jobst.brandt wrote:

I routinely give mine about 5-10 lbs more air than it calls for anyway.
Since you're not a heavy rider, km, why not over inflate a bit? Of
course I'm not running skinny tires, so YMMV.


That may work if you don't make any steep descents, but after you have
blown a tire off the rim, you may think differently about that. If you
don't ride in mountains then it's probably safe.

I like to descend and corner fast, and for that rock hard tire is not
ideal.


ditto, I recently switched to 700x28s on the roadie for that reason--I can
run the recommended max pressure, 85-90psi, and get nice
grip over the rough pavement around here. Skinnies have their place I
suppose, but I don't ride in ideal conditions and find cornering much more
comfortable on the slightly wider and softer tires. The ride is *much*
improved on the flats, and try as I might, I can't perceive any more RR
than a set of 23s.

If I lived in the desert with nice glassy roads then things might be
different...
 




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