Tire Pressure measurement-Presta Valve

Discussion in 'Cycling Equipment' started by E & V Willson, Apr 27, 2003.

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  1. How do you measure the pressure in tires with tubes that have presta valves. Are special (portable
    i.e. pencil type) gauges available, or is it just done with the gauges on pumps?

    TIA, Ernie
     
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  2. Ken

    Ken Guest

    E & V Willson <[email protected]> wrote in news:[email protected]:
    > How do you measure the pressure in tires with tubes that have presta valves. Are special (portable
    > i.e. pencil type) gauges available, or is it just done with the gauges on pumps?

    Hand guages are available, but I don't know anyone that takes them on bike rides. Everyone I know
    either counts pump strokes or just pumps up the tire until it feels hard enough.
     
  3. Michael Dart

    Michael Dart Guest

    "E & V Willson" <[email protected]> wrote in message news:[email protected]...
    > How do you measure the pressure in tires with tubes that have presta valves. Are special (portable
    > i.e. pencil type) gauges available, or is it just done with the gauges on pumps?
    >
    > TIA, Ernie
    >

    Accu-gauge makes a presta compatible dial gauge that is great.

    Mike
     
  4. Jobst Brandt

    Jobst Brandt Guest

    Ernie Willson writes:

    > How do you measure the pressure in tires with tubes that have Presta valves. Are special (portable
    > i.e. pencil type) gauges available, or is it just done with the gauges on pumps?

    Tire pressure is not a parameter that needs to be more accurate than 5% or so. Learn to feel what
    your tire feels like when you reach your preferred pressure with your pump with a gauge. The high
    pressures often mentioned here in this newsgroup are too high and unsafe if you plan to descend any
    steep hills that require a lot of braking. 140psi is about the blow-off pressure, tire size having
    no effect on the separation pressure from any given rim.

    Tiny cross section tires have no benefit anyway, they having more RR than fatter tires with the same
    tread thickness. That is the difference between the Avocet Criterium and TT tire that are otherwise
    identical.

    Jobst Brandt [email protected] Palo Alto CA
     
  5. Openworld

    Openworld Guest

    Tyre pressure is as important as you want it to be. Knowing how your bike handles at set pressures
    is great for us techies. Cheap option-presta-schraeder adapter £2 from all chain stores- 50pence
    from your local shop. This is also handy when you forget your pump and have to borrow from a
    mountain biker. <[email protected]> wrote in message
    news:[email protected]...
    > Ernie Willson writes:
    >
    > > How do you measure the pressure in tires with tubes that have Presta valves. Are special
    > > (portable i.e. pencil type) gauges available, or is it just done with the gauges on pumps?
    >
    > Tire pressure is not a parameter that needs to be more accurate than 5% or so. Learn to feel what
    > your tire feels like when you reach your preferred pressure with your pump with a gauge. The high
    > pressures often mentioned here in this newsgroup are too high and unsafe if you plan to descend
    > any steep hills that require a lot of braking. 140psi is about the blow-off pressure, tire size
    > having no effect on the separation pressure from any given rim.
    >
    > Tiny cross section tires have no benefit anyway, they having more RR than fatter tires with the
    > same tread thickness. That is the difference between the Avocet Criterium and TT tire that are
    > otherwise identical.
    >
    > Jobst Brandt [email protected] Palo Alto CA
     
  6. Kbh

    Kbh Guest

    Accugage works well (on sale at Cambria Bike) . I mostly use it to check pressure to see if I need
    to add any air before a ride, not so much to dial in an exact pressure.

    "E & V Willson" <[email protected]> wrote in message news:[email protected]...
    > How do you measure the pressure in tires with tubes that have presta valves. Are special (portable
    > i.e. pencil type) gauges available, or is it just done with the gauges on pumps?
    >
    > TIA, Ernie
     
  7. A. Birko

    A. Birko Guest

    What about in terms of aero advantage? I've read (don't remember where) that if the tire is wider
    than the rim you get worse aero performance. I was planning on setting up my TT bike with a 20mm
    front and 23mm rear for better aero up front and better rolling in the rear. Thoughts?

    -Andy Birko

    <[email protected]> wrote in message news:[email protected]...
    > Ernie Willson writes:
    >
    >
    > Tiny cross section tires have no benefit anyway, they having more RR than fatter tires with the
    > same tread thickness. That is the difference between the Avocet Criterium and TT tire that are
    > otherwise identical.
    >
    > Jobst Brandt [email protected] Palo Alto CA
     
  8. Jobst Brandt

    Jobst Brandt Guest

    Anady Birko writes:

    >> Tiny cross section tires have no benefit anyway, they having more RR than fatter tires with the
    >> same tread thickness. That is the difference between the Avocet Criterium and TT tire that are
    >> otherwise identical.

    > What about in terms of aero advantage? I've read (don't remember where) that if the tire is wider
    > than the rim you get worse aero performance. I was planning on setting up my TT bike with a 20mm
    > front and 23mm rear for better aero up front and better rolling in the rear.

    If you are concerned about such microscopic differences you must be preparing for some world record.
    Aerodynamics of tires fall far behind wearing a jersey that is not skin tight knit-wear. I think
    your effort is misplaced. What is your current best time for a 25TT?

    Jobst Brandt [email protected] Palo Alto CA
     
  9. Openworld <[email protected]> wrote: [In response to Jobst]
    >Tyre pressure is as important as you want it to be. Knowing how your bike handles at set pressures
    >is great for us techies.

    "Techies" as opposed to Mr. Brandt, who as we know is perpetually mystified by the technical aspects
    of bike operation?

    You've managed JB and Sheldon - try telling Chalo Cholina something about bikes for big blokes to
    collect the whole set?
    --
    David Damerell <[email protected]> Distortion Field!
     
  10. E & V Willson wrote:
    > How do you measure the pressure in tires with tubes that have presta valves. Are special (portable
    > i.e. pencil type) gauges available, or is it just done with the gauges on pumps?
    >
    > TIA, Ernie

    The spare tubes I buy come with a little gizmo that I can just place over a presta valve. A rod will
    shoot out and you can read off the pressure fairly accurate. You can definitely see if it's 8.0 or
    8.5 bar for instance.

    --
    Perre

    You have to be smarter than a robot to reply.
     
  11. A. Birko

    A. Birko Guest

    So, in your snide remark and "clever" misspelling of my name, were you just doing the typical usenet
    dork thing a flaming a stranger because you can, or just trying to inflate your ego? Well I guess it
    really doesn't matter.

    The reason I asked is because I don't know the answer, hence the question mark at the end of my
    first sentence.

    In fact, I'm training for something far more important than a world record, I'm preparing for a
    personal best in a 40k (I'd like to do a sub 60min). At the moment, I think I'm going to fall around
    2 to 3 minutes short (need around 40 more watts) and am looking for as much [cheep] aero advantage
    to make up the difference.

    I'm going to assume by "microscopic" you're trying to say that the difference between a 20mm and
    23mm tire is not measurable physiologically and possibly analytically. Is this what you're
    trying to say?

    Regards

    -Andy Birko

    p.s. what's your best 40k TT time?

    <[email protected]> wrote in message news:[email protected]...
    > Anady Birko writes:
    >
    > > What about in terms of aero advantage? I've read (don't remember where) that if the tire is
    > > wider than the rim you get worse aero performance. I was planning on setting up my TT bike with
    > > a 20mm front and 23mm rear for better aero up front and better rolling in the rear.
    >
    > If you are concerned about such microscopic differences you must be preparing for some world
    > record. Aerodynamics of tires fall far behind wearing a jersey that is not skin tight knit-wear. I
    > think your effort is misplaced. What is your current best time for a 25TT?
    >
    > Jobst Brandt [email protected] Palo Alto CA
     
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