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  1. #1
    Senior Member BikeOnly's Avatar
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    Checking Pressure - Presta Valve

    I bought a new bike and am having my first experience with Presta valves. I have a perfectly working floor pump with one exception - the dial of the pressure gauge was broken long ago. The pump has a fitting that is marked to fit both Schrader and Presta valves so I guess I can top off the tires.

    But how do I measure the pressure? My pencil gauges that I use on Schrader valves don't look like they will work on Presta valves. Right or not? (I do have a Presta-to-Schrader adapter).

    I am hoping not to have to buy a new pump with a working gauge. The good ones look like they cost $60 or more.

    Is there a cheap gauge that works on Presta valves?

    If it makes a difference, this is a flat bar fitness bike that the shop owner said to keep tires at 75 to 85 PSI.

    Thanks.

  2. #2
    Senior Member mrrabbit's Avatar
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    Just buy the teeny little presta to schraeder adaptor - usually about 3.00 at most LBSes.

    Loosen the presta nut 1-2 turns and tap the presta nut once, install the adaptor. Then use your pencil guage as you would with a regular schraeder valved tube.

    When done, you can store the adaptor in your bag or take the adaptor off - close the presta nut - and then put the adaptor back on.

    But it might get stolen...

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  3. #3
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    A problem with using a gauge to check pressure as you are pumping up the tire, besides the hassle of taking the pump chuck on and off, is that you will lose a little air each time you remove the chuck and when you measure the pressure so you will never be really sure what it is. That "pfftt" of air can result in a significant pressure loss in a low-volume tire.

    There are pressure gauges on EBay for less than $5.00; if you don't want a new pump I'd consider getting something like that and "teeing" it into the pump's air hose.

  4. #4
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    Or just buy a pump with a gauge. You can get decent ones for $25. I have a Specialized that works very well for that price.
    You're just trying to start an argument to show how smart you are.

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    For the commute and general bicycling, presta valves were a PIN for me. (Pain in the neck if that one is new to you.) My rims take 700 - 32 tires, my preferred size. I checked with a lbs and was told I could drill out the valve stem hole to take Schrader valves. The owner said 'yes, no problem.' (But you don't want to leave sharp or abrasive edges around the hole.)

    The proper size is a 21/64 bit. I didn't have one and used a 5/16" and wiggled it a bit while drilling to make the hole larger.

    I also started a topic here about 6 months ago about it just to double check. There was good advice on it. The consensus among people who had done it was that it was perfectly ok.

    Some people prefer the Presta valves, and you might be one of them when you get used to it. They do have their good points but for commuting and general riding I don't see a good reason for them.

    For narrower rims it might be that drilling them out would not be advisable.
    Last edited by Closed Office; 09-12-12 at 02:10 PM.
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  6. #6
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    Had this one for years. Iy still works and is more accurate than the gauge on my floor pump. http://www.amazon.com/Zefal-Twin-Bic.../dp/B0011W9Q06

  7. #7
    Ride, Wrench, Swap, Race dddd's Avatar
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    Those regular Shraeder-to-Presta mini-adapters will work with your Shraeder guage, but you likely will have to shorten the threaded neck with a file until the Shraeder guage just depresses the valve core as the guage's sealing ring is getting compressed.

    You can then fine-tune the length by slightly turning the adapter either way on the Presta valve.


    "A problem with using a gauge to check pressure as you are pumping up the tire, besides the hassle of taking the pump chuck on and off, is that you will lose a little air each time you remove the chuck and when you measure the pressure so you will never be really sure what it is. That "pfftt" of air can result in a significant pressure loss in a low-volume tire."

    This can be avaided in two ways:
    Firstly, by having the valve positioned at 12:00 on the wheel, the valve shutting will be assisted by gravity, as Presta valve cores use no spring.
    Secondly, by keeping the pump head in line with the valve while it is removed, the movement of the nut on the end of the valve core will not be impeded, so that the valve will already be closed before you even start to remove the pump head.
    The pfft you hear will be only from compressed air escaping the pump hose, not from the tire, and the guage pressure will be exactly representative of the actual tire pressure if the guage itself is accurate.

    I suggested shortening the Presta adapter for the same reason, i.e. so that the valve will be closed before the compressed guage sealing ring loses it's seal.

  8. #8
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    There are a number of reasonably priced Presta Valve pressure gauges. Many are dual, ie. work with PV or SV, and so are pretty versatile. Or you can use a pump with built in gauge.

    One advantage of a pump gauge, is that you can get the reading as you pump, rather than trial and error stopping, removing the head, checking, and starting all over again if low. The other advantage of a pump/gauge for PV, is that no air will be lost when you remove the hose (unless you have a thumblock set too far in).

    Hand gauges, though make more sense for testing to see if pumping is necessary.

    People obsess about accuracy, but it isn't critical. As long as you use the same device the same way you'll get consistent readings. They may not be accurate in absolute value, but what you call 95psi will ride the same every time, even if it's really only 85psi.
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  9. #9
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    I picked up a Sunlite dial gauge with both presta and shrader connections. I also put in new slime tubes which are presta valves so I paid I think $2 for to adapters. It actually is a nice setup. The dial gauge cost me $20 and it holds the pressure reading on the dial until you release it. So before I ride, I check the pressure and if it needs air, then I put my adapter on and use my regular pump.
    This dial gauge is the best $20 I have spent other then buying the bike. Deadly accurate and I like the "hold the reading" function. Keep the pump, buy a nice dial gauge and the adapters and you'll be good to go for less then $25 !!! Hope this helps!

    Chop

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    Get a separate pressure gauge if you really want.

    I have one of these which works for Schrader and Presta. It seems to loose about 2.5psi out of a 700C 25 tire when used:

    http://www.amazon.com/Zefal-Twin-Bic...d_sim_sbs_sg_3

    This one is Presta only, but just $13

    http://www.amazon.com/AccuGage-Press.../dp/B0011W6M4Y

    That said the pump gauge is _MUCH_ _MUCH_ more convenient because without it you pump more than you need to and let air out a few times. You should fix the pump instead (Park gauges are replaceable; perhaps other pumps are too).
    Last edited by Drew Eckhardt; 09-17-12 at 12:41 AM.

  11. #11
    Senior Member cyclist2000's Avatar
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    is your pump gauge replaceable? If it is, you should replace it with a new gauge.
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  12. #12
    Ride, Wrench, Swap, Race dddd's Avatar
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    Even with a good pump with a guage, I recommend keeping a dedicated separate pressure-check guage handy.

    This way, if you have a problem with your pump, or want to check and compare the readings from an additional or replacement pump, you'll still have a reference standard handy.

    Over time, it doesn't even matter if the guage is accurate, since you'll get to know what pressure reading gives a good ride and long tread life, and that is still high enough to prevent pinch-flats on the road surfaces that you ride on.
    Quoting FB:
    "As long as you use the same device the same way you'll get consistent readings. They may not be accurate in absolute value, but what you call 95psi will ride the same every time, even if it's really only 85psi."
    For this reason, I keep a couple of guages handy, one in my truck, one in the garage, and one near the side door with my pump, and these are just the ones I keep at home.
    With a couple of guages, the standard can be preserved and referenced if any pump or guage is lost, broken or is suspected of inaccuracy.

    Lastly, bike tire tread lasts longer and wears more evenly at lower pressures.

  13. #13
    coprolite fietsbob's Avatar
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    But how do I measure the pressure?
    Get a separate pressure gauge.
    pretty much the plan . there are floor pumps with gages, but you can't always
    be home.

  14. #14
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    Quote Originally Posted by BikeOnly View Post
    I bought a new bike and am having my first experience with Presta valves. I have a perfectly working floor pump with one exception - the dial of the pressure gauge was broken long ago. The pump has a fitting that is marked to fit both Schrader and Presta valves so I guess I can top off the tires.

    But how do I measure the pressure? My pencil gauges that I use on Schrader valves don't look like they will work on Presta valves. Right or not? (I do have a Presta-to-Schrader adapter).

    I am hoping not to have to buy a new pump with a working gauge. The good ones look like they cost $60 or more.

    Is there a cheap gauge that works on Presta valves?

    If it makes a difference, this is a flat bar fitness bike that the shop owner said to keep tires at 75 to 85 PSI.

    Thanks.
    I have never understood the need for expensive floor pumps for the average home user. You can buy a perfectly functional, quality pump for less than $30 or $35. I think the cheapest Park tool pump costs about $28 at my LBS. I also have a ~15 year old Performance classic floor pump which was the cheapest available when I bought it, and a more modern (~10 years old) Peformance pump, again, the cheapest available when I bought it. Will they last a lifetime? I have no idea, but at the rate I use them, probably. And if not, who cares?

    As for accuracy, they all measure a given tire within a very few pounds of each other, less than 5 psi difference from highest to lowest, plenty accurate enough.

    I'd just buy a new pump, and don't get hung up on getting an expensive one. I top off my tires almost every day and can't imagine putting up with the hassle of pumping, checking, re-pumping, etc. What a pain that would be, and I've never been confident that using a gauge on a Presta valve is accurate. Try one sometime.
    Last edited by Camilo; 09-12-12 at 11:04 PM.

  15. #15
    Ride, Wrench, Swap, Race dddd's Avatar
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    I pretty much agree.

    I've seen inexpensive pumps last through a couple of years of professional use.

    But definitely get a pump with a guage that you can comfortably read while pumping.

    For me, that means its a top-mounted guage.

    I also add a few drops of Shimano Green oil to my pumps annually.

  16. #16
    Senior Member BikeOnly's Avatar
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    Thanks for a lot of good advice. In the end it seemed buying a new pump made the most sense.

    I bought this floor pump - http://www.sunandski.com/Serfas_Fp_2...2064550605.htm

    Why I picked this one?
    - It was in stock at a local bike shop
    - It was moderately priced (not too expensive, not too cheap)
    - It was on sale $10 off ($45 MSRP = $35 sale)
    - It looked sturdy
    - Parts look easily replaceable
    - It has a "lifetime warranty"
    - Gauge has a large dial and is placed near the top
    - I love the color - canary yellow

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