Putting air in the tires & checking pressure. How?
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  1. #1
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    Putting air in the tires & checking pressure. How?

    My new Trek 1200 has those funny little valves (forgot the name) so when I bought the bike, I got one of those adapters that allow you to use car-type air gauges on these strange valves.

    The adapter is threaded on one end and looks sorta like a thimble on the other end. I can see how the threaded portion screws onto the tire valve but how do you connect it to the air gauge or air compressor? Am I missing another piece?

  2. #2
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    Track Pump.

    Im not exactly sure what your describing, but why not buy a track pump with air gauge built onto it.

  3. #3
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    .....

    Quote Originally Posted by Astro951
    My new Trek 1200 has those funny little valves (forgot the name) so when I bought the bike, I got one of those adapters that allow you to use car-type air gauges on these strange valves.

    The adapter is threaded on one end and looks sorta like a thimble on the other end. I can see how the threaded portion screws onto the tire valve but how do you connect it to the air gauge or air compressor? Am I missing another piece?
    Yea get a pump with a built in gauge. I remember years ago trying to use those car guages, but they aren't designed for the funny little valves (Presta valves) that typically come on bikes, especially high pressure road tires (you have to use that silly adapter), plus I question the accuracy, not to mention that you lose too much air trying to use them. By the time you get a reading and lose air taking the thing off what you end up with isn't really necessarily what the reading was. It doesn't take much lost air out of a high pressure road tire to alter the pressure significantly.

  4. #4
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    Don't take the cheap and easy way out on this.

    For starters, I agree with everybody who says to buy a real bicycle pump. In fact, buy two--a floor pump to keep in the garage and a frame-fit pump to carry with you on EVERY SINGLE RIDE, because you're going to have a lot of flats. Don't rely on compressors--the small ones take five minutes to pump a tire to 100psi, if they'll do it at all, and the gas station kind will explode your tires in a heartbeat, and you won't have either one with you when you need it.
    As for the adapter, I keep one screwed on a valve for emergencies (for instance in case my pump breaks and some farmer comes by with an ordinary pump that only fits car-type valves), but I haven't had to use it in years. I don't see what your problem is with attaching it to anything, though. You open the presta valve by unscrewing the little knurled nut on top (you ARE doing that, right?), then screw the adapter onto the valve stem, big end toward the tire, then put the chuck of the air hose or tire gauge on the adapter just like it was a car valve. When you're done, unscrew the adapter, screw the knurled nut back down tight and put the adapter back on. If you keep it in the tool kit, it bounces our or gets lost somehow and you won't have it when you need it.

  5. #5
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    If you've already bought a pump, it might be cheaper to buy a pressure gauge designed for presta (skinny) valves. Go to your local bike shop or look for it online. another problem with using a schraeder (standard car) gauge is that very few car tires are run at 90 - 120psi, as on bike tires. It's quite possible that a schrader pressure gauge isn't that accurate at such high pressures. your adaptor is still useful for emergencies when you flat and you somehow don't have access to a presta pump. Here's how you use most adaptors:

    1) Unscrew / open the presta valve.
    2) Press down momentarily to release a little pressure and unlock the valve.
    3) Thread on the female end of the adaptor onto the valve core.
    4) Use the schraeder pump to pump up the tire.
    5) Remove the adaptor, and screw on/close the presta valve.

  6. #6
    Arrogant roadie.....
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    Frankly, I've yet to see a pump gauge that works at all well-most are 10-20 psig off. You really need to buy yourself a decent floor pump, a good frame pump (Blackburns are the best), and a presta air gauge.
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  7. #7
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    More data than you thought you needed . . .

    Everything said above is correct . . .

    Let me clarify some things.

    Presta valves --
    These are the "skinny" ones on your bike. The "core" in these is secured against the gasket inside the stem with screw tension. The tension is set with the knurled brass "nut" on the exterior end of the valve. Because it's screw tensioned against a gasket at the other end, the seal against the gasket often "sets" and merely pumping air into the tire won't release this "set." -- So you open the knurled nut (unscrew) and press the end of the valve to release this "set" before pumping air. You should hear a "click" while pumping as the air moves past the core and then the core clicks back closed.

    Schraeder valves --
    These are the ones you see on "fat bikes," kids bikes, and cars. This valve is bulky enough that it's like setting a small weight on one edge of the wheel, which throws it slightly off balance. Also, they're nearly as wide as a racing tire rim, and the hole for it would weaken the rim.

    Adapters --
    This is the "brass thingie" . . . threaded on one end and wider with a knurled shoulder on the other end. The knurled shoulder fits on the valve end of the valve stem. Again, like Schraeder valves, this adapter acts like a small brass weight on the wheel. To minimize this balance/weight issue, mfg's have made these adapters shorter than they used to be. Shorter is lighter.

    The problem with the shorter adapter is that it often exposes the end of the Presta valve stem to the depression function on a standard service station type air hose valve chuck. This depression action releases air from your tire -- unless of course you've got a tight connection and are pumping air into the tire.

    Sometimes . . . sometimes . . . you can back off the adaptor a bit. Unscrew it about a half turn. Sometime this provides just enough clearance on the pump chuck that you don't lose pressure. Sometimes you can back off the nut on the end of the valve core too, and this will help with the bleeding problems -- but adaptors are temperamental and an "emergency fix" for on the road situations where you lack a pump with a Presta valve head.

    Service station pumps / Air compressors --

    Although road bike tires carry 100 PSI or more, the VOLUME of air in the tire is very small. One tiny little "Pffffffffftttt" on the valve can lower pressure in the tire maybe 15 PSI. So it's crucial that you engage and release the pump off this valve without getting the Pfffffffttt of air out of the tire.

    Service station pumps are designed to move a LOT of air, to fill auto and truck tires. One little blast into a road bike tire from a service station hose can blow your tire to bits! When using a service station pump or air compressor, fill the tire in very short bursts -- like a quarter second. Then check pressure. Be careful! This too is an "emergency fix" and a bike tire pump is always a better option.

    A GOOD bike pump for road bike tires has a Presta fitting which seals around the valve with a gasket. It does not depress the end of the stem. Presta heads have a release lever which prevents air escaping when removing the pump from the valve.

    Pressure gauges --
    You need a gauge designed specifically to measure high pressures using a low volume air sample.

    That "car gauge" you have in the garage with the Scraeder head and the long read-out stem -- the one you got from Western Auto -- requires a lot of air for a high pressure reading. Also, because of it's design and intended use it's not going to be very accurate at high pressures.

    Dial gauges designed for Schraeder valves are a bit better, but they require that you use the valve adapter (the brass thingie) and that brings with it all the issues noted above. Also, these gauges are not typically designed to read accurately at high pressures and low volumes -- road bike tires.

    I have a dial gauge with a Presta valve designed specifically for road bike tires. Low volume and accurate at high pressures. Also, it releases the valve without letting out the Pffffffffftttttt of 15 PSI escape from your tire.

    You want a dial gauge where the needle sets and is released by a button. I've never seen them designed without this feature, but you need to ensure that this feature is on the one you decide to buy.

    Tire pumps --
    CO2 bike pumps -- small, light, easy to stow in the bag under the seat. CO2 cartridges come in "gram" sizes. 12 grams puts the standard road bike tire at about 90 PSI. A 16 gram cartridge puts about 120 -130 PSI in the tire, a bit much. I've asked around, because my CO2 cartridges are 10 yrs old, evidently CO2 cartridges don't "go bad." If they do go bad, someone please fill me in.

    Small frame pumps -- light, don't take up a lot of room on the frame. They mount BESIDE the bottle cage so you can use the cage and have a pump. Because the tires don't take a lot of VOLUME in air, these pumps evidently work. They're able to provide pressure, and they don't need to move a lot of air volume. I've never used one. I don't like the side mount feature.

    Full size frame pump -- fit between the bottom bracket and top tube, typically without any mounts or brackets. Because of the way they fit, they need to be purchased in sizes according to the size of your frame. DON'T trust the label! I see pumps in sizes that don't fit my size bike. I'm sure I don't have the only bike where this is the case.

    Full frame pumps are sort of bulky, but they fit nicely on the frame -- although you can't use the bottle cage on the seat tube. One mfg notes "Dogs hate 'em" . . . Frame pumps have long been used to whack a chasing dog. The pumps used to be made from alum. and would bend when you whacked it. Now they're space age plastic and more durable.

    Pump heads --
    On ANY pump you want the Presta Valve or "auto adapt" head (for both Presta and Schraeder). There should be a "release" feature on the head to allow removal from the valve without the Pfffffffffttttttt . . .

    Pumps run about $25. My view is to get a nice one, some have pressure gauges. But I'd stick to the Presta valve only type. My thinkng, and I could be wrong, is that the more specific the head is for a Presta valve, the better it will work on these valves. Schraeder valves are for CARS !!! You don't need a bike pump with a Schraeder head.

    Floor pumps --
    The good ones have a gauge. The really good ones have an ACCURATE gauge. Accuracy is affected by the gauge design, but also by the amount of air in the pump hose. I have a floor pump where the gauge doesn't read accurately until the air in the hose is brought up to pressure. Because the hose is rubber (I don't know what sort of "core" but evidently something that stretches.) the hose stretches a bit and readings at 100 PSI and over are a bit suspect.

    Serfas makes a floor pump with a nice head, AND the hose is steel wrapped. This seems both accurate and durable. The Serfas runs about $50.

    I used to check tire pressure on a road bike with my thumb against the tread -- sew ups. Tread, tire, thumb, temerature can all toss off "readings" in this method. Tires running 80 PSI and 105 PSI can feel similar. Buy a good gauge.

    Pumps and gauges are part of the "gear head" aspect of cycling. You need to check pressures EVERY RIDE . . . Tires bleed air even overnight. Temperature can affect tire pressure. Check pressure for each ride.

    So, you should have a floor pump with a good hose, good head, and a gauge. A bike pump -- shop around a lot for this one and find what works for you. A hand held tire gauge. Much easier to check pressure for each ride with a hand gauge rather han hooking up to a pump with a gauge.

    Properly inflated tires ride best. You get the most speed for effort on a correctly inflated tire, also handling and cornering are best on accurately inflated tires. Wheels stay true and rims stay undamaged when tires are properly inflated. Tires get damaged when underinflated or overinflated. Because there's so little volume in a road bike tire, they're easily under and over inflated.

    Invest in some pumps and gauges. They last forever, and will pay off in the long haul -- literally.
    Last edited by RodeRash; 06-24-2005 at 10:06 AM.

  8. #8
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    "When you're pumping a Presta valve you can hear the "click" on each pump stroke as the valve stem opens and closes.

    In fact, if you can't hear the "click" of the stem, you're not getting an efficient pumping action and you need to remove the pump, depress the valve to release the "set" on the core and then start pumping again."

    I just purchased a road bike with Presta valves. I am using a pump that has a built-in gauge and both Presta and Shraeder heads. When I use it on a Shrader valve I get an instant pressure reading on the gauge when I attach the pump to the tire. When I use it for the Presta valve I do not get a pressure reading until I start pumping the tire. I have been unscrewing the knurled top portion of the valve, but have not been depressing the valve to release the set. I felt somewhat uneasy about the way the pump functioned and the pressure readings. Should I get an immediate pressure reading when I attach the Presta head to the inflated tire.?
    Thanks, Lee

  9. #9
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    No, as you noticed the presta has a mechanical seal or "set" that isn't activated by your pump head as in the schrader valve. The only way to get the pressure reading is to break that "set" with higher pressure from your pump. Tapping the presta a bit helps in that regard as you said. Some presta valves, I've reached > 175 psi trying to break the set and it still won't give. I find it easier to lower the pressure in the tire first then pumping it up to running pressure.

    First time I tried to pump up a friend's road tire, ( I was always MTB and schrader user before then) I was completely baffled. It was funny.

    glen

  10. #10
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    Great advice here mates. I just got a mini pump designed for presta valves (no gauge on it though). It seems to be working great, without putting in too much effort. Not sure if I am hearing the "click" described above, but it still pumps it to proper pressure.

  11. #11
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    Back from the dead

    Quote Originally Posted by fiets View Post
    Great advice here mates. I just got a mini pump designed for presta valves (no gauge on it though). It seems to be working great, without putting in too much effort. Not sure if I am hearing the "click" described above, but it still pumps it to proper pressure.
    You do realize that the last post in this thread was over 7 years ago, right?

  12. #12
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    haha. Yes indeed. Some advice can be timeless. =)

  13. #13
    'brifter' is a lame word.
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    damn, if you think you have to go back 7 yrs to get your post count up...wow.
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