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Old 09-04-07, 01:03 AM   #1
CityRoamer
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Normal road tire air loss??

Hi,

I have a Cannondale CAAD9 that I bought at the beginning of this summer. It is a great bike and I treat it like my baby! The only problem I have is that I am losing significant air in my tires. I have already replaced the tubes twice, and I am sure these do not have any leaks or tears, but they are doing the same thing as the first set.

I ride about every 4-5 days, and everytime I want to go ride I notice that the tires lose about 40-50 PSI just from sitting there.

To make sure it wasn't from the previous ride, I measured the air pressure at the beginning and at the end of a typical ride, and I had only lost 2 PSI. Is it normal to lose this much pressure between rides? What could be wrong?
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Old 09-04-07, 06:45 AM   #2
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Yes, that's normal. You should inflate before *every* ride.
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Old 09-04-07, 06:49 AM   #3
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Mine lose about 5 PSI per day just from sitting around.
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Old 09-04-07, 06:53 AM   #4
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Mine lose about 5 PSI per day just from sitting around.
Mine loose 5-10 per day. Always pump to your desired pressure before every ride.
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Old 09-04-07, 07:08 AM   #5
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All tubes lose air pressure over time. Some lose it faster than others.
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Old 09-04-07, 07:10 AM   #6
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if you use high tech tubes and tires they will lose pressure. drop from 130 to 80 in a 5 days is normal.

tubulars...ditto, they go flat by the week. gotta pump up right before a ride

if you use thick cheap tubes then they will keep pressure longer, but the ride won't be as supple

a very tiny amount of the liquid goo in fix-a-flat will keep the tires up for a long time, but it can clog the valve so this really isn't done often. but it does work
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Old 09-04-07, 09:34 AM   #7
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I was wondering the same thing. I ride everyday to work and a little more on the side and noticed that I had to pump them up every couple of days. I knew it wasn't my tubes so I just assumed it was natural. Good to know I was right. Good information guys
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Old 09-04-07, 10:07 AM   #8
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Same darn problem I am running into with the bikes I have on display . I like them to have air but they do not agree .
We are fighting about it now.
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Old 09-04-07, 07:40 PM   #9
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I wonder how nitrogen would do? The suppliers claim less pressure loss, plus less increase in pressure from heat in automotive use.

John
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Old 09-05-07, 12:01 AM   #10
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Air is 78% nitrogen.
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Old 09-05-07, 07:46 AM   #11
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Same darn problem I am running into with the bikes I have on display . I like them to have air but they do not agree .
We are fighting about it now.
When I worked at a shop we just inspected the bikes every time they went out. Between air loss, crappy bike builders and little demonic children playing with the shifters, we just assumed they needed attention every time they went out for a demo. Regardless, it ALWAYS ticked me off when someone was looking at a sweet dual suspension or high performance road bike and was like "the tires are low."

On the bright side, you get really good at tuneups...
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Old 09-05-07, 12:49 PM   #12
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Air is 78% nitrogen.
And 21% oxygen. 1% other stuff.
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Old 09-06-07, 11:49 PM   #13
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Use the cheap heavy tubes and they'll hold air for a long time. I tried the ultra lightweight tubes in my MTB bike - I pumped them up in the morning when I left for work and when I went out to ride at lunch they were low again. PITA. I got tired of that and evetually went back the standard tubes.
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Old 09-07-07, 04:37 AM   #14
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I wonder how nitrogen would do? The suppliers claim less pressure loss, plus less increase in pressure from heat in automotive use.

John
The less pressure fluctuation for auto-racing applications is due to N2 not having water vapor that evaporates-condenses in the tire as a result of temperature changes.

Since N2 has a smaller diameter than air's other major component O2, N2 would actually deflate faster than air.
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Old 09-07-07, 05:09 AM   #15
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[snip]I am sure these do not have any leaks or tears[snip]
I'll take the contrarian view: in my experience, you're losing too much air too quickly. When you say that you're sure there are no leaks, what did you do to ascertain this? Did you submerge the inflated tubes in water and look for bubbles? Sometimes the problem is a leak at the valve stem; sometimes it's a very tiny pinhole leak, often hard to locate unless you do the water test.

And, meaning no disrespect, I'll also ask this question: assuming you have presta valves, you do screw shut the little valve cap or round nut after inflating your tires, right? Sometimes people simply forget to do this, and a slow leak results.
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Old 09-07-07, 08:30 AM   #16
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So what is the deal with tubes today ?... Many moons ago when I was a kid we seldomly had to pump up the tires on our Schwins etc.. They just never seemed to loose air without the assistanve of a nail or something :-).. I can't remember us even having an air pump but we probably did.. I can recall going to the gas station after fixing a flat and blowing them up... Sometimes literaly...
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Old 09-07-07, 10:28 AM   #17
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Same darn problem I am running into with the bikes I have on display . I like them to have air but they do not agree .
We are fighting about it now.
Heh, heh, heh. When I had my shop I bought a portable air tank. Whenever I saw one of the guys sitting around I'd have him top up all of the tires on the floor bikes.
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Old 09-07-07, 10:33 AM   #18
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So what is the deal with tubes today ?... Many moons ago when I was a kid we seldomly had to pump up the tires on our Schwins etc.. They just never seemed to loose air without the assistanve of a nail or something :-).. I can't remember us even having an air pump but we probably did.. I can recall going to the gas station after fixing a flat and blowing them up... Sometimes literaly...
The greater the pressure differential, the greater the propensity for air pressure loss. Your old balloon tire Schwinn probably only used around 35psi in it's tires.
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Old 09-07-07, 09:23 PM   #19
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The greater the pressure differential, the greater the propensity for air pressure loss. Your old balloon tire Schwinn probably only used around 35psi in it's tires.
+1, agree. My commute bike has Panaracer Pacela Tourguard 700x35 tires with a regular (not thin) Nashbar butyl presta tube. I pump them up to about 75 psi once a week, Monday morning. I ride a 30 mile round trip each workday, Monday to Friday. This evening I just checked and they read 71 psi. For a commute and errand bike that gets ridden several times a day, every day for transportation, you can't be fiddling around with air pressure all the time. Fatter tires are the only way to fly, takes away all the hassles.
I have a lightweight classic road bike that uses 700x32 Pacela tires at 90 to 95 psi. I ride it just a few times a month, and it can lose 2+ psi per day compared to less than 1 psi per day from my 700x35.
I would not be surprised if a 700x23 high pressure tire (120+ psi) is going to lose 5+ psi per day.
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Old 09-10-07, 07:33 AM   #20
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I was offered free nitrogen for my SUV from a friend at a dealership and read all the perks about it and this and that, and they all lost air. Quicker than I've ever noticed my tires losing normal compressed air so I'm not sold on Nitrogen.
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Old 09-10-07, 02:52 PM   #21
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I wonder how nitrogen would do? The suppliers claim less pressure loss, plus less increase in pressure from heat in automotive use.

John
I assume you mean air from those portable air canisters. It has been my experience that I tend to lose more air between rides when I have used a canister that when I have used a pump.

The basic fix is to ALWAYS, ALWAYS, ALWAYS top off air pressure before each ride If you don't have one, you would do well to invest in a quality floor pump with pressure gauge. I like the one with the pressure gauge built into the foot of the unit as opposed to mounted on the pump barrel. If you tip the unit over, you stand a greater chance of damaging the gauge, the higher it is mounted. I also like a two-in one pump head (that is one single pump head that accepts both Rresta and Schreaer valves.) Double pump heads are not bad either, but I would avoid the type where you have to dissasemble the unit to change the type from one to the other.
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Old 09-10-07, 03:35 PM   #22
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And, meaning no disrespect, I'll also ask this question: assuming you have presta valves, you do screw shut the little valve cap or round nut after inflating your tires, right? Sometimes people simply forget to do this, and a slow leak results.
The air pressure inside the tube forces the valve closed, all the nut does is keep dust out and eliminates the possibility of accidentally bumping the valve open.

High pressure road tires need to be pumped up before each ride.

Al
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Old 09-10-07, 03:40 PM   #23
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The rule of thumb I've heard quoted is that standard tubes lose about 3% of pressure per day.
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Old 09-10-07, 05:58 PM   #24
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The air pressure inside the tube forces the valve closed, all the nut does is keep dust out and eliminates the possibility of accidentally bumping the valve open.
Sheldon Brown: "Presta valves have built-in valve caps, which must be opened before you can pump them up. These caps are "captive" nuts, which cannot be removed. Since there is no spring in a Presta valve, this knurled nut must be retightened after inflating the tire, or the valve may leak slowly."
This "knurled nut" is what I was referring to, not the little plastic cap.
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