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Old 09-25-08, 01:43 AM   #1
cyclezealot
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Normal Tire pressure loss following a ride.

I am in the habit of checking tire pressure each ride... Should I need air, i'd rather do it with the floor pump at home... My clue as to a potential minor leak is how much air one looses during a 20 mile plus ride... Normally , It is like 3-5 lbs... For quite some time, on my commute bike the front has been loosing 7-10 lbs. range and the back less than 5. But, it has been quite some time.. And so far, it has not gone flat.. How much air do you expect to loose during a ride and has it any significance.
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Old 09-25-08, 03:58 AM   #2
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How much air do you expect to loose during a ride and has it any significance.
Depends on how much beans i been eating. Sorry couldn't resist
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Old 09-25-08, 05:59 AM   #3
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I am in the habit of checking tire pressure each ride... Should I need air, i'd rather do it with the floor pump at home... My clue as to a potential minor leak is how much air one looses during a 20 mile plus ride... Normally , It is like 3-5 lbs... For quite some time, on my commute bike the front has been loosing 7-10 lbs. range and the back less than 5. But, it has been quite some time.. And so far, it has not gone flat.. How much air do you expect to loose during a ride and has it any significance.
It depends a lot on what pressure you are running and how wide the tires are. Also tubes vary. That said I would think that on a 20 mile ride you should lose more by checking them with a gauge than you lose by any leakage. I would say that even on my high pressure narrow tires I don't lose an amount that I can reliably measure in a 20 mile ride. It takes mine a couple days to lose 3-5 pounds whether riding or parked.
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Old 09-25-08, 06:04 AM   #4
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My 700x23 road tires and tubes seem to be very tight as well with 120 PSI. I always release and repump before every ride, but when I check they are usually over 110 PSI.

But I am new and not an expert.
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Old 09-25-08, 06:13 AM   #5
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I inflate my rear tire to 120 psi and my front to 110 psi before every ride. When I re-inflate before the next ride, they're usually each at around 95-100 psi.
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Old 09-25-08, 06:37 AM   #6
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My 700x23 road tires and tubes seem to be very tight as well with 120 PSI. I always release and repump before every ride, but when I check they are usually over 110 PSI.

But I am new and not an expert.
You let air out and then pump them up again? Why?
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Old 09-25-08, 07:10 AM   #7
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I inflate my rear tire to 120 psi and my front to 110 psi before every ride. When I re-inflate before the next ride, they're usually each at around 95-100 psi.
How much time between rides?
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Old 09-25-08, 07:20 AM   #8
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^. As for me, I often ride 5 days out of 7. RIght now the bike in question is my local commute bike. 700 x 28... I'd say most of my tubes are almost always Performance's butyl, non - thin tubes.
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Old 09-25-08, 07:21 AM   #9
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I find that I lose 5-10% over a 24 hour period. This is for a tire inflated at 85 psi or above. The lower the normal pressure, the less it will lose over time. Seems like I lose more when the air is warmer outside.

Seems like them little molecules of air sneak out better under pressure.....
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Old 09-25-08, 07:29 AM   #10
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How much time between rides?
I've been riding 4-5 days per week, so usually 24 hours, sometimes 48.

I should also mention that I have two bikes, one with 700x23 tires, and the other with 700x25. Both are rated for 120 psi, and my experience with each has been similar.
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Old 09-25-08, 08:31 AM   #11
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You let air out and then pump them up again? Why?
Why, because fresh air is livelier than the old stagnant air that's been cramped-up in your tire for a week. Old air is restless, and trying to escape; fresh air is less jaded.
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Old 09-25-08, 08:39 AM   #12
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If you filled up with CO2, it'll lose pretty quick. The stuff bleeds through the rubber in the tube.
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Old 09-25-08, 08:53 AM   #13
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You let air out and then pump them up again? Why?
I don't let it all out. Just bleed off a bit.
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Old 09-25-08, 09:27 AM   #14
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Why, because fresh air is livelier than the old stagnant air that's been cramped-up in your tire for a week. Old air is restless, and trying to escape; fresh air is less jaded.
That sounds reasonable. I want the air in my tires to have a good attitude.
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Old 09-25-08, 09:28 AM   #15
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I don't let it all out. Just bleed off a bit.
What purpose does the bleeding-off serve? Just curious.
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Old 09-25-08, 01:24 PM   #16
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What purpose does the bleeding-off serve? Just curious.
If I don't give my QBP valves a good burp before reinflating they don't like to let the fresh air in.
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Old 09-25-08, 09:05 PM   #17
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I haven't filled my tires in two weeks. I commute 30 miles a day.
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Old 09-25-08, 09:31 PM   #18
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three to five psi lost in a single ride seems high to me, but nowhere near disastrous (I check at the beginning of a ride but not at the end, so I don't actually know how much gets out). Time seems to be more of a factor than miles--I lose a few pounds over a few days whether I ride the bike or it sits in the garage. FWIW, I think the idea that you're losing more air in the checking process than through a small leak is probably accurate, but it's easy enough to put the inflated tube in a sink or big pot of water and look for bubbles if you suspect trouble.
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Old 09-26-08, 01:03 PM   #19
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You should not lose ANY air over a four or five hour period unless there is a leak in the tube or valve. Temperature differences can make it seem as if you have lost air. If you are riding at 90 degrees at the beginning of a ride, but at 70 degrees at the end of the ride, the PSI reading might be a tad lower...not from loss of air, but from the cooler temperatures.
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Old 09-27-08, 10:16 PM   #20
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You should not lose ANY air over a four or five hour period unless there is a leak in the tube or valve. Temperature differences can make it seem as if you have lost air. If you are riding at 90 degrees at the beginning of a ride, but at 70 degrees at the end of the ride, the PSI reading might be a tad lower...not from loss of air, but from the cooler temperatures.
Has any considered that there is some leakage that occurs when putting the pressure gauge on the valve there is some tire pressure lost? Also, what kind of gauges are you using? Digital?
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Old 09-27-08, 11:37 PM   #21
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My tires lose about 10% of their pressure per week, whether they're 50psi tires on a mountain bike, or 100psi tires on my trike.
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