Hello everyone,

I'm a bit perplexed after having two flat tires in one day with no apparent reason (at least for the first flat).

I was about to leave for my daily commute to work and noticed that the front tire was flat after having ridden the bike from work the day before and having it sit overnight inside my apartment. After removing the inner tube and checking out the tire itself, I didn't find anything embedded in the tire itself so I changed the tube with a new one and left for work.

Leaving work, I noticed that the rear tire was deflated in which I pumped the tire up and rode it to a LBS where the mechanic checked the rear tire for debris and again found nothing. He then preceded to change the tube and unfortunately threw away the old one (I was too tired to think to ask him about the old tube and paid and left the shop).

Upon arriving home, I thoroughly checked the original front tube I changed in the morning by submersing it in water and could not find any puncture or air leak anywhere, and so far both new tubes haven't lost any air so I don't think either the mechanic or I missed something when we where checking the tires.

The only thing that I did previous to having both flats is washing the bicycle the previous day with dish washing soap and very low pressure from a garden hose.

Any ideas on what could cause at least one flat tire (or almost total loss of air from a seemingly good inner tube)?

At least half my flats these days are ar the juncture of the valve and tube. There was a design change some years back, and the current design depends on a glue bond between the base of the valve stem and the tube. When the valve is wet, it corrodes and the bond fails. These are tricky and can be intermittant, sometimed holding or leaking based on the valve angle.

However, I get a fair number of these, especially the morning after riding in the rain.

My current fix is to fit a small O-ring onto the valve before installing the tube, and a second on the outside under the locknut. These seem to be keeping eater out of the problem area, and failures there are way down.

Now I's back to mostly punctures, but the summer was fairly dry here in NYC, so I don't know what winter holds.

Anyway, next time you get a flat, remove the tube, inflate it, and flex the valve around to see if there's any separation there.

Did just that a little while ago... I got a little carried away and almost tore the valve off, and amazingly there was 0 loss of air!

TBH, this is my first bicycle flats in years, EXCEPT for having two valves separate from the tube this year... one ended up causing a blowout (I wrote about this a while back here at BF).

I do like your idea on putting o-rings on either side of the rim... how do I go about getting some? (this bike has Schraeder valves, while my tourer has Presta).

Since you have schraeder valves and can't find the leak, check to make sure that the valve core is screwed in tight enough. Sometimes that's an issue, sometimes not. I have seen loose valve cores cause issues.

On my motorcycle, I was losing 3 or 4 psi a day but the valve cores were tight. I replaced them and the air loss stopped. Apparently, they can have manufacturing defects.

Good luck finding the problem!

To my knowledge, the system for attaching Shrader valves to tubes hasn't changed, and they're not unusually prone to the bonding issue I described. However, all my bikes are PV so I haven't looked closely at SV tubes since I stopped selling tubes in 2008.

I'd tell you to go to Tru-Value for O-rings, but I don't think they're in Athens. If you want I can get a bunch and stick them in an air mail letter. The letter postage is about $1.00, and I think the O-rings are about a dime or so. BTW you might find them locally, since the size isn't critical. Bring a valve from a dead tube (or a new tune) and but the smallest ring that's a snug fit on the valve stem. The ones I use are approximately 5mmID, 8mm OD eyeball measurement.

I've seen bunches of schraeder valves that are poorly bounded to the tube and have failed there. I'm not familiar with a corrosion problem, though. I see mechanical failures just outside the stem.

Good quality tubes don't have this problem. I've had good luck with tubes made (or at least branded) by good tire companies -- Michelin, Continental, and Schwalbe, in particular.

Just reached my office and so far both new tubes haven't lost any air, which means that there's nothing embedded in the tire, and before leaving home, I checked to old front tube which doesn't seem to have lost any air.

FB, thank you for your offer on the o-rings. I'll check and see if the local market have some available, and if not, I'll get in touch with you.

I always use brand name quality tubes (cry once...), but this specific bike still had the original CST tubes installed (the bike is late 2012, early 2013 production, and I did manage to ride the tube over 700 miles).

FWIW, plodded along from Dublin to SW Ireland and to Aberdeen Swcotland [killing time and hanging out as well]

for 6 months , puncture free, Tour

thorn resistant thick P/V tubes and just one , 'thats not rock hard, but probably OK'
ride , back here, with an under inflated tire and the valve sheared to failure in the tube.
tire shifted on the rim and the tube followed it. <guess>.

on tour I kept the PSI up because I could feel the rolling resistance go up if they lost air. ..

Know the feeling fietsbob...

After weeks (or months) or not being able to go on a day trip, I finally managed to find some time last Sunday so I can follow a group of other cyclists to a nice place a bit out of Athens. Woke up early, proceeded to ready the bike and when inflating the rear tire, the P/V stem totally detached from the tube!

TBH, I was expecting it to do some at some time since the new Michelin Protek tubes has all failed at that specific spot, albeit after having at least 1000 miles on them (which is around the time they have to be changed because of the slime drying up inside them).

After all the trouble of having to change the tubes, thankfully i decided to check the net for any changes in the start of the ride and it had been cancelled! It could of been worse since the start was 10 miles away and I would have waited there for a while when no-one was coming!