Bicycle Mechanics - Mystery Tire Problem...Your Theory?

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Neil1966
04-27-08, 12:00 PM
I've got this strange tire problem that I have never encountered before

Equipment:
Conti Sprinter tubular mounted to deep aero rim with valve extender.

Problem: Tire seems to go flat randomly then stays full for days and days

Yesterday, for example, the tire had been holding air fine for awhile, so I fill the tire up just to top it off to 100psi (from about 80 psi), then go get dressed to ride and when I come back to ride, the tire is almost out of air????

So, I fill it up again and go for my group ride. After 1.5 hrs, we stop and the tire is still all full. I go inside a restaurant and eat and when I come back the tire is a little soft--I would say about 70psi. But I decide to leave it as is to finish my ride (because I didn't want to hold the group up while I did a tire change), hoping I could make it back home.

Well after about 30 minutes, the tire probably has 30psi, so I stop and fill it up to 100psi with my CO2 pump, being pretty sure that would get me home. I get home and the tire is still full. I check this morning and the tire is still full.

Whats going on???


bikeman715
04-27-08, 12:57 PM
check your valve and the valve extender . one of them have a slow leak . if it does try tighten it. Try some soapy water and look for bubbles .

Old School
04-27-08, 02:46 PM
Whats going on???
I may be going out on a limb here, but I would say you have a leak... just my theory. :rolleyes:


dervish
04-27-08, 05:15 PM
use the soapy water test, easiest way to find a leak...as to why it seems to occur randomly, i cannot really say

mikepoole
04-29-08, 02:29 PM
Air-eating bacteria colonies inside the tube. They eat, get full and lay off for a while. Then they get hungry again. I think Continental had a problem with these back in the 90's as well.

reverborama
04-29-08, 03:01 PM
Do you have a roommate/spouse/child who likes to play pranks?

Neil1966
04-30-08, 09:43 PM
Mystery solved.

The tire started to lose air all the time now.

I removed it and there was a small tear where the valve enters the tire. Just a slight movement in the valve determined whether it leaked or not.

Richard_Rides
04-30-08, 10:10 PM
OK, I was just about to suggest checking for a tear near the valve. Looks like you found it.