RandomTroll

• I put a new tube in my rear tire Tuesday. I pumped it to 105 psi. The next day it was at 60. I took it off, couldn't find a leak, even in clean soapy water after inflating it as much as I could. I put it back on. The next day it was at 48. I replaced it with a new tube. It's now hanging up, as inflated as I can a free tube, not showing any sign of losing pressure 8 hours later. It's a cheap Kenda tube, regular thickness. I don't care about the cost, but I'm curious as to what could be happening. I can't find anything wrong with the tire, even with a cotton ball.

fietsbob

Sunk it under water? No Bubbles ?


Have a piece of detritus in the tire ? remove it .


Use a Thorn resistant Heavy tube.

cny-bikeman

You're there, we're not. I don't see how anyone here can provide a definitive answer, considering you did everything correctly to find the problem.

DrIsotope

When I get a slow leak, 9 times out of 10 it's the Presta valve.

AlexCyclistRoch

1) piece of glass in tread
2) wire from bead sticking out
3) spoke poking through rim tape
4) sharp edges on valve hole
5) leaky valve
6) crappy tube
7) you damaged it with the tire levers

ltxi

Assuming newest tube is holding air, I'd just throw it out and chalk up to mystery of the universe.

Vintage_Cyclist

Just had that happen recently

prathmann

How much did you think you "could" inflate it? I've pumped up tubes until they were over 6' in diameter and quite a few inches in width in order to find a slow leak when I didn't have any water tub in which to dunk it.

If you really want to find the leak keep pumping it up until you've got some substantial pressure in it. Even a defect in the valve will show up then.

Trakhak

Outside of a tire, a tube will explode before it reaches more than a few psi.

Unless you happen to have a skeleton tire made of twisted wire. The oldest bike shop in the town where I grew up had one of those for finding slow leaks.

Crankycrank

Try wiggling the valve around while under water and inflated. Sometimes tears at the base of the valve don't show up until physically moved.

Papa Tom

What he said. I used to run a bicycle recycling program and we would spend certain days just testing tubes for several hours at a time. Whether Presta or Schraeder, the valves would often "hide" leaks until you jerked them around a little bit.

rm -rf

I've sprayed dish detergent & water on the inflated tube and couldn't find the slow leak. I finally dunked it in the tub, with most of the tube under water. A tiny air bubble very slowly appeared, then reappeared after I wiped it off. (I had to wipe off a bunch of other little bubbles stuck to the tube.)

Dish detergent & water usually finds it.

prathmann

Yes, I doubt I'm getting over 5 psi, but I've found that to be sufficient to find all leaks - incl. those due to valve issues. But don't be so afraid of the tube bursting so you only inflate the tube until it's a couple inches in width. I've never had a tube burst even when it's been inflated to several times its normal width and when it's at least 6 - 8' in diameter.

The other way to check for a valve problem since the tube is now mounted back in the tire is to inflate to normal pressure and stick the tire/wheel in a tub of water and watch for bubbles at the valve.

SquidPuppet

In that condition there is not enough pressure to cause the tiny hole to open up.

kevindsingleton 

Sounds like something you'd hear on the Sunday morning talking head shows!

RandomTroll

It's a schrader valve. I've already dunked it in clean, soapy water. I've put as much pressure in it as a free tube will take - I've exploded tubes before. After another day hanging out, it's still as inflated (judged by measuring the width of the bulgiest part) as it was yesterday. I checked the valve.

As I wrote, it's a $2.5 tube, not worth the trouble. I was just curious if there was another reason for failure I hadn't thought of.

Since it's a schrader, I think I'll take out the valve, put in some soapy water, check for a leak reversely.

1nterceptor

When I have one of this "mysterious" leaks; I pump the tube till it's much bigger than the tire it goes in.
Then I squeeze/pinch the tube while slowly rotating the tube near my ear. I'll either hear or feel the air
escaping. Dunking in water also helps; but don't forget to pinch/squeeze the tube while rotating it in the water.

Delmarva

Could be one of several causes. The only way to replicate the leak is to reinstall the tube and pump it to 105 psi. Time to pitch the tube and move on.

Rollfast

^^^ +1


Get a valve tool.

Kitsap

Pull the valve..... Chances are that you have a bad valve. Some of these tubes have leak sealing gunk inside that gets into the valve. Solution is to junk the tube and buy a better tube.