Go Back  Bike Forums > Bike Forums > Bicycle Mechanics
Reload this Page >

Can't find the leak

Notices
Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

Can't find the leak

Old 07-03-20, 12:01 PM
  #1  
merlinrkd
Member
Thread Starter
 
Join Date: Jul 2019
Location: Yuba City CA
Posts: 25

Bikes: BMZ Performance Touring

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Can't find the leak

Feeling dumb about this. Been fixing flats tires for 50+ years but this one isn't getting resolved. Recent 90's Conley MTB. Very clean. Deore components. Came with very recent Kenda tubes and Komfort tires. Am losing 2psi a day out of the rear. Pumped the wheel to 65 psi and submerged it in 6" of water in my laundry utility sink. Don't see any bubbles. Watched it for quite a while. Pulled the tube and pumped it up to about twice the tire size. Not a bubble. I'd like to pump the tube up more. Is there a general rule on how big an unconfined tube can be safely expanded?
merlinrkd is offline  
Old 07-03-20, 12:09 PM
  #2  
Iride01
Senior Member
 
Iride01's Avatar
 
Join Date: Jul 2017
Location: Mississippi
Posts: 4,314

Bikes: '20 Tarmac Disc Comp '91 Schwinn Paramount '78 Raleigh Competition GS

Mentioned: 26 Post(s)
Tagged: 0 Thread(s)
Quoted: 1622 Post(s)
Liked 515 Times in 395 Posts
Right up until it bursts. I wouldn't worry about 2 psi a day. Although that is a little higher than what I'd consider normal. You check your tires before every ride don't you? I normally expect to put a stroke or two of floor pump in my tires every other day.
Iride01 is offline  
Old 07-03-20, 12:25 PM
  #3  
hrdknox1
Senior Member
 
hrdknox1's Avatar
 
Join Date: Apr 2014
Posts: 148
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 62 Post(s)
Liked 39 Times in 29 Posts
Could be leaking from the valve core if you didn't submerge that.
hrdknox1 is offline  
Likes For hrdknox1:
Old 07-03-20, 02:25 PM
  #4  
JohnDThompson 
Old fart
 
JohnDThompson's Avatar
 
Join Date: Nov 2004
Location: Appleton WI
Posts: 21,727

Bikes: Several, mostly not name brands.

Mentioned: 126 Post(s)
Tagged: 0 Thread(s)
Quoted: 2251 Post(s)
Liked 646 Times in 434 Posts
I'm with @Iride01; 2psi/day is not enough to get worked up about. If it really bothers you, pull the valve core and pour in some sealant.
JohnDThompson is offline  
Old 07-03-20, 03:09 PM
  #5  
Elvo
Senior Member
 
Join Date: Oct 2006
Location: Orange County, CA
Posts: 4,426
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 467 Post(s)
Likes: 0
Liked 135 Times in 78 Posts
2 psi per day is negligible especially if there is a lot of temperature fluctuation in the storage area
Elvo is offline  
Old 07-03-20, 03:21 PM
  #6  
tyrion
Senior Member
 
tyrion's Avatar
 
Join Date: Oct 2015
Location: San Diego, California
Posts: 3,008

Bikes: Breezer Radar

Mentioned: 23 Post(s)
Tagged: 0 Thread(s)
Quoted: 1616 Post(s)
Liked 707 Times in 348 Posts
Originally Posted by Iride01 View Post
Right up until it bursts.
Then back off a couple pumps.
tyrion is offline  
Likes For tyrion:
Old 07-03-20, 03:27 PM
  #7  
merlinrkd
Member
Thread Starter
 
Join Date: Jul 2019
Location: Yuba City CA
Posts: 25

Bikes: BMZ Performance Touring

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Likes: 0
Liked 1 Time in 1 Post
The stem was completely under water in the sink. Neve saw a bubble. That was fully inflated inside the tire.
merlinrkd is offline  
Old 07-03-20, 03:35 PM
  #8  
merlinrkd
Member
Thread Starter
 
Join Date: Jul 2019
Location: Yuba City CA
Posts: 25

Bikes: BMZ Performance Touring

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Likes: 0
Liked 1 Time in 1 Post
This is my grab and run a quick errand bike of the 4 I have. Used sporadically. My 2 road bikes have latex tubes so pumping is a daily deal. The Conley front wheel can go for a couple months. I'm just mystified with my leak detection methods and that 2 psi/day doesn't show a bubble.
merlinrkd is offline  
Old 07-03-20, 04:21 PM
  #9  
tyrion
Senior Member
 
tyrion's Avatar
 
Join Date: Oct 2015
Location: San Diego, California
Posts: 3,008

Bikes: Breezer Radar

Mentioned: 23 Post(s)
Tagged: 0 Thread(s)
Quoted: 1616 Post(s)
Liked 707 Times in 348 Posts
Originally Posted by merlinrkd View Post
The stem was completely under water in the sink. Neve saw a bubble. That was fully inflated inside the tire.
At 2 psi loss per day the bubble will form very slowly, teeny tiny and pretty much invisible. The bubble will stick to the tube and when it gets large enough it will break away and go upwards.

You can put your hands in and get a death grip on the entire tube, wait for the water to settle and squeeze and you might get an idea of where the leak is. But do you really want to chase this?
tyrion is offline  
Old 07-03-20, 04:32 PM
  #10  
Crankycrank
Senior Member
 
Join Date: Jan 2009
Location: San Diego, CA
Posts: 1,714
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 285 Post(s)
Liked 93 Times in 76 Posts
Also try removing the tube pump it up to big sausage size and stretch a section at a time under water. This makes the hole a little bigger. Also check the base of the stem by wiggling it around under water. Sometimes tears at the base only show up when the stem is moved.
Crankycrank is offline  
Old 07-05-20, 07:06 AM
  #11  
Pop N Wood
Senior Member
 
Join Date: Jun 2020
Location: Maryland
Posts: 480

Bikes: 1982 Bianchi Sport SX, Rayleigh Tamland 1, Rans V-Rex recumbent, Fuji MTB, 80's Cannondale MTB with BBSHD ebike motor, 70's vintage Schwinn Continental and Suburban

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 226 Post(s)
Liked 164 Times in 109 Posts
New tubes are $5
Pop N Wood is offline  
Old 07-05-20, 07:10 AM
  #12  
tomtomtom123
Senior Member
 
Join Date: Jan 2017
Posts: 964
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 316 Post(s)
Likes: 0
Liked 100 Times in 71 Posts
Originally Posted by Pop N Wood View Post
New tubes are $5
No they're $3.
tomtomtom123 is offline  
Old 07-05-20, 09:23 AM
  #13  
davidad
Senior Member
 
Join Date: Feb 2009
Posts: 6,280
Mentioned: 16 Post(s)
Tagged: 0 Thread(s)
Quoted: 441 Post(s)
Likes: 0
Liked 65 Times in 59 Posts
Mount the tire and inflate the tire to at least 50% Above the max pressure on the side wall and submerge the tire. I have used this method and found a thin wire that acted as a plug and deflated the tube when I removed it.
davidad is offline  
Old 07-05-20, 09:55 AM
  #14  
cyccommute 
Mad bike riding scientist
 
cyccommute's Avatar
 
Join Date: Nov 2004
Location: Denver, CO
Posts: 22,948

Bikes: Some silver ones, a red one, an orange one and a few titanium ones

Mentioned: 113 Post(s)
Tagged: 1 Thread(s)
Quoted: 3488 Post(s)
Liked 956 Times in 594 Posts
Originally Posted by merlinrkd View Post
Feeling dumb about this. Been fixing flats tires for 50+ years but this one isn't getting resolved. Recent 90's Conley MTB. Very clean. Deore components. Came with very recent Kenda tubes and Komfort tires. Am losing 2psi a day out of the rear. Pumped the wheel to 65 psi and submerged it in 6" of water in my laundry utility sink. Don't see any bubbles. Watched it for quite a while. Pulled the tube and pumped it up to about twice the tire size. Not a bubble. I'd like to pump the tube up more. Is there a general rule on how big an unconfined tube can be safely expanded?
2 psi per day is about the average for the diffusion rate of air out of a bicycle tube. You wonít see bubbles because the air is coming out at the molecular level through the bulk rubber. The diffusion isnít linear so you lose more at higher pressure than at lower pressure. But, generally, I expect to have to pump up bicycle tires on a daily basis.

Bottom line: If the tire goes flat overnight, thatís a puncture. If it only drops a little (<10 psi) overnight, thatís just diffusion and you shouldnít worry about it.
__________________
Stuart Black
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Days of Wineless Roads. Bed and Breakfasting along the KATY
Twisting Down the Alley. Misadventures in tornado alley.
cyccommute is offline  
Likes For cyccommute:
Old 07-05-20, 12:16 PM
  #15  
mrrabbit 
Senior Member
 
mrrabbit's Avatar
 
Join Date: Dec 2007
Location: San Jose, California
Posts: 3,403

Bikes: 2001 Tommasini Sintesi w/ Campagnolo Daytona 10 Speed

Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 90 Post(s)
Likes: 0
Liked 16 Times in 12 Posts
Originally Posted by cyccommute View Post
2 psi per day is about the average for the diffusion rate of air out of a bicycle tube. You wonít see bubbles because the air is coming out at the molecular level through the bulk rubber. The diffusion isnít linear so you lose more at higher pressure than at lower pressure. But, generally, I expect to have to pump up bicycle tires on a daily basis.

Bottom line: If the tire goes flat overnight, thatís a puncture. If it only drops a little (<10 psi) overnight, thatís just diffusion and you shouldnít worry about it.
You should change your sig:

"Your Daily Dose - Common Sense Rx"

=8-)
__________________
5000+ wheels built since 1984...

Disclaimer:

1. I do not claim to be an expert in bicycle mechanics despite my experience.
2. I like anyone will comment in other areas.
3. I do not own the preexisting concepts of DISH and ERD.
4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
5. My all time favorite book is:

Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life
mrrabbit is offline  
Likes For mrrabbit:
Old 07-05-20, 05:37 PM
  #16  
dscheidt
Senior Member
 
Join Date: Jul 2008
Posts: 1,405
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 18 Post(s)
Liked 5 Times in 5 Posts
Originally Posted by cyccommute View Post
2 psi per day is about the average for the diffusion rate of air out of a bicycle tube. You wonít see bubbles because the air is coming out at the molecular level through the bulk rubber. The diffusion isnít linear so you lose more at higher pressure than at lower pressure. But, generally, I expect to have to pump up bicycle tires on a daily basis.

Bottom line: If the tire goes flat overnight, thatís a puncture. If it only drops a little (<10 psi) overnight, thatís just diffusion and you shouldnít worry about it.
I wouldn't accept a tube that leaks 2 psi overnight on a mountain bike. On a road bike, with skinny tires at 100 psi, I'd exepect that. I run michelin airstop tubes, mostly, my bike with 700X50 tires loses about 2 psi a week (40 psi front, 50 rear). That's checked inside, so temperature isn't an issue. I would expect to be able to find a 2psi overnight leak with leak detection fluid, but maybe not in a sink.
dscheidt is online now  
Old 07-05-20, 08:53 PM
  #17  
cyccommute 
Mad bike riding scientist
 
cyccommute's Avatar
 
Join Date: Nov 2004
Location: Denver, CO
Posts: 22,948

Bikes: Some silver ones, a red one, an orange one and a few titanium ones

Mentioned: 113 Post(s)
Tagged: 1 Thread(s)
Quoted: 3488 Post(s)
Liked 956 Times in 594 Posts
Originally Posted by dscheidt View Post
I wouldn't accept a tube that leaks 2 psi overnight on a mountain bike. On a road bike, with skinny tires at 100 psi, I'd exepect that. I run michelin airstop tubes, mostly, my bike with 700X50 tires loses about 2 psi a week (40 psi front, 50 rear). That's checked inside, so temperature isn't an issue. I would expect to be able to find a 2psi overnight leak with leak detection fluid, but maybe not in a sink.
Thatís why I said that diffusion isnít linear. A mountain bike tire at 40 psi is going to diffuse at a lower rate than the same tire at 60 psi. And the 60 psi wide tire is going to diffuse at a slower rate than narrow road bike tire at 100 psi.
__________________
Stuart Black
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Days of Wineless Roads. Bed and Breakfasting along the KATY
Twisting Down the Alley. Misadventures in tornado alley.
cyccommute is offline  
Old 07-05-20, 09:35 PM
  #18  
zacster
Senior Member
 
Join Date: Jul 2004
Location: Brooklyn NY
Posts: 6,936
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 22 Post(s)
Liked 205 Times in 166 Posts
2 psi is within the margin of error of most gauges. Why are you even worried about this? I'm happy with a 5psi range.
zacster is offline  
Old 07-05-20, 11:30 PM
  #19  
tFUnK
Senior Member
 
Join Date: Jun 2002
Location: San Jose, CA
Posts: 2,699

Bikes: Too many bikes, too little time to ride

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 102 Post(s)
Liked 46 Times in 41 Posts
Check the valve where the stem meets the tube. Wiggle it around and check for separation.
tFUnK is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.