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Help me solve a mysterious slow leak?

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Help me solve a mysterious slow leak?

Old 10-03-18, 12:42 PM
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Danhedonia
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Help me solve a mysterious slow leak?

Was riding +/- 30 to 40 miles a few times a week this summer. Road bike, aggressive pace for old fat guy.

For 10 years I'd ridden the same Ksyrium wheels, with Panaracer Stradius Pro's and various tubes. I always inflate to 140 PSI. I emphasize that because a) it's higher than most people do; and b) I do think it's significant that I've been doing that for 30 years with little/no issues. In fact, the Panaracers were originally purchased because they're rated for that higher PSI.

Last month, I kept getting a slow leak on my rear wheel. Tire was checked for wear and issues -- it was a bit aged, but there were no tears, tiny thorn tips, etc. Tube was changed out a few times (don't ask, I have a lifetime supply of tubes). But it just wouldn't stop going flat overnight. I'd pump up to 140 (or 115), and it didn't matter.

I worried that the wheel was out of true, but nope. I even put on a new Panaracer tire, and still: leaks.

After a couple weeks I got sick of it and put on two new very cheap Chinese Contis. Still inflating to 140. Problem disappeared.

WTF? Why did I have that slow leak? The tubes were NOT getting compromised under the tire -- and in fact, the front wheel, which had the same rim and tire combo, had no issues. And it's not like I went to a 'high quality' tire (though no complaints about those Chinese Conti's, which are doing quite fine in the height of goathead season here in NM).

After switching out the tires, I've wondered - where did that leak come from? If that model tire is so bad for my rims, why did it take 10 years for the issue to show up? Why didn't the front wheel leak? WTF?
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Old 10-03-18, 01:46 PM
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Ironically, cheap tires tend to hold air better than lightweight racing tires. This is because holding air is a joint effort by the tube and tire combined, and the cheaper tires tend to have more rubber, especially in the sidewalls. Still, going completely flat overnight is well beyond what you should expect, even with light tires and latex tubes.

So that leaves tubes as the primary culprit. Did you remove the flatted tube, inflate it like a balloon, and stick it underwater? It's possible you have a very tiny sharp thing sticking into the inside of the tire, something that only shows up when the tire is used. I've seen 'Michelin wires' do this, and even replaced a tire once because it was doing exactly what you are describing.
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Old 10-03-18, 03:36 PM
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flat overnight can only be the tube/valve stem-remove tube and inflate and submerge in water and you will find the leak
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Old 10-03-18, 03:44 PM
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When was the last time you replaced your rim tape? If it is old Velox - it is a good practice to refresh it every few years because it can shift and potentially expose spoke holes or little burrs on the interior of the rim.
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Old 10-03-18, 07:54 PM
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I've had a steel rim puncture a tube. Could be the hole for the valve has a splint of rogue metal, with the steel rim it was the folded flange on the inside (not there on alloy).

also a Schwalbe Fat Frank had a rogue splint of steel belt which punctured a tube, it was a nearly new tyre so a new tyre can still do it - bit of a coincidence if in this case though...
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Old 10-03-18, 07:57 PM
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Sounds like perhaps like there may be some type of debris in the old tire. Run your bare fingers aggressively around the inside of the tire and if you pull back a bloody stump you will know there was some hidden shrapnel or glass shards.
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Old 10-03-18, 09:11 PM
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Originally Posted by Doctor Morbius View Post
Sounds like perhaps like there may be some type of debris in the old tire. Run your bare fingers aggressively around the inside of the tire and if you pull back a bloody stump you will know there was some hidden shrapnel or glass shards.
Save your fingers...Wad up some tissues or grab some cotton balls and run it around the inside of the tire. It'll catch on the tiniest imperfection.
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Old 10-03-18, 09:54 PM
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I see a lot of valves fail at the Base, especially when they are kept at higher pressure. Just a theory, but forcing air through the valve heats it up and makes it brittle after a while? Not sure, but cracks around the valve don't always show up when tubes are filled with air when outside of the tire.
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Old 10-03-18, 11:17 PM
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Meanwhile, 140 psi! Ouch. When I was young and dumb and thought 19mm tires were the bomb, I still only pumped them up to 130.
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Old 10-04-18, 08:49 AM
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I have not have a flat till now. Two in a row within a week so far. When I match the puncture location against the tire, I can see/feel a tiny wire protruding. The hole on the tube is miniscule (impossible to see without tub of water). When I went to grab a needle nose plier to remove the wire, it seems to be gone. So I stuck a piece of duct tape on the tire where I thought the wire was. Changed to new tubes, pumped it up and went riding. Tonight, noticed that I have another flat. Opened it up, and I see/felt tiny wire again.

​​​​​​​Question, this tiny wire, could it be part of the tire? Like possibly the tire manufacturer, in order to strengthen the tire, they run a layer of rubber with wire mesh embedded? I am close to 3000 km on these pair of tires.
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Old 10-04-18, 09:42 AM
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Lots of steel shards on the road. Worked at the dump and watched the trucks come in from different manufacturers in the area. Every bump, dust and metal shavings would filter out under the doors. We had a tow behind magnet to suck up most of it, but you can imagine how much would shake loose before it made the landfill.
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Old 10-04-18, 12:42 PM
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Danhedonia
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I did search -- extensively -- for an imperfection in the tire, but then why would changing to a new tire (and tube) recreate the problem?

Similarly, if there's a problem with the rim, wouldn't it recur with the new tires?

I did NOT do the bathtub / sink thing with the tubes, and not sure why I was lazy about it. That said, the only variable that wasn't changed at least twice is the rim. BUT everything is fine now.

Totally mystifying to me.
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Old 10-04-18, 02:57 PM
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I am puzzled as to why you would just keep putting new tubes into the same tire. After a couple, I would think you would want to figure out what was going on and the first place to start is by figuring out where the leak was.

As others have said, there could have been some very small sharp object stuck in that tire or something else that was puncturing the tubes.
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Old 10-04-18, 03:12 PM
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Yowza! 140 psi Yikes! I'd be real concerned about brake track integrity regardless of what the tire itself is rated at. But I guess if some is good, more is better, right?

Anyways, I agree with the valve stem comments. I'd look there and wouldn't think much of a tube developing issues as it ages. I have a tricycle that has 2 patches on either side of every valve stem due to crap manufacture. It comes with the territory.
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Old 10-04-18, 06:15 PM
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Originally Posted by dahoneezz View Post
When I match the puncture location against the tire, I can see/feel a tiny wire protruding. The hole on the tube is miniscule (impossible to see without tub of water). When I went to grab a needle nose plier to remove the wire, it seems to be gone.
Obviously, it's not gone. And it's not a manufacturing defect. You ran over it and it worked its way into the tire over time. If you can't get it out, replace the tire.
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Old 10-04-18, 06:35 PM
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Originally Posted by curbtender View Post
We had a tow behind magnet to suck up most of it, but you can imagine how much would shake loose before it made the landfill.
Very true. When I was a child my dad owned a company that sold magnets for just these purposes. Picking up steel from food products and everything else. The little magnets were fun but when we visited the shop and played around with the big magnets it was really fun. As in dangerous. Like six feet long bars with similar sized keepers. Put them near each other and try to not let them slam together. The salesmen had small two inch horseshoe magnets that we could occasionly make off with. Eriez magnetics still in business today. Make friends with a sales guy and get a lesson on how great magnets still are.
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Old 10-04-18, 07:33 PM
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I opened up the tire again to find the wire. This time I used a reading light so that I can see better. Rubbing my fingers on the inside of the tire, I did not feel anything. So I used a needle and start picking out the little pieces of stones and glass from the outside surface of the tire. Then I hit metal. I start to dig it out, its the tiny wire. Woohoo!!! Pulled it out with a needle nose plier. I wanted to save it for evidence, but I dropped the dang thing on the floor and I could not find it. It was so tiny. Hopefully that was the cause of my puncture.
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Old 10-04-18, 07:44 PM
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Just turn off the lights and walk around bare foot, you'll find it...
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Old 10-04-18, 08:04 PM
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Ha ha ....

Here little wire ... come to papa ... Anyways, I swept the floor and gathered the sweepings into a dustpan to check for the little wire. Nada. Hopefully thats the end of it. Opening up tires, dunking tubes in bucket of water, sanding, patching, ... ugghh!
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Old 10-05-18, 09:12 AM
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Originally Posted by dahoneezz View Post
I opened up the tire again to find the wire. This time I used a reading light so that I can see better. Rubbing my fingers on the inside of the tire, I did not feel anything. So I used a needle and start picking out the little pieces of stones and glass from the outside surface of the tire. Then I hit metal. I start to dig it out, its the tiny wire. Woohoo!!! Pulled it out with a needle nose plier. I wanted to save it for evidence, but I dropped the dang thing on the floor and I could not find it. It was so tiny. Hopefully that was the cause of my puncture.
That sounds right to me. I started carrying a needle nose pliers with me in my patch kit just for those little wires. They can be buggers to find and, once you do find it, your problems are just beginning because they can be so hard to root out of your tire. Hopefully that solves your problem.
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Old 10-05-18, 09:19 AM
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Investigating the old tubes would've helped answer the problem.
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