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Corroded valve
#1
I discovered this weekend that the rear tube on my gray bike had a thoroughly corroded valve. Not only was it leaking, but I was not able to unscrew the valve to put in a replacement. It is a Schraeder valve; CST branded tube, less than a year since purchase of the tube, and only a couple hundred miles on it at most. The climate here in San Jose, CA is very mild, and no salt or similar. I always put the valve cap back on too.

I had pumped up the tires a couple of weeks ago, and went for a short (~8 mile) ride. It had been sitting since then since I usually ride my red bike. I was going to take the gray on Saturday, and noticed the flat tire. When I got back, did my standard debugging - pump up the tire and listen. Strong hiss and blowing out the valve. I loosened valve half a turn and re tightened. Much better, but still leaking. Okay, pull out the valve and put in another - but the thing was so corroded that it would not come out.....

Fortunately I had a replacement tube (Slime heavy duty, thorn resistant) Noticeable heavier.....

Anyone had similar experience? The small group of replacement valves I have are mostly brass with a stainless steel pin. The one in the problem tube looks like steel.
Nigel
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#2
Yes definitely, don't recall the name of the tube. What might have happened is some condensation got in there from a pump you used and if you don't regularly pump up your tire the corrosion will form. You already know this ,but air compressors, tire pumps, and hand pumps all contain moisture. Air compressors have a nasty habit of holding water at the bottom of their tanks. Sometimes a good few drops will go right through the nozzle in the tube Sad .
Good maintenance to your Bike, can make it like the wheels are, true and smooth!
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#3
You can bet that I will be looking at tubes before purchasing to make sure that they have brass valve cores for now on. Smile
Nigel
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#4
Lol I do too! I even take a stem puller with me to find out.
Good maintenance to your Bike, can make it like the wheels are, true and smooth!
  Reply
#5
I agree! You should check the valve material when buying a new tube. Even if you never pump air into a tube with a brass stem and steel valve body, corrosion will occur just because of the two unlike metals staying in contact with each other without some sort of inhibitor involved. In this case, I am willing to bet that the metal valve body was the object of the corrosion.
HCFR Cycling Team
Ride Safe...Ride Hard...Ride Daily
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#6
(05-02-2011, 01:20 PM)JohnV Wrote:  I agree! You should check the valve material when buying a new tube. Even if you never pump air into a tube with a brass stem and steel valve body, corrosion will occur just because of the two unlike metals staying in contact with each other without some sort of inhibitor involved. In this case, I am willing to bet that the metal valve body was the object of the corrosion.

Actually brass and steel are a good combination to prevent corrosion. The problem one was all steel, and the metals corroded (almost welded) into a single lump.
Nigel
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#7
Hmmm! That's odd. So the stem on the tube was steel and not brass as most of them are?

When I was in my 20's and 30's, I worked as an electrician and saw more than my share of brass grounding lugs bolted onto the grounding bars corrode where the steel bolt held them together. There is no current flow on a grounding wire (unless there is a ground fault), so that would not have a play in the corrosion. We had to use an inhibitor grease to keep that from happening, but the grease only prolonged the corrosion. If we needed to remove the grounding lug, it almost always meant snapping the head off the corroded bolt. When that happened, you could see the result of the electrolysis between the two metals. Looked like someone poured salt into the hole.
HCFR Cycling Team
Ride Safe...Ride Hard...Ride Daily
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#8
Nigel - CST (Cheng Shen Tire) is one of the worlds largest tire / tube mfrs and I wouldn't suspect the brand. Something else must have happened if both front & rear were the same tubes and only one had a problem. I've seen a lot of weird stuff over the years. Maybe a mouse pee'd on it? Wink
Wheelies don't pop themselves. (from a QBP fortune cookie)
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#9
(05-02-2011, 06:18 PM)RobAR Wrote:  Nigel - CST (Cheng Shen Tire) is one of the worlds largest tire / tube mfrs and I wouldn't suspect the brand. Something else must have happened if both front & rear were the same tubes and only one had a problem. I've seen a lot of weird stuff over the years. Maybe a mouse pee'd on it? Wink

front and rear are different brands - the front is still original, rear not.
Nigel
  Reply
#10
(05-02-2011, 05:31 PM)JohnV Wrote:  Hmmm! That's odd. So the stem on the tube was steel and not brass as most of them are?

When I was in my 20's and 30's, I worked as an electrician and saw more than my share of brass grounding lugs bolted onto the grounding bars corrode where the steel bolt held them together. There is no current flow on a grounding wire (unless there is a ground fault), so that would not have a play in the corrosion. We had to use an inhibitor grease to keep that from happening, but the grease only prolonged the corrosion. If we needed to remove the grounding lug, it almost always meant snapping the head off the corroded bolt. When that happened, you could see the result of the electrolysis between the two metals. Looked like someone poured salt into the hole.

One other thing reminds me of this, automotive battery contacts! Yes the bolts that squeeze the clamps on the posts! On the cheaper ones I've seen this happen. Not bicycle related but I understand the difference in metals and the corrosion.
(05-02-2011, 06:18 PM)RobAR Wrote:  Nigel - CST (Cheng Shen Tire) is one of the worlds largest tire / tube mfrs and I wouldn't suspect the brand. Something else must have happened if both front & rear were the same tubes and only one had a problem. I've seen a lot of weird stuff over the years. Maybe a mouse pee'd on it? Wink

Then the mouse ran up the clock lol Big Grin .
Good maintenance to your Bike, can make it like the wheels are, true and smooth!
  Reply


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