wire in tire

[handlebar]

Radpower says you have to add air to bicycle tires every few days. That was not my experience with butyl rubber tubes. For some reason, I had to add air to my Radrunner tires every ten days or so. Eventually, the front improved, while the back got erratic. It could hold pressure for weeks and lose a lot overnight, even going flat. I thought it had to be the valve. Replacing the core, cleaning, greasing, and screwing on a metal cap tight didn't cure the problem.

I removed the tube, pumped it up, and held it under water, section by section. I didn't see any bubbles. When the problem persisted, I replaced it with a Velo tube. Again, I pumped up the old tube and held it under water. I didn't find anything, but it lost pressure overnight. This time I found bubbles from two holes an inch apart, too tiny to see even with a 20x microscope. I'd never seen leaks so tiny. I thought the tube must have been faulty.

With a 4" tube in a 3.3" tire, maybe the tube can shift within the tire, so that some times it can be pushed shut and other times stretched wide open.

In a week or so, the new tube began losing air. When I swapped tubes, I checked the inside of the tire by looking and feeling. I didn't find anything. When I checked the tube I'd removed, I found a tiny hole near the centerline of the tread, like the other holes. I must have missed something tiny when I checked the tire. externally, I checked the center of the tread carefully. All I found was a sort of grain of sand embedded in a lug. I got it out with a little screwdriver and tweezers.

The third tube soon started losing air. This time, I marked the sidewall of the tire on the sprocket side at the valve. I also marked the tube on the sprocket side. That way, when I found the leak, I could lay the marked tube on the marked tire to see exactly where to look. It was another Velo tube, and with that brand I could see the tiny holes with a 20x microscope. I saw a tiny bit of metal lodged in the hole.

I found the exact spot in the tire. There was a discolored spot, and I felt a pinprick. On the lug, I saw something tiny. With a wire, I pushed it enough to grab the inside end with pliers.

It was 1/4" of wire as thin as sewing thread or the wire used for window screens. It was so exceptionally fine that I wanted to measure the diameter. I had it on my fingertip with my hand on a white counter as I turned on my caliper with my  other hand. The wire fell off, and it was so tiny I couldn't find it.

If I'd run onto 1/4" of such thin wire, it would have bent or broken without penetrating even a millimeter. The only way I can imagine to stick it through the thick part of my tire would be to grip it with pliers a millimeter from the end, shove it in, slide the pliers back a millimeter, and repeat, one millimeter at a time.

Sometimes my front tire still loses a little air. That's not normal for butyl rubber. I'll mark the tire and the tube. If I find a leak in the tube, I'll know where to look in the tire.

[JimInPT]

I must be lucky; the CST Big Boats that shipped with my 1-year-old MiniST can go 3-4 weeks and only lose a single PSI from my routine 30, and I just topped up both tires a couple weeks ago after sitting since early November in the cold and snow - they were both low by about 2.5 PSI.

So kudos on your persistence - do you think the wire might have snuck in on its own or is it part of the materials used to make the tire tread?

[Eric7]

First I am sorry it happened to you.

Now that you found it, I hope your problems are solved forever. I wonder if some sealant would have helped if it ever becomes a problem again.

Thanks for sharing.

[handlebar]

I must be lucky; the CST Big Boats that shipped with my 1-year-old MiniST can go 3-4 weeks and only lose a single PSI from my routine 30, and I just topped up both tires a couple weeks ago after sitting since early November in the cold and snow - they were both low by about 2.5 PSI.

So kudos on your persistence - do you think the wire might have snuck in on its own or is it part of the materials used to make the tire tread?

When pinprick holes appeared in more than one tube, I thought maybe the tire had a wire belt and a strand had come loose. They aren't advertised as belted tires, and off the rim, the tread felt too pliable to be belted. Besides, the wire went through from the outside, and it went through perpendicularly from the center of a knob in the center of the tread.

If I hadn't found the wire, I might have bought Tannus Armour and spread the word that this was the solution. Foam plastic for $150 sounds very profitable.  I don't know enough about Tannus to say if they might be paying someone at the Kenda factory. Kenda QC would have a hard time spotting it.

For 12 years I rode English bikes at 60 PSI and never had to add air unless I put on a new tire or got a puncture. I rode up to 2500 miles a year. If I had a puncture, it was usually because I'd worn the tire thin. Then for 7 years, I depended on motorcycles with butyl tubes. I didn't have to add air except to put on a new tire. Then for 24 years I rode a motorcycle with latex tubes. I had to add air sometimes because latex rubber is porous, but I've never had a motorcycle puncture.

I'm glad to see that someone else runs 30 PSI. My tires are quieter now, and rolling resistance is incredibly low. My Bolton display says I've run 81 miles on this charge, and I still have 43 volts. I don't need a suspension because I've moved the seat back 7". I did it to stabilize my upper body for safer steering. I'd forgotten two other big advantages. Pedaling or coasting, I can keep most of my weight on the pedals so my legs can absorb bumps. My knees don't have to bend past 90 degrees, which means I can apply more power with little muscle fatigue or knee strain.

I think seating position was the big reason the 1885 Rover was such a breakthrough. In a 1930 documentary, it allowed a 10-year-old girl to pedal 100 miles on hilly terrain one day on a Raleigh Sport. Interviewed in her 90s, she said she and her father pedaled home the next day. The Dutch still make bikes with this seating position, which allows even those in their 80s to make 2/3 of their trips by bike. They don't wear helmets because with their feet well forward of their saddles, crashing doesn't throw them on their heads.

[handlebar]

First I am sorry it happened to you.

Now that you found it, I hope your problems are solved forever. I wonder if some sealant would have helped if it ever becomes a problem again.

Thanks for sharing.

In fact, I tried a sealant I had on hand for a tubeless mower tire. It's a milky latex propelled by a harmless variety of refrigerant. The results were the same as for the next two tubes, without sealant. Sometimes the pressure stayed up, sometimes it dropped 5 or 10 pounds over night, and sometimes it went flat overnight. I guess a tube is too thin for this kind of sealant to stay in place.

I'm getting fast at removing the back wheel, but a different design would make it easier. Vulcanizing patches are cheap and work great. For some reason, it's harder to be sure the tube is out of the way of a mounting lever, than it was in past experience. The other day, I pinched a hole in a tube for the first time in my life. I had to change tubes twice in one day. My back is recovering.

Amazon has a bicycle pump that's hardly bigger than pocket size, and it has a built-in stick gauge. That could be just the thing for a slow leak.