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View Full Version : Fun time mystery - unexplained flats



jrenaut
02-04-2016, 05:08 PM
So, the rear tire on the Xtracycle keeps going flat. This is especially awesome because it's no fun at all to get the wheel on and off - it's a giant heavy bike with bags in the way, almost no clearance between the skewer and the derailleur, and disc brakes on a 20" wheel. It's the perfect storm of giant pain in the butt.

The first flat was yesterday. It was slow - I didn't notice until I got home and was carrying the bike inside. I pulled out and inspected the tube and couldn't find anything. I inspected the tire and couldn't find anything. So I got a new tube and everything seemed fine. 2.5 miles with the kids to school, 2.5 alone home, 2.5 back to school, 2 to the grocery store with the kids, and when we came out the tire was flat again. 666 on the trip counter, too.

One of the mechanics at Bicycle Space looked at it and couldn't find a hole in the tube or a problem with the tire. She pumped up the old tube and I rode home with no issue.

I have an extra tube and tire, so I'm going to put those on tonight, and probably take the other tube and tire to The Bike Rack after Coffee Club tomorrow.

What could be causing the flat? Something on the wheel? It's a super slow leak, whatever it is. I feel both better and worse that Bicycle Space couldn't figure it out. If you're at Coffee Club tomorrow you can examine the tire and tube yourself.

hozn
02-04-2016, 05:26 PM
I would vote for putting the tube in the bathtub and finding the leak. Then, assuming you line up the valve stem with the tire label, you will know where (or two possible places) the leak is on tire. Or on the rim; check rim tape to see if something sharp is exposed (like edge of a spoke hole).

DismalScientist
02-04-2016, 06:06 PM
Are your kids occassionally deflating your tire just for yucks?

jrenaut
02-04-2016, 06:12 PM
I would vote for putting the tube in the bathtub and finding the leak. Then, assuming you line up the valve stem with the tire label, you will know where (or two possible places) the leak is on tire. Or on the rim; check rim tape to see if something sharp is exposed (like edge of a spoke hole).
The mechanic tried putting the tube in water and couldn't find anything. I haven't checked the rim carefully, I'll do that when I take the tire off

Rootchopper
02-04-2016, 06:15 PM
I have also found a very fine piece of wire embedded in my tire. Not perpendicular to the tube but at an acute angle. Really hard to find. I think these come off of car tires. The only way to find it was to slowly run my bare finger over every millimeter of the inside of the tire until it snagged.

Are you booting the spare? If you have a hole in your tire and don't boot the spare tube, the hole will ever so gradually open and close on the tube causing a flat. You may see a scuff mark on the tube.

Not that you don't know this but this will drive you mad.

Mikey
02-04-2016, 06:19 PM
+1 for the bathtub. May be a very slow leak and could just look like a bubble stuck to the tube instead of a stream of bubbles. If you can't feel the foreign material it could be glass. It likes to hide in the rubber and only come out when under strain or pressure, you would need to flex the tire between your fingers and feel for hard knots , then look for a very small cut on the surface. Happy hunting!

AFHokie
02-04-2016, 07:07 PM
I have also found a very fine piece of wire embedded in my tire. Not perpendicular to the tube but at an acute angle. Really hard to find. I think these come off of car tires. The only way to find it was to slowly run my bare finger over every millimeter of the inside of the tire until it snagged.

This happened to me this past summer...after a week of random repeat flats, I pulled the tire and dunked the tube. Even with soapy water it still took some time to find. I had to work my way around squeezing every six inches or so. The hole was so small it didn't bleed air unless I squeezed the tube and built up enough pressure to leak. It was indeed a small piece of wire (size of the wire in a twist tie) stuck in the tire. I think they're most likely pieces of wire broken from braided cables. Like what you'd find in a winch, crane, etc.

jrenaut
02-04-2016, 07:27 PM
Ran my finger over the rim pretty carefully and couldn't find anything. I put the new tire and tube on.

As I said, I'm bringing it to Coffee Club tomorrow. If you find the problem I'll buy your coffee (maybe next time since you'll have already bought it this time, but whatever).

If I get motivated to put some water in the bathtub I'll check it later. I'd hate to have to ditch a pretty new tire because I can't find some foreign object.

jrenaut
02-05-2016, 08:50 AM
There was a piece of glass in the tire. Making tiny, tiny little holes in the tubes.

hozn
02-05-2016, 10:07 AM
Depending on how large a cut the glass made in the tire, you may wish to use superglue or something to seal up the hole. Otherwise, sand/rocks/more glass may work its way in and cause more flats. You can also patch the tire itself from the inside with a tube patch, which in my experience has helped but I have heard the superglue should do a better job of keeping stuff out.

(So I guess this is another anecdote of bike-shop mechanic incompetence?)

jrenaut
02-05-2016, 11:06 AM
(So I guess this is another anecdote of bike-shop mechanic incompetence?)
I wouldn't say incompetence. Two people missed the glass, a third found it. That tire is demoted to back up status anyway, so I should be good for a while.