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Archive for October 22nd, 2010

Another Bike Flat: Michelin Hair

Rode around the big block on some errands, stopped at the Vassar Farm garden to haul some squash home, rode off… and the bike handled poorly. Well, with a few dozen pounds of produce in the panniers that’s not unusual, but this was worse. Yup, another flat.

This time, however, our daughter was home and could rescue me in the van. Back in the shop, I found this obvious suspect:

 

Embedded glass fragment

Embedded glass fragment

 

Once again, however, this wasn’t the problem, as the tire liner was barely scuffed. Those are glass fragments inside the gash, which might actually be the same one as before.

There weren’t any other pointy objects embedded in the tire, but the tube wouldn’t stay inflated long enough to find the leak. I took the tube upstairs, submerged it in a pan of water, and found a rash of holes. Not pinholes, not a failed tube, but a series of punctures.

 

Steel wire fragment

Steel wire fragment

 

Examining the tire liner revealed the cause: a strand of what my buddy DBM calls Michelin Hair poking through the tire liner. It’s a fragment of the steel belt from a car or truck tire, most likely shed from a disintegrating semitrailer recapped tire.

There is absolutely no defense against these things, because they have razor-sharp points on both ends where the wire fractured. When the tire picks one up, every rotation drives it through the rubber, the Kevlar belt, the tire liner, and the tube. The usual symptom is a slow leak, eventually followed by a row of holes in the tube as it shifts position under low pressure.

In fact, the tube had a slow leak since I installed it a few weeks ago after a tube failure. I wondered if I’d inadvertently installed a fold, but now I think I ran over this wire during the first few rides and it’s been getting worse ever since.

That tube is a goner! I installed another Schwalbe tube and we’ll see what happens; one has been working fine on Mary’s bike for the last three months.

Here’s a look at the steel wire from the side:

 

Steel wire fragment through tire liner

Steel wire fragment through tire liner

 

It was completely through the liner, with only a stub sticking out on the tire side. There’s certainly a matching hole somewhere on the tire, but it’ll be indistinguishable from all the other nicks and gashes.

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