Saturday, February 24, 2007

Rim tape blow out

       Yes, I must be a little bored to write about this, but who knows? It might help someone out there someday :-)

       I will state for the record that this has never happened to me. Maybe the rim tape on this wheel (borrowed from Dominic) is old, or maybe I pumped the pressure too high on the tire (my floor pumps usually come with a pressure gauge). Anyways, I was cruising along at a good clip (about 26 mph / 41.6 km/h) when I heard a loud pop and hissing from my rear wheel. The first thing that came to me was, "That's odd. The Specialized Fat Boys have Kevlar™ Flak Jackets. Not even broken glass can get through them." I pulled over anyway, and sure enough, my rear tire was rapidly deflating. O....kay.

       I felt the inside of the tire carcass but felt no foreign object. I checked the outside of the tire and found nothing either. So, before I installed my spare tube (I try not to do roadside / trailside patch ups), I pumped up the deflated tube to locate the puncture. The puncture turned out to be on the inner circumference of the tube. Using the valve as a reference, I quickly found out the cause of the puncture. The rim tape gave way over one of the spoke holes, resulting in the tire tube pushing itself against the sharp edge of the spoke hole and blowing out. A patch kit is not going to fix this. Installing a new tube would just result in an immediate blow out.

       I stood and thought about it for a while. This is the first ride I didn't bring an emergency tire boot which I can trim to fit over the blow out. (Don't you love Murphy?) I recalled a piece of advice from a biking magazine: a PowerBar™ wrapper can function as emergency tire boot to get you home. I looked at my packet of energy gel and thought, "Energy bar. Energy gel. Po-tay-toe. Po-tar-toe. It just might work."

       After consuming the contents of the energy gel, I used the tab as an emergency "rim tape boot." As luck would have it, the tab was exactly wide enough to span the width of the Mavic 220 rim :-) Don't you just love serendipity? I made sure both sides of the emergency rim tape boot are held under the bead of the tire, installed the new tube, inflated it, and was on my way.

       Here are some pictures (I'm at home now, of course):

Here, you can see how 100 PSI (or 105, or 110 PSI. The tape was old and it was a hot day.) in the tire tube might have caused the Velox™ cloth rim tape to fail, allowing the tire tube blow through the spoke hole.

The tab from Crank e.Gel™ energy gel packet.

Energy gel tab installed as an emergency rim tape boot. The tire has been removed for clarification. There is no need to completely dismount the tire, you can simply slide it under the tire bead on the side that's not removed. Refer to next picture.

How the repair is accomplished (and should look like). From here, install a new tube, making sure that the emergency patch hasn't slid around, inflate, and you are on your way.

The puncture. Not very pretty. I'm not sure if a regular patch will hold it.

As a precaution, I replaced the rim tapes on both wheels with superior variants. The Velox™ cloth rim tape is identical to the Zéfal™ rim tape in the picture. I upgraded to Xero™'s lightweight rim tape. (As a general rule in cycling, whenever you break something, it is the perfect excuse to upgrade :-P ) The Xero™ rim tape is four times the price of the regular cloth rim tape, but it is non-adhesive (no mess when uninstalling), lighter, synthetic (i.e. doesn't rot when wet like cotton does), and, is a literally a snap to install — simply align it to the rim's valve hole, stretch it over the rim, and you are done.

Xero™ rim tape installed on front wheel. That's a 1991 Mavic™ Paris Gao Dakar Commemorative Hub, by the way. It still spins as smoothly as the day I bought it. You can spin it, go take a shower, come back, and it will still be spinning. That's Mavic™ for you.

       Happy trails :-)

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