Flat city!

The statistics are alarming. Out of sixteen riders, only four were flat-free, seven had one flat, the remaining five averaged three flats each, and the record was four. Let's take the record holder. How did he get four flats? Cactus needles? Hitting rocks at sixty? Nails? Not enough tire pressure? A cheap tube? Actually, he picked up only one nail and then spent the rest of the ride fixing the same puncture over and over again. Other riders with more than one flat also had the same problem - the patch failed. Those who took their tubes to the local LLantera for repair, however, tended to have better luck. What do these statistics tell us? They say there's something to be learned. So, here we go.

Got a flat?

The first thing you need to know is when you have a flat. This isn't so trivial. Pirelli MT21's are a rugged, stiff-walled tire, and you can go a ways before you realize something's wrong. For my first flat I found out the fun way. We had stopped on the airport road to talk with some fans watching the San Felipe 250. They had the right idea: cold beer, a little shade, a boom box. As I was getting ready to kick the XR back to life, the race fan in the tight white shorts put her arm around me and cooed in my ear, "I think you've got a flat." Damn, she's right. Now I know why I thought my suspension was so soft and squishy. A few days later, outside the Loreto supermarket, a gringo with a scraggy beard leaned out the window of his battered pickup and said to me, "My, that's a big nail in your tire." Less nice is when your friends point to your back tire and say, "Hey, guess what." Worst of all is when it's getting dark, you're riding by yourself and the back end starts fish-tailing. By now, you recognize the problem right away and can imagine how you'll spend the next hour.

Things you already know.

Removing the wheel, prying the bead off the rim and getting the tube out isn't the focus of this treatise. (You wouldn't have come on the ride in the first place if you didn't already know how to do this, right?) . There are lots of tricks to make this part of the job go faster, however. The best way to learn is to watch someone who knows what he's doing, like Nick Hayman, for example.

What you can learn here.

We're interested in how to patch the tube and have the patch hold up under the trauma it will receive once you start riding again. If it doesn't hold up, you'll have to go through the whole awful business once again, and again.

To find the secret, I watched what they did in the LLantera, I visited a couple of truck tire repair shops in Berkeley afterward, and talked with a salesman for tire repair equipment. I got pretty much the same story everywhere.

The right stuff.

To start with, you need good glue and good patches. Then you need something to clean and roughen the surface of the tube, and finally, a stitcher. (A stitcher is a little roller-wheel with a serrated edge.)

Glue and patches: Most of the time, any tire-repair cement (cold vulcanizing fluid, or self-vulcanizing cement are the technical names) will work with any patch, but the technical people say there are some minor differences to be aware of. To avoid potential mismatches you can get the glue and the patches from the same manufacturer.

For a simple puncture, the patch should be about an inch and a half to two inches in diameter and about as thick as the tube. It will have a protective transparent plastic film on the front side and a feathered or tapered edge at the circumference. The patch should be intended for a truck-tire inner tube, not for a bicycle tube. (If you just throw a bicycle patch kit into your pack before the ride and think you're covered, you're wrong.) The thin patches intended for bicycle tubes will disintegrate under the heat and flexing experienced in a rear tire.

Where to get glue, patches, and a stitcher? The hardest item to find is the stitcher. If you can't find one anywhere, get a little plastic wheel, like from a caster or shelf roller. (That's what the LLantera in San Ignacio used.) You can get an inexpensive ($7) combination stitcher and rasp at Myers Tire Supply, 7305 Edgewater Drive, Oakland, tel. 510 632 3404. Myers carries a full line of products from "The Patch Rubber Company" - glue, patches, tools - and distributes to tire stores. They have expertise and are generous in sharing it.

You may also be able to buy glue and patches from a truck tire repair shop. (I got some from Don's Tire Service, 820 Gilman, Berkeley). Just bring a sealable metal container to hold a few ounces of the glue. Both tire repair shops I visited used Rema glue and patches. ("Rema" is the brand name of a German company. If you've ever owned a BMW and looked at the tire patch kit in the green, red, and white box that came with the bike, it was from Rema.)

To find out what works best, you should get an old tube and try different combinations of glue and patch. You also want to practice the techniques described below for roughing the tube, applying the glue, and stitching the patch. The combinations most resistant to peeling off the patch (after some hours of curing) will be the best.

Getting to work.

You've got the tube out, located the puncture and are ready to fix it.

Step 1. Prepare the surface. The purpose of roughing up the surface of the tube is to expose fresh, clean rubber for the glue and patch to adhere to. The danger is always that you will not rough and buff the surface enough, rather than too much (as long as you're not using a power grinder). Use a knife edge to scrape the surface first, then a rasp (like you get in a tire patch kit) to grind away the surface rubber, and then use sharp, medium grit sand paper. The roughened area should be about a half an inch larger than the patch, all around. When finished, use the knife edge again and a puff of air from your lungs to get all the loose rubber bits off. You should not be able to recognize any vestige of the surrounding tube surface (pattern or markings) in the area you roughened. Don't touch the fresh surface.

Step 2. Apply an even layer of glue. This is best done with a brush, like an acid brush, or with the brush in the gap of the glue can. If you don't have a brush, place the opening of the glue tube directly on the inner tube and squeeze the tube gently as you move it in ever wider circles. (The point is NOT to use your finger to spread the glue.) Use enough glue to cover the entire buffed surface with a generous but even layer. If the application is uneven, proceed anyway. Just be sure to let it dry long enough so that the thicker areas of glue are also completely dry. Keep your fingers out of the glue you spread on the tube.

Step 3. Wait for the glue to dry - bone dry, not tacky, and certainly not wet. This can take anywhere from three minutes to ten minutes, depending on the glue and the temperature. Again, don't touch the glue surface.

Step 4. When the glue is dry, peel back the protective cover from the back of the patch. Avoid touching the back surface of the patch. Don't peel the cover all the way off because you can use some of this protective cover as a handle to hold the patch as you position it over the puncture and then set it down onto the tube. Try to have the first contact between patch and tube be at the center of the patch (or at one end) and then have the contact point move continuously toward the outer edges (or opposite edge). This will help prevent air bubbles and ensure a smooth, uninterrupted contact between patch and tube.

Step 5. Place the patched area on a hard, smooth surface (gas tank, fender, or such) and begin with the stitcher, rolling back and forth vigorously first at the center of the patch and then working out toward the edges. The stitching process is important because it initiates the chemical and mechanical bonding processes. This is also your last chance to get rid of any air trapped between patch and tube. Stitch in all directions. Press hard, as hard as you can.

Step 6. Remove the thin plastic film from the outside of the patch, and you're ready to install the tube and finish the rest of the job.

Repairing a tire.

If the tire itself is damaged (a cut or tear) such that it could damage the tube, then you will need to repair the tire as well. The patch to be used for this is different (larger, thicker, stronger, and less flexible) than a tube patch. The procedure for patching the tire is the same, except now you're working inside the tire, on a concave surface, and it will be much harder to roughen the surface properly. (The Myers stitcher has a curved rasp that can be used for this.) It wouldn't hurt to carry a couple of tire patches along with your stock of tube patches.

Postponing the patch.

Patching a tube adds about fifteen minutes to your time in the broiling sun. If you'd rather patch your tube with greater care later, in the evening shade along with a cool drink, you might consider skipping the roadside repair and using your spare tube. If you do this, you may also have the option of taking the punctured tube to the LLantera the next morning and have it patched professionally, for a buck and a half. (I recommend this). Next year, I'm going to carry a spare tube for the back tire as well as for the front. Of course, next time I won't get a flat, and I'll have to find something else to write about.

Flat sociology.

Fixing a flat on the road is a rite of passage that we all experience sooner or later. What a pity it would be to experience this all alone. It means a lot when there is someone there to offer moral support, helpful advice, find your valve core in the sand, help you get the wrinkles out of the 21" tube you're trying to stuff into your 18" rear tire, or go for help if you really screw up So, my thanks to Tony Slocum and T.J., who helped me through my rite of passage on the San Felipe airport road (and on other occasions as well) and to Nick Hayman and Mike Crowe for providing expert help and dry humor, respectively, that morning on the road out of Loreto.

RGS, April 1996