I got a flat the last hill of my 100 km bike trip last Sunday. Thank heavens it did not happen at km 50 or something. I went to a bike shop in Shinjuku today to get a replacement tube, and they were kind enough to tutor me on how to replace it.
How to Change that Tube
Here’s the process I learned at the bike shop:
Purchase a tube, tire levers (they come in sets of three, usually) and rim tape of the appropriate size. My rims are 26 inch with 1.5 Schwalbe Marathons on them now, and you just have to be sure what you buy is the right size. If you can give them the rim size, that’s better too. The tubes come with various valves, and I have “French” valves now so that is what I got. All told, the cost to buy the parts was about JPY 1300 (USD 13).
Remove the wheel with the flat from the bike. I have Shimano Deore XT rim brakes, and there’s a place you hook the brake wire’s flange in, which if released, gives you the leeway to get the tire off.
On the opposite side of the wheel from the valve, insert a tire lever between the rim and the tire, and use it to lever the tire out, in that area. Take care not to pinch the tube while you do it, just in case you want to fix and reuse it. You’ll notice there’s a kind of hook on the one end of the lever - this goes onto a spoke to keep the lever in place, holding the tire edge out and away from the rim.
A couple of spokes away, do the same thing again with the second lever, to get more of the tire out.
Now you should be able to slide the third lever under the edge of the tire, and rotate it along the rim and tire edge to get the tire out. You can keep the one edge of the tire in the rim.
Slide the flatted inner tube out, taking care not to damage it if you want to repair it.
Inspect the tire inside and out for damage. There could be something sharp embedded in the tire. Remove any sharp objects puncturing the tire. In my case there were two pieces of a broken spoke embedded in the tire and in the rim tape. I could only find the one embedded in the tire by running my hand along the inside. The rim tape problem was quite obvious!
If you either remove the tire completely or just push it to one side, you should be able to see the rim tape, which prevents the inflated tube from working its way into the nipple bolts for the spokes. Rim tape prevents flats, but, in time it gets worn out too. If it has been mashed into the nipple bolts too much, and there are sharp edges, replace it. Rim tape is basically like a big rubber band with a hole for the valve. You can use a flat blade driver or an awl to work old rim tape out, and to lever new rim tape on. In my case, the yellow rim tape was two years old and starting to get dry, and, it had been punctured by the old spoke bit, so I replaced it.
Put a little air into your new tube, because it is easier to work with the tube if it is slightly inflated.
Insert the valve through the rim tape and rim, and put the valve bolt on to secure it.
To put the tire back, this time start on the valve side (removal starts opposite the valve). You can use the tire levers to get started putting the tire back into the rim, but be careful not to pinch the new tube. Having the tube slightly inflated will make things a little easier to maneuver. Once you get the tire in a little, use your hands to kind of “knead” the tire back in, working around it. Schwalbe Marathons are a little tough, as they have Kevlar inside and are consequently a bit harder rubber.
Check that the valve is 90 degrees to the rim. If it is angled, work the tire and rim until you can rotate it so it is perpendicular to the rim.
Inflate the tube to the correct psi pressure. Confirm that it’s holding air and that you have not damaged the tube.
Deflate the tube once, then re-inflate. The bike shop said this last step really helps to prevent flats.
Hope this procedure helps someone with their tube troubles. Happy riding!