PROBLEM: You install your bike tire, pump it up, and a section bulges or dips.
SOLUTION: Bulging is urgent. Quick, let out some air! A section of tube is under the tire bead (the inner edge around each side). If you continue to add air or try to ride, chances are high that the tube will pooch between the tire and rim and cause a big and possibly dangerous blow out.
Once the tube is deflated, work on the problem area. Lift, squeeze and massage the tire until the tube no long appears under the bead. Then cautiously add air, watching to make sure all is well.
In a properly seated tire, the bead line — the thin line molded low on each sidewall — will be just above the rim all the way around on both sides.
Dipping bead line. If the bead line dips below the rim, the tire will feel lumpy as you ride. To correct this when you have a high-pressure floor pump, you can sometimes keep adding air beyond maximum inflation, but only if you have alloy rims. This extra pressure with allow rims may pop the bead into place with a snap you can hear (then let out the excess air). WARNING! Don’t try this with your carbon wheels. Overinflating carbon rims can weaken, crack or ruin them and put you in big danger!
A safer way is to deflate the tire and massage the dippy section. Put it in the same position on the rim as the rest of the tire. Inflate and all should be well.
No again? Deflate again and rub something slippery on that bad bead. Lots of things can work, but don’t use bike grease, which could harm the rubber and get on the rim. Try a little liquid soap, bar soap or saddle soap. Good old spit can work, too, and might be the only choice if this is happening during a flat repair out on the road.
Pump up the tire again. OK? Good! Now skip today’s upper-body workout because you just had it.
Another thing that works well to lubricate the tire is talcum powder (baby powder). It’s good to use on the inside of the tire to keep the tube slippery as well. When I fist started riding wheels that had a more aggressive hook (to make them tubeless compatible) I found that after fixing a flat out on the road, I had a lump. It concerned me enough to stop and go through the steps you describe (lower pressure and massage the tire, then pump it up really hard). The lump was reduced but not eliminated. I wasn’t too far from home so I decided to ride home to my big floor pump where I knew I could put in enough pressure to pop the tire into place. In a couple of miles of riding, the rolling of the tire served the same purpose as hand massage, but with more force and frequency. The lump was gone.
Tires failing to seat completely has long been a problem, especially when combining cheap alloy rims with cheap (and sometimes not so cheap) tires.
Several years ago I purchased from Schwalbe Tires a liter bottle of their bead seat solution, a slippery soap-like solution. I just keep a small piece of sponge around, saturate it with the solution, and swipe it around both sides of the installed-but-not-inflated tire bead. It has always worked, allowing good bead seating without overinflating the tire. It seems to dry and leave no residue on the tire or rim. The liter bottle lasts a long time.
Talc applied to the tube and inside of tire casing is also very helpful.