Bubble In Tire

[cdat]

I have what is probably a stupid question, but I have a reoccuring problem with air bubbles in my rear tire. I have changed tires, I have a brand new rear rim, I have replaced the rear tube several times. When I inflate the tire, I get a buldge in the rear and an annoying thump when I ride. I never have it happen up front, it is always the rear. What am I doing wrong?
Thanks

 

[domaindomain]

Is the tyre seated properly on the rim?

 

[bikeguy]

When you a put a tube in, make sure it isn't twisted and lays flat. Also, inflate the tube slightly before putting the tire on, then inflate all the way. Hope that helps.

-Bikeguy

 

[el Ingles]

Is the tyre seated properly on the rim?

is the wheel round ? very often the rim is slightly off round and on a cycletrainer , for example , this effect can be quite notable .
also lots of tyres aren´t that well made and this is one of the effects ( used to be worse with tubs )

 

[artemidorus]

I have what is probably a stupid question, but I have a reoccuring problem with air bubbles in my rear tire. I have changed tires, I have a brand new rear rim, I have replaced the rear tube several times. When I inflate the tire, I get a buldge in the rear and an annoying thump when I ride. I never have it happen up front, it is always the rear. What am I doing wrong?
Thanks

This usually means that the threads are breaking in an old tyre, not that there is an "air bubble". Is it an old tyre?