Possible reasons for tire bead seating unevenly on rim bed

[weisan]

When inflated, tire is seating unevenly on the rim, causing "bounce." Have tried several different tires and used soapy water, yielded same result. No problem at all when the same tires are mounted on different wheel. What could possibly be the explanation?

Said wheel is new, freshly built, true and round.

[fa63]

Is there excess rim tape between the rim bed and the bead hook? Sometimes having too much rim tape can prevent the tire bead from snapping into place.

Originally Posted by weisan

When inflated, tire is seating unevenly on the rim, causing "bounce." Have tried several different tires and used soapy water, yielded same result. No problem at all when the same tires are mounted on different wheel. What could possibly be the explanation?

Said wheel is new, freshly built, true and round.

[robt57]

Tape most probably IMO

[dddd]

If the tape layer is consistent, then the likely reason for the lifted bead is that it isn't resting tight enough against the ledge seating diameter under it.

And if there is any free play or slop there, then the tire will tend to accumulate all of the slack in one location around the rim (this due to the increases cross-sectional area of the tire in that location, whereby the added cross-section causes a local increase in the tire casing tension, resulting in greater-yet local stretching and growth).

The looseness I am describing may not be present during mounting, but may be in response to the tire stretching and the rim contracting, both in response to subsequent inflation.

Additional tape thickness would increase the tension in the bead, above level of tension where your chosen air pressure can allow any irregularity/asymmetry of the bead seating.

It's also possible that some portion of the bead hasn't moved far enough outward laterally to rest against the rim sidewall, causing a low spot in this location while possibly allowing slack and lifted bead in another location along the rim. This could be down to a too-tight fit (too thick tape and/or too little spoke tension), or could have to do with the shape of the floor inside of the rim tending to trap the bead inboard of the ledge/rib.

With the installed tire deflated, you can try pushing one bead fully seated onto it's mating ledge in the rim, which should inform as to the level of bead tension being imposed by this rim (it should be difficult).

[MikeD]

Tubed or tubeless? Maybe the tire isn't snapped onto the bead shelf/seated against the rim wall. It can sometimes take a lot of pressure to seat a tire. However, don't exceed the tire max pressure rating. Lubing the tire beads with soapy water (high concentration of soap) can help a lot.

[weisan]

Thank you everyone for your suggestions, especially dddd pal for writing such a thorough response. I am happy to report that the problem is solved by switching to a thinner and narrower rim tape that only covers the channel.