One problem related to tire bulge has been reported for the 1998 Toyota Sienna. The most recently reported issues are listed below.
Tire seemed out of balance at narrow range of speeds (60-65mph), but smooth at 68mph for months; recently noticed vehicle rocking when cold and at low speeds; today saw an outward bulge in rear tire tread (directionally outward from axle). Am seeking a replacement tire before tread separation.