Sounds like you need to take it to a repair shop and have it checked out. It could be other things than a tire out of balance. A weight could have come out or it could be a problem like a bad bearing (it doesn't sound like a bad bearing, but it could be).
Jeff
About six weeks ago I purchased a used Ford Explorer EB 2000 with 36K
> miles on it. It came with an almost new set of tires (9/32 tread)
> Good Year Wrangler RT/S 255/70/16. I did not have any problem with
> tire noise for almost a month. The tires were apparently balanced when
> mounted (have balancing weights on them).
>
> Now, at low speeds (30-40mph) I hear a thumping noise that appears to
> be coming from the right front wheel, there does NOT appear to be any
> vibration associated with it. As the driving speed increases, the
> pitch of the noise gradualy changes to whining noise.
>
> I did not hit a curb or any significant pot hole, the vehicle does not
> pull to a side with the steering wheel left free when driving, so
> alignment does not appear to be disturbed. The noise from wheel(s) is
> loud enough to produce the feeling as if a window has been left open,
> while it is not so.
>
> Any ideas as to what might be happening and how should I approach this > issue?
>
> Thanks, In advance.
>
> Matt