Mk3 Golf making odd noise whilst travelling
 

I have a 1996 1.8 Golf GL which has been making a bit of an odd noise for quite awhile now. Its a low rumbling/knocking sound which I think is coming from the front end when moving and its generally more noticeable when travelling faster.

I originally noticed it when I had a bearing go on the left front. That was making a horrible noise under braking and I thought both noises were related. Replacing the left front bearing cured the noise under braking but this rumbling/knocking noise was still there.

I thought it might be right front bearings but the speed of the knock doesn't change under braking (like the left did) and there doesn't seem to be any excess play in the hub, so I didn't want to change it unnecessarily.

Anyone have any ideas?
Thanks,
Tom