I have an older Bianchi Strada road bike that I ride. For as long as I can remember, when I hit speeds of over 30mph off hills, I feel a bit of unevenness....not sure how to describe it, almost like brakes occasionally dragging, as if wheels were out of alignment, just a mild "pulsating". It's a "forward to backward" motion, not "side to side".
Mechanic at LBS suggested I try removing the reflectors from my wheels.
Ever heard of reflectors causing such a problem?