How tall of a tire? 26" tall or less, I'd probably go 2.76. 27-29" tall, 2.94, 30-32" tall, probably 3.23's

I had 3.55's and 27" tall tires and HATED it on the interstate (speed limit 70). was buzzing along at 3000-3300 RPM. I'd get a headache after about a half hour from the noise. I kept them but put in an A500 OD, and dropped it to an effective 2.45....

another option would be to use an A833OD (.73 OD) or a Passon OD (.8 OD). would turn your 3.91's into 2.85's or 3.13's effectively....