My primary objection to anything larger than 15" on pre-1980 classics is that their suspension is not designed/calibrated for larger rims/lower cross section tires. My '66 Barracuda has 17 Torq-Thrust with 225 45R17 Yokohamas mounted on them. It rides terrible compared to my first '66 that had 15" with Goodyears mounted on it. The lower cross section tires do not have enough compliance to absorb bumps etc that the larger 15 inch rubber has. I will change them out ASAP when tire time comes around. A set of steel Magnums in 15" is perfect for me.
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