I seem to remember going through this myself but the details are foggy. I think some of the wheel covers are harder to get the clips in than others....perhaps.

The steel wheels are thinner in section than the aluminum wheels so the steel clips will be too tight on the alloy wheels.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.