I've personally only owned the iron caliper setup, but I will say that with them, inducing wheel lockup was never a problem-tire adhesive traction was the limiting factor with regard to braking.

I will say, though, that I've driven 2 500Es with the alloy brembo calipers, and they felt and acted the same as the 500SL iron binders. I'd think the biggest potential benefit to the alloy bits would be unsprung weight, but in that regard I was unable to tell the difference (didn't have the opportunity to drive the different setups back-to-back).

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"If God had meant for us to walk, why did he give us feet that fit car pedals?" Sir Sterling Moss

Michael
2014 E63S Estate
2006 SLK55
1995 E500
1986 Porsche 944 turbo