The C43 suspension is probably the stiffest of all the AMG cars -- fine for the driver, but not much fun for passengers on long trips. I found that ride improved somewhat in switching from Michelin Pilot Sports to Sumitomo ZR-IIs.

I suspect that you would spend a lot of $$ in trying to switch a C280 to AMG suspension specs and you'd still have only a C280 -- why not just go ahead and trade up for a C36 and get the real AMG engine, brakes, exhaust, etc. instead of pouring $$ into the C280 that you'd never get back. C36s are available now down around $20M.

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'98 C43 AMG
'88 420SEL
'93 190E Limited Edition (including factory Sportline package)