I'm one of the folks who did it on my car WITHOUT using a spring compressor - just lowered the control arm, and observed that when it's fully lowered, the spring is barely compressed and does not "pop" out like everyone says it will (as long as you lower the control arm very slowly). In fact, I had to use a prybar to get the spring out of the control arm indentation. I think the risk of injury using this method is very minimal as long as you do things slowly, and for added safety I managed the jack from the opposite side of the car, reaching across underneath. HOWEVER - I did this on my W124. I have no idea if it will work on the W210, but am researching the matter as I plan to replace a ball joint soon. If you find out, please post back!

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280