In the "real world" you'll find they are hard as bricks and will make you regret the choice every day. You'd be far better off getting the spare if you want "piece (sic) of mind". The side walls are extremely stiff and will really make you feel every bump in the road, not to mentions strips on concrete roads.

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'07 CS, Meteor Grey, stone grey, 19" Carrera Sport with meteor grey spokes/polished rim, headrest crests, bi-xenons, Bose, power seats, rain sensor, fire extinguisher, heated seats, dimming mirrors, FabSpeed Maxflo II catback
'06 CLS 500, white, beige
'04 Black Ranger Edge