After using the recommended lift point for my mazda 3, the front crossmember seems dented in by the floor jack. I think I should have used wood, but the manual indicated to use only on the rear crossmember. What if any would be the problems associated with a dented crossmember?
Cross members are added to give the vehicle strength, support, and reduce flex. A dented cross member will be weakened just like putting a crease in a metal can. If it is badly out of shape it could cause misalignment in body panels, or may affect wheel alignment. To reduce the vehicles weight the cross members are shaped to give strength to relatively light weight metals.
Your dent changes the shape and weakens the cross member. How much of a problem it is depends on the purpose of the cross member and the extent of the “dent”. A body shop is the best place I can think of to get a dependable opinion on whether this is a big deal, or not.