dictionary.reference.com/

(emphasis mine)

WRACK
noun
1. wreck or wreckage.
2. damage or destruction: wrack and ruin.
3. a trace of something destroyed: leaving not a wrack behind.
4. seaweed or other vegetation cast on the shore.

verb (used with object)
5. to wreck: He wracked his car up on the river road.

RACK
noun
1. a framework of bars, wires, or pegs on which articles are arranged or deposited: a clothes rack; a luggage rack.
2. a fixture containing several tiered shelves, often affixed to a wall: a book rack; a spice rack.
3. a spreading framework set on a wagon for carrying hay, straw, or the like, in large loads.
4. Pool.
a. a wooden frame of triangular shape within which the balls are arranged before play.
b. the balls so arranged: He took aim at the rack.
5. Machinery.
a. a bar, with teeth on one of its sides, adapted to engage with the teeth of a pinion (rack and pinion) or the like, as for converting circular into rectilinear motion or vice versa.
b. a bar having a series of notches engaging with a pawl or the like.
6. a former instrument of torture consisting of a framework on which a victim was tied, often spread-eagled, by the wrists and ankles, to be slowly stretched by spreading the parts of the framework.
7. a cause or state of intense suffering of body or mind.
8. torment; anguish.
9. violent strain.
10. a pair of antlers.
11. Slang. a bed, cot, or bunk: I spent all afternoon in the rack.

verb (used with object)
12. to torture; distress acutely; torment: His body was racked with pain.
13. to strain in mental effort: to rack one’s brains.
14. to strain by physical force or violence.
15. to strain beyond what is normal or usual.
16. to stretch the body of (a person) in torture by means of a rack.

So yes, both can be used. But which seems better: the word for which the primary definitions match the meaning, or the one for which only a few rarely-used instances do?

[img]http://picturehoster.info/images/82024001544574379864.gif[/img]