As a rule of thumb, you will feel front rotor warpage in your hands at the steering wheel. You will feel rear rotors in your ass.
Get the car up to speed with no cars around then hit the brakes fairly hard. See where you feel it, your hands or your ass.

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'85 300SD (formerly california emissions)
'08 Chevy Tahoe
'93 Ducati 900 SS
'79 Kawasaki KZ 650
'86 Kawasaki KX 250
'88 Kawasaki KDX200
'71 Hodaka Ace 100
'72 Triumph T100R