I like this routine (28.5" thighs here)
5 minutes on a stairmaster to warm up (not joking)
3 sets of barbell squats: 15, 12, 8 (15 reps means you fail at 14 but you tried as hard as you could without dying to get 15)
2 sets of Hack squats OR Leg press: 12, 10
*1 set of leg extensions (optional) of 12 reps followed by 2 drop sets or 5-10 forced reps with a partner.
Stiff leg deadlift: 12, 10, 7
standing calf raise (or on leg press machine): 3x 10-12 reps
seated calf raise 2x 15
now go do 5 more minutes of max speed on the stairmaster (not joking)