*Keep in mind, these are only general recommendations for spring rates to get you close for your weight. Optimum spring rate is affected by countless variables including riding style, preference, pace, track layout and surface finish, and bike geometry and suspension setup. Generally faster racers will prefer springs at the stiffer end of their range.
OEM Fork Springs are .70-1.07 progressive rate, OEM Shock spring is ___
| Kawasaki Ninja 400 / Z400 (all years) | ||
| Rider Weight (not including riding gear) | Fork Spring Rate | Shock Spring Rate |
| <120 | .66 kg | 400 (70N) |
| 110-140 | .70 kg (7.0N) | 425 (75N) |
| 120-150 | .725 kg (7.25N) | 450 (80N) |
| 130-160 | .75 kg (7.5N) | 475 (85N) |
| 140-170 | .775 kg (7.75N) | 500 (90N) |
| 155-185 | .80 kg (8.0N) | 525 (90N) |
| 175-205 | .825 kg (8.25N) | 550 (95N) |
| 190-220 | .85 kg (8.5N) | 575 (100N) |
| 210-240 | .875 kg (8.75N) | 600 (105N) |
| 225-255 | .90 kg (9.0N) | 625 (110N) |
| 235-275 | .925 kg (9.25N) | 650 (115N) |
| 250-280 | .95 kg (9.5N) | 700 (120N) |
| 270-300 | .975 kg (9.75N) | 750 (130N) |
| >290 | 1.0 kg (10.0N) | 750 (130N) |