Z31 Suspension Spring Differences
Looking to upgrade the handling or stance of your Z31? If your rear is sagging or you want a firmer ride, this guide covers everything you need to know about Z31 (1984-1989 300ZX) springs—stock, aftermarket, and interchangeable options.
Swapping Factory Springs
- Spring swaps between years/models: Any Z31 spring fits any Z31. You may see minor changes in ride height or stiffness depending on which model's springs you use.
- Factory Performance: 1987–1989 Turbo models have stiffer springs than Non-Turbo models.
- Stiffest Stock Option: The 1988 Shiro Special Edition springs are the firmest you can get from the factory.
Aftermarket Spring Options
- Popular brands: Eibach, Tokico, and more are available for the Z31.
- Progressive Rate (Variable) Springs: Eibach springs, for example, are variable rate. They offer a smooth ride in normal driving and stiffen up during hard cornering for better handling.
- How to identify: Progressive springs have one end with tighter coils—these compress first for comfort, while the rest engage for performance as you push harder.
*WARNING* - Do this modification at your own risk. We Are not responsable for any issues of your own doing.
Spring Lookup Tool
Use the charts below to identify the model and specs of your Z31 springs. Clean your spring and look for the color code—it will be two dots painted on the spring coils. The color combination identifies the spring model, and you can check the rates listed in the tool below.
Front Springs
| Spring # | Color Code (Top / Bottom) |
Wire Diameter (mm/in) |
Coil Diameter (mm/in) |
Free Length (mm/in) |
Spring Rate Constant (N/mm / kg/mm / lb/in) |
|---|---|---|---|---|---|
| 1 | red / white | 13.5 (0.531) | 170 (6.69) | 293.5 (11.56) | 23.83 (2.43) (136.1) |
| 2 | white / white | 13.5 (0.531) | 170 (6.69) | 306.0 (12.05) | 23.83 (2.43) (136.1) |
| 3 | yellow / white | 13.5 (0.531) | 170 (6.69) | 300.0 (11.81) | 23.83 (2.43) (136.1) |
| 4 | white / white | 13.8 (0.543) | 170 (6.69) | 306.0 (12.05) | 23.83 (2.43) (136.1) |
| 5 | yellow / white | 14.0 (0.551) | 170 (6.69) | 300.0 (11.81) | 23.83 (2.43) (136.1) |
| 6 | blue / white | 13.8 (0.543) | 170 (6.69) | 312.5 (12.30) | 23.83 (2.43) (136.1) |
| 7 | yellow / white | 13.8 (0.543) | 170 (6.69) | 294.5 (11.59) | 25.5 (2.6) (146) |
| 8 | yellow / orange | 14.8 (0.583) | 170 (6.69) | 268.5 (10.57) | 34.3 (3.5) (196) |
| 9 | blue / orange | 13.9 (0.547) | 170 (6.69) | 318.5 (12.54) | 23.83 (2.43) (136.1) |
| 10 | orange / pink | 14.5 (0.571) | 170 (6.69) | 263.0 (10.35) | 36.3 (3.7) (207) |
The table above shows the color codes and specs for all factory Z31 front springs. The chart below shows which models came with each type of spring from the factory.
| Spring Code | Year | Seats | Model | Roof | Engine |
|---|---|---|---|---|---|
| 1 | 1984 | 2 | SF/GL | All Roof Type | Non-Turbo |
| 1 | 1984 | 2 | All Trims | All Roof Type | Turbo |
| 2 | 1984 | 4 | All Trims | All Roof Type | Non-Turbo |
| 3 | 1984 | 2 | GLL | All Roof Type | Non-Turbo |
| 3 | 1984 | 4 | All Trims | All Roof Type | Turbo |
| 4 | 1985-1986 | 2 | GLL | All Roof Type | Non-Turbo |
| 4 | 1985 | 4 | All Trims | All Roof Type | Turbo |
| 5 | 1985 | 2 | All Trims | All Roof Type | Turbo |
| 5 | 1985-1986 | 2 | SF/GL | All Roof Type | Non-Turbo |
| 6 | 1987-1989 | 2 | All Trims | All Roof Type | Non-Turbo |
| 6 | 1985-1986 | 4 | All Trims | All Roof Type | Non-Turbo |
| 7 | 1984 | 2 | 50th AE | T-Top | Turbo |
| 7 | 1986 | 2 and 4 | All Trims | All Roof Type | Turbo |
| 8 | 1987-1989 | 2 and 4 | All Trims | All Roof Type | Turbo |
| 9 | 1987-1989 | 4 | All Trims | All Roof Type | Non-Turbo |
| 10 | 1988 | 2 | Shiro | T-Top | Turbo |
Rear Springs
Here you will find the Color Codes and rates for the Stock Rear Springs installed in the Z31 Chassis.
| # | Color Code (Top / Bottom) |
Wire Dia. (mm/in) |
Coil Dia. (mm/in) |
Free Length (mm/in) |
Spring Rate N/mm (kg/mm) [lb/in] |
|---|---|---|---|---|---|
| 1 | 1 Red / 2 Yellow | 12.8 / 0.504 | 110 / 4.33 | 364 / 14.33 | 24.5 (2.5) [140] |
| 2 | 1 Yellow / 2 Yellow | 13.0 / 0.512 | 110 / 4.33 | 370 / 14.57 | 24.5 (2.5) [140] |
| 3 | 1 White / 2 White | 13.0 / 0.512 | 110 / 4.33 | 376 / 14.80 | 24.5 (2.5) [140] |
| 4 | 1 Red / 2 White | 13.2 / 0.520 | 110 / 4.33 | 382 / 15.04 | 24.5 (2.5) [140] |
| 5 | 1 Red / 2 White | 13.2 / 0.520 | 111.2 / 4.38 | 382 / 15.04 | 24.5 (2.5) [140] |
| 6 | 1 White / 2 Yellow | 13.0 / 0.512 | 110 / 4.33 | 376 / 14.80 | 24.5 (2.5) [140] |
| 7 | 1 White / 2 Yellow | 13.2 / 0.520 | 110 / 4.33 | 376 / 14.80 | 24.5 (2.5) [140] |
| 8 | 1 Purple / 2 Yellow | 13.8 / 0.543 | 110 / 4.33 | 336.5 / 13.25 | 33.0 (3.36) [188.2] |
| 9 | 1 White / 2 Yellow | 13.0 / 0.512 | 111.0 / 4.37 | 376 / 14.80 | 24.5 (2.5) [140] |
| 10 | 1 Purple / 2 Yellow | 13.8 / 0.543 | 111.8 / 4.40 | 336.5 / 13.25 | 33.0 (3.36) [188.2] |
| 11 | 1 Green / 2 Yellow | 13.3 / 0.524 | 111.3 / 4.38 | 388 / 15.28 | 24.5 (2.5) [140] |
| 12 | 1 Pink / 2 White | 13.8 / 0.543 | 111.8 / 4.40 | 341.0 / 13.43 | 33.0 (3.36) [188.2] |
| 13 | 1 White / 1 Purple | 13.5 / 0.531 | 110.0 / 4.33 | 317.0 / 12.48 | 39.2 (4.0) [224] |
Standard spring rates are 24.5 N/mm (2.5 kg/mm or 140 lb/in) unless noted. Shorter/stronger springs are for sportier applications.
Color codes are marked on the coil (top / bottom).
The below table will show you what models had what rear springs installed from the factory.
| Spring Code | Year | Number of Seats | Model Trim | Roof Type | Engine |
|---|---|---|---|---|---|
| 1 | 1984 | 2 | GL | Hard Top | Non - Turbo |
| 1 | 1984 | All | GL | All | Turbo |
| 2 | 1984 | 2 | GL | T-Top | Non - Turbo |
| 2 | 1984 | 4 | GL | All | Non - Turbo |
| 2 | 1984 | All | GLL | All | Turbo |
| 3 | 1984 | 4 | GLL | T-Top | Non - Turbo |
| 4 | 1985 | 4 | GLL | T-Top | Non - Turbo |
| 4 | 1985 - 1986 | 2 | GLL | T-Top | Non - Turbo |
| 5 | 1987 - 1989 | All | GL | T-Top | Non - Turbo |
| 6 | 1985 | All | GLL | All | Turbo |
| 6 | 1985 - 1986 | All | GL | T-Top | Non - Turbo |
| 6 | 1986 | 2 | GL | Hardtop | Non - Turbo |
| 7 | 1986 | 4 | GLL | T-Top | Non - Turbo |
| 8 | 1984 | 2 | 50th AE | T-Top | Turbo |
| 8 | 1986 | All | All | All | Turbo |
| 9 | 1987 - 1989 | 2 | GL | Hardtop | Non - Turbo |
| 10 | 1987 - 1989 | All | GL | All | Turbo |
| 11 | 1987 - 1989 | All | GLL | T-Top | Non - Turbo |
| 12 | 1987 - 1989 | All | GLL | All | Turbo |
| 13 | 1988 | 2 | Shiro | T-Top | Turbo |
Sources Used
- 1984-1988 Nissan 300ZX Factory Service Manual
- Information on Spring rates and color coding by - Paul "Az-zbum" Hillman