Springs

From Nissan 350Z & 370Z Wiki

Aftermarket springs can improve performance, feel, and looks of you 350Z. The stock suspension is designed to accommodate a wide range of drivers but you should tune the suspension to fit your personal taste. A lower car will have a lower center of gravity resulting in less body roll through corners.

Stiffer springs can help plant the car better, but choosing springs that are too stiff will result in undesirable feel and handling. If excessive stiffness is wanted, shock absorbers should be changed along with springs.

It is impossible to recommend the best spring for any application without defining which shock absorber is used. The 10kg/mm spring in most Japanese coilover kits are perfectly suited for the shocks they come with, but coupled with the OEM shocks (that were a 4.9kg spring) the ride and handling would be woeful.

Contents 1 OEM Spring Identification 2 Under 1" Drop 2.1 Cobb Tuning Sport 2.2 Espelir GT Springs 2.3 Hotchkis Sport 2.4 kgmm Street Sport 2.5 RSR Down / Ti2000 2.6 Tein H-Tech 2.7 Tein S-Tech 3 Over 1" Drop 3.1 B&G Sport 3.2 B&G Sport (convertible) 3.3 Eibach Pro Kit 3.4 Eibach Sportline Kit 3.5 H&R Sports 3.6 KG/mm Racing 3.7 Megan Racing 3.8 Nismo SCCA T2 3.9 Progress Sports 3.10 Skunk2 3.11 Sprint: Performance 3.12 Swift 3.13 Tanabe: Sustec GF210 3.14 Tanabe: Sustec NF210 4 G35 Specific 4.1 Eibach Pro Kit 4.2 RSR Down /Ti2000 4.3 Tein H-Tech 4.4 Tein S-Tech 5 Spring Comparison Table 6 Spring Types 6.1 From Car Bibles Web Site

OEM Spring Identification

OEM 350Z springs can be identified by the color coded dots on the rear springs. All 350Z front springs math out to the same 314lbs spring rate.

Coupe:

03/04 unrevised rear springs have 2 red dots and one white dot or all red dots. (342lbs in rate)

04.5-06 revised rear springs have 2 red dots and one light purple dot. (427lbs in rate)

Roadster:

Front: 1 light blue dot (314lbs in rate)

Rear: 2 red 1 light blue (427lbs in rate)

In the end a 427lbs rear spring will have a thicker wire diameter then a 342lbs spring has.

Under 1" Drop

Cobb Tuning Sport List Price: $300 Found Price: $275 Part #: 9A1750 Design: ? F Drop: 19mm (.75in) R Drop: 24mm (1.0in) F Stiffness: 345 R Stiffness: 438 Manufacturer: Cobb Tuning	Espelir GT Springs List Price: $280 Found Price: $225 Design: appears to be linear F Drop: 10mm (.4in) R Drop: 10mm (.4in) F Stiffness: 6.9 (385) R Stiffness: 9.2 (514) Manufacturer: Espelir	Hotchkis Sport List Price: $174 Found Price: $149 Design: Linear F Drop: 15mm (.6in) R Drop: 19mm (.75in) F Stiffness: 6.1kg/mm (340lb) (+8%) R Stiffness: 5.9kg/mm (330lb) (-3%) Stiffness transfer: 12% to Front Manufacturer: Hotchkis	kgmm Street Sport Found Price: $309 Design: Dual Rate F Drop: 15mm (.6in) R Drop: 15mm (.6in) F Stiffness: 4.4-7.1kg/mm (260-419lb) R Stiffness: 4.5-7.3kg/mm (266-431lb) Manufacturer: Kgmm
RSR Down / Ti2000 List Price: $249/349 Found Price: $220/300 Design: Linear F Drop: 15mm (.6in) R Drop: 15mm (.6in) F Stiffness: 6.2kg/mm (345lb) (+10%) R Stiffness: 7.5kg/mm (417lb) (+22%) Stiffness transfer: 12% to Rear Manufacturer: RSR Notes: Ti2000 is titanium	Tein H-Tech List Price: $220 Found Price: $165 Design: F: Progressive R: Linear F Drop: 7mm (.3in) R Drop: 4mm (.2in) F Stiffness: 6.4kg/mm (358lb) (+14%) R Stiffness: 6.7kg/mm (375lb) (+11%) Stiffness transfer: 3% to Front Manufacturer: Tein	Tein S-Tech List Price: $210 Found Price: $158 Design: F: Progressive R: Linear F Drop: 17mm (.7in) R Drop: 14mm (.6in) F Stiffness: 6.9kg/mm (386lb) (+23%) R Stiffness: 7.2kg/mm (402lb) (+16%) Stiffness transfer: 7% to Front Manufacturer: Tein

Over 1" Drop

B&G Sport List Price: $299 Found Price: ---- Design: Progressive F Drop: 25mm (1in) R Drop: 25mm (1in) F Stiffness: ---- R Stiffness: ---- Manufacturer: B&G	B&G Sport (convertible) List Price: $299 Found Price: ---- Design: Progressive F Drop: 25mm (1in) R Drop: 25mm (1in) F Stiffness: ---- R Stiffness: ---- Manufacturer: B&G	Eibach Pro Kit List Price: $369 Found Price: $249 Part #: 6364.140 Design: Progressive F Drop: 25mm (1in) R Drop: 25mm (1in) F Stiffness: 296-384 R Stiffness: 316-421 Manufacturer: Eibach	Eibach Sportline Kit List Price: $369 Found Price: $249 Part #: 4.6463 Design: Progressive F Drop: 30mm (1.2in) R Drop: 30mm (1.2in) Manufacturer: Eibach
H&R Sports List Price: $389 Found Price: $292 Design: ---- F Drop: 33mm (1.3in) R Drop: 25mm (1in) F Stiffness: ---- R Stiffness: ---- Manufacturer: H&R	KG/mm Racing List Price: 42,000yen Found Price: ---- Design: Dual Rate F Drop: 30mm (1.2in) R Drop: 30mm (1.2in) F Stiffness: 4.5-8.1kg/mm (266-478lb) R Stiffness: 4.5-8.6 (266-507lb) Manufacturer: Kgmm	Megan Racing List Price: $160 Found Price: $139 Part #: MR-LS-N3Z Design: ? F Drop: 32mm (1.25in) R Drop: 32mm (1.25in) F Stiffness: ? R Stiffness: ? Manufacturer: Megan Racing	Nismo SCCA T2 List Price: ---- Found Price: $395 Design: Progressive F Drop: (1.0in) R Drop: (1.0in) F Stiffness: 10.7kg/mm (600lb) R Stiffness: 12.3kg/mm (690lb) Manufacturer: Nismo
Progress Sports List Price: $189 Found Price: ---- Design: ---- F Drop: --mm (1.0in) R Drop: --mm (1.0in) F Stiffness: ---- R Stiffness: ---- Manufacturer: Progress Group	Skunk2 List Price: $239 Found Price: $179 Part #: 519-07-1920 Design: ? F Drop: 64mm (2.5in) R Drop: 64mm (2.5in) F Stiffness: ? R Stiffness: ? Manufacturer: Skunk2	Sprint: Performance List Price: $329 Found Price: ---- Design: ---- F Drop: 44mm (1.75in) R Drop: 44mm (1.75in) F Stiffness: ---- R Stiffness: ---- Manufacturer: Sprint	Swift List Price: $369 Found Price: $307 Part #: 4N903 Design: ? F Drop: 20mm (.8in) R Drop: 16mm (.6in) F Stiffness: ? R Stiffness: ? Manufacturer: Swift
Tanabe: Sustec GF210 List Price: $330 Found Price: $240 Design: Linear F Drop: 25mm (1in) R Drop: 30mm (1.2in) F Stiffness: 6kg/mm (335lb) R Stiffness: 6.7kg/mm (374lb) Manufacturer: Tanabe	Tanabe: Sustec NF210 List Price: $330 Found Price: $240 Design: Linear F Drop: 30mm (1.2in) R Drop: 30mm (1.2in) F Stiffness: 5.6kg/mm (313lb) R Stiffness: 6.3kb/mm (352lb) Manufacturer: Tanabe

G35 Specific

Eibach Pro Kit List Price: $369 Found Price: $249 Design: Progressive F Drop: 25mm (1in) R Drop: 25mm (1in) F Stiffness: 229-337 R Stiffness: 274-463 Manufacturer: Eibach

RSR Down /Ti2000 List Price: $249/349 Found Price: $220/300 Design: Linear F Drop: 15mm (.6in) R Drop: 15mm (.6in) F Stiffness: (315lb) (+0%) R Stiffness: (315lb) (-8%) Stiffness transfer: 8% to Front Manufacturer: RSR

Tein H-Tech List Price: $220 Found Price: $165 Design: F: Progressive R: Linear F Drop: 7mm (.3in) R Drop: 4mm (.2in) F Stiffness: (324lb) (+5%) R Stiffness: (260lb) (-22%) Stiffness transfer: 27% to Front Manufacturer: Tein

Tein S-Tech List Price: $210 Found Price: $158 Design: F: Progressive R: Linear F Drop: 17mm (.7in) R Drop: 14mm (.6in) F Stiffness: (358lb) (+14%) R Stiffness: (274lb) (-18%) Stiffness transfer: 32% to Front Manufacturer: Tein

Spring Comparison Table

Below, we have all of the currently available Nissan 350Z performance springs (at least from reputable companies - we do not believe in endorsing cheap eBay crap). There are two sections below: springs with a mild drop (under 1 inch), and springs with a more aggressive drop (springs 1 inch and over).

Use the spring rates and other data as reference, and keep in mind spring rates may be measured differently between manufacturers. Rates are converted as 1Kg/mm = 56 lb/in. and 1Kg/mm = 9.86 N/mm.

OEM Spring Rates 03-04

• F: 314
• R: 342

OEM Spring Rates 04.5-On

• F: 314
• R: 427

Spring	F Drop	R Drop	F Rate	R Rate	Type	Price
B&G	25mm	25mm	---	---	Progressive	---
Eibach	25mm	25mm	---	---	Progressive	$250
Espelir	25mm	25mm	6.9	9.2	Linear	$225
Hotchkis	15mm	19mm	6.1	5.9	Linear	$149
H&R	33mm	25mm	6.9	9.2	---	$292
kg/mm Street	15mm	15mm	4.4-7.1	4.5-7.3	Dual Rate	$309
kg/mm Racing	30mm	30mm	4.5-8.1	4.5-8.6	Dual Rate	---
Nismo	25mm	25mm	10.7	12.3	Linear	$395
Progress Sports	25mm	25mm	---	---	---	$189
RS-R	15mm	15mm	6.2	7.5	Linear	$220/300
Sprint	44mm	44mm	---	---	---	$329
Tanabe GF210	25mm	30mm	6.0	6.7	Linear	$240
Tanabe NF210	30mm	30mm	5.6	6.3	Linear	$240
Tein H-Tech	7mm	4mm	6.4	6.7	Linear	$165
Tein S-Tech	17mm	14mm	6.9	7.2	Linear	$158

Spring Types

There are two types of spring designs: linear and progressive. This refers to their rates as the spring is compressed.

Linear springs have the same spring rate from the initial compression all the way to full compression. If a linear spring is rated at 6.2kg/mm (and lets say its range of movement is 50mm) then it takes 6.2kg to compress the spring from 0mm-1mm and 6.2kg to move it from 49mm-50mm.

A progressive spring will have a softer rate for its first few mm of travel, which then increases as you increase the load on it. Lets say we have a progressive rate spring with the same range of movement as above. While it may only take 4.4kg to move it from 0mm-1mm, it may need 7.1kg to move it from 49mm-50mm.

A progressive rate spring is clearly a compromise between softness for ride and firmness for handling. As such, it is more suited for the street. The softer initial rate gives it better compliance, especially over a low amplitude bump. But once you start loading up the suspension the firmer it becomes, so your flat-out cornering is improved.

A linear rate spring would be a better choice for the track, where you do not need to compromise handling for anything. Consistency in the spring rate gives you a better feel, since the car's weight shift isn't as variable. Since your springs are at maximum stifness, initial response is quicker as the car won't want to lean onto its outside suspension as much before the spring resists the movement and the car starts to turn.

From Car Bibles Web Site

Source: http://www.carbibles.com/suspension_bible.html
These come in three types. They are coil springs, torsion bars and leaf springs. Coil springs are what most people are familiar with, and are actually coiled torsion bars. Leaf springs are what you would find on most American cars up to about 1985 and almost all heavy duty vehicles. They look like layers of metal connected to the axle. The layers are called leaves, hence leaf-spring. The torsion bar on its own is a bizarre little contraption which gives coiled-spring-like performance based on the twisting properties of a steel bar. It's used in the suspension of VW Beetles and Karmann Ghias, air-cooled Porsches (356 and 911 until 1989 when they went to springs), and the rear suspension of Peugeot 205s amongst other cars. Instead of having a coiled spring, the axle is attached to one end of a steel shaft. The other end is slotted into a tube and held there by splines. As the suspension moves, it twists the shaft along it's length, which in turn resist. Now image that same shaft but instead of being straight, it's coiled up. As you press on the top of the coil, you're actually inducing a twisting in the shaft, all the way down the coil. I know it's hard to visualise, but believe me, that's what is happening. There's a whole section further down the page specifically on torsion bars and progressive springs.

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