Why the G and the Z Need Different Suspension Setups

The Nissan Z and the Infiniti G share a platform. They do not share a wheelbase, they do not share a weight distribution, and they should not share a rear suspension setup. Yet if you shop coilovers for a G35 or a G37, you will find that most of what's on the market is a Z kit with a different part number on the box.

We build for both. We've valved a lot of these cars for time attack, HPDE, and autocross, and the rear of a G does not want what the rear of a Z wants. This article covers why — the geometry, the objection that gets raised against it, what we've actually found building these cars, and the damper hardware it takes to do anything about it.

Start with the numbers nobody puts on the box

Here is the platform, laid out properly:

Two things jump out.

First, the G35 coupe and the G37 coupe run the same 112.2-inch wheelbase. Infiniti did not move. (The G37 sedan is 114.2 inches, for anyone who wants to be precise about it.)

Second, the Z is what changed. The 370Z came back shorter than the 350Z — 100.4 inches, down almost four inches. So the gap between the Z and its Infiniti sibling grew from 7.9 inches in the Z33/V35 era to 11.8 inches in the Z34/V36 era. Nearly a foot of wheelbase, on cars that share a chassis family and, in most catalogs, a coilover.

Why wheelbase changes the math

Longitudinal weight transfer — the load that moves rearward when you get on the throttle — comes out of a simple relationship:

ΔW = (W × a × h) ÷ L

Where W is vehicle weight, a is longitudinal acceleration in g, h is center of gravity height, and L is wheelbase.

Wheelbase sits in the denominator. A longer car transfers less weight for the same throttle input. Run the geometry and the G35 transfers about 7% less of its weight rearward than a 350Z; the G37 about 11% less than a 370Z.

That's the number. There's one objection worth dealing with before we go further, because it comes up every time.

"But the G is heavier — doesn't that cancel it out?"

On a showroom-stock car, partly. Weight sits in the numerator. A G35 carries roughly 220 lb over a 350Z and a G37 roughly 300 lb over a 370Z, and that mass moves rearward under throttle along with everything else.

Now look at where that weight lives. Almost all of the G's penalty over the Z sits behind the driver: the rear seat and its supporting structure, the rear interior panels and trim, the sound deadening Infiniti used to make the car quiet, the extra sheet metal that comes with a longer body.

That is exactly the weight that leaves a track car first. Gut a G35 or a G37 and you delete a back seat the Z never had, strip the rear interior, and pull the deadening. In track-prepped form, a G lands within a few dozen pounds of a comparably prepped Z. The weight gap is a street-car artifact.

Center of gravity height follows the same pattern. Most of the G's height advantage over the Z is interior — the taller factory seating position and the trim around it. Fit a properly mounted race seat and that difference largely goes away too.

So on the cars we actually build for, W converges and h converges. Wheelbase doesn't. It is the one term in that equation that survives a track prep, which means 7% and 11% aren't a theoretical best case. They're the operating condition.

There's a second-order effect worth noting on top. Stripping weight out of the rear shifts the distribution forward, so a prepped G's rear axle is carrying less static load to begin with — and then receives a smaller share of the car's weight on throttle. Both directions point the same way.

What that costs you on corner exit

Grip scales with load. When the rear axle gains weight under throttle, the rear tires gain grip, and that is what lets you get back to power early and stay there. A 7% shortfall on a G35, or 11% on a G37, is a direct reduction in the extra grip the rear tires are handed on every single exit.

The geometry compounds it. The same amount of rear suspension travel spread over a wheelbase a foot longer produces a smaller pitch angle. The car rotates less about its lateral axis, so the rear tires see less dynamic camber change and the driver gets a weaker signal that the car has taken a set.

The net is that a G does not get the same free grip on exit that a Z does. The Z loads its rear tires hard and rewards you for it. The G is more grudging about it.

What we've found building these cars

Here's the part that matters more than any equation: we've built and valved a lot of Z and G kits, and the pattern is consistent.

Take a rear spring rate that works beautifully on a 350Z or 370Z and bolt it into the corresponding G, and the car goes numb on exit. Not loose, exactly — numb. The rear never settles into the tire. It skates across the surface instead of digging in, and the driver ends up waiting for grip that never quite shows up. On a long, throttle-dominant corner, that's tenths.

The G wants a softer rear spring and softer rear compression damping than the Z. You want to let the rear squat. You want the load transfer that is available to actually arrive at the contact patch, slowly enough that the tire can use it, rather than being fought by a spring and a compression stack specified for a shorter chassis.

Stiffening the rear of a car that's already stingy about loading its rear axle is exactly backwards. It's the most common mistake we see on customer cars that arrive with someone else's kit already installed.

Why you can't just turn compression down

This is where the setup runs into the hardware.

Say you accept the argument and decide you want less rear compression damping. On a conventional damper, softening compression means softening the whole valving character. You get your squat — and you also get a rear end that floats, pitches, and takes too long to settle. Come off a curb or hit a compression, and the car takes a second bounce you didn't ask for. You've traded exit grip for platform control, which is not a trade worth making.

The two motions are asking for opposite things:

• Compression — the damper being squeezed as the rear squats. You want this soft, so the tire loads progressively and plants.
• Rebound — the damper extending as the rear comes back up. You want this stiff, to control how fast the car unloads, kill the second bounce, and keep the platform from wallowing.

Soft one way, stiff the other, on the same corner of the car. On a damper where those two circuits share a path, you can't have both.

The check valve

The way we solve this is a check valve that separates the compression and rebound circuits inside the damper, so oil takes a different route depending on which way the shaft is moving.

Because the paths are separate, the two can be valved independently. We can run genuinely soft compression on the rear of a G — soft enough to let it squat and plant the tire the way the chassis needs — while holding stiff rebound to control the return stroke. No float. No wallow. No second bounce. The rear loads on throttle and then comes back up under control.

That's the mechanism that makes a G-specific rear setup possible at all. Without circuit separation, "softer compression, stiffer rebound" is just a thing you say. We go deeper on the hardware itself in our tech tip on what a check valve does in a performance damper, and every kit we ship includes CVP and PVP dyno graphs so you can see the split — our guide to reading shock dyno sheets covers how to interpret them.

What this means for our own kits

Worth addressing directly, because you'll notice it on our product pages: our 350Z/G35 and 370Z/G37 kits are listed as combined fitments, with published spring rate baselines like 20k front / 8k rear for Track/Race.

Those published rates are baselines, not the spec you receive. Every TL-ONE and TL-PRO kit is built to order, and we contact you before anything is assembled to confirm the car, the use case, tire size, sway bars, ride height, how far the car has been stripped, and corner weights if you have them. A G build does not leave with the Z's rear spring and the Z's rear compression stack. The chassis is confirmed during the build and the rear is specified for it.

That is the actual difference between a build-to-order kit and a box on a shelf. The box cannot know which car it's going on. We ask.

If you're setting up a G right now

A few things worth getting right beyond the dampers:

• Don't chase the Z's rear spring rate. Whatever number your friend runs in his 350Z is the wrong starting point for your G35, and the gap is wider still between a 370Z and a G37.
• Tell whoever is valving your dampers how far the car is stripped. A gutted G and a full-interior G are different cars, and the rear is where the difference shows up.
• Rear compression is the adjustment that matters most on exit. If your kit only offers combined adjustment, you're tuning a compromise.
• Get the rear geometry sorted first. Spring and damping decisions assume the rear suspension is actually locating the wheel — see our notes on true rear vs OEM rear on the Z and G platforms and on track alignment basics for these chassis.
• Baseline rates are a starting point. Our breakdown of track, street, and drift spring rates for the 350Z and G35 walks through how we pick them.

If you want to see where this ends up in practice, our G35 time attack build spotlight covers a car set up this way.

The short version

Same platform, different wheelbase. Eight inches on the Z33/V35 pair, almost twelve on the Z34/V36 pair. The G's extra street weight is rear-biased and comes out during a track prep, so wheelbase is the term that actually reaches the car you're driving — roughly 7% less rear load transfer on a G35, 11% on a G37.

The G wants a softer rear spring and softer rear compression than the Z, with stiff rebound holding the platform. Doing that requires a damper that separates the two circuits. Everything else is a compromise dressed up as a fitment.

Frequently Asked Questions

Getting a kit spec'd for your chassis

Our TL-ONE single-adjustable and TL-PRO 3-way systems are both built to order for the Z and G platforms, with the rear specified for the car it's actually going on:

• 350Z / G35 TL-ONE Coilover System — single-adjustable, true rear
• 370Z / G37 TL-ONE Coilover System — single-adjustable, true rear
• 350Z / G35 TL-PRO Coilover System — 3-way, remote reservoir
• 370Z / G37 TL-PRO Coilover System — 3-way, remote reservoir

Tell us the chassis, how the car is built, and how you use it, and we'll spec the rear for it.