I am wondering if they are really the same or have they lowered the spring rates on the G35 Coupe 6MT?

My primary interst points are the LSD, springs and shocks, the brakes, and the 6MT transmission. Can someone confirm for sure that both cars use the same components or are there subtle differences?

Thank you all.

 

The Brembo brakes on the 350Z Track and G35 Coupe 6 speed are the same. The G35 has the same size tires front and rear as the Z but has a better compound tire (why I don't know).

Suspension. Well, although everyone says they are the same, there are slight differences. The spring and shock rates are a little softer. The actual suspension pieces (i.e., control arms, geometry, etc.) are the same, BUT.....the G35 does lack some of the underbody frame braces that the 350Z has. If you watch the Best Motoring 350Z video, they point out all the differences between the two cars, and in particular, how the 350Z has additional braces under the body to stiffen up the frame, something the G35 lacks.

 

Thank you vry much for the response, I appreciate.

If they kept the same spring rates between the two cars, the G35 would feel softer due to ~200lbs more weight, but if they actually lowered the rates, then that is not too good. But at the same time, reviews seem to praise the G35 handling.

Oh well, best way is to test drive one I guess, as if that is at all possible

 

A little softer, whoa, their's a big differance between them.

Here's the spring rates for the 350Z and the G35 coupe and sedan with sport suspension. I am currently testing 350Z springs and struts on my sedan.

350Z: 426/385 (F/R)
G35coupe & sedan w/sport: 355/308 (F/R)

Their are other differance's to add beside's the firmer dampning on the Z struts, which is logical given the Z's higher spring rates. In no way would I equate the differance as a little, they are allot firmer or I would NOT have done the swap. The Z strut bodies are shorter, 1" shorter in the rear and 3/4" shorter in the front. Also the springs themselves on the Z are shorter as well. This is why any published drop for Z springs will lower a G35 more. Z front springs are 1" shorter and the Z rear springs are. 1 1/4" shorter than the G35 springs.

 

Your on to something, drive the Z. If is certainly firmer than the G35. It is setup to let you push it to the limit more easily than the G35. Your able to actually get to it's limits and do it over and over much more easily than the G35, you may have higher peak numbers in the magizine test's. But the Z excell's at letting you reach it's peak number much more easily and with better repeatability. That is the differance. If your able to take a test drive in the Z and your able to reach it's limit's, along the way, you'll get your understanding.

 

Now this is good info. You know this for sure? If this is the case, then Tein Flex' 560f/560r springs should be great improvement, but I do not know if they fit the G.

I test drove the Z about 3 weeks ago for a good, long drive; several interstate ramps in/out and at that time, I noted that the Z took corners, in average, 10 mph faster than my 330Ci. The body lean was moderate and ride was not harsh. I was really impressed.

Unfortunately, I need the back seats of the G; and I do not want to make an assumption that the Z's and G's suspensions are identical. As your numbers point out, they are quite different

Any suggestions on which and where to get a coil-over system with may me 560# f with 650# r?

 

Well hold on, I may have jumped the gun. I had a engineer that I know work the spring rates up for me. He volenteered and I confirmed with gordon at Koni that this method is very accurate. Thing is I did not clarify with him if the rates he gave me are initial rate (no weight applied to the spirng) final rate (fully compressed till the coils bind) or if the rate is with the weight of the car resting on them. I'm rather certain the the rates he worked up for me are final rates, but I've emailed him for clarification. With the G35 springs off the car and the fact that I have a extra set of 350Z spring laying around I was able take the measurements my engineer friend needed.

wire diameter
number of active coils
width of the spirng itself

BTW, here's the spring rates for the Eibach springs, their spring rates are shown as initial rate and then the final rate. Word to the wise, Eibach's development car for the sedan did not have the sport suspension. Also the Eibach springs are progressive, vs the linear springs that come stock with the G and Z. It is very rare to find coilovers that don't use linear springs.

Eibach 350Z spring rates front 296/384 rear 316/421
Eibach G35 sedan front 259/334 rear 359/413

As far as the rates you want in a coilover. If has been said that Tein is willing to do custom spring rates on request. Contact them via www.tein.com But given the balance of the car, I'm a much bigger fan of chassis tuning in ways that can easily be changed at will. I would keep the spring rate front to rear ratio as close to stock, not going past 50/50. If your out to kill off understeer, get the 350EVO adjustable swaybars.

 

308 in the rear on the coupe - no wonder there is so much axle wind-up! GCoupe35, excellent post. Now if someone only made firmer springs that did not lower the car...and some 50/50 rear shocks with 70/30 fronts...

Any ideas?

 

OK, let's clarify few things first:

Spring Load and Spring Rate are often confused. Spring Load is the amount of weight it takes compress the spring to a given height, in lbs.

Spring Rate is the amount of weight it takes to compress the spring one inch, in lbs-in.

Spring Rates do not change for the life of the spring, but spring load does. The springs do settle after 2-3 weeks of use to a lower ride height compared to the height when the springs were first installed.

For example, if the spring compression is 1 in. and spring rate is 150 lbs, then spring load is also 150 lbs. If compression is 2 inches, spring rate is still 150 lbs, but spring load is 300 lbs

Spring Rate is calculate with the formula (G*d^4)/(8*N*D^3)

G - Torsional modules for material used (all materials are very close to one another nowadays, you can take is as 11.25x10^6)

d - wire diameter in inches

N - number of active coils

D - Mean coil diameter in inches

8 - a constant for all coil springs we use.

With this formula you get a good sense of the spring rates you may want to use or have one built to specs. However, there are other factors that you will need to know before applying this formula and that is the Wheel Rate. It's too long to explain here, but what you really need to know is the unsprung and sprung weights. I do not know of a way to measure that without pulling the car apart, lol.

So, what I am truly left with is comparisons to other good setups on the market. For example, some setup E46 M3s (which is also an FR layout) with 560# f and 700 # rear spring rates. That car is roughly 3450 lbs in running weight and has a weight distribution of of roughly 50.3% f/49.7% r. Using the percentages, approximate spring rate figures can be found for the Z and G.

In terms of sway bars, they are fine tuning tools. In race situation, they are the last resort of tuning; you always have multiple spring sets to try first. It is easier to control the car with springs that sway bars in my opinion. Why, because a sway bar increases the roll stiffness to the power of 4 compared to springs; Stiffness=D^4, where D is the diameter of the bar (given the same geometry). You can have huge jumps in stiffness. But with springs you can make few lbs adjustments.

So, with these thoughts, the second numbers you provided seem significantly lower than what I expected. What a crappy conclusion after all this write-up, eh?

 

Given the above, I have no reason to question what the numbers I was given reflect. And it settles one other importand issue, comparison. Nice to know the numbers I have reflect the same measurement system employed for any other linear spring that has published data.

I'm really curious about the M3 rates, what is the location of the E46's rear springs. As I'm sure your aware, some suspension design's locate their springs in places that require unusually high rates to leverage the same force. Honda's current civic platform is a excellent example. 700lbs doesn't make sense to me given the cars weight distbution. Something else has got to be in play, I don't think it's a safe notion to draw on the car as a model. I'd rather see what the various teams that are starting to campain the Z are doing.

I know one chief benefit with coilovers is the ability to easily swap springs to tune. Certainly anyone thinking of tinkering with excessively high rear roll rates certainly had better be prepaired to do just that. However since I don't buy into the logic of such high rates, I'll take comfort with the spring rates already used by HKS and Tein. They tuned their springs equal front to rear, being that I except that logic, spring tuning is pointless for me and I move to the final step, tuning via sway bars.

 

I cannot disagree with you actually. From a practical perspective, for my type of car usage - auto-x, occasional DEs and few other track events - I cannot afford to carry multiple sping sets to test out and change for given conditions. Hence, your logic stands. I would do the same; get something from HKS or Tein, and adjustable A/R bars and do the tuning with the bars. However, I would love to talk to the Tein or HKS guys, or 350EVO and Stillen guys to see how and why they are choosing their spring rates specifically for the 350Z and G35 respectively.

But, at the end, there is absolutely nothing wrong with your conclusion and we're on same page.

P.S. M3's suspension design is quite different than that of the Z. As far as I can tell, same location for suspension but with coils around the tubes and not inverted. The Z's is not inverted either I believe, right? Any how, the M3 needs higher rear spring rate compared to the fronts and heavy front negative camber to really dialout the understeer. But, I still heard from a club racer that he is still not too happy with the setup and he would like to actually get more rear weight bias than ~50/50; his choice: 996 911 I will have to do with a G35 or Z

 

great thread guys!!

some real number and intelligence re: the actual cars and their technology. If you ever go to g35driver.com its really funny b/c those guys seem to think the G and Z are *exactly* the same excpet the G has "back seats, sunroof, more luxury etc".

My contribution to this thread is re: nissan's choice of "lesser" stock tire compound. I learned from my experience that the Zs re040s are run-flat tiures vs the pilots - while grippier are not. I'm not sure if ALL Zs get the RFs or just the ones with the tire pressure monitor. I took two nails toi my L rear and R rear two weeks apart. Its really nice not having to change a flat. The tire apparently seals itself from the inside and permits uninterrupted use of the tire for "extended periods until a replacement/repair is available".

 

Aaah, I did not know that about the RE040s, interesting. No wonder their lateral grip is lesser then

Thanks for the info.

 

First, huh? The Z comes with Potenza RE040s. These are actually an OEM touring tire that comes on Lexus IS300s and SC430s. G35 Coupe 6-speeds and sport option cars come with Michelin Pilot Sports, which are one of the best performance tires made. The statement about the G getter better performance tires has also been commented in several of the car magazine articles. If you look back at Z32 Turbos, they came with Michelin MXX3 which were one of the best performance tires of their time too.

Well, I do know that the control arms between both cars. I don't know if the sway bars are the same diameter, but the G does push more so the rear bar may be smaller. The corner brake assemblies are the same between the non-6-sp G35s and the non-Track Z's. The G35 coupe 6-sp and the Track model have teh same corner assemblies. I do not know if the master cylinders and proportioning valves are the same. Keep in mind that they G is a bigger and heavier car. The propertioning of the brakes may be different as a result. In most articles on the G35 coupe they note that it is softer than the Z. The Z is the sports car and the G is the touring car(making the tire issue even stranger). The G actually has the same rear brace as the Z has, it is just hidden. That big plastic thing in the back of the Z taking up half the cargo room is actually just a cover. The real brace is inside. In the back of the trunk in the G35, below the rear deck is the exact same rear upper brace that is hidden inside the Z's plastic structure.

There are some commonalities and minor differences in wheels and tires. Non-sport auto G35s have the same size tires as lower model Z's, but the Z has .5" wider rear wheels. The G35 Coupe 6-sp and sport option have the same size wheels and tires as the Performance and Touring Zs, but the Track has .5" wider rear wheels.

The drivetrains are the same with the exception of the driveshafts. Both cars use the same transmissions, clutches, converters and diffs. The axles are even the same and not-such-a-coincidence, they have the same track. The entire engine assembly is the same, but they have unique intakes and exhausts which make up the power difference. Other than that, they share no body panels, interior trim or even instrumentation with each other. The only things in common are below the skin where it really counts.

 

And the thing that gets me is when I see moderator's comment on the side of them being exactly the same. It's just as important to know how they are the same as it's important to know how they are different.

I'm on G35 driver as Gsedan35, (I asked the administration here to change my username to that, but as you can see,...well). I just did a post in the coupe section at G35driver on a G vs Z thread. I know exactly what your saying, same thing happens on freshalloys g35 forum, where I'm also registered as Gsedan35.

 

It happens on all boards, you should see some of the stuff going back and forth in BMW boards, its amazing. One has to do his/her homeword however before opening their mouth with a strong opinion one way or another; especially in "Internet" boards

Frankly, that is what I am trying to do. I do not have strong opinions on these subjects, I am only trying get accurate information by asking quite a bit of questions on various boards. For example, what you have provided and several of Loren's statements seem to be accurate overall and are really good information. But, in truth, I try to cross-check the information to ensure I am not misinformed; obviously that does not happen with dealers, LOL

Thanks for all the information, it has been a good conversation. I'll be around for more questions however .

 

No offense, but in Best Motoring, they took the plastic cover of the rear brace out... and inside, you don't see a 'small' bar... it's all steel and not smaller than the whole plastic thing, it's a THICK bar there...
And did you mean that the corner brake assemblies are different on the 350Z track/non-track, and G35 6speed/5speed?

 

To clarify on the brakes, there are 2 unique sets of brake assemblies: Brembos and non-Brembos. The non-Brembos on the non-track model Z's are the same as the non-6-sp G35's. The Brembos on the Z track are the same as the G35 6-sp.

 

Should read,

"The Brembos on the Z track are the same as the G35 coupe 6-sp."

Sadly, of course the 6mt sedan doesn't get those brembo's.

 

is this true ?
i remember reading somewhere that the z track brembos are 4 pot, while the g are still 2.
dunno though...