All --

I've been lurking around here for a few months now, trying to suck up as much info as I can before dropping obscene amounts of money into the suspension on my 2011 xS Coupe, and I think I've finally reached the point that I'm going to put my needs out to the community and hope for some firsthand feedback that will get me the results I desire.

Currently the car is completely factory original, but I'm ready for new rubbers, and since I live in CO, common sense tells me I should just grab new rims at the same time so I can run snow tires on the stockers. What I've found so far is that it appears to be cheaper to go to 20" rim/tire combo, but either way I'm going to a 9" wheel with a slightly more aggressive offset (+35 vs +43) which leads me to the suspension conundrum.

In all of my searching, I've come across a couple of good threads detailing different spring rates, but they are all based on the non-X coupes. OEM, IPL, Swift Spring Comparison and Lowering Spring info chart for RWD coupe I can't find any information specifically for the xS coupes, so I'm hoping someone around here does.

So, what I'm looking for is a slight drop, with no loss of performance from stock and preferably not a teeth rattling ride. Basically, I just want to lose about half the current wheel gap. That being said, this is what I've found so far:

Eibach Pro-Kit: about 1K stiffer spring rates F/R with about 1.3/1.0 drop on the xS. The drop seems reasonable, but my concern here, is that based on previous experience with Eibach, the rear end will be sloppy as hell, because they are progressive and way too soft at the start.

H&R: I can't find any hard numbers, but most sources say they are about the same rates as Eibachs. From what I've seen of posts with people that have them, they drop much further than advertised though. I'm not looking to tuck tire.

Swift: They don't make xS Coupe specific springs, but I've seen a couple with the regular coupe ones installed. Spring rates are F - 10.3kg/R - 9.7kg based on one of the threads I linked with a mild 1.3/1.0 drop as well. These seem to be the springs to go for, based on user feedback in the forums, but without knowing the stock spring rates, I'm not sure what kind of performance I can expect. In addition, they apparently cause "droopy bum" on the X, which can be easily rectified with a spacer, but if it's due to a lower spring rate, I'd worry about balance.

BR Racing coilovers: I'm not really looking to spend $1000 for a 1" drop, but if this is the route I need to go, so be it. These are the ONLY coilovers I can find that fit the X, but I'm a little concerned with the cross compatibility with the sedan. I find it odd that the coupe and sedan can run the exact same spring rates, and that the X version is 2k softer front and rear than the regular coupe version. According to the BC site, these are 10k/8k vs the 12k/10k for the standard coupe.


Any way I go, I'll pick up a full camber kit (F/R) from SPC and I'll be installing Hotchkiss ARBs as well.

Again, performance is my number one concern, so if it comes down to "none of these are better than or equal to stock" I'll just deal with fender gap. That being said, any experience, additional information, or options I missed would be greatly appreciated!

Thanks!

 

I'm in the same boat. I want to lower my '11 xS coupe, but I haven't been able to decide which way to go. On the one hand, I want to get rid of the fender gap and improve the handling even more. On the other hand, I just don't feel like messing up anything and just try to ignore the fender gap.

At the rate I'm going, I think I'm just going to leave it alone.

I don't know why Infiniti has to set the car so high. BMW and Audi don't set their AWD coupes that high.

 

I'd look at Tanabe, seems about the best option for a mild drop, similar to OEM ride, low price and since you're doing it right w/ the camber kits you shouldn't have any issues. There's only a couple X coupe applications for springs and maybe 5 coilover options. Here's the Tanabes
Tanabe USA R&D Blog | Infiniti G37 Coupe
Here's a good thread on X coilover sets
https://www.myg37.com/forums/brakes-...r-options.html

 

I was in a similar position recently. The limited options for the X make it a hard decision, but I settled on the Eibach springs. After looking at Tanabe's website, it appears that they have the same part number for EVERY TRIM of the coupe. We obviously know that the weight distribution of the AWD and RWD are different, so this makes me question how much R&D really went into these springs.

My 2 day review of the Eibach's are good. Ride comfort is maintained and overall handling is improved enough for a daily driver. The X from the factory has a very "floaty" feeling that the Eibach springs eliminate. Going over a bump is less of a "wave/bounce" and more of a "thud". There is not any noise or unusual quirks to this setup. Right now my car is currently sitting at 27" all around, so the drop is dead even. For reference, my X started at 29" front, and 28.5" rear fender to ground measurements. Eibach has an entirely different part number for every trim of the G37 which means they at least put thought into the engineering of the springs, and for this reason, I approve. I do need spacers pretty badly though...

Before:


After:

 

blnewt -- I looked at the Tanabe springs, but the spring rates seem really soft compared to stock (at least for the RWD coupe). I don't really want the handling of a mattress. I didn't see any coilover applications for the X model at all.

I also glanced through that thread, and it appeared that all of the available options (except the BR Racing) were for the Sedan. Even the BR Racing seems to be sedan or coupe, so I guess my question is with those, are the stock spring rates that similar between the two? I would think the sedan would run stiffer rear springs than the coupe, due to the extra weight. If someone can confirm they are in fact similar enough to be interchangeable, I'd probably jump on the BC Racing, Megan, or KSports. Anyone have experience with one or the other?

bassy -- to your point, I don't get it either. Seems like most of the Japanese luxury/sport cars sit a lot higher than their German counterparts. If 17" wheels would clear the Akebono brakes, I'd totally run some low profile All Terrain tires in the winter just to prove a point.

 

Thanks for the feedback. That is precisely the look I'd like to have, but I'm concerned with the performance of the Eibach's vs the Sport springs. I know they're an improvement over stock, but I'm not sure they provide much (if anything) over the Sport springs.

It would be great if you could post back after driving on them a little while longer and let me know how it goes.

 

I'll be sure to report back after some more time with them on, but I don't see much changing since I have lowered a car previously, on Eibach, and it was a similar experience. Here is another member who has the Eibach springs on his X coupe with a very similar experience:

https://www.myg37.com/forums/build-t...37x-coupe.html

I don't think the sport springs are any more firm than the journey springs. The additional firmness and sport characteristic comes from the larger sway bars, so I wouldn't worry about that.

 

Just a slight update on this...

I had a friend that owns a body shop do some digging in his parts locator for me a few days ago. He got back to me just a little bit ago, and confirmed some part #s for me. Assuming his system is correct, which I have to assume it is, the springs for the base Coupe, x Coupe, both models of S, and the Sedans share the same part number for the front and rear springs. 55020M(Rear) and 54010M(Front)

I think to Ryne's point, this means the sport package is just heavier ARBs as far as suspension is concerned.

In any case, I think what this means for me is I'm going to give the Swift springs a shot. They seem to be a crowd favorite around here, and according to the Swift website, the drop is mild enough to stay within factory alignment.

Here's a link to someone that has done it before. G37x on Swift springs

Unless someone chimes in refuting my findings, I'll probably order these up this week. Worst case, they're terrible, and I resell them and get coilovers anyway.

 

Swift doesn't make springs for the X coupe. That install used springs designed for some other trim of the G37 (he never discloses which ones). Also, he said when he called to inquire about the install, they said they had to add a plate to even the drop (never discloses how thick of a plate was required).

It seems a lot more risky to go this route opposed to something that was developed for the car specifically. The Eibach kit comes with replacement bump stops and dust boots, I am not sure what would need to be done to make the Swifts work. Afer looking at his pictures the drop doesn't look very even front to back. The front looks a bit higher than the front, but this is hard to see in the pictures. I would be interested to know what his measurements are.

If your up for the risk/challenge then I wish you the best of luck and be sure to post your results. It would be nice to give another option to the X community.

 

I'll be using the standard coupe springs in my "trials". Based on the factory spring parts being the same, I don't see any reason they shouldn't work. I haven't looked into the Swift as a kit much, but I have to assume it also includes any needed hardware.

From what I've seen, none of the drops look incredibly even front to back, even on the standard coupe. They all seem to tuck more in the rear. Even though the fender to ground measurements may be level, the fender to tire measurements look off.

In any case, my plan is to go this route Droopy bum fix if need be to get the fender gaps even.

 

The drop is even if the fender measurements are even. For example, my fender to ground measurements are 27" all around on Eibach. Using the measurement style in the "Droopy Bum" link you posted I am 4.5" all around. There is just a perception that the drop isn't even since the offsets are not correct. The body of the car is designed for the RWD staggered wheels, not the square wheels on the X. When spacers are added, or properly sized wheels are installed, the drop will show that it is even.

These pictures tell the story a little better:

Front:


Rear:


Note to any observant members: Yes, I know I didn't have to label front and rear but I have learned in life that you can never be too clear, lol.

 

You're right. They do look far more even straight on. Stupid offsets.

 

So after much digging and researching, I came to the conclusion that the Swift springs were going to be too stiff for the front and most likely introduce understeer. As such, I ended up going with the Eibach pro-kit.

I like the stance, and the ride is pretty bearable on all but the worst of the roads. It does seem a little soft in the back until you really get into it, but once I get the ARBs on, I think this should go away.

One thing I do see, is the Eibachs definitely appear to drop a little more on the Sport model. Anyways....apologies on the crappy cell phone pics.

Before:


After:


A little better profile:

 

Nice even drop, looks good ^^^^

 

Thanks! Now I just need to get my wheels here, if the master of all things offset answers me in the other thread. (That's you , by the way.)