[edit] This may be a good read, but the mod is a fail. Go read Post #32. Damn it.

In April 2014, I bought a set of Vossen CVT, in a 19” staggered configuration. Immediately after installing the wheels, I came face-to-face with the awful realization that the car looked silly. These Vossens are an amazing upgrade from the original duckfeet, no doubt. But the tire-to-fender gap was suddenly very noticeable, and the wheels poked. They just did, and I hated it. While driving and looking down the side of the car through the reflection in the side-view mirror, I could actually see the wheel sticking out from the car. It was so silly looking to me, so amateur, that it hurt. Here’s a picture from back then. Pretty wheels, but the car looked ridiculous:



The solution seemed simple enough, right? Just drop the car. Doing so would reduce the gap, while introducing negative camber that brings in the top-of-wheel perspective to the fender edge. Thanks to our Sedan Moderator (Brad), I had a crash course on the positive effects of negative camber (Pun! LOL) So I bought a set of Swifts for the RWD Sedan. After the springs were installed, the poke was gone, and the gap problem satisfied. There was a little bit of offset discontinuity between front and rear, which I addressed good-enough with 3mm wheel spacers on the front.



And all was right with the world… or so I thought. While the wheel fitment was MUCH better than otherwise, I couldn’t deny the fact that the rear gap was significantly narrower than the front. At first I was content to ignore it, but AroundTheG37 is persistent (Hi Todd), and eventually I came to a point where I saw this fail every single time I approached the car. I had a Droopy Bum, damn it. It’s worth saying that for some people, this is the end-game and they love the look. However, I’m not one of those people. I would prefer to have at least some continuity front-to-back, with reasonable gap… because it’s a daily driver, not some low-riding clown car. This picture is a bit exaggerated, on a stony, uneven surface, but it clearly shows the effect:



This next picture is actually a better example, with the car flat on a level, smooth surface. This was taken in Fall of 2014, just after re-installing my duckfeet with snow tires and 15mm wheel spacer adapters. I gamma corrected the image so that you can see into the shadows. Very clearly, the rear gap is approximately 1/2” more narrow than the front.



The expensive and perfect solution to this problem: coil-overs. But with only 20k miles on these OEM Sport shocks, and having already spent good money on parts & labor for the springs, going coil-over seemed an extreme idea… like using a sledge hammer for a carpet nail. Don’t get me wrong, CO’s are definitely in my future, but not for a few years yet. So I think it was Brad again who directed me to this 6 year old thread over on G35Driver.com, which I completely whored over the last month:

My 09 G37xS (AWD) Lowered on Tanabe - Droopy Bum fix too!(PICS) - G35Driver

The OP there had purchased a set of Energy Suspension polyurethane coil-spring bushings that were 5/8” thick on the ledge. They were just the right specifications to fit above our rear springs, between the spring and the rubber Top Seat. Well, almost right... they needed some customization to fit. Specifically, the inner/lower edge of the bushings needed to be beveled to match the conical contour of the Top Seat. Accomplishing that turned out to be relatively easy for a wood-working friend of mine. Clamp a drill into a vise, pointing upward, then use a 1” heavy-grit barrel bit on the drill, and rotate the bushing around the barrel bit until you get the right amount shaved off. Oh, and to do this, you need an extra Top Seat as a guide. That runs about $30 each, shipped.

2011 Infiniti G37 Parts - Infiniti parts

The end result of our efforts was pretty good, IMO. After which, the parts sat in my office for about 4 months. Because winter. I hate winter.



Come springtime, after The Winter That Wouldn’t End, I had my mechanic install the bushings. The installation was simple with the car on the lift: support, unbolt and drop the lower spring bucket, slip the bushings in place, and bolt it back up. I say simple because he’s skilled; it actually takes some finesse and elbow grease.



Immediately, we could see the car was higher in the rear, but awkwardly higher. WTF? Seriously, man… WTF?!?!? I gave it a few days to settle, which it did about a quarter inch, maybe. But still, it was really high. And the reduced negative camber meant I had some poke return to the mix. Both of those observations were unexpected and very disappointing. I mean, was it better than it was before? To my eye and my automotive values: yes, it was better, but still not right. Also, the car drove funny when pushing into turns. I swear I was feeling more body roll. While that might have been in my head, perception is reality, so there it is.

I didn’t take any pictures, because I was p1ssed off at myself. It happens, sorry. Use your imagination.

Eventually I came to realize that when springs “settle”, they also settle into the soft rubber of the top-seat. However, the polyurethane bushings are a harder material, which didn’t allow for that interaction. So although the bushings were only 5/8” thick, my effective height change was well over a full inch. I would say that’s a heck of a lesson learned the hard way. Here’s a chart I made of measurement stats after a few weeks. On average, the rear was actually 0.6” higher than the front. So while this is an improvement over the Droopy Bum, it went too far in the other direction, and was simply wrong. Once again, the car looked wrong to me.



So here I go back to Square One, and bought a second set of poly bushings. But this time, they were 3/8”.

Energy Suspension 9.6101 - Coil Spring Isolators - Style A - 96101. Energy Suspension ENE-9.6101G

Unfortunately, there really isn’t enough poly material to shave the inner edge of the 3/8” bushing. So I got to thinking: If I can’t make the bushing fit the top-seat, what if I make the top-seat fit the bushing? That turned out to be an easy task. Just spin up the grinding stone and roll the top-seat along the side to create a 90* edge where the cone meets the flat. If you don't have a grinding wheel, I guess a Dremel Tool would work, but it would take a lot longer. The one thing I do know is that you'll get nowhere with a boxcutter. You need to grind the rubber to an edge, like so:



The end-result was a perfect fit. When I was done, I felt that I deserved a freaking medal for this, LOL. Then I bought a second top-seat (another $30), and ground that to fit, too.



I went back to my mechanic, and he swapped top-seats and bushings. And now I’m in my happy place.

Oh, and that sense of added body roll? That’s completely gone, and validates what I was feeling. Go figure.

Here are current measurements, taken this morning. And here's the methodology: I identified a location nearby that has a large, relatively new, expanse of blacktop. (That would be our Middle School. Not a lurker, LOL) I parked the car in a spot, and measured floor to fender, accurate within 1/16th ticks. Then I turned the car around and did it all over again, in the same parking spot. Then I moved it to another parking spot, and did it again. Then yet again in a third spot. The thinking is that few places are *truly* level, and there will almost always be variations in how the car sits, based on surface materials and pitch. Tire pressure certainly is a factor, so let's just assume correct and consistent pressure all around.



And here’s a side profile. Honestly, I couldn’t be happier.



I went overboard with gamma-correction so that you can clearly see the uniform gap. Here’s another picture:



In a perfect world, where you don’t suffer the pangs of trial & error, you’ll need:

• Pair of 3/8” Energy Suspension Coil-Spring Isolators, #96101 at EnergySuspension.com, for $22 shipped.
• Pair of OEM Rear Suspension Top-Seats, approximately $60 shipped.
• One hour labor charge at a trusted mechanic, approximately $80.
• Yet another alignment.

For the DIY crowd, you could simply customize the upper-seats that are already on the car, and do the install yourself, making the total cost for this project a measly $22 + alignment. As you can guess, this cost me a whole lot more than $22, but hey... that's the hobby after all.

If you have aftermarket springs and a Droopy Bum on your RWD Sedan, I highly recommend you give this idea fair consideration. You won’t be disappointed.

 

Here's yet another perspective: photos of the front and rear wheels, each taken at the same distance from the car, and aligned to one another based on the line of curb & grass seen behind the car through the underside.

Damn-n-n-n-n. And this time, I'm saying that with such relief, you can't imagine. Very psyched how this turned out.

 

Gets my vote for "Post of the Year"
Very well documented & detailed (as is expected from John aka Rochester).

So glad you found that happy place, it took a lot of diligence, but like almost all of your mods it's paid back in spades

Should be very helpful for anyone that has Swift or Tanabe srings, or any lowering springs that have settled more in the back over time.

With the large rubber cone isolator in the back it's something that seems to be inevitable over time.

Great work sir!

 

Thank you God, there is some one with more extreme OCD than I have!!

I think Im going that route. My rear Swifts are a little droopy on my coupe.
Notice Im still doing this as Im trying to sell it.

 

John, sometimes I think you go over the top with some of your comments (which I actually enjoy because who doesn't love some good banter......) but this my friend is the perfect example of why you are such a valued member of this community. Excellent post and that uniform tire to fender gap looks great. I actually would have done this exact same thing if I wasn't so impatient. Kudos.

 

Thats how you do a write up.

 

Glad you enjoyed reading it. I certainly enjoyed writing it.

More importantly, I'm ecstatic to no longer look at my car and think there's something not quite right going on.

 

Is it just me or is the real problem the Swift springs? Why didn't you just try Eibach or H&R instead?

 

Pretty sure it's just you. Thanks, man.

AFAIK, the droopy bum effect isn't a thing only endemic to Swift Springs on the RWD Sedan. And while I don't know first-hand, I've read enough to get this 3rd-hand opinion that Swifts are a more comfortable ride than Eibach and H&R, with a less severe drop. But really, the most important reason I went this route was that I had already purchased the Swifts, already installed on my car. And on top of all those reasons... the front was fine, it was just the rear which needed a little tweaking.

So yeah, it actually is just you. No offense.

 

Nice write up John, Can agree more with the value you add here ! I will remeber this thread if or WHEN a I have droppy bum. LOL Yes I know how that sounds,

BTW so far my car is still going the other way, My front is lower,

 

so your car is indeed a RWD and not AWD, correct?

 

Thanks! Kind words.

The AWD Swifts and the RWD Swifts certainly do not share the same ride-height observations. Most of the opinions I've seen here are that the AWD Swifts provide a nearly even and conservative drop.


Mine? It's RWD with VLSD. All 6MT's are RWD.

 

I thought the Swift springs had the largest drop, then H&R and Eibach with the least drop.

I'm going to be putting Eibach springs on my car soon which is 2011 sedan 6MT so I'll take pictures to compare. I hope it will have some rake to it still but we'll see.

 

That's not the consensus I interpreted when buying springs. Doesn't mean I didn't get it wrong, it's just the opinion I gathered at the time.

According to the Swift website, (click here) RWD springs for the G Sedan drop the front 1.2" and the rear 0.8". Sure seems to me the rear dropped more than that, but I didn't take measurements before the install. It would have been awesome if I had, particularly if I took the same approach that I did here.

Sadly, I don't have those numbers. Perhaps someone else running OEM springs on a RWD Sedan would be interested? If you want, click here and use this spreadsheet. Just fill in the blanks, and the average calculations will take care of themselves.

To repeat what I did:

• Assuming proper tire pressure...
• Assuming an empty trunk and back-seat...
• Assuming a half-tank of gas (because that's what I had at the time)...
• Find a flat and smooth surface parking lot, and target what seem to be level parking spots.
• Take floor-to-fender measurements accurate to 1/16" of all four corners.
• Turn the car around in the exact same spot and do it all over again.
• Rinse and repeat for two more parking spots.

 

In order of drop~
H&Rs are almost slammed (unless they have another version they've added)
Tein S-Techs similar to ^^^
B&G S2s same as S Techs
Eibach & Swift are milder
Tanabe & Tein H Techs are the mildest.

John, If you want to ditto this thread and post in the DIY folder I'll sticky it, or eventually move this one over, just let me know.
B