Hi all, I searched around for this but can't find a definitive answer.

I had someone install Eibach ProKit springs on my 2008 G37 coupe but it turns out the part# used (Eibach, 6390.140) is for a 2009 Sedan and not Part# 6388.140 like what's listed for an 08 coupe.

Should I be worried? The fitment is great, one-finger gap. The install went fine, everything fit perfect and the ride is good.

My only worry is about the weight difference between coupe and sedan, and I don't know how it will work later on down the line.

I have about 300 miles on the springs so far. The car has 25k.

Anyone have any insight? Should I go back and have the coupe springs installed instead?

 

The weight of the cars are different so that might be a ride quality problem. I don't think it's that big of a deal...

 

If it doesn't drive weird and if the drop looks nice then you shouldn't be worried.

 

^ I agree with Sam. Heck, if its a dead even drop, you might even see people with coupes intentionally put sedan springs on their car.

I would gander that the spring rates for the sedan are going to be close to the coupe... but you wouldnt happen to know the drops and the springrates exactly for the front and rear would you?

You can sometimes tell by the numbers how the springs will drive on your car. Say for example the springs give you a 2 inch drop but the springrate doesnt increase that much to compensate for the drop, the car might ride like a boat and be a little bumpy. That might cause your stock shocks to wear much much faster than they should but other than that, it shouldnt hurt your car at all provided the springs are the correct diameter and fit properly.

 

Thanks for the input guys. I am in fact worried about the struts wearing out too quickly but I guess thats expected with lowering springs. I might need to contact Eibach or something, just want to know this is safe to ride on.

 

I would find out what the springrates of the sedan springs are and compare them to the coupe.

Also, what amount of drop did you get in the front and in the back? How many inches, not fingers. If you can measure from the ground to your fender, we can tell you how the drop compares to the eibach for the coupe.

I did a review of the tanabe fronts and eibach rears. I posted dimensions of the eibach coupe drop.

https://www.myg37.com/forums/brakes-...ach-rears.html

Take measurements of your fenders and let us know how much the sedan springs drop your coupe.

https://www.myg37.com/forums/brakes-...springs-2.html

 

If you call Eibach and tell them your problem and that you want to speak to one of the technical staff, then usually you can get past the person that answers the phone no problem. Just make it sound real techical and they will transfer you. Once you get to the techs, they will ask some questions for their records and then I found they were very helpful. That is the only way you are going to get a definitive answer.

 

Their are plenty of guys running G35 springs on their G37, its safe but ur shocks will wear quicker.

 

^^Actually, depending on the drop and the springrate, this may or may not be true.

If the drop of the sedan springs is less, and depending on the springrate, they might actually wear his shocks LESS than the eibach coupe springs do, which have a 1.5 inch drop in the front.

 

In addition to possible spring rate differences, weight is going to affect the drop.

Curb Weights:
Coupe 6MT Sport: 3653 lbs
Sedan 6MT Sport: 3640 lbs
Coupe AWD: 3830 lbs
Sedan AWD: 3807 lbs

The weight difference b/t the coupe and the sedan is negligible. Just make sure your girlfriend doesn't gain any weight and it equals out. So it shouldn't be something to worry about.

6MT Sport Vs AWD versions is a different story...AWD is like adding an extra person in weight. I would be more concerned about that mistake.

 

^ good point JLai, I was going to point that out as well.

It still amazes me why the coupes are heavier though.

 

Thanks for the input all.

I got a hold of Eibach tech/install support and here's the summary:

Kit# 6388.140 (2008 G37 Coupe)
Drop = 1.2 (F), 0.8 (R)

Spring Rates:
Front: 228lbs/in initial, up to 548lbs/in
Rear: 371lbs/in initial, up to 531lbs/in

--

Kit# 6390.140 (2009 G37 Sedan)
Drop = Same???

Spring Rates:
Front: Same as #6388.140 (The guy said it was the exact same spring? Weird, but ok).
Rear: Progressive spring, 359lbs/in up to 466lbs/in

I questioned the safety of this and the meaning of the different spring rates (noob here). He explained that the ride will be softer due to the lower spring rates in the rear and the drop might be a bit lower. He stated that this was not "recommended" but could not see it being a major issue. He also stated that because the springs are softer the shocks are likely to wear out LESS than the coupe kit (thats cool I guess).

So there it is. I guess I'll stick with these and see how it goes. I love the drop, I keep staring at my car and find any excuse to go outside to look at it!

Thanks again guys.

 

Hmm, do you have these numbers for 5AT? Not G37x either

 

I grabbed those off the Infiniti website. They won't have the exact 5AT curb weight, as the new ones are 7AT. You may want to try Google for your answer.

 

Post pics!

If the front spring is the same and the rear spring drops a little more, anyone looking to get the Eibach coupe kit might be interested in getting the sedan springs as one of the complaints about the coupe kit is that the rear spring doesnt drop as much as the front one does.

Although its not "recommended" by eibach, the springs are pretty close in springrate, so think of it as you are driving around on custom springs.