Lately, I've noticed my car has a pretty harsh and slightly uncontrolled ride in the rear. Overall, it just feels
"busy". It has been very cold for the past two weeks which will attribute to some harshness. I've got Intrax springs which lower the front ~1.8" and the rear ~2.2". I've got Knoi adjustables in the front and stock replacement KYB GR-2s in the rear. The GR-2s have about 15K miles on them and have been under the load of a lowered suspension since they were installed. At first, I had ST springs which dropped the rear by 1.5" and then 3 months ago, I switched to the Intrax springs. The Intrax have a smoother ride than the STs at first, but once you compress the springs, the rate is much tighter. My car seems very controlled in the front with the Konis at 1/2 turn (out of 2 turns). The rear feels a bit wobbly in turns, a bit bouncy on bumps, busy, and harsh on bumps. I'm starting to believe that the GR-2's valving can't keep up with the higher rate spring. So what ends up happening is the spring ends up doing some of the rebound work which isn't good. I've done the "bounce" test with the rear and the car doesn't bounce at all. It goes up and levels out quickly. I don't think this test can really apply to a car with such a big drop in the rear.

Anyone else think it be time for adjustable struts?



Dave

 

I have Koni's all around with Sprint springs (which I believe have a lower drop) and haven't experienced any of the symptoms that you've described.

Koni's all around are nice

Aren't the GR-2's intended to be stock replacements with stock springs? Do they claim that they can handle the drop?

 

Try adapting some real struts from a SVT, instead of those cheap OEM replacement ones.

"For the majority, Maxima owners aren't "riceboys". We're typically an older crowd with more money and sense than the typical Import crowd. We give guys crap all the time about putting "altezza style" taillights on their Maximas. We don't like mellon shooting exhausts, loud exhausts, "Touring wings", excessive body kits, larger than 17" rims, hood scoops, windshield banners that read "Team Riceboy.com", stickers on fenders displaying aftermarket parts on the car or in your garage. I've seen all these "rice" mods on Contours in my area and on this org (except for the Altezzas). "

Yea right. I don't know how you wrote that without laughing so hard that you gave yourself a heart attack.

 

KYB doesn't recomend using their products with any more then 1.5" drop. So chances are there starting to fail. I think it's time for a set of rear AGX's for you. At least you can adjust them if they get soft after a few years. Remember, any more then 1.5" drop and your SOL when it comes to warranty issues.

 

Very interesting observation. I would bet that your rear GR-2s are wearing out too quickly because they are being forced to work under a more than 2" drop. Staying compressed for too long. It correlates erfectly, because you started having problems soon after you replaced your ST springs with the lower Intrax springs

This observation is also interesting because alot of people have trashed Tokicos. I've recently upgraded to them. They are fine on my car. I'm on H&R springs. I think the Toks were trashed because people were dropping their cars more than 2" as well. With H&Rs, the drop is 1.4" at the most. Most people with Eibachs and Toks are fine, too.



DW

 

It's not the drop, it's the spring rate. The HP springs have much higher spring rates, and higher natural frequency. On rebound it pulls the shaft out of the strut much faster than a stock spring. This is what overloads the strut and wears it out early.

 

Thanks guys. I guess I'll have to spend the cash and swap out my struts. I think it was only a matter of time before they wore out. And yes, KYB doesn't recommend going any lower than 1.5" on their GR-2 I guess when you push the struts too hard, they fail pretty quickly (~6000 miles).


Dave

 

Are you going to put Koni's or AGX's in the back?

 

I'm usually not one to mix 'n' match but if you are going to replace the back, I'd put a vote in for AGX. You don't have to take the spring/shock down to adjust it like you do for KONI rears. Also, since you have the fronts on moderately stiff, even if AGX are slightly stiffer than KONI, it won't be an issue. At least on the bright side, the rears are pretty easy to replace on an already lowered car.

 

Yeah, I'm gonna get the AGXs. I'd much prefer the ability to change valving in a minute instead of having to remove the shock and experiment. The valving on the Koni and AGX are adjustable which will make it easy to find that right setting plus I have no problems running another "bastardized" setup in my car. Hell, for a while I was running Prelude seats in my Maxima


Dave

 

I have 325lb springs in rear and 450lb front. I have GR2s as well. I feel that the GR2s do a good job of dampening. Not that there isnt room for improvement, but I don't get multiple oscillations or anything...

 

I've tried GR2s on other cars and they felt worn out when new - i.e. hardly any damping. I'd expect them to be pretty useless with stiffer springs.

 

Same thing?

Spring rate is a function of the length of the spring, right?? So, when you shorten a spring, aka drop the car more than 2", then the spring rate changes. Even if you don't shorten the spring, but compress it so the car drops 2", the spring rate still changes.

So, spring rate, drop, are relative functions of each other.

DW

 

Not quite correct. Spring rate is not a function of the length of the spring but on the number of coils in the spring, the diameter of the spring, and the diameter of the steel tubing used in the spring. The type of material obviously also affect spring rate (stiffer vs softer alloy).

If you take a set of springs and heat sag them so you get a drop, you'll have the SAME spring rate as before because all of the parameters I mentioned above are the same. Doing thus to a spring is a bad thing to do, though because you're using the same spring rate with a less ground clearance. Bottoming out becomes a real issue. Spring rate changes when you remove coils (cut the springs) or use different springs (thicker/thinner coils, less coils, etc).

 

Oh, OK. Next I'll say number of coils. Thx.

DW

 

The spring rate is the spring rate. The spring rate is determined by the cross sectional area of the steel rod the spring is made out of (not tubes), its length and the modulus of elastisity of the steel. The flex in a coil spring is the same as that in a torsion bar, i.e. the bar is twisted. Imagine uncoiling a spring into a straight rod. Clamp one end and apply a torque (force) to the free end. For a given torque there will be a corresponding twist to the rod. Cut down the rod and apply the same torque and there will be less twist. The spring rate is higher. Recoil the shorterned rod so that spring has the same free length that it did before, and it will have a higher spring rate than it originally had. The length of the spring doesn't determine its spring rate; the length of the rod does.

 

In other more consise words, length IS a fucntion of spring rate! Aha! Like I orirginally deduced.

DW

 

"In other more consise words, length IS a fucntion of spring rate! Aha! Like I orirginally deduced.

DW "

Spring rate is not as a function of the spring length, it's a function of the length of the rod the spring was wound from. Two different things, don't confuse them

 

OK. That is what I meant, I'll admitt I'm not making myself clear. My understanding was that the spring rate was a function of the length of the spring . . .when it's straight. Or, as you put it, the rod it came from.

DW