Might as well name this thread this from the start since it will inevitably end up named this once a mod reads it. My vehicular situation has changed, and my car has gone from being the track car to needing to do a good bit of DD duty for a while.

My 9k/6k springs on my Teins Flex coilovers are intolerable on the poor excuse for highways we have here. Segmented cement roads are almost impassable as the car becomes a bucking bronco at anything over 40 mph. This is with the Tein's set at 12 F / 14 R (higher = softer). I've tried increasing the rebound and reducing it, with no improvement in ride quality.

My question is this:
Will moving down to softer Tein springs fix the ride quality issues I'm having, or am I fighting the natural shock curve of the Teins? Is a good ride quality possible with the Teins?

Other relevant suspension mods: 15x8 6uls, 225/45/15 RS2's, Hyperflex bushing kit all around, FM front sway, rear sway removed, FM endlinks in front.

 

I don't have any useful input, but nice move on the name . Beat them to the punch. Whats the conversion from #k to lbs in spring rates. 6k something in the 400's or 500's? I would imagine softer springs might help, but I don't know how much livable it would be.

 

9k= 504 in/lbs
6k= 336 in/lbs

I'm looking at Shaik's suspension sheet. My bounce frequency right now is 2.01.

Moving back down to 7k springs in the front and dropping the rears to 5k would yield a new bounce frequency of 1.77. According to Shaik's spreadsheet, that still puts me a little over where I would want to be for a street car, but it's hellsa lot better than I am now.

 

Just installed mine. I need to check because I was thinking 7K/6K springs but that ratio seems odd. Running 15 F/R I think it is very liveable and really like it. On old pavement that has funky slabs it will rock a bit. They were used and I didn't look at the spring rates on the front, but the rears were definitely 6K.

How low is your car? If you are any lower than 12.5" front (on an NB) you are on the bumpstops and lighening the springs won't do a lot. Mine is 12 7/8" and I have about 1/2" of shock travel before touching the stops.

 

I have a good relationship with tein, and could probably get you a reasonable deal on the springs if you decide to move that way.

 

Its worth a try. Springs couldn't be that much. If it doesn't work out, you could always sell them, or sell the original springs to make back some of it.

 

Might throw your question at Emilio. He's pretty good at answering tech questions he receives, even if it's not likely to end up in a sale. Move those 6's to the front and put 4's in the rear? The big question would be whether the valving on the Teins will work with significantly lower spring rates to get you the more forgiving ride you want. Over damped soft springs are likely worse than a properly damped stiff spring.

 

I've driven the section of I-20 between Dallas and Monroe lots of times on 7/6 springs. Dallas to the state line is fine. State line to Shreveport/Bossier is okay-ish. After Bossier, I think the roads haven't been touched since the 70s, and I get the same rocking motion you describe. Pretty nasty.

Frankly, if your area is anything like that stretch of highway, I'm not sure how much more liveable you'll be able to make that drive. I think a good deal of the issue is the wheelbase of the car; you might not be able to dial out too much of the road topography.
Just be glad you're not on Azenis sidewalls.

 

Some people swear that they can feel the difference in two clicks. y8s runs full soft all the time. Try bumping it all the way down. But, if it's the rocking motion, I don't know if that will help. Mine does that full soft in the right conditions.

 

FWIW I have the standard Tein 7fr/6r rate springs on my Tein Basics and they are about as stiff as I think I would want them on a DD. They are fine, and much better than stock (way too mushy for me), but not intolerably stiff. If for example I ever had to tune them by changing rates, I would probably try going down on the rear first than going up on the front to avoid making them much stiffer.

 

I'm thinking the difference between the front springs and rear springs in my case leads to some weird behavior on normal streets. Let's say I'm going up an overpass on the interstate. The overpass is composed of concrete sections. As I hit the joint between sections, it feels like the front just crashes over it. There is almost no give. This causes the front to jump up abruptly. Then the rear kind of coasts over it, but because of the energy in the suspension from the abrupt hit, the rear ends up having to absorb the impact, so the rear ends up hitting the bump stops and my head goes through the softtop. Now do that over and over again, with the crappy road extending for miles, and you see my problem.

At first, I thought my rear shocks felt blown. (which, being BRAND NEW Tein Flex's, I highly doubt). I'm wondering if this behavior is due to the larger spread front to rear in spring rates with the 9/6 over the 7/6. I'm thinking allowing the fronts to absorb more impact with a softer rate would make more sense in not affecting the car so badly on crap pavement.

Does this sound right? I'll admit I'm hardly a suspension expert.

 

Just got off the phone with Emilio. He is suggesting that what I'm actually feeling is bottoming out of the front suspension. I didn't put any preload on any of the springs, so he suggested about three turns of preload in the front and rear as a starting point (making a simlilar adjustment to the shock height to keep from jacking up my alignment). I will try that this weekend.

 

Someone already told you the actual answer, but let me tell you how to get it yourself... Google does conversions for you.

For example, paste this into the search field on google.com:
9kg/mm to lbs/in

 

*****!

i daily drive my 350z with 9kg/mm rear and 6kg/mm front springs and rear shocks set on full stiff!

 

You should also make sure you aren't getting any coil bind. I had my tein ss binding in the rear and it felt like i was being rear ended mid corner on some bumps.

I'd also suggest running full soft, I run 14f/16r and it is not too bad with my 7/6 setup. I wouldn't want to go with much softer springs for fear of riding the bumpstops through corners. I also cut my bumpstops a little bit (tein tech recommended it)which helped a tad.

 

Word. When I first put in my Teins, I set the rear preload a little higher than the upper range on the instructions. Not much, like less than 1/4". Spring bind. When the rear compressed, it made a loud clunk, not good. As soon as I backed off the preload a bit it was fine. So if you increase the preload, and your problem gets worse, maybe try decreasing it.

In fact, in my case, I could see where a light layer of dust had been knocked off of the tops of the spring coils where they were hitting each other.

 

this is all excellent information. thanks a ton guys.

I'm going to try this tomorrow.

 

just as a point of confirmation, i rode behind the car while my dad drove it up a nearby overpass, and i observed that the front end seems to not move much. It looks about right, but the rear just bounces everywhere. I'm going to start by measuring droop travel and adjusting the preload on the rears tomorrow and see what happens. If the droop travel seems out of spec for the fronts I'll adjust them too.