I keep seeing questions about different coilover setups and spring rates always pop up as a sign of what would be comfy. My question is, how do you decipher? I mean some are sayin 12k and 10k, or 10k and 8k...what does this actually mean? Also, I saw a set of Tein's I am interested in and they are rated by pounds not K (kg I presume) F:672lbs and R:560 so how does that matter in comparison? Can someone please shed some light? Thanx peeps

 

Here's the Tein Basis Zs, if you look at the specs, the 2nd number is kg, so they are 9k front 8k rear. And I've yet to find the spring specs for OEM damper springs, but I'm guessing they're in the 7-8k front 6-7k rear.
TEIN USA | COILOVER KIT & SPRING KIT SEARCH ?INFINITI?G37 COUPE?2008+?STREET BASIS Z

And FWIW the Flex Z here (which are the ones you were interested in) are 12k/10k, so the Basis Z should give you a ride more like stock, and the Flex Z quite a bit firmer.

http://www.tein.com/srch/us_search.p...%2b&item=FLEXZ

My Megan Street LP coilovers run a 12k/10k setup and it is pretty stiff when set to optimal street adjustment.

 

^^^Thanx. I'll look into the other set. I dont want it to bee too stiff, I want the adjustable but I daily so I need some comfort as well
How do you get 12Kg and 10Kg from the numbers I gave? What am I missing? OH, and the set you mentioned...Street Basis Z?

 

I'm not sure how it's calculated either, but 1 Pound/Foot{3} = 16.01846 Kilogram/Meter{3}

So your F:672lbs calculates to 10764.41 Kilogram/Meter{3}

The {3}=Cubed. I just didn't have a key on my keyboard to show it properly.

Like I said..... I'm not sure how it's calculated. So I'm going to grab me some popcorn and see what the experts say.

 

Click on that second link~
TEIN USA | COILOVER KIT & SPRING KIT SEARCH ?INFINITI?G37 COUPE?2008+?FLEX Z
Scroll down to the coilover spec data, then go to the far right column, You see "Spring" in the green box, you'll then see "RATE" in the teal blue box w/ (lbs/in / Kgf/mm), then scroll down to the front & rear springs in the teal blue boxes and you'll see the first number in lbs, 2nd in kgs.

 

It's pretty much a direct translation - like you have above. Spring rate is the amount of force needed to compress the spring a certain amount - a 14kg/mm spring takes 14 kilograms to compress that spring 1mm, with the same in standard measurements, is around 780lbs to compress that same spring 1 inch.

Higher numbers = stiffer spring, because it takes more force to compress that spring a given amount.

Here's a convenient calculator for you:
kg/mm to lb/in Converter, Chart -- EndMemo

From what I understand, the stock spring rates on an S model G37 run around 8k/7k F/R, but I could be wrong. It's not a direct relationship to stiffness though, as there's a bunch of other variables that come into play (motion ratio, tires taking up some of that compression, etc) but stiffer is stiffer.

For what it's worth, my car runs a 14kg/mm (lol) front and an 8kg/mm progressive spring in rear, which is a special kind of spring that ramps up it's spring rate as it compresses, going from soft to stiff.

 

BP thanks for the calculator...still a little confusing but this helps a lot. I guess the main confusion is no one really knows the real spring rate for the stock springs on an S coupe. Ah well...I can get close now. Thanx for all the help, and BLNewt, you may have saved me a few hundred bucks because of it! LoL

 

So I know the IPL soring rates are 9.8k front, 8.05K rear. Everyone tends to use "K" as an abbreviation for Kgf/mm. And since the car is Japanese and everything is in metric, just makes more sense that way. I would assume the sport springs are a 1k drop (less) front and rear.