Spring rate help?

GSS138 · 08-12-2014, 03:40 PM

Completely depends on corner weights and if you are trying to lean the car towards more understeer or more oversteer.

On my first set of coils(soon to be installed). I have opted for 10KF/12K rear. This will produce a front ride frequency of 2.0 and a rear of 2.3
2.0/2.3 = ~.86 which is on the understeer side, and is almost identical to the OEM ride frequencies. It's also almost the exact ride frequencies of the swift spec-R.

The mfgr's tune to this frequency on purpose, understeer is safe. Almost every single OEM vehicle is going to be close to this ride frequency. I figure I will stay close to OEM, but at a stiffer spring/wheel rate, as to not make too drastic of a change. The car will behave similar to it does now, but won't roll over as bad.

Now if you wanted to dial in some oversteer which is more typical of a race car setup(looser). You would bring the front rate much higher. Something like 14k/10K on oem spring location would produce

2.3/2.1 = 1.12. Which would be mild oversteer and is pretty well balanced and is probably what I will do next for a stepping stone.

The big no-no is to do something like 2.1/2.0 = ~1 as was explained to me by an engineer(this is not my math I just know the equations).

As he described it to me, anything in the range 0.9-1.1 is flirting with some real problems and can get you into trouble. You always want to aim outside of those numbers either towards understeer or towards oversteer.

wstar · 08-12-2014, 04:36 PM

Well, in my case I've switched to true-type rears, so I can't directly compare the ratios from the stock spring setup anyways. The rule of thumb for avoiding near-1.0 (I assume for harmonic reasons between front/rear bounce) makes sense, but I'll have to figure out how to do the freq calculations for my setup first.

My current setup is definitely oriented in the oversteer direction (not that I know the math, I just know that every single time I get close to being in trouble, it's from oversteer not understeer, even in a faster sweeping corner

), and I'm pretty comfy with that.

03threefiftyz · 08-12-2014, 05:22 PM

Quote:

Originally Posted by GSS138

Completely depends on corner weights and if you are trying to lean the car towards more understeer or more oversteer.

On my first set of coils(soon to be installed). I have opted for 10KF/12K rear. This will produce a front ride frequency of 2.0 and a rear of 2.3
2.0/2.3 = ~.86 which is on the understeer side, and is almost identical to the OEM ride frequencies. It's also almost the exact ride frequencies of the swift spec-R.

The mfgr's tune to this frequency on purpose, understeer is safe. Almost every single OEM vehicle is going to be close to this ride frequency. I figure I will stay close to OEM, but at a stiffer spring/wheel rate, as to not make too drastic of a change. The car will behave similar to it does now, but won't roll over as bad.

Now if you wanted to dial in some oversteer which is more typical of a race car setup(looser). You would bring the front rate much higher. Something like 14k/10K on oem spring location would produce

2.3/2.1 = 1.12. Which would be mild oversteer and is pretty well balanced and is probably what I will do next for a stepping stone.

The big no-no is to do something like 2.1/2.0 = ~1 as was explained to me by an engineer(this is not my math I just know the equations).

As he described it to me, anything in the range 0.9-1.1 is flirting with some real problems and can get you into trouble. You always want to aim outside of those numbers either towards understeer or towards oversteer.

I think you need to go back to that engineer and have him run you through it again...you didn't grasp it the first time.

2.0f/2.3r is going to be loose, 2.3f/2.1 is pretty nuetral and 2.1/2.0 is a little soft and probably still on the nuetrul side (tending towards oversteer)....

Fwiw, my race car sits in the 2.4f/2.25 and tends towards slightly loose on corner exit and that is with no rear bar.

DEpointfive0 · 08-12-2014, 05:50 PM

Which one of you true type rear coils guys needs SPL toe arms?!?!?!

Shamu · 08-12-2014, 05:56 PM

Quote:

Originally Posted by clintfocus

Don't run the rear Hotchkis, way too stiff and most likely contributing to the inside rear tread lift. Go back to stock rear and see how it goes

Agreed im running stock nismo bar in the rear

synolimit · 08-12-2014, 06:31 PM

have to find out first. all i know right now im 57/43 weight ratio so the rear is way happy!

finally someone talking about frequency! i have no idea what youre talking about but was trying to tell someone and couldnt say it right so he had no idea what i was talking about. if you could PM we wont thread jack, i have a ??

Quote:

Originally Posted by GSS138

Completely depends on corner weights and if you are trying to lean the car towards more understeer or more oversteer.

On my first set of coils(soon to be installed). I have opted for 10KF/12K rear. This will produce a front ride frequency of 2.0 and a rear of 2.3
2.0/2.3 = ~.86 which is on the understeer side, and is almost identical to the OEM ride frequencies. It's also almost the exact ride frequencies of the swift spec-R.

The mfgr's tune to this frequency on purpose, understeer is safe. Almost every single OEM vehicle is going to be close to this ride frequency. I figure I will stay close to OEM, but at a stiffer spring/wheel rate, as to not make too drastic of a change. The car will behave similar to it does now, but won't roll over as bad.

Now if you wanted to dial in some oversteer which is more typical of a race car setup(looser). You would bring the front rate much higher. Something like 14k/10K on oem spring location would produce

2.3/2.1 = 1.12. Which would be mild oversteer and is pretty well balanced and is probably what I will do next for a stepping stone.

The big no-no is to do something like 2.1/2.0 = ~1 as was explained to me by an engineer(this is not my math I just know the equations).

As he described it to me, anything in the range 0.9-1.1 is flirting with some real problems and can get you into trouble. You always want to aim outside of those numbers either towards understeer or towards oversteer.

clintfocus · 08-12-2014, 07:13 PM

Quote:

Originally Posted by Shamu

I run 1000 lb fronts and 550 lb rears and thats not enough spring for slicks. You are way undersprung upfront. low front spring rate allowing rear to lift like that.

We are going to 1100 front and 700 rear maybe more! I drove on streets for couple years with 1000 lb springs and JRZ coilovers. Was downright comfy.

1000lbs springs are still softer then bump stops

Quote:

Originally Posted by GSS138

Would agree with all the above. The rates are low. In the pic, the front right is rolling over(as is probably the rear), and the rear sway is lifting the rear left.

Clint's suggestion is definitely the fastest, least expensive change though. Long term I would look at something more like 16kF/10KR if you otherwise like your current setup.

before any spring rates get changed around, i think that rear Hotchkis needs to go and be tested with stock. then further tuning from there.

Quote:

Originally Posted by synolimit

I was told by the company I bought my 2 ways from that the front and rear rates need to be closely matched for even balance. Like if you need a harder front you might also need to step up your rear. He advised to stay within a 5-6k range unless you're a drifter then it changes. Anyone else follow this rule?

I see Shamu is at 8k difference now but would like 7k and bkleeman is within that range.

with both the weight balance of the 370 NOT being 50/50,. and the high amount of both front grip potential with sqaure tire setup, decently high levels of unsprung weight, and the wishbone suspension, i think the front really needs a good amount of rate. depending what rear rate you need depends on spring location (stock or true coilover), sway bar selection in back (large, stock, or none), power level, and LSD.

Quote:

Originally Posted by Shamu

Agreed im running stock nismo bar in the rear

I run G37S coupe rear bar

wstar · 08-12-2014, 07:15 PM

Ok one more thing: I know the exact brand and type of coils on my RS1's: they're HyperCoils, and their model number system is pretty simple (they go by "free coil length", basically a coil count, the I.D., and the spring rate). So the ones I have now are 8A0500 rear (8 coil, 2.25 ID, 500 lbs/in), and 6A0650 front (6 coil, 2.25 ID, 650 lbs/in). You can see their catalog page here: http://www.hypercoils.com/skin/front...Catalog_12.jpg , but basically I can pick any reasonable rate and coil count I'd want.... do I need to change the length when I change the rate, or keep the same length as the ones I have and just change rates?

03threefiftyz · 08-12-2014, 07:30 PM

Make it easy on yourself, just get a pair of springs in 50lb increments from 600-1500lb....

GSS138 · 08-12-2014, 08:32 PM

Quote:

Originally Posted by 03threefiftyz

Make it easy on yourself, just get a pair of springs in 50lb increments from 600-1500lb....

Best answer!

GSS138 · 08-12-2014, 08:35 PM

Quote:

Originally Posted by synolimit

have to find out first. all i know right now im 57/43 weight ratio so the rear is way happy!

finally someone talking about frequency! i have no idea what youre talking about but was trying to tell someone and couldnt say it right so he had no idea what i was talking about. if you could PM we wont thread jack, i have a ??

Syno, you actually setup perfectly for doing doughnuts in the snow.

GSS138 · 08-12-2014, 09:07 PM

Quote:

Originally Posted by 03threefiftyz

I think you need to go back to that engineer and have him run you through it again...you didn't grasp it the first time.

2.0f/2.3r is going to be loose, 2.3f/2.1 is pretty nuetral and 2.1/2.0 is a little soft and probably still on the nuetrul side (tending towards oversteer)....

Fwiw, my race car sits in the 2.4f/2.25 and tends towards slightly loose on corner exit and that is with no rear bar.

350 completely and respectfully disagree. Disagree since the freq calcs include corner weights, The guy I am talking to is Gordon Benson from Koni that engineered the 2812 long body. I know Koni these days isn't the "cool kids" choice of dampers, but math is math. If you want email him at Gordon.benson@itt.com. Guy is awesome and will even get into the calculus of it.

Every post market "spring kit" out there tunes to something around .80-.85
because they can sell that product and not kill someone. Or at least not be sued for creating an "unsafe ride rate" as per the DOT.

that being said, I don't drive your car that you know intimately. I see what you are saying, because you know your car's frame, your sway bars, your tires, what you like, etc. better than I do, and are a much more experienced driver. But as for a baseline tuning point, and to understand how a suspension works(regardless of the car) the Front ride Freq/ rear ride Freq, tells you how the car is setup. <1 induced understeer. > 1 induced oversteer. That's not my opinion that's just physics. Doesn't tell you how to drive it fast, doesn't make you push the throttle when you know you maybe shouldn't, it's just a reference point.

clintfocus · 08-12-2014, 09:19 PM

wstar · 08-12-2014, 10:01 PM

Quote:

Originally Posted by 03threefiftyz

Make it easy on yourself, just get a pair of springs in 50lb increments from 600-1500lb....

I'm sure I'll end up closer to that than I want to be, eventually. But the nature of my earlier question, if it wasn't clear, is more like: if I change a spring rate dramatically and want to maintain approximately the same suspension stroke and ride height, do I need to buy shorter springs when I buy stronger springs, because they won't be as compressed when the car is static?

Super Werty · 08-12-2014, 10:09 PM

Quote:

Originally Posted by bkleeman

Get the front as stiff as you can - you probably won't over do it. We're running between 1000 - 1200 lb/in front springs (900-1000 in the rear) with a custom swaybar made from .120 wall roll bar tube and the front still rolls over more than we'd like. See pic:

Hotchkis is the stiffest off-the-shelf bar that I know of tho, so you're left with just upping the spring rates.

Who made the sway bar? I wonder if they would sell some.

What end links do you use with this front bar?

Do you guys run a rear sway?

08-12-2014, 03:40 PM	#16 (permalink)
GSS138 Track Member Join Date: Mar 2013 Location: Mission Viejo, CA Posts: 769 Drives: '12 370Z 6M Sport Rep Power: 13	Completely depends on corner weights and if you are trying to lean the car towards more understeer or more oversteer. On my first set of coils(soon to be installed). I have opted for 10KF/12K rear. This will produce a front ride frequency of 2.0 and a rear of 2.3 2.0/2.3 = ~.86 which is on the understeer side, and is almost identical to the OEM ride frequencies. It's also almost the exact ride frequencies of the swift spec-R. The mfgr's tune to this frequency on purpose, understeer is safe. Almost every single OEM vehicle is going to be close to this ride frequency. I figure I will stay close to OEM, but at a stiffer spring/wheel rate, as to not make too drastic of a change. The car will behave similar to it does now, but won't roll over as bad. Now if you wanted to dial in some oversteer which is more typical of a race car setup(looser). You would bring the front rate much higher. Something like 14k/10K on oem spring location would produce 2.3/2.1 = 1.12. Which would be mild oversteer and is pretty well balanced and is probably what I will do next for a stepping stone. The big no-no is to do something like 2.1/2.0 = ~1 as was explained to me by an engineer(this is not my math I just know the equations). As he described it to me, anything in the range 0.9-1.1 is flirting with some real problems and can get you into trouble. You always want to aim outside of those numbers either towards understeer or towards oversteer. __________________ Current Mods: Vorpal Weapon +5.

08-12-2014, 04:36 PM	#17 (permalink)
wstar A True Z Fanatic Join Date: Mar 2009 Location: Houston, TX Posts: 4,024 Drives: too slow Rep Power: 3594	Well, in my case I've switched to true-type rears, so I can't directly compare the ratios from the stock spring setup anyways. The rule of thumb for avoiding near-1.0 (I assume for harmonic reasons between front/rear bounce) makes sense, but I'll have to figure out how to do the freq calculations for my setup first. My current setup is definitely oriented in the oversteer direction (not that I know the math, I just know that every single time I get close to being in trouble, it's from oversteer not understeer, even in a faster sweeping corner ), and I'm pretty comfy with that. GSS138 likes this. __________________ 7AT Track Car! Journal thread / Car setup details

08-12-2014, 05:50 PM	#19 (permalink)
DEpointfive0 Premium Member Bitches Join Date: Jan 2012 Location: SoCal Posts: 14,824 Drives: a lot Rep Power: 17151	Which one of you true type rear coils guys needs SPL toe arms?!?!?! GSS138 and synolimit like this. __________________ Do YOU want to know what/where I got my username from? ( Click to show/hide ) NSFW due to language:

08-12-2014, 07:15 PM	#23 (permalink)
wstar A True Z Fanatic Join Date: Mar 2009 Location: Houston, TX Posts: 4,024 Drives: too slow Rep Power: 3594	Ok one more thing: I know the exact brand and type of coils on my RS1's: they're HyperCoils, and their model number system is pretty simple (they go by "free coil length", basically a coil count, the I.D., and the spring rate). So the ones I have now are 8A0500 rear (8 coil, 2.25 ID, 500 lbs/in), and 6A0650 front (6 coil, 2.25 ID, 650 lbs/in). You can see their catalog page here: http://www.hypercoils.com/skin/front...Catalog_12.jpg , but basically I can pick any reasonable rate and coil count I'd want.... do I need to change the length when I change the rate, or keep the same length as the ones I have and just change rates? __________________ 7AT Track Car! Journal thread / Car setup details

08-12-2014, 07:30 PM	#24 (permalink)
03threefiftyz Track Member Join Date: Apr 2010 Location: MD Posts: 536 Drives: 03 350z 6mt Rep Power: 16	Make it easy on yourself, just get a pair of springs in 50lb increments from 600-1500lb.... andy_meng1024, GSS138 and milmast like this.

08-12-2014, 09:19 PM	#28 (permalink)
clintfocus Track Member Join Date: Jan 2011 Location: los angeles Age: 38 Posts: 933 Drives: 370z, EK Civic, F150 Rep Power: 15	DEpointfive0 likes this.

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