G_3_5

Anyone driven/been in a Z or G and can characterize the differences in these setups.

What is the benefit of having the stiffer spring rates in the front. The Tanabe's spring rate in the front is 560 while in the rear is 448, while the basic's are 504 all around. Why would you want the front to be stiffer than the rear...I would expect that you would, want the rear to be stiffer-if anything. If the fronts are stiffer wouldn't you expect to feel the bumps in the road a lot more because they would get most of the abuse? How do the characteristics affect the understeer on the G and Z on these two setups.

Finally, the basic's seem to be more comfortable when lowered more, is this also true with the SO-C's?


All comments are welcome and appreciated...THANKS

Edit...any problems with clearance on a 19x9.5/10.5 rim with +26/+24 offsets

Gsedan35

iTrader: (10)

You can +or- the spring rates on Basics by 56lbs or 1Kg. While it's not much of a differance, it can be felt, though changing the rates carries a cost, not sure the benefit ratio matches up. Call Tanabe to see if they have specs on their coilovers as far as how much you can change rates, doubt it will be more then 1Kg like the Basics since neither dampner is adjustable.

I have run 560/448, 448/427, 448/375 and 448/342 setups (and many others that are out of context) and all of them differed. The idea in the front is to use enough spring to leverage the tires to keep them in the game, to keep their contact patches as optimal as possible while still maintaining tire contact in spite of how the road surface may or may not be properly maintained. In the rear, lower rates work to improve traction on corner exit.

I recommend that you go to this thread for more insight on spring rate setup. You'll notice that I start off being very skeptical about having softer rear spring rates. https://my350z.com/forum/showthread....ght=truechoice

G_3_5

Anyone have clearance issues with any of their coilovers with agressive offsets?...mine aren't too agressive but was wondering if anyone had encountered some problems when installing their c/o.

Q45tech

Members forget that in general the spring stiffness at the wheel/tire [corrected for mounting and motion angle] should reflect the front to rear weight distribution........of course this changes with acceleration and braking vs static..............most designers just use static weight.

If a vehicle is 54%/46% static the front springs need to be 54% of total AT THE WHEEL STIFFNESS.

Obvious wheel base and tuning speed [time at some speed 55-75 mph] between the undulations/bumps/seams on the highway to minimize pitching.

Front tires having more weight on them [obviously have a more NONLINEAR SLIP CURVE] thus the tendency to understeer which is then tuned out by reducing the rear traction [by increasing turning load with a rear sway bar].

Get the springs right for the weight then fine tune with sway bars and rear tires.

YOU CANNOT USED PUBLISHED SPRING RATES....YOU MUST CORRECT FOR THE DIFFERENT FRONT AND REAR MOTION RATIOS!

G_3_5

So how do you calculate for the ratio described above?
Or, is it that we would assume-using the weight ratio stated above-that in TOTAL, the rate of the front springs should be 8% higher than in the rear?

I'm a bit confused!?!

FritzMan

I've often questioned the different bias vendors offer. I've concluded that those with the stiffer rear bias are designed to work with stagger - hence promote more oversteer to offset the widers rear tires.

I've played with quite a few different spring rate combinations and found the car handled best (to my driving style) with an equal or slightly softer rear spring rate compared to the front. I run non-stagger.

IMO, the rear seems to be quite a bit more sensitive to changes than the front. 106lbs/in (2 kg) increase in spring rate in the rear was a lot more obvious in ride quality than in the front.

Note that the rear inboard spring design actually reduces the spring rate compared to the front coil-over design. So a hypothetical 500 lbs/in spring rates installed on front and rear doesn't equal to identical spring rates at the hub.

G_3_5

The Tanabe SO-C rates are 10kg/n (f) and 8kg/n (r). My G, has been reported to have a 50%/50% weight distibution-with the driver in the car.
So , if I were to lower the rate of the front springs to equal the rear (8kg)...I would expect the front rates to actually be higher in the front at the hub, right?
Would this mean that this setup would be more ideal because my weight distribution is equal, my spring rates are equal (actually higher in the front)...but because of my staggered setup, I will still get some benefit of the added oversteer.

BTW...this car doesn't get tracked so, I am trying to find a compromise between performance and comfort. So I don't want to raise the rates in the rear-I'd rather lower the fronts.

Gsedan35

iTrader: (10)

2003-2004 oem
314lbs front x.53 motion ratio x .96 angle correction = 160lbs wheel rate
342lbs rear x .36 motion ratio = 123lbs wheel rate

If I have this figured out right,......
54% = wheel rate 148lbs front or a 290lbs spring
46% = wheel rate 136lbs rear or a 378lbs spring

2004.5
314lbs front x.53 motion ratio x .96 angle correction = 160lbs wheel rate
427lbs rear x .36 motoin ratio = 154lbs

Again if I have this right,....
54% front = wheel rate 163lbs
46% rear = wheel rate 151lbs
HOWEVER, remember that front sway bars on 04.5+ car's are 17% stiffer

That being said, my own verification, ya know the testing that your supposed to do to verify things, doesn't support the idea of higher rear spring rate biases. I started out wanting to agree with the textbook to support it, reality in use however I didn't end up their or in agreement. I agree with the Unitech race team and their findings in setting up their coilover product made by Truechoice with 500/425 spring rates.

500/425 = wheel rates of 254/153
75% 25%

560/448 = wheel rates of 285/161
78% 22%

448/448 = wheel rates of 228/161
67% 33%

Curious,...Jic Flta2
560/672 = wheel rates of 285/242
58% 42%

and again,....(here's a spring rate setup I used to hammer but don't anymore)
Cusco Zero 1 or 2
560/392 = wheel 285/141
84% 16%

Gsedan35

iTrader: (10)

Their are a lot of published resorces that should be read. I support their info as well as their direction to alway's verify and be willing to make adjustments.

Fred Puhn, "How to make your car handle."
Carroll Smith "Prepare to win",
Carrol Smith "Tune to win"
Carrol Smith "Engineer to win"
Author unknown "Race car engineering"

Gsedan35

iTrader: (10)

Being that your talking about a non adjustable dampner, do not consider at 2Kg change. And even if they were adjustable, confirm with that companies techs that said dampner has the range to deal with the change.

Gsedan35

iTrader: (10)

Never ever seen a G or Z that has 50/50 weight disturbition or anything that was really any different that what the factory reports. Are we talking about a SR20 swappped car?

G_3_5

What would be the negative effect of decreasing the rate by 2KGs? I see a problem with increasing the rates-damper not being able to handle the increase...but, what are some negative effects of iputting in lower rated springs...faster wear on damper internals???

As for the weight distribution, I believe it's actually listed as 52/48...But I found a car and driver writeup that stated that it was nearly 50/50 with the driver. http://www.caranddriver.com/article....rticle_id=7580

Gsedan35

iTrader: (10)

Overdampning or too much control. Here's Tanabe's contact info, give them a call. I've never spoke with them so I can't tell you how they are.

Tanabe Racing Development USA, Inc.
1849 Western Way
Torrance, California 90501
USA
tel (310) 783-0200
fax (310) 783-0020
e-mail info@tanabe-usa.com

Your coupe has a 54/46 percent weight dist, the Z has 53/47.

zillinois

iTrader: (6)

I ran the Tein Basics for about 35+ track days and I would have liked to lower the rear spring rate about 25-30lbs. Had just a touch of oversteer on exit which prevented me from gettting on the gas as hard as I would have liked. Not suprisingly, that is close to what the unitech team came up with as well.

G_3_5

Well according the the sticker in the door panel:
Total Weight: 4360
Front: 2107
Rear: 2253

So the distribution is 48.3(F) / 51.7(R)...so this is probaby why car and driver believes is pretty close to 50/50 with driver in the car. Different for 2005+ G's?!?!

Wasn't quite sure what the effects of over dampening was...so is this what you meant?
BTW...interesting article, link found below.

"If the dampening is to[o] high the shock will act as a secondary spring or spring bumper which will not allow the vehicle to transition through rapid changes in direction easily. Over dampening will smooth out the ride of a vehicle over minor bumps by making them almost invisible to the springs. Major bumps will cause the vehicle to become unstable. The major of concern of over dampening is that the car will become sluggish through chicanes and in avoidance maneuvers...

If the dampening is to[o] low the shock will not be able to control the spring causing the car to oscillate (bounce continuously) causing a loss of grip over any bump. Transitions in a low dampening situation will be extremely quick, most of the time too quick. The main concern of this situation is that the car becomes extremely unstable under any situation. The one thing that an underdampened situation help is that it is able to absorb large bumps with ease.

It is better for the car to be over dampened than under dampened because an unstable car is uncontrollable. The optimum dampening should be just enough to stop the spring from oscillating."

http://www.penguinrc.com/information...ssprings.shtml

G_3_5

Is it true that depending on the diameter of the spring, the spring will "feel" different. Therefore, no two springs(unless they have the same diameter) will be the same; and depending on what the diameter of the spring is, the advertised s[ring rate is actually not a good indicator on how it will actually feel/perform? For example, if we have two spring-one for a car and another for a truck, both are rated at 6kg that they will feel completely different because the diameter of the spring.

If true, would you EXPECT that the truck spring would feel "harsher" than the narrower spring for a car? or vice versa. I assume that the diameter of the spring on the truck is larger.
Does this explain why springs on a c/o is usually smaller in diameter than a non-c/o setup, leading to an unexpected softer ride with really HIGH spring rates?

FritzMan

I'm not quite following your posting except I believe that the spring's coil thickness, material, and number of windings dictate spring rate.

There was a noticeable difference in the wire/coil thickness btw my JIC 9kg and 12kg even though the OD and number of windings were identical.

Gsedan35

iTrader: (10)

I have run a set of 448lbs front springs on my Koni's at were two different diameters. One was a tapered spring 90mm at top, 70mm at the bottom. The other was 65mm. They felt the same. Can't really say that going from a 448lbs 65mm rear spring felt much different from a oem diameter 427lbs rear spring either.

G_3_5

Facts:
I.)The design of a spring affects how well the vehicle will ride and handle. A spring that absorbs lots of energy will generally offer a comfortable ride. After all, it can absorb most of the road shock (energy) that is being generated by the road surface

II.)The other main part of a car's suspension is the shock absorber or damper. Contrary to its name, a shock absorber plays a minimal role in absorbing impacts taken by the suspension. That's the spring's job.

III.) There are only three things that affect spring rate:
1. Wire diameter. This affects rate since greater diameter wire is stronger than lesser diameter wire. So, when wire diameter is increased, spring rate increases.
2. Mean diameter of spring. Mean diameter is the overall outside diameter of the spring less one wire diameter. When mean diameter increases, the spring rate decreases.
3. Active coils. Determination of the number of active coils varies according to spring design. Count the total coils minus two for springs with both ends closed (includes all AFCOILS). Count the total coils minus one for springs with one end closed and one end open. As the number of active coils increases, the spring rate decreases.


Assumptions:
I have 2 coil springs with the same spring rate=504lbs or 9kg.

Hypothetical Spring Setups:
Spring A has a wire diameter of .5 inches, mean diameter of 2 inches and 10 active coils, and
Spring B has a wire diameter of .5 inches, mean diameter of 4 inches and 5 active coils


Question:
Will the different designs of Spring A and Spring B, with the same spring rate, absorb the same amount of energy-therefore, handle and feel the same?

Resolute

iTrader: (2)

Traditionally, as is textbook, the higher wheel rate should be placed at the driven end of the vehicle to balance the car without resorting to a bigger anti-roll bar. The bar, for those that don't already know, will lift the inside tire and remove otherwise available traction for acceleration that would be available if a higher spring rate was used instead. Of course, too high a spring rate will cause discontinuity with the tire's contact patch over rough pavement. The disparity seen on the Unitech spring rates and textbook example, is due to the freakishly high amount of anti-squat designed into the rear suspension. (Yet another reason I don't like the use of spring on damper set-ups for the rear, with their one to one motion ratios) Too high of a rear spring rate in the Z33, and the wheelhop will be too severe. Some people have machined the traction rod mount and relocated it to a level spot further down the frame to reduce the anti-squat, and they can more successfully run a higher rear spring rate without resorting to a thicker anti-roll bar.
Will