strut,spring vs. coilover

[TurboKA37]

ok im looking to upgrade my suspension soon and ill be getting alot of other components such as stabilizer bars, strut bars, etc. ive been looking at alot of the suspension possibilities and i need to kno how much a difference there will be between say some nice JIC coilovers and a AGX/Tech-S combo? i need to kno if it is really worth the extra $500-700 to get coilovers over the strut/spring combo. i am looking to make my car be superior in handling. im a high school student that has saved up money for these mods so im making sure i make the right decision.

[f8sjester]

what do you want the car to do? are you active in auto-x or track racing? or do you just want superior street handling?

seems like the concensus is that if you just want a daily-driver that can carve the occasional canyon then a proper strut/spring combo will do you fine. . .

coil-overs are great but most people will never really re-adjust the set after the initial install unless they are serious about adjusting their suspensions due to specific track conditions. . .

for a daily driver. . . save your money on coilovers and drop it on something more worthwhile. . .

my .02 cents

[Q45tech]

Remember the purpose of springs is just to hold the body up and to push the tires down over bumps.

Whether the body sways on the springs doesn't change the tire load 1 pound.......[except that as the body sways the camber changes on the tires and that changes the shape of the contact patch].

It is rare for ANY spring redesign to materially affect [more than 2-3% improvment/change] the handling as measured with test equipment on the street.

Weight and tires are much more dramatic in their effects!The fastest wearing stickiest tires will change things to the better much more significantly.

Generally a 18-20mm [or there abouts] rear sway bar will be more cost effective than any springs.

The front tires have the most weight so that is where you concentrate first by adding a higher load index tire as a 10% stronger [high max load] tire will slip 4-5% less [the slip angle will decrease] at the same cornering load.

Cars without rear sway bars have way too stiff front bars.....that are loosely coupled in the first inch of body sway but get progressively more as the body roll increases. When you add a rear bar you can decrease the front bar diameter 3,4,5,6,7% and increase the coupling ratio [the sloppy slack in rubber mounting and end link bushings]........a few metal washers to increase the rubber compression or urethane type isolation bushings.

What you want is to reduce the front roll couple and increase the rear roll couple resistance, moving the car from severe understeer to a more neutral [in dry] situation.

Unless you are driving in rain the front is always the limiting factor in increasing handling.

[Dori Dori]

The fastest wearing stickiest tires will change things to the better much more significantly.

And body roll would increase greatly as well.

[Ceptos]

sound advice for the spring/shock combo. tho for some reason i could never convince myself to take it =) my intensions are basically street, but my goal for my car is to make it into a new car that will last me 200,000+ miles, so i want to buy my setup once, and have something that will last and fit a variety of uses. i went with the JIC FLT-A2's, they are not installed yet tho. with the right combo of springs, shocks, bushings, sway bars and tires your car will handle very good.

by just stiffening your cars suspension, you are not improving its handling very much, body roll does not cause weight transfer. reducing it does reduce camber change. reducing weight transfer is key to improving handling, lowering your car will reduce weight transfer. if you are not tuning for abrupt shifts in weight, such as autox, then you only need your springs stiff enough to keep your suspension from bottoming out, any further reduction of body roll can be achieved with sway bars. you also want to think about controlling the tire across bumps, a spring shock combo will be much more bump friendly than a coilover.

with the right street setup you could easily get your car to handle around the .95-1.0g, thats about as good or better than a new lancer evo.

[Dori Dori]

You are wrong. Body roll does increase weight transfer. As the center of gravity changes and shifts, weight follows.

[Q45tech]

When you divide the center of gravity by the treadwidth you see that within reason [a 1-2" drop] is not very meaningful in the amount of weight transfer.........with a 22" C of G and a 61" TW the transfer is 0.360 with a 21" C of G it is 0.34426 or only 1.574% less weight transfered on a 3,100 pound unsprung weight [at say 53% F/R] =1,643 x 0.01574= 25.86 pounds.

Assuming that a FRONT tire has a static load of 900 pounds and a transfer load of 360 pounds due to G forces/body roll, 1260 vs 1234 pounds, a 2% change in load might affect the tire slip angle by 2.25% at the maximum [assuming a 1400 pound load index tire]........at most a 0.021 G change...........but every decimal point helps.

In a properly designed suspension the instant C of G won't change much due to 3" body roll now the REAR roll couple pivot point is another thing entirely due to the IRS. The rear C of G is higher [2,3,4"] but the static weight is much lower [on RWD front engineed Nissans]............therefore the weight transfer is more but the lower static tire load make the total handling tire load just about equal front or rear.

If you increase the front tires load index by 100 pounds each you will achieve much more G increases than lowering 1" due to being down in the more linear range of the slip angle vs load. graph.

The industry allows tires to be used that only have a 12% safety margin to maximun load.

[Ceptos]

thanks for clearing that up q, my point is that reducing body roll does not reduce weight transfer, there is weight transfer even at zero body roll, say a go-cart. the more important aspects of body roll are tire traction and affects on aero dynamics at higher speeds.

[Dori Dori]

Reducing body roll will reduce weight transfer. Since Q45tech has become your demi-god, re-read what he is saying and you'll see that. End of story.

Here's a picture d00d:

Also Q45tech, do you know what the height of CG is on the 240? I'm curious.

[TurboKA37]

Wow! i am thoroughly confused! i obviously need to go learn some more on suspension. ill look around here and possibly go buy a book. are there any good books that cover suspension? thanks for all the help guys.

[TurboKA37]

ok, lets say i am going to spend around 3k on suspension, wheels, and tires with a .95-1G in mind. lets say i get some AGXs with some Tech S springs (i kno this wont be worth the money for handling but i want a bit of drop on my car anyways) thats going to be around 600-700 shipped. then wheels i am planning on spending 150-200 per wheel so lets say thats about 700 then get some nice tires (what do u guys think about the parada spec-2 or AVS ES100?) so the strut/springs, wheels, and tires are going to run me about 2000 once everything is done. that leaves me 1000 for some sway bars and some other things like strut tower bars. will this stuff get me near .95 Gs?

[Grant@tirerack]

While the Parada Spec 2 looks real nice, on the skid pad, the AVS Es100 was the better tire. On the same course, same vehicles, over 80 drivers who test tires as part of their job 38 weeks out of the year:

Parada Spec 2- .92AVS Es100- .93

The AVS Es100 is also a great tire if you like to hear yourself talking to your passenger. The Parada is probably one of the loudest tires I have ever driven on.

[TurboKA37]

thanks for the help grant

[Exar-Kun]

I would think body roll would change the load on the tire, more from an "inertial load" standpoint, esspecially if the contact patch of one tire suffers because of excess body roll....

but thats just me. I would also say that springs can affect the rate of roll, as a stiff spring would not compress under an inertial load as easiliy(in mid-turn, or even turn in) tuhsly keeping the body from leaning toward that corner(the spring), while the effect may not be as dramatic and strengthening the link between the suspension peices(sway bars) it does still happen.

anyways, dennis needs to quit with all that damned math and just get to the point! It makes our heads hurt!

hehe.anways, the ES-100 is a far superior tire to the spec-2. neither wear spectacularly, but hey..do you want good grip or long tire wear? :p

Also, just a side note, the slalomn numbers of the greddy/TEIN 350Z went up by a nice margin (up I think 6mph) in road and track, and added another few units of skidpad handling when they installed the coilovers.... just a thought.-chet

[Dori Dori]

ok, lets say i am going to spend around 3k on suspension, wheels, and tires with a .95-1G in mind. lets say i get some AGXs with some Tech S springs (i kno this wont be worth the money for handling but i want a bit of drop on my car anyways) thats going to be around 600-700 shipped. then wheels i am planning on spending 150-200 per wheel so lets say thats about 700 then get some nice tires (what do u guys think about the parada spec-2 or AVS ES100?) so the strut/springs, wheels, and tires are going to run me about 2000 once everything is done. that leaves me 1000 for some sway bars and some other things like strut tower bars. will this stuff get me near .95 Gs?

SCC hits 1g in the new issue (just got today in the mail).

Funny thing is they had to reduce the spring rates to do it (they compensated w/ anti-roll bars though)...point is, I bet you can come damn clost w/ $3k!

[TurboKA37]

thats what im thinking. i just need to do more research so i understand what to buy and how to tune better

[Q45tech]

Adding, subtracting, multiplying, and dividing isn't considered math. Every car's weight and tires are different without some simple manipulation you cannot translate the numbers I provide.Remember I think Q and 4300 pounds is a lot different than 3,000 but the concepts are identical.

[Grant@tirerack]

You can also check out our track test figures for quite a few setups we have tested in house here:

http://www.tirerack.com/a.jsp?....html

It will show you the hard numbers for lap times and skid pad times, with stock springs, different aftermarket springs, and springs with swaybars. That would give you a general idea of what you can expect with these upgrades.

[Q45tech]

When you study all the TR data you will see tires can provide up to 2.5-3% improvement, springs 1% improvment and sway bars 1% improvent..............not necessarily totally additive.These are generic fixes and assume that another 1-2% is available if bars are fine tuned and alignment errors corrected.

But giving benefit of the doubt with the whole gamut ---- 5% even 6% decrease in lap times seems obtainable with lots of thought and work.

Note that you can over do it also with mods providing no improvement and in many cases making things worse......too large wheels and tires.

Note they never give /do much wet comparison testing as the springs and bars and tires may decrease wet performance when you get on the ragged edge in dry handling!

Without tireracks diligence we would be much less informed!

Now if they would only buy a Q or LS430 or Crown Vic to do some heavy RWD car testing.

[Grant@tirerack]

With our new test track we have added the ability to test in wet conditions as well as dry. We have also added a new timing system to generate seperate times in each section of the track as well as braking distance and g force on the skid pad. All of our testing starting this Spring includes those stats.

[jdmfreak]

So if you do the spring/shock combo, what else could you do with suspenion without over doing it.

[Q45tech]

Try adjustable sway bars before the springs and get ONE with the car, till you can feel a 20 pound difference as you change bar rates.Find some higher load index front tires.

[TurboKA37]

Try adjustable sway bars before the springs and get ONE with the car, till you can feel a 20 pound difference as you change bar rates.Find some higher load index front tires.

"one"? one of what with the car?

[TurboKA37]

what about the suspension techniques f/r sway bar combo? are they any good? or should i go with the more expensive cusco sway bars and if so which one(s)?

[Exar-Kun]

I got a ST sways, good stuff. rolls much less, transitions during hard cornering are much more precise.-chet

[Q45tech]

You do the mathematics and determine the bar's stiffness and decide which you want.

A sway bar should provide no more than half the total stiffness at the upper extreme[racing on track]............20-25-30% is a good place to start in the rear for street use. 240sx ~~~18-19-20mm.

[dr!ft]

What about the Cusco sway bars? Better than the ST's?

[TurboKA37]

ok so i tried converting the ST sway bar measurements into mm and i think it comes out to about rear: 18mm and front: 27mm. these measurments are by comparing the mm side to the inches side on a ruler so they may not be perfect but pretty close. i dont plan on doing much autox but more just for street use. from what i have gathered i think this should be a descent set-up with some new wheels/tires and strut/springs. what do u guys think about using these parts?

[Q45tech]

You're missing the point, better than what. It's all interrelated with tire size and compound and road/tire temperature and the coefficient of friction/roughness of the road.......bump per mile and height of bumps.Each owner will have slightly differing requirements.

Generally one can adapt to a rear bar with 30,40,50 pound inch of added wheel roll stiffness..........the factory rear bar on a 300zxtt is 45, a Q45 active is 40, a Q45t is 15,.........all with approximately the same rear spring rates ~~120 pounds per inch.On my 90 Q I run Eibachs with a 20mm [40 pound] rear bar.The 1" roll stiffness is 145 pounds, the 2nd inch is 180 pounds, the 3rd inch is 240 pounds. It would take 560 pounds to roll the rear body 3" vs 370 pounds stock. Instead of rolling 3" the rear rolls 2.25".........roughly a 25% decrease at the exact same G force.

You must KNOW the roll couple ratio ......how much stiffer the front is vs the front rear weight ratio and make sure what ever you do the front KEEPS a ratio higher than the rear by what ever the weight ratio is.For example on a car has 54% of weight on the front, the front total stiffness] should be stiffer than this by at least 5% ........use 60% as a safe number in dry weather and 65% if you are not an expert race driver in the rain.

Factory designs uses 75% [70-80%] to create understeer for non race experienced drivers and severe rain where rear friction is low with any acceleration.

You must decide how much on the edge you can live with and take resonsibility for.............ending sentences with prepositions but it sounds good.

[C-Kwik]

You are wrong. Body roll does increase weight transfer. As the center of gravity changes and shifts, weight follows.

Body Roll is more of a result of weight transfer. The harder tou turn, the more weight transfers. The more weight transfers, the more the body will lean or want to lean. There is some weight transfer that occurs with body roll, but it is minimal. Look at a front or rear view shot of a car under full turning load. The Center of Gravity will have shifted maybe a couple of inches at most. Now imagine putting something under the tires on one side to simulate body roll(Not the suspension) at a state of rest. You'll notice a slight increase in suspension compression on the side that it lower, but not near as much as you would see in a turn.

That being said, since weight transfer can't be avoided for the most part, controlling body roll should be concentrated on minimizing the effects of weight transfer. Each car needs to be approached differently. Particularly when dealing with different types of suspension. Cars with double wishbone suspensions and their variants can have less roll stiffness since more negative camber is added as the car leans. Cars that use struts need stiffer sway bars to try to keep camber changes during turns to a minimum. This will reduce the need to dial in more static negative camber. While you can certainly adapt the static camber setting to the amount of roll, adding more static negative camber will reduce the straightline contact patch(braking and accelerating).