Matthew91-Z28

OK....I own a 91 convertible z28. As far as suspension I have done
1)eibach prokit springs
2)new stock shocks/struts
3)boxed in LCA's
4)adj. panhard rod
5)wonder bar
6)alston SFC's (welded in)
7)ws6 front and rear sway bars

I used to drive an '00 TA w/ t-tops; that car always felt so much more 'together' than my 3rd gen despite all the mods. Maybe its b/c its been a while since I drove it and nostalgia is taking over.

I do know that 4th gens beefed up the front end a little to make it sturdier than prev years. Either that or I have a really good suspension set-up but don't have the LS1 to back it up to see how it'd really feel under pressure.

Everything is tightened up. The only other things I'd consider doing would be a STB (that prob should have been my first mod) and a 4-pt roll bar. But it sounds silly that I'd have to weld in a roll-bar to get the 4th gen feel, but hey, it is a convertible.

ANyone else in here drive 4th gens and have an opinion on the suspension differences?

Keith5

I know what you mean! My Formula always felt like it handled great until I drove my 4thgen. I feel like I'm in an airplane with the 4thgen. It is the best handling car I've ever driven.

The rear suspension is the same. The front is a lot different and the 4thgen has rack and pinion steering. I'd say that makes a huge difference between the two generations.

rscamaro305

iTrader: (1)

my friends '02 SS handles like a gocart and i love the way the thirdgen handles. but the SS just out classes it all the way. I think the 40 series tires help a lot too. Just my observation.

Keith5

My 4thgen and my 3rdgen both have 245/50/16 tires.

zman1969

iTrader: (9)

never owned a 4 th gen but have owned my 87ta since 90,i always thought it rode good but started reading this board .never knew wha a wonder bar was,and was suprised my car (ws6 w 16")didnt have one! dont know why only iroc's got em? so i found one in the boneyard and put it on. i'd say a little difference and weighs almost nothing! then i bought a edelbrock STB for carb motor,i was beefy and lightweight ,MAN WHAT A DIFFERENCE!!
i am currently waiting for SFC from tds -alston weld in , im ready to see what they do for it . the old cars got 153k on it now so far id say its better than new. i decided against spohns as i dont like how they weld to the frame and body. i just dont see how theyd do much ,but people give good reports on their performance.
in the plans now: alston sfc, slp 1 3/4" headers,new cats(old rattled out)flowmaster y-pipe,1le frt brakes rebuilt 92 rear w 3.42s.

Matthew91-Z28

yes I'm sure the rack and pinion helps alot w/ handling. Don't know if thats all though. From what I recall, 4th gens have a beefier subframe. The biggest difference between the two is in the front where the transmission crossmember attaches (I think). I suppose that the short horizontal bars from spohns SFC's would do the trick.

From what I hear, alstons are great as far as chassis stability in general. And they did help alot with straight line driving after I got them, but not much w/ cornering. I've heard spohn gives the best support in that area. I'm going to fab up something like spohn's to that extra stability. Wouldn't be difficult. Just a few pieces of steel tubing cut to length. Only hard part would be the passenger side, which has a little bend in it.

I think I'm going to get a STB next. From what I hear, it makes a huge difference. And I do have problems that I think the STB will def take care of (i.e. I notice alot of wandering on grooved pavement and bumps in the road).

I think the biggest diff I made in my suspension was the panhard rod and boxing in the stock LCA's. WOW!

ShiftyCapone

iTrader: (7)

I geuss I am the only one here that is going the other way. My thirdgen will hand my fourth gen its *** in any race around the twisties. Then again my 4th gen has a stock setup and my thirdgen is not exactly stock, however, my roomates 2002 SS has Hotchkis springs, LCA relocation brackets, panhard rod, subframes, and $400 bilstien shocks and I still don't think it handles as well as my thirdgen. The two cars even have the same exact Eagle F1 GS's on as well. He has the SLP chrome 17x9 ZR1's and I have 17x9 snypers. I have not even put my sub frames or wonder bar on yet. 4th gens still have a lot of body roll when you watch them in action. I have followed my roomate in my 95 and watch him get on it around corners and I know my thirdgen does not roll like that. Don't get me wrong it still handles amazing but I think the overall height and weight really favor the thirdgens. My fourth gen is just all over the place and I get scared at 125mph. My thirgen is just scary sometimes the way it handles. My roomate and I always rag on each other and he always says "you will get in and out of the corners before i will, but I will run ya down in the straights."

joshp14

My wonder bar on my 88 does...well...wonders. The steering on my 88 seems to be a little better than the steering on my 95. Although the 95 overall suspension system takes corners better and keeps it stuck around corners a little better.

jaredi

Well, let's see. 4th gen cars came out with a coil-over design which is inherently superior in the first place, plus it has an upper control arm to provide negative camber under compression. Coil-Over makes for a stiffer wheel rate, but an increased ride quality over 3rd gen style separated shock/spring setup, so 4th gen is one-up there. The negative camber under compression, well, I'm not familiar with the 3rd gen's tendencies suspension travel, but it does lack the UCA. I know on a Mustang, with it's horrid geometry the car gains positive camber under compression (BAD). This can be fixed with a suspension with a UCA type setup.

Plus rack and pinion...

As far as comparing the two cars, it depends alot on the shape of the car you are driving. I drove a 94Z with 104K on it and it felt awful. But, I drove 94Z that my friend has with only 45K on it, never wrecked or anything, and it was very nice, it would turn a little better than the 92RS I drove, and they were equipped with the same size wheels/tires. I rode in a 00 SS all stock and it was ungodly. Talk about a car feeling planted to the road...

The hardest cornering car I ever rode in is a 94 V6 with TT2's, Eibachs, and 275's all the way around. The guy scared me just a bit. That car cornered HARD, or at least it felt like it

There's probably more, but that's all I can think of right now.

Jared

Momar

The thirdgen uses struts instead of shocks like the fourthgen. This actually helps the handling. Also, the thirdgens w/ the quick ratio box has a better steering ratio, but have extra weight because it is not rack and pinion like the fourthgen. The fourthgens were designed to ride better which is nice, but not to important to me. With a thirdgen and fourthgen that are in the same shape and have equivilant wheels, tires, and mods the thirdgen will outhandle it. The main reason that fourthgens appear to be better is because the suspension in them is so much newer normally. There was a long thread discussing this a while back. I will see if I can find it. If I recall right the thirdgen 1LE's pulled more g's than the fourthgen 1LE's out of the box also which is the top of the line of both suspension setups as far as stock goes. I will look for that thread.

Ben

jaredi

Who told you that and how do they plan to back it up?

Please do. I am open to the idea that I may be wrong, but I think I am right with my whole point about 4th gen being a superior design.

The 4th gen does have a weight disadvantage though.

My main idea is, if you were to mod out the suspension, the 4th gen will yield better results. Prove that statement wrong, seriously. I WANT to believe my third gen suspension is better for a modded car, but I can't do it.

It's just the fact that a 4th gen car with 900# front springs and Koni DA is a fully streetable setup, and to get the equivalent wheel rate out of a setup like on a thirdgen, you have to have some equivalent shocks and somewhere around a 1600# spring(or something to that effect...) Talk about jarring your guts out every time you hit a pothole...

Jared...

I WANT TO BELIEVE

ShiftyCapone

iTrader: (7)

The suspension set up may be better from a design point on the fourth gen but when you take into considerations like weight and basic body height and design the thridgens handle better. They do not have upper control arms. They have A arms up top and down low. Like I said my roomate has a fully suspenioned 2002 and my thirdgen still handle better. The ride quality is better in but the overall performance of the car in the corners is better with my thirdgen. And mileage does count. A worn out thirdgen will feel no where as responsive as a newer fourth gen. All of our cars have low miles so they are on pretty equal playing ground. The RS has 35k and 95 Z has 41k and roomates 02 has 7k. I to remember that article about the two 1LE cars and the thirdgen being better.

jaredi

I get you there, not that I completely agree, but I can't say that I don't... I haven't had enough seat time in a 4th gen to compare stock vs stock to a 3rd gen. I do know the 4th gen felt alot more confident (excluding that POS 94Z that I test drove...) in the corners.

My bad. I guess I don't know the difference... Isn't the lower A arm considered a LCA?

I don't know as I've never driven either gen 1LE.

My point is, the 4th gen is a better design, and as such it will take better to modding. For example, an LS1 car with 900# front coilovers and Koni DA shocks and a 175# rear coilover, lowered an inch all the way around with some stiff sta-bars, will going to walk all over a thirdgen, IF power is equal, and the front suspension is equal with the different design...

*BUT*

To have the equivalent front suspension from a 3rd gen car, you would have to run equivalent shocks, and hellacious spring rates. I am gonna go outside in a few minutes and measure my lower A ARM and see just what the efficiency is. For a 79+ M*stang it is about 25% on the traditional setup and about 95% efficiency on the coil-over kit from Maximum Motorsports. I would imagine the thirdgen can't be much better, although geometry HAS to be better.

My whole point here is that once modding begins, 4th gen will yield better results. Even if you could get a spring stiff enough to keep up with a 900# coilover, you would NEED a track that's smooth as glass to utilize it without screwing yourself over in the process.

I guess I'm in the wrong thread because this one says STOCK 4th gen vs. modded 3rd gen...

Jared

SLP IROC-Z

iTrader: (1)

hmm, i know i raced 98 or newer firehawk on back twisty roads and he couldnt hang with me on the corners. one car may feel more nimble then the other but the proof is in the skid pad, slalom and road course times.

TransAm12sec

Why is it 4th gens are heavier with an all aluminum motor?

Momar

https://www.thirdgen.org/techbb2/sho...ack+and+pinion

In the link I posted above, it lists a couple of the advantages of the thirdgen. There are advantages and disadvantages of both, but even in stock form according to people who have seen the tests the thirdgens usually do better. I have also read in several posts that scca guys usually prefer to use thirdgens.

Ben

jaredi

Alot of that is driver. Most is driver. I ran off and left a Thirdgen on my road and all I was driving was a Thunderbird... Dude said he didn't know the road well enough or he could have kept up...

Actually I don't know about LS1 cars, but LT1 is Iron block... At least I've always thought they were....

I still don't see any really strong arguments as to why the 3rd gen is superior.

Taller car=bad. Agreed. You CAN lower the car though, especially with a set of adjustable coil-overs. It makes the difference less obvious.

Threw out the separate strut/spring design and added coil-over shock design. I must disagree. This may not be the best for sheer performance out of the box but if you get on a rough track you will appreciate it because it is WAY more forgiving.

As for the smaller front bars... Who is really gonna keep the stock front bar anyway? Another guy posted about 4th gen and understeer, it's all about how your car is tuned. You can get a heavier spring in the back and it will fix your understeer problem.

As for SCCA A/S, it's alot easier to carb a 3rd gen. Also another thing just popped into my head, I think alot of guys that are quoting SOTP and skidpad numbers aren't thinking about an open track application. I will agree that a thirdgen will do just fine mod for mod in AutoX or on a skidpad, but on OT, the coil-over really begins to show it's advantages, especially on a rough track, it's not all about Ride Quality ya know

4th gens, at least modified ones, don't do too shabby in OT

I still don't quite get why 4th gen is an inferior platform. All it's disadvantages can be easily overcome, then what are you left with? A great handling car that does damn good even on a rough track. I think maybe what I'm tryin to say is 4th gen setup is a superior design and once modded and tuned would be better for a real world application rather than a skidpad number. For example, Enzo Ferrari on a 200ft Skidpad does 1.05G. (Car and Driver) and is rated at 650 HP and 485 ft-lbs of torque. Get a thirdgen, fourth gen, hell Z06, with a skidpad of 1.05 and the same HP/TQ and all you will see is a nice set of Enzo tail lights provided equal drivers.

Well...I think I'll stop now...

Jared

ShiftyCapone

iTrader: (7)

Jaredi,

You make great points. Where do you get your info for springs rate equivalencies and such. I am very intrigued by this and would love have access to the same knolwedge/information. I didn't realize that the spring rates would have to be so drastically different. In thoery the fourth gen it is a better design but some of the thirgen characteristics even out the playing field. If you had a built fourth gen suspension (front, rear is the same) in a thirdgen, you would have a better handling set up than the same thirdgen with a built thirdgen set up. A lowered thirgen is lower than a lower fourth gen, roof line that is. Its center of gravity is slightly lower all the way around. Add to that the better weight characteristics and that helps off set the difference in suspension design. It is obviously a better design or GM would not have spent the time and money to develop it and change away from what they had. The rear set up must have been good because the did not touch it, besides nit picky things, between the generations.

About the all aluminum being lighter. That is false. An LS1 is actually heavier than a taditional small block. I remeber reading that is was roughly 30 or so pounds more than an L98, Lo3 and all the other gen one blocks in thirdgens. I will double check that and report back. It is aluminum for many reasons one being because if it were iron it would weigh some un goddly amount and the wiehgt distribution on fourthgens would be horrible. Plus with aluminum there needs to be more material mass around certian parts of the block to make up for its lack of strength characteristics compaired to iron. Most fully optioned t-top fourth gens dial in at about 3500-3600 pounds. Sometimes even more. My buddies fully optioned T-top RS weighs a mere 3200 pounds and that is with him in it.

jaredi

Well, think about the lower A arm as a Second(I think) class lever. I will use the Mustang for an example since it has the same type of setup and I have yet to get out and measure my control arm. But on the A Arm, the farther the wheel is away from the spring, the more mechanical advantage the wheel has on it. On Mustang the spring is about 1/4 of the way down the control arm from the K Member. So, the wheel has alot of leverage on that spring, making it only 1/4 effective at the wheel. A heavy OT spring for a Mustang coilover is about 450#, and since the coilover is about 90% efficient (because it's mounting point is right beside the wheel, then the wheel would see 395# of spring, whereas with the same 450# spring in the stock location, the wheel would only see 112.5# of it. The rest is absorbed by the bushings and K member and goes directly into Noise/Vibration/Harshness. So, this means to get the same spring rate at the wheel, on a Mustang it takes roughly 4 times as stiff a spring as with the coilover setup. If you were to run an 1800# spring on the front of a Mustang.... You might just be better off trying to fabricate some sort of steel rod to replce the spring The Mustang's stock front spring rate is IIRC something like 425# that is either stock or for the Motorsport C Spring, but that equates to ~105 at the wheel. So if you were to run a 120# CO, the car would ride like a Caddy and still have a stiffer wheel rate. Going to a 425# CO however will not ride as good as stock because you're shock isn't going to be as soft as a stock one, unless something is bad wrong with it

So, giving the thirdgen the benefit of the doubt and saying the stock located spring is 45% (not accurate, just pulled it outta the air) efficient, to keep up with that 900# coil over kit, you'd have to run a 2000# regular spring. Any idea what stock spring rate is? Something like 550#? So imagine a spring 4 times as stiff as stock to keep up with the wheel rate of that 900# CO. And that's not to mention changing springs out in 15 minutes, or the infinitely adjustable ride height...



That is exactly why I want to run Coil overs on mine along with a Tubular K member. I think, if the geometry is preserved, having no upper A arm won't make that big of a difference. I just need to find someone with OT experience with the CO kits for our cars and find out what they think and see if the "weak" strut tower is holding up. Steeda used the same argument as a reason for not producing a Mustang CO kit, but Maximum Motorsports proved their theory incorrect. Now you won't see a serious OT or AutoX mustang without a set, unless they're trying to prove something

What is weight distribution F/R in a thirdgen? I know on a LT1 Camaro it is something to the effect of 53/47. It always helps to locate the back 1/4 of the motor UNDER the windshield If my motor was back that far maybe I could have fun changin spark plugs too



But aren't the LT1 blocks Iron? I know heads are aluminum, but I thought the block was iron, and engine position is no different and their weight distribution is still about 53/47 which isn't too bad.

I think I just figured it out....n/m



We just weighed a 97 Mustang GT vert last night, without either of us in it it was 34xx pounds. That's not too shabby for a vert. I know a friend who pulled up on the scale in a stripped down, gutted 89 Mustang LX Coupe 2.3L and tipped the scales at 1900#s with him and a system in it. course he only weighed 130 and the system only about 50 and the scale is only accurate to the nearest hundred pounds (It's one the semi's pull up on out in front of a factory in town) so I'm guessing weight of the car was around 1800#.


Jared

ShiftyCapone

iTrader: (7)

Yes the LT1 is an Iron block and because of its weight it is positioned as you mentioned. Deep under the firewall. That is the main reason for the "jerry rigged" opti spark. There is no room for a distributor. But the LS1 is still a touch heavier but because of its posistion is helps even out the front to rear ratio.

I have no idea what the spring rates for a stock thirdgen are but I am doing a little research of my own. Not saying your wrong, but I am trying to take your numbers and come up with a simple mathmatical explanation without getting to technical. I geuss I don't understand your efficieny numbers. What exactly is 90% efficient? Don't forget that the mechanical advantage you talk about applies forces in three directions. The spring only compresses with one. You have two other directional forces that are dissapated throught the rest of the suspension. The angle of the spring in relation to the wheel determines that. The springs may compresses with the same force because of where the other forces are directed. You can press diagonaly on a spring and get it to compress. However your applied horizontal force is wasted and you have to press harder to get your applied vertical force to compress the spring. If you stood right over it or stood on it you are isolating the force and it compresses a lot easier. If it takes 100lbs to compress a spring and you push on it with a 45* angle downward or upward you have 50lbs of force in two directions and not enough to compress the spring. So you would need 200lbs of applied force to compress the spring. This is the simplest case and a real quick way to understand. I am still pretty sure the spring rates are closer than you think.

Momar

I am not a physics major or anything, but with the way that the thirdgen is setup wouldnt why would the ride be harsher if the spring rate at the wheel was less? I would think that if at the wheel it took less to compress it that it would feel similar to a lighter spring on a fourthgen? If I am seeing this right(I probably am not. lol) then the harsness of the spring, and the firmness of the spring would be somewhat tied together so that the rate at the wheel is really what makes the difference. Ok, I am going to stop on that line because I dont think I am making much since. lol

However I do know that for the higher end thirdgens the stock springrate was around 750 if that helps anyone.

Ben

paul_huryk

I'm gonna throw my 2 cents in here...

The third gen uses struts in the front... the fourth gen uses coil-over shcocks with unequal length control arms... fyi - the 911 and boxster use struts (with coil-over springs). All the fourthgen has an advantage in is ride quality - you can use a lower spring rate... But GM in all its glory made a couple of mistakes that keep the front end to be not a handling demon (4th gens). Stupid GM.

The rear suspension is the same... but you knew that.

As for the weight, a thirdgen is gonna be on average lighter with a lot lower center of gravity. Even the lowest 4th gens are still 2 or 3 inches taller than a stock 3rd gen... it makes a big difference.

I don't care much about the 4th gen steering box vs the 3rd gen - its a steering box, who cares... as long as it works correctly.

As for the feeling of 4th gens feeling like they are one with the road, fine, but it doesn't mean it has higher handling performance - that only means it feels confident. My Camaro feels very loose if you drive it normally - the nature of the beast. Drive it at 80% or better and it feels like a race car - one that takes some skill to drive but is an ***-kicker at all speeds. Considering that at 80% the car can outhandle BMWs that are "the ultimate drivng machine", what happens at 90-95%? Feelings cannot hide the truth - the thirdgen while older, more technologically deficient and frowned upon is still the best handling solid axled car to come out of Detroit... those are the facts.

AGood2.8

I don't know who taught you this partner but you are completely opposite of reality. An upper a-arm suspensio will promote POSITIVE camber Based on lowered geometry (lower CG- present in most roadcars). Third gens with strut type front suspensions promote more NEGETIVE camber in compression travel- You have your facts backwards.
Dean

jaredi

Lemme fix that before someone spots my error, Mustang creates negative camber under compression just not nearly enough.

The spring when mounted on a coil-over, because it's closer to the wheel (i.e. closer the force on the lever).

Yes, but still the spring only compresses with one direction, because when the pitch angle of your car changes, the K member changes pitch with it, and if the K member changes pitch, then the control arms have to change their pitch as well, keeping the angle of force directly down on the spring. With a CO it's no different because the body and K are fixed as one, and the strut towers don't move (enough to be significant) separate from the K member (and A arms).

If you can explain it a little more in detail so I can see where you're getting at. I can't quite see it right now, but I'm trying, and I think I see where you are going. I am definitely going to have to pull my front wheel off and take a gander in there now.

(Sidenote, I just found the friggin QUOTE button!)

Momar, I see what you are thinking, it seems logical, but if the wheel only gets say, 50% of the spring rate, where does the other 50% of force go? It is absorbed by bushings and the mounting points of the A Arms. It makes a bump into a jolt, adding to NVH. Do you see what I'm getting at? Going back to the lever, if you lay a board down with one end in the dirt and the other end propped up on a table, and hit it with a sledgehammer down where it's close to the ground, the table will feel some shock, but the ground will feel far more. You get me now?

You CAN use a lower spring rate and have a better quality ride, but what happens when you use the same spring rate? You get a stiffer wheel rate with a comparable ride. And as for ride quality, over a bumpy track, you will be glad that you're car isn't as harsh. Bumps suck, they suck even worse in a thirdgen. There is a place on my road where pavement changes with a bump for about a 50 ft section and then theres another bump. Before I bought my car I was driving my friend's 92RS and the bump sits right in a curve. I didn't think anything about taking it at 45 because I did in my Thunderbird all the time. As soon as I hit those bumps it was BANG, CHIRP as the front hit and bounced a little and then another BANG as the rear hit. It boggled my mind at the time that his car was that stiff. My other friend had the 94Z 'Vert out, and through the same section of the road he was goin about 40 and nothing of the like happened. It's my theory that he could go through that part faster than the thirdgen because he wouldn't bounce and lose contact with the road. Bumps suck. THIS picture is what happens when you get into some bad bumps in a braking zone. (Yes I know that's a 4th gen but just as an illustration Here is the story behind it.

Maybe those statements are related I have been thinking the same thing myself, but seems alot of people see it as an advantage.

I'm not so much disputing that as I am everyone saying the thirdgen has a superior suspension than 4th gen.

I agree 100% with this statement by ShiftyCapone

I'm also gonna step out on a limb and say a highly modded and tuned 4th gen will be better overall than a highly modded and tuned thirdgen. Maybe not a lot on a smooth track, but when they hit a rougher track, the 4th gen will be showing a nice set of tail lights. One thing's for sure, I WILL find out one day

You are right, to an extent. Camber gains under compression are determined by length of the upper arm and angle of it relative to the lower arm. When the suspension compresses, if the arm is parallel to, and the same length as, the lower arm, then it will force positive camber under compression, but if the arm is shorter and angled upward, then the arc of the upper arm will be much shorter than the arc of the lower arm, thus forcing negative camber under compression... GM saw this one coming.... THIS time The 4th gens do a pretty good job creating negative camber under compression. On a separate strut/spring setup, roll center is important as well, not so much so on a 4th gen setup.

Here is a picture of Jon Aadland's Z. Very top of the page. Even though the car isn't rolling much, you get the idea, the picture ain't showing positive camber.


That's all for now... Off to bed...Third shift is so great...

Jared

AGood2.8

Jared, Whoi taught you that camber gains under compression is a good thing? If the car is setup correct- then proper camber is present throughout suspension travel (or lack of for that matter) The only time you would even want camber gain is under hard braking and an understeer sinerio. When a car is braking hard and not turning, weight transfer increases over the front and will further deform a proper tire contact patch (sidewall roll). A double A-arm car can be setup Via use of Caster to run say -2 1/2* camber at straight and -3 1/2* camber at full lock. This will help compensate for a driver that is **** to make errors. and the only time one would want camber gain.

Dewey316

hey jaredi, looks like i am not the only one who hangs out at corner-carvers


btw, after all this camber talk, what was the original post? :-p

ShiftyCapone

iTrader: (7)

I am going to have to pull a wheel off on both vehicles of mine and take some measurements. I will then try to explain why the springs rates are most likey very similar to each other. The geometry of the wheel in relation to the angles and distance of the spring/shock/coilover effects the way the suspenion travles and compresses. I do not really know much about chamber characterisitics under loading so and I will take your word on that. But as for the spring rates go it is simple statics and that I do know. Ok, I will try to exaplin this without getting too technical.

A spring/shock located in the front of your suspension is in a three dimensional space. Therefore forces acting upon it can travel in three directions along three axis. If you rotate your axis so that one of them lies parallel to the shock only forces in that direction can compress the spring. If you press on that spring from an angle, a portion of that force is directed in all three directions depending on that angle. Therefore, if you apply a leverage force from your wheel at an angle it will take more force to compress the spring than what it is rated at. That leverage is being transmitted over your three directions, and only one direction actually compresses the spring. The sum of all forces in any given direction is always zero. You have an applied force from the weight of the vehicle, a normal force from the car pushing back on the spring, and an force from your shock pushing up on the spring.

jaredi

OK...so...

The strut controls camber (Right?) so when the car rolls, and the strut moves out (right?) then the spindle is forced down (if the first two are right then this one is right, right?) which produces positive camber gain (in relation to the ground, right?)... So, to overcome this we set static negative camber, right? So that when the body rolls, the camber never goes into the positive range (in relation to the ground). Seeing this in my head, it would seem to me that the perfect setup would see about the same amount of camber (in relation to the ground) throughout suspension travel. That way if your static camber was -3.5°, under full compression it would still be -3.5°, (in relation to the ground) although (in relation to the car), the wheel has gained negative camber. If you see what I' saying... Camber gain in relation to the ground is bad, but in order to keep the camber the same as static, the camber will need to increase (in relation to the car) to compensate for the strut moving outward...

If you followed all that you are a heck of a guy

I found the site when I had my M*stang (yeah I know... ). I hang out there and read alot, but I've never posted. Not alot of Thirdgen specific stuff there though.

I see what you are saying now.. Finally But wouldn't the same principles apply to the coil-over spring? And also, wouldn't the forces in the other directions be absorbed by other components (bushings mainly) before it got to the spring anyway?

While you are under there, see if you can get measurements from the center of the bolt on the A Arm mounts to the face of the rotor, and then from the A Arm mount to the center of the spring, so we can compare our mesurements and make sure I'm accurate with my measurments I am going to have to pull that wheel off and measure again because I did it like a moron. Anyway, what I came up with was a ~20 inch length from the center of the A Arm to the wheel mounting point on the hub, the measurement was pretty close on both A Arm mounts. I measured about 12 inches from the forward mount to the center of the spring, and about 16 inches from the A Arm mount to the strut mount. So yes, the spring rates are going to be closer than what I originally thought, with the spring being about 60% efficient by my current measurements and with the coil-over it would only increase to about 80% efficiency. BTW, I don't have a 4th gen handy to take measurements from, if you do have one can you take measurements from it as well? If the A Arm is longer or has a different strut mount, the efficiency may me a little better on them... maybe. I also wish I had my Mustang back for a while to take measurements from it and see if they coincided with what I had believed to be the efficiency ratios.

Jared.

ShiftyCapone

iTrader: (7)

Yea will do. I am going to be changing the brakes on my 95 Z one of these weekends and I will draw it all up and do some calculations on it. When I hed back home I will bust out the thirdgen and do the same. This was an excellent discussion guys. Pleasure doing science with you.

jaredi

I was thinkin the same thing. Thanks in advance for those measurements :hail:

Now after having the wheel off the second time and getting much more accurate results, here they are (DISCLAIMER: All results are the best of my abilities and are not 100% accurate as most are rounded to the nearest 1/16th or so):

From the rotor face to the hub (wheel mounting surface) is 1.25"
Rear A-Arm Mounting bracket to Rotor face 16.5"
Front A-Arm mounting bracket to rotor face 18.75"
Rear A-Arm mounting bracket to center of spring 10.5"
Front A-Arm mounting bracket to center of spring 8"
Center of spring to Rotor face 11.5"
Strut mounting point to rotor face 2"

And no I wasn't smoking anything when I took the first ones


I haven't calculated everything up yet, not sure my math skills are up to it yet (Shifty?), but I'll be sure to post my results. Right now I'm trying to decide how to triangulate exactly where the force is coming down on the A Arm from the spring, being that the length is different front and back and the spring is mounted more toward the front of the arm than the rear, which puts it's effective position somewhere...

Jared

AGood2.8

.

jaredi

OK guys, now you can bust on my ballin azz math skillz y0

Number one, my numbers don't work even close to exact so I'm gonna try to use the most accurate ones.

Using the overall measurement from the front mount of the LCA to the mounting surface as 20 inches (hey I wasn't off too far) by taking distance to the rotor face, 18.75 + 1.25 length of the hub, and using the distance of the center of the spring to the LCA as 8 inches, it yields an efficiency (I keep thinking that's the right word to use...) of 40%

Using the overall measurement of the rear mount of the LCA as 17.75 inches by taking the distance to the rotor face, 16.5 + 1.25 length of the hub, and using the distance of the center of the spring to the LCA as 10.5 inches, it yields an efficiency of 59%

Here's where it gets sticky (for me... )

Since the spring is located closer to the front mounting point, reason says it would be more affected by the efficiency of the front mounting point. I decided to apply a weighted average of the two to use as overall efficiency. To figure out how much the front should get vs. the rear, I took the length from the front LCA mounting point 8 divided by the length from the rear 10.5 and came up with 76%. Since I have long forgotten how to do a proper weighted average, I called it close enough to .75 for me and took 40% efficiency and multiplied it by three, then added 59% efficiency and then divided by 4, which gave me 44.75% total overall spring efficiency.

I know I've screwed up somewhere... probably measurements, but other than that I'm not smart enough to figure out where

Using the same calculations for the C/O setup, I got 83% effective on the front arm and 82% on the rear arm, yielding 82.75% overall for the C/O setup.

So, no the spring rates aren't going to be quite so far off as I had first imagined, but still a significant difference.

Hopefully someone more mathematically inclined than me can look over this and correct or confirm it...

Jared

slow305

iTrader: (2)

As far as which suspension is "better," I think it comes down to someone's personal "feel" or driving habits. I never got the hang of driving my girlfriend's '96 Z28 1LE (talking autocross not taking it tHr0uGh tHe tW!StAyZ, y0!). But every thridgen I've autocrossed has just felt more comfortable to me. Now my girlfriend doesn't like driving my car or any other thirdgen, and I have a friend with a modded fourthgen who doesn't like the feel of thirdgens either.

As others have pointed out, the front suspensions are different. But arguing over which one is "better" is pointless, IMO. You can bring out math equations and draw stuff on paper, but it doesn't matter much. Both cars do different things, and I think they are equal in the end. 2+2 still = 4, but so does 1+2+1.

Pat
'90 Formula (LB9)
'96 Z28 1LE (not mine but it's in front of my house right now ... and I drove it yesterday )

RegaPlanet

I'll put my car up against any 4th gen on a twisty course. If I lived closer to you, AGood2.8, I'd love to find out the difference in handling between a v8 with aluminum heads and intake to your v6. I can understand why you have a 5pt harness now as I can very easily fall out of my seat with the factory 3pt ripping around.

89 Iroc Z

The LS1 is about 120-150 lb’s lighter then a Gen I SBC with iron heads. Not sure about the Gen II, I would assume that the LS1 is around 100lb’s lighter because Gen II SBC’s come with aluminum heads, but still are iron blocks. Ask anyone who has put a LS1 in a thirdgen they will tell you their front-end rose about an inch and a half just from the lighter LS1.

Tom84L69

A 4th gen won SCCA A Sedan at the Runoffs this year.

4th gen is a better design.

If you need examples of good handling cars with SLA front suspensions, you don't have to look far before noticing most sports cars have SLA front suspensions. Porsche must have used the strut setup on the 911 and Boxster for space requirements.

Whoever said the C4 Vette handled better than a C5 is full of it. Untrue unless you are reading a mag that happened to post a better G reading on a skidpad. Hardly the way to measure handling. Plus, ALL corvettes have an SLA front suspension.

Lotus used an SLA on the 7. Triumph on the spitfire, TR6. New Mazda RX8. I mean the list goes on and on. Also, look at Trans Am cars, they use SLA. Look at Indy cars, F1, and all formula cars, they use a form of SLA( albeit with optimized geometry).

Struts are used to save cost and space. They can be made to handle well, but an SLA is superior. Also, a 3rd gen has a modified MacPherson strut front suspension, it is not a normal strut, the spring is seperate, unlike a Porsche. comparing the thirdgen to a porsche front suspension is ridiculous. GM used the strut to save money, the control arm is just like the one on a G body! It still has the hole for a shock mount! I'm not saying a thirdgen is a bad handling car, i love mine and it's stock, but a 4th gen is a better, more expensive design.


Now, here is why an SLA has better camber gain curves (by better I mean less camber gain). The arc that the suspension moves through during travel is a larger arc on an SLA. That means there is a larger radius on the arc for the wheel to travel through, lessening the camber gain. This is hard to describe w/o a picture. A strut has only a lower control arm, which means the arc is not made with a combination of pickup points. It comes from the pickup points for that one lower arm. Right about now, a picture would be worth a thousand words.

As for weight, a 4th gen is heavier due to more luxury amenities such as power seats. Also due to more sensors, diagnostic equipment, computers and safety stuff like airbags, door beams. They also have more speakers and bigger brakes. All this small stuff adds up to the weight diff. I'm not sure about body panels, though I know a 4th gen uses some plastic. And as for the aluminum LS1, well that should help the 4th gen as well.

Tom84L69

Oh yeah, when I say better, I mean for ride AND handling. I say this because they are interconnected and manufacturers are not only concerned with skidpad numbers. If they build a 4th gen that pulls numbers as good as a 3rd gen but rides much better, that is a win in their book. And even still, an SLA is better for ultimate handling.

Tom84L69

Here is what Mazda's assistant manager-chassis says about why the RX8 uses SLA over strut:

"However, RX-8's elegant and expensive aluminum double-wishbone front suspension and 5-link independent rear suspension, “is going to be (Mazda's) base sports car platform,” says Komiya, who spent two-and-a-half years honing the RX-8's underpinnings.

He says the sophisticated double-wishbone front suspension was favored for a variety of reasons over a MacPherson strut arrangement, which has become the default front suspension architecture for many sport-oriented and front-wheel-drive vehicles.

The double-wishbone setup allows a high degree of flexibility for suspension geometry."

Tom84L69

What? 3 good posts by me and no arguments/opinions?

Matt87GTA

Hey you pretty much said it all Tom . I just got here and was itchin to post, but alas I got to the end and there is no need! Jared, you need to do some serious homework because you never got the camber gain thing right even after all of that math of yours. *** help us if people from CC see this :nono: !

And most of this debate is ridiculous in the first place as nobody here is talking lateral Gs or lap times or anything else that would actually back up a claim that one "handles" better than the other.

Bottom line is an SLA is better than a MMS setup. No two ways about it. But that doesn't necessarily mean jack $hit..... Wheels, tires, sway bars, driver, blah blah blah....

jaredi

I come here to learn, educate me. Not tryin to be a smart *** or anything, just seriously, tell me how it works.

I am under the impression that in a corner, the suspension should make more negative camber to make up for the car rolling, to keep the tire/ground angle the same. Maybe you are taking what I say the wrong way. I'm trying to say that the wheel/tire should maintain the same angle to the ground throughout suspension travel. When I say camber gain I am not meaning camber in relation to the ground, just in relation to the car.

Like I said waaaaay back up to the top,

That is the attitude I have on it. If you can enlighten me please do because I don't like being ignorant.

Jared

chymos

Since camber is defined and measured as the direction a tire leans side-to-side when viewed from the front of the car *in relation to the ground*, the camber *measurement* should not change through suspension travel.

However, Jared, you are correct in assuming that as the body of the car rolls in a curve, the angle of the tire *in relation to the body* should change. But the camber measurement is still in relation to the ground, not the body of the car. Hope that clears it up for you

RegaPlanet

Camber is indeed defined as the outward or inward tilt of the wheel at the top when compared with a true vertical line at the centerline of the wheel. However, all wheels are attached to one end of a pivoting beam so the wheels movment is not in a true vertical line so camber will change with suspension movement under heavy braking and cornering. It is actually more of a circular path that it follows and this path can be found by charting out certain chassis and suspension points and ploting them to first find your roll centre and instant centre. From there you will find how much camber change your suspension may actually go through it's entire travel and this measurment is also used to determine how much initial static camber one should set their car at. This is by no means a perfect science and is just used as a good theoretical starting point. From here one would take their car through any course and then take tire temps and make adjustments from readings and feeling/driving style.

jaredi

Thanks, I think I got it now I have been refering to camber gain as in relation to the car so it could keep camber measurement at the ground the same throughout travel. I will refrain from that from now on

Jared

slow305

iTrader: (2)

How about comparing autocross results, like from the past few Solo II National Championships? This will clear things up over which generation of F Body handles the best:

2003: F Stock -- ESP
2002: F Stock --ESP
2001: F Stock --ESP

Yup, about as clear as mud!

Matt87GTA

All due respect, but autocross is quite a bit more dependent on driver skill.... I was referring to something like driver X that is familiar with such and such 3rd gen and such and such 4th gen and turns A lap times with the 3rd gen and B lap times with the 4th gen at a track that driver X is also familiar with.... But even that is tough really..... I mean in the interest of keeping things even you could go down the list with modifications until you are blue in the face.....

I am going to retract that statement all together... The term "handling" is the ridiculous part and there is no way to answer this question/settle this debate. Just way too many variables/opinions involved.

BTW, looks like you can put Strano in anything and he goes fast! .....lol.

slow305

iTrader: (2)

I brought up autocross because it's the only place where 3rd and 4th gens compete against each other with similar mods (like stock and street prepared) ... and the lack of power from a 3rd gen (especially compared to an LS1) doesn't usually affect the outcome. I think when comparing lap times from a road course, you're going to see 4th gens will usually be faster because they just have more power to start off with.

Although A Sedan is probably a good comparison because they at least have the same engines/power.

Tom84L69

Yeah too bad the 4th gens had John Heinricy in A sedan this year! Ouch!! SLA or Strut, Heinricy would probably win.

prockbp

i've autocrossed them both

the 3d gen is more nimble(which is why it wins nats in solo2.. or maybe it's because of the 9bolt )

the 4th gen is way less scary at high speeds though... very stable...
if the solo2 rules ever change and allow lengthening the camber slots on 4th gen k members... then the 3d gen will lose some of it's advantage in autocross


but Tom is right about Heinrocket... wouldn't matter which car he drove.. he prolly would've won AS


and Matthew... those boxed control arms are killing your rear ends' articulation..... stock control arms or rod ended control arms will make your rear end MUCH more stable during turns