Buying new suspension @ End of Week

[tsunari]

Have been lurking/reading all of the posts/articles I could get my hands on concerning upgraded suspension setups for the 2G GST/GSXs. Was hoping to run it by some of you GURUs and get some feedback and possibly some last minute questions answered

Current setup:
'stock' 97 GST
ES Bushings (master kit)
RM front & rear swaybars
Front & Rear Camber Kits

Planning on getting a set of Koni Yellows along with some GC Coilovers. As far as spring rates, I was looking at 450f/350r. I really was hoping to not go much higher than that for now (don't feel like sending the Konis out to get revalved just yet

Now, a couple of questions . . . this is a daily driver and sees more AutoX and twisties than she does a drag strip. Being a FF setup, are these spring rates going to be fairly ideal as far as trying to get rid of some of the understeer and set it up more towards a neutral handling? The RM anti-sway bars have already done wonders, but just not enough for my tastes. If this isn't ideal, should I drop the fronts down to say 400? or perhaps bump the rears up a bit?

Question #2 . . . will I need to get the GC upper plate or a pillowball mount from RRE (are they the same thing??) Also, I've heard mention in a couple threads that coupled with either the GC bushings or ES bushings, the upper plate may cause some damage to the shocks? I could never really find a definite reason/answer to that . . . anyone know?

Thanks in advance for the time and space

 

[Boostd20psi]

perosnally..and honestly...if you want a good setup thats almost the same price as the GC and koni's...first of all i heard koni's on a 2g is bad...2nd of all I would go with the Tein Basic Coil Over Kit. It is a lot better than Ground Controls, and all that you would need is Goldline camber correction kit as long as your at it to make sure u keep everything in geometry

Kenny

 

[tsunari]

Out of curiosity, what's the problem with Koni's and the 2g's? Also, is the Goldline kit 'better' than the Ingalls kit?

perosnally..and honestly...if you want a good setup thats almost the same price as the GC and koni's...first of all i heard koni's on a 2g is bad...2nd of all I would go with the Tein Basic Coil Over Kit. It is a lot better than Ground Controls, and all that you would need is Goldline camber correction kit as long as your at it to make sure u keep everything in geometry

Kenny

 

[jtmcinder]

I have only two suggestions: first up the rears to 400#. Konis can take this and bringing the rears to within 50# of the fronts makes a noticeable difference. I really like 500/450 (which is darned close to 450/400).

Second, you need flatter front shock plates. One option is the plates from GC, but remember to toss those nasty black bushing that GC includes in the trash. Do not pass go ... straight in the trash. Get some ES bushings and carve them down to fit. Or, don't get the GC plates at all; get pillowballs from RRE.

Then set your camber to max negative in the front and about half to two-thirds as much in the rear.

You're going to love it.

- Jtoby

ps. Ignore people who have merely "heard" things, especially when what they have heard is patent nonsense.

 

[tsunari]

Thanks Jtoby . . . that's the kind of feedback I was looking for So the rear Koni's will be able to handle the 400 without needing a revalving? I was under the impression that the 'limit' of the yellows was 450 front and 350 rear . . .

So- there IS a difference between the upper GC plates and the pillowballs from RRE? (I'll have to assume they are just two totally different mounting methods huh?) As for AutoX . . . I shouldn't have to worry about damaging the Konis? I seem to remember a thread on here somewhere mentioning that the tight turn radius seen in AutoX as opposed to say . . . road racing might do some damage- but perhaps what was if it was coupled with the GC plates & bushings. Please someone DO correct me if I'm wrong

Oh! Is the 'magic' phrase still 'Eric wouldn't lie' down there @ RRE?

I have only two suggestions: first up the rears to 400#. Konis can take this and bringing the rears to within 50# of the fronts makes a noticeable difference. I really like 500/450 (which is darned close to 450/400).

Second, you need flatter front shock plates. One option is the plates from GC, but remember to toss those nasty black bushing that GC includes in the trash. Do not pass go ... straight in the trash. Get some ES bushings and carve them down to fit. Or, don't get the GC plates at all; get pillowballs from RRE.

Then set your camber to max negative in the front and about half to two-thirds as much in the rear.

You're going to love it.

- Jtoby

ps. Ignore people who have merely "heard" things, especially when what they have heard is patent nonsense.

 

[njshift]

Just curious, are different spring rates preferred between fwd and awd cars? It seems to me that many (fwd and awd) cars are choosing similiar spring rates between one another.
I understand that we are all trying to accomplish generally the same thing. Less understeer and better handling. Does the drivetrain play a major role when choosing springs?

 

[jtmcinder]

I've had two years on 400# rears and then one season on 450#s and my rear Konis were fine. One front was shot, but that's the other story (next). But keep in mind that the higher motion ratio in the rear makes 400# rears on the edge of nasty on the street. My then-3-y-o daughter loved it, but my wife doesn't.

OK, now the damage to Konis. This comes from running GC plates with the little black bushings that they include. Those bushings are rocks - no, I did not say that they rock; I said that they are rocks - and they don't allow the shock shaft to pivot at all. This will kill a front Koni because our funky twin offset lower balljoints cause all sorts of angles to be produced, especially when the wheels are turned more than 3/4 of a turn. (This last point is why they cause much less grief when road racing; if you can turn the wheel that far, you ain't going fast enough.)

"Eric wouldn't lie" no longer seems necessary (probably because John Mueller takes care of these requests). It'll run around $200 for a pair of plates. John convinced me to get rear pillowballs, too. I suspect that this was overkill, but I (try to) listen when someone who knows that much speaks.

As to FWD vs AWD spring-rates, this depends on your differentials. If you have OE diffs, then your AWD is darned close to being a FWD, especially at corner exit, which is where it matters, so we set them up pretty much the same way. Mostly we move a ton of weight transfer to the rear, try to cook the outside rear and get the pig to turn.

In contrast, if you have a front Quaife and something better in the middle (or an AWD, obviously), then you can get away with much more front weight transfer (as long as you don't go so far as to lighten the inside front tire at corner exit to the point where the front Quaife goes open on you.

If you cruise lots of DSM lists, then you know about my "relationship" with Dennis Grant. He runs 900/400 springs, which, at first, I thought was moronic. But that was before I drove a car with some decent diffs.

- Jtoby

ps. don't worry, I still think he's a jerk (as he does of me); just not an unintelligent one.

 

[MNGSX]

I'm running 450/350 for rates and it works good and remains streetable.

On the street or rougher tracks excessive spring rates are'nt smart. Also I think it is the least desirable way to get what people look for when they are doing it. Swaybars should limit roll not the springs. You have good bars and some spring rate increase will be good too but I don't think I'd go to 500+ on the fronts... I'd look for stiffer sway bars and eliminate unsprung weight.

 

[kiakarimi]

Swaybars should limit roll not the springs. You have good bars and some spring rate increase will be good too but I don't think I'd go to 500+ on the fronts... I'd look for stiffer sway bars and eliminate unsprung weight.

You could look at this differently though, because with stiff springs used to eliminate body roll, you're working one corner of the car at a time. But with swaybars, you're working one end of the car at a time, and the biggest loss of traction you can have is lifting a wheel off the ground...

 

[jtmcinder]

Bingo! If you pick up a wheel - or even get one light - then you're toast. Only a hard locking diff will get you out the corner and most of us are on OE boxes of goo or Quaifes. If you has Kaaz diffs, go wild with the swaybars (I even looked into having my rear RM redrilled for added stiffness, but then thought better of it). Otherwise, do a lot of the shifting of weight transfer to the rear using springs.

- Jtoby

 

[tsunari]

Well what would the handling be like if I did 400/350 as opposed to 450/400? They would both be within 50 of each other . . . although perhaps the ratio of the 450/400 might be a little better and help understeer a bet more- Or am I calculating my 'ratios' wrong?

Don't get me wrong . . . I dont want something that rides like a caddy . . . I just dont want to drive around some of these nasty roads that are under construction Barney Rubble-Style :laugh:

And thanks to JToby for finally clearing up what kills Koni's . . . BTW- do you think the rear pillowballs were worth the extra $$$?

I'm running 450/350 for rates and it works good and remains streetable.

On the street or rougher tracks excessive spring rates are'nt smart. Also I think it is the least desirable way to get what people look for when they are doing it. Swaybars should limit roll not the springs. You have good bars and some spring rate increase will be good too but I don't think I'd go to 500+ on the fronts... I'd look for stiffer sway bars and eliminate unsprung weight.

 

[MNGSX]

Bingo! If you pick up a wheel - or even get one light - then you're toast. Only a hard locking diff will get you out the corner and most of us are on OE boxes of goo or Quaifes. If you has Kaaz diffs, go wild with the swaybars (I even looked into having my rear RM redrilled for added stiffness, but then thought better of it). Otherwise, do a lot of the shifting of weight transfer to the rear using springs.

- Jtoby

I have seen tandem swaybars before... Linked one above the other.

This is the best way but nobody can afford it.


http://www.penskeshocks.com/hyraulic.htm

 

[DG-FNR]

So JToby has moved from calling me names and claiming that I'm wrong, to calling me names and admitting that I'm right.

I suppose that's a type of progress.

Alright, let's talk springs for a little bit. I'm a little hamstrung on this topic, because there are things I am keeping to myself in order to retain a competitive advantage, but there are some things I can discuss openly.

When determining spring rates for a vehicle that is primarily street driven, you need to consider the following things:

1) The motion ratios of the front and rear suspension (more on that in a second)

2) The maximum corner weights of the car as it is expected to be driven.

3) The amount of maximum suspension travel at the fully loaded ride height.

The aim of the exercise here is to make sure the suspension never bottoms out.

The "motion ratio" is an expression of how much mechanical advantage the wheel has over the spring. Car springs are not mounted directly over the wheel like a motorbike front fork; they are offset some distance inboard of the wheel, and often canted at some angle relative the the motion centre of the suspension arm. The effect is much like a wheelbarrow, where the car's wheel had ahold of the "handles" on the wheelbarrow, the spring is mounted in the "bucket", and the suspension pivot point is the "wheel".

The farther towards the "wheel" you move the "bucket", the easier it is to lift the load - which in this case, is the spring - and so the less force the spring can exert on the suspension to resist motion.

Specifying the exact instant motion ratio requires 3D gemometry software and some calculus, but on a 2G DSM it can be approximated at about 0.75 on the front, and 0.86 on the rear.

That being the case, we immediately know that we're going to need more spring on the front in order to match the rear.

Now we need to know the weights on each corner. On a race car, we corner-weigh the car all the time - before and after each race - but on a street car we can afford to be a little bit more approximate. DSMs are nose-heavy, on the order of 60% front, 40% rear. Depending on the individual car and how it is loaded, that can move around a couple of percentage points, but 60/40 is a reasonable approximation. Figure the car at 3350lbs fully loaded, 60/40 front split, and 50/50 left/right split, and you get 1000lbs on each front wheel and 675 lbs on each rear wheel - more or less.

Now we need to know static ride height. This is going to vary by individual taste and by how stiff of a vehicle you can tolerate - the lower the car gets, the stiffer it needs to be. 2 inches is a reasonable start point.

Now, a trick.

When the car rolls, weight transfers from the inside wheel to the outside wheel. At 100% weight transfer, the inside wheel comes off the ground and all the weight of that end of the car is on the outside wheel. This is unlikely to ever happen on a street car (not enough grip, for one) but if we pretend that it could, we want to make sure that the car doesn't run out of suspension travel before it hits 100% lateral weight transfer. So we can use the corner weight over the wheel travel to determine the wheel rate we need.

So for the front, 1000lbs/2in = 500lbs/in, and for the rear 675lbs/2in = 338lbs/in

That gets us wheel rate, but we're trying to pick springs here, so we have to account for motion ratio.

Wheel rate = spring rate * (MR^2) so that works out to 889 lbs/in front and 457 lbs/in rear

Now this is a pretty good guess for a car that has no roll bars, but we have roll bars, so we need to soften things up a little bit. If we assume that half the roll resistance comes from the bars, we can try 444lbs/in up front, and 228 lbs/in in the rear. Rounded up to springs we can actually buy, that'd be 450 lbs/in front, 250 lbs/in rear

And at this point I cheat, and I look at my little secret thing, and I confirm that's a pretty reasonable number. This is NOT the same process I use to choose springs for race cars, but I can cross-reference my rule-of-thumbing against that process and see that I'm within reasonable tolerences.

As it turns out, running roughly twice as much front spring as rear spring works out to be a pretty good rule of thumb. A heavier, lower car needs more spring, a lighter, higher car needs less spring, and the actual weight distribuition changes the ratio, but that ratio of 2:1 is in the right ballpark for most cases.

As the car moves more towards pure competition use, and less towards street use, you can get more agressive on the spring rate. The problem is that you'll need much better shocks to control those springs than are commonly availible.

DG