GXP FE3 Suspension not the FE3 from ZOK as advertise by GM

[achieftain]

LV, couple of things to ponder that I don't think have been addressed. Watching NASCAR on Sunday, to tighten up a car whose front end comes loose they "loosen" the rear springs (taking out a "rubber"). What you feel at teh back end coming loose will be much less affected by what you do at the back of teh car than at the front (other than dropping 200# of play sand from Toys R Us in the trunk)

The other thing is are you 101% sure that the installed springs on your car are th proper ones and that an error was not made in production (like this has never happened) There may be a metal tag or permanent bar code strip on the spring itself which would identify the part compared to the same part on a N/A. With that info you may find an answer that gives you back the handling you had.

[SolsticeMan]

Never underestimate the effect of lowering a car, either.

[Miles@tirerack]

While GM may have softened the GXP for the average GXP buyer you may be able to tighten it up by using the Z0K springs. They'll drop the car a little and even though they are supposed to have the same spring rate it should make the car handle a little crisper.

But before I did any of that I would have the alignment checked. Just having a sub-standard alignment could be making your car handle like a pig.

I'd go and have them lazer align the car to be just barely within the green range (on the agressive side), maybe a little more negative camber than "acceptable" in the front.

I know GM does not spend a lot of time aligning the cars out of the factory. My factory alignment on the Z0K had huge cross-toe and cross-caster. I'd spend the money to have a good alignment tech look at your car.

Definitely put some more negative camber in the front and rear.
(Front spec is 0.10-1.10 degrees, I'd go with 1.10-1.30; Rear spec is 0.00-1.00, I'd go wtih 0.7-0.95)
Go with 0 toe for tire wear, and have them max out the caster in the front.

If the tech can, make sure he gets everything as close as possible side-to-side and make him give you a print out of the specs before and after.

[JUSTICE]

This is what I was complaining about months ago when everyone started releasing the skidpad test numbers for the GXP. They were all lower than the base model test numbers but everyone kept saying the GXP should still handle the same or better than the base model. I was irritated at the thought of the performance model not handling as well as the base model. There weren't many others that agreed with me or were concerned at the time. Anyway, my car is getting bigger rear wheels and tires and lowering springs as soon as possible. Hopefully it will handle better than the base model then.

[Krazed Kanary]

First things first! Without having knowlege of the driver and their goals, throwing around changes and numbers is irresponsible and possibly dangerous IMHO.

First one must define the objective they are after:
Street handling
Drag racing
AX handling
Drifting
Road racing

Next define the parameters:
Rules that must be adhered to?
Self satisfaction without limitation?

Then the budget alloted:
little to no out of pocket
willing to buy a stickier set of street tires to put on stock wheels
willing to buy dedicated race rubber and lightweight wheels
willing to buy aftermarket suspension components or have custom parts built
I've got a rich daddy and I love to spend his money

Finally an honest assessment of the driver's ability:
I can't get into a parking space at the mall in less than 3 tries
I watch NASCAR
I'd define understeer as a cow from Australia
I can go fast in a straight line only, twisty roads make me sick
I've been on a dragstrip but never on a road course
I have autocrossed on street tires/less than 10 times
I have AXed on race rubber for more than 1 season but usually finish in the bottom half the field
I participate in time trials on actual roadrace courses
I AX as often as possible and finish in the upper 25%/have taken several Evolution or other professional driving schools
I have trophied at the SCCA Solo National Championships
I race wheel to wheel in club/professional racing.

If you do not fall into one of the last four categories of driving ability, IMHO you should stop worrying about the handling of the car and spend your time/money/efforts on improving your driving skills. You will never be able to appreciate/evaluate the real differences in handling, or be able to set up the car to handle at the maximum possible. In fact if you fall into the first 6 categories of driving abilities a perfectly neutral or slightly loose handling car could be out and out dangerous in your hands. Street cars are designed to understeer badly when pushed for a very good reason, most drivers would kill themselves or others in an emergency situation otherwise.
Finally NEVER test out the handling of a vehicle on public roads, they are not designed with enough safety buffer should you get in trouble, and innocent bystanders deserve to live safe healthy lives.

[SolsticeMan]

How I'll set my car up when I get it:

First off - I'll set the front and rear camber to -1.0 with a full fuel tank. I'll set the front caster right on spec, and the rear caster (assuming it makes it) to the spec (-4, IIRC). Toe-in will be set to spec, a tenth toe in front and rear, too.

I'll see how that works. I suspect it will work well.

Then, when I'm fully in the summer mode, I'll put the GMPP springs on my car, (18% stiffer springs, should lower the car a tad too) and put on a set of either 245/40R18 PS-2's or GS-D3s or RE050A PPs. Haven't decided yet on the tire, but I like the size and think it results in a decent setup.

This is to become my daily driver. Still haven't settled on the color, but possibly leaning toward aggressive.

IF I decide to autox it, I'll cross that bridge when I come to it. Depends on the hot tire and my experiences in it as a daily driver.

that's me. Your actual mileage will vary.


Miles - I know more than a few people that work in assembly plants for many manufacturers that would debate you. The more likely scenario is that the alignment system in the assembly plant is more accurate than the best system in a garage. We're talking million $$ machines capable of aligning cars at a very high rate of throughput and a stunningly high degree of accuracy. Alignments are set in the assembly plant dynamically (meaning the wheels are rolling), and in the case of cars like the corvette or the kappas, they use a direct caster tool for setting caster, which is more accurate than field methods of measuring caster.

Front cross toe is a misnomer - if your steering wheel is straight, cross toe (and individual toe in the front) is nearly meaningless. What matters is total toe in the front with a straight steering wheel, and total toe and thrust angle in the rear. There's just too much slop in the steering system to get an accurate and absolute measurement of the front individual toe.

[Miles@tirerack]

Originally Posted by Krazed Kanary First things first! Without having knowlege of the driver and their goals, throwing around changes and numbers is irresponsible and possibly dangerous IMHO.

I suggested making sure the alignment was correct, hardly dangerous. I recommended an alignment spec that was either in spec or at most 0.2 degrees out of spec on the front and within spec on the rear. These are still very mild alignment specs, as I'm sure you know, and if his alignment wasn't done correctly at the factory this would make his car safer.

SolsticeMan,

Thanks for the clarification on toe. I looked at my alignment sheet and while the total toe was "in the green" it was still just barely correct (0.28 total toe when max is 0.30). All the toe was in the right side of the car where the left side was at or very close to 0. Camber was actually set at 1.25 degrees in the front (out of spec) and there was almost a degree difference in the caster left to right. Maybe I'm picky about my alignments but if had paid for that alignment I would have made them do it again.

[Krazed Kanary]

Miles, wasn't directed at you, but there are at least three similar threads going at once, and I'm guilty of posting numbers in some as well. No, yours are quite mild. My point was that without the driving skills to utilize/appreciate/evaluate ultimate handling, discussing how to achieve it is a moot point full of nothing but opinions (and you know what they say about opinions...), and we are both wasting our time.
Solstice man, if they use such a maching on the GXP, it must have been broken when mine was built or the delivery guy must have hit a curb with it because mine was not within factory specs nor the same side to side when delivered. I'd be pretty confident the final adjustments are made by hand rather than a machine, and the alignment equipment is only as good as the guy holding the wrenches and how many seconds they give him to set it.

[SolsticeMan]

Originally Posted by Krazed Kanary Miles, wasn't directed at you, but there are at least three similar threads going at once, and I'm guilty of posting numbers in some as well. No, yours are quite mild. My point was that without the driving skills to utilize/appreciate/evaluate ultimate handling, discussing how to achieve it is a moot point full of nothing but opinions (and you know what they say about opinions...), and we are both wasting our time. Solstice man, if they use such a maching on the GXP, it must have been broken when mine was built or the delivery guy must have hit a curb with it because mine was not within factory specs nor the same side to side when delivered. I'd be pretty confident the final adjustments are made by hand rather than a machine, and the alignment equipment is only as good as the guy holding the wrenches and how many seconds they give him to set it.

Which would you trust, a caster derived from steering the front wheels left to right and trying to identify hundredths of a degree change in camber, ignoring the effect of the suspension geometry, and having an outdated lookup table, subject to the possibility of not having the brakes properly locked when measuring it...


...or a digital angle gage with a direct measurement of tightly controlled, machined holes in an aluminum knuckle? This inclinometer can be checked just like a bubble level, and used on all four corners (yep, the same instrument).



maybe it's just me, but I'll take the ability to measure it directly every time, TYVM. I had a local alignment shop (Belle Tire, no details on location ) that had ZERO idea that rear caster was even an adjustable measurement when I was helping someone set up their Solstice. (If you read this, you're very welcome, thanks for letting me snoop underneath at the same time... )

When I got the alignment shop to borrow a caster gage from a local dealership, the difference between the 'top of the line laser alignment hunter machine derived caster' and using the caster gage was quite staggering and disappointing. We ain't talking hundreths or tenths, we're talking differences of over 3/4 degrees.

[LatinVenom]

I will start by having the aligment check, then go from there, but I still say shame on GM, it delivered a better performer but not a better handling car and GM should have.

[birdliver]

If you do not fall into one of the last four categories of driving ability, IMHO you should stop worrying about the handling of the car and spend your time/money/efforts on improving your driving skills. You will never be able to appreciate/evaluate the real differences in handling, or be able to set up the car to handle at the maximum possible. In fact if you fall into the first 6 categories of driving abilities a perfectly neutral or slightly loose handling car could be out and out dangerous in your hands. Street cars are designed to understeer badly when pushed for a very good reason, most drivers would kill themselves or others in an emergency situation otherwise.
Finally NEVER test out the handling of a vehicle on public roads, they are not designed with enough safety buffer should you get in trouble, and innocent bystanders deserve to live safe healthy lives.


Then 99.99% of people shouldn't buy performance/sports cars?
I don't do those four things, but I know that my GXP does not handle as well as my base Sol did and I'm displeased that it doesn't and I can tell the difference quite readily. I have driven several N/A Sols now and they were consistant in their performance when driven aggressively on twisting roads. My GXP doesn't handle as well as they do as a group. I have not been influenced by others in my opinion because I learned it before it was reported here. I had a very early delivery of my GXP. So, like LV, I am dissappointed with the GXP's handling performance out of the shute. I'm assuming that mine is typical of what's being delivered, but I don't know. I realize that this can probably be corrected and when the answer is shared here, I will upgrade my car. I am posting to agree with LV's take on this and feel as he does because I was a base Sol owner and have learned the difference and am hoping that GM will take notice.- bird

[SolsticeMan]

I checked the handful of cars I had collected weights on. Most of the GXPs are around 52.6-53% front with a full fuel tank, and I have to estimate the average of the base Solstice closer to maybe 52.2-52.5%

I have one Z0K measured by someone else, it came in around 52.3% front too.


That doesn't seem like much. I'd estimate the average weight gain for a GXP at close to 125 lbs - that doesn't seem like much either. It's half of me...

So, a half percent more front weight, plus an additional 125lbs total, at the same ride height of the base car...



The only thing I can see different between the cases shown is the Z0K runs on the FE3 spring rates, and is lower. IOW (thinking as I type) the Z0K has essentially the same suspension PARTS, but

-lower height
-125 or more less lbs,
- 0.5 to 0.7% less front weight distribution.


If you're comparing the cars on the production tires, well, that's something totally different. A tire can change the whole character of a car.

LV, you are talking about a looser feel given SAME tires? Didn't you put the same tires on your GXP that you had on your N/A car? Were they the same sizes or is that another variable?

Generally, when people complain of handling, they are complaining of having too much understeer or push. If you are looking for how to get your car to be more stable, that's a different ball of wax - most of the changes ennumerated would already be in the direction of more push (especially when comparing a Z0K and a stock GXP).

Some simple things to do - knobs you can turn with minimal work and no $$$:

-Try disconnecting the rear stabilizer bar. This should definitely create a difference in the car. If it makes your assessment of the handling worse, then thats a clue. If it improves it, then that's another clue. (I would NOT advise disconnecting the front stabilizer bar. )

-Start with your tire pressures at the sticker or whatever you normally run, and change them in +/- 5 psi each direction from placard on each axle and take it for a short test run each time. THese are large changes (if you think its too much, try +/- 3), and you'll have seven different setups plus your original 'stock' setting. (*front/*rear; +front/*rear; +front/+rear; -front/*rear; *front/-rear; -front/-rear; +front/-rear; and -front/+rear) This will take a few hours, but VERY telling. Your route doesn't have to be long, just something you can do consistently.

I guess I'm a bit lost when I try to figure out what the complaint is, and if I'm lost, any of the lurkers reading this would be lost too. More roll or less roll? Pushier or looser? Steady conditions or when there are rapid changes in steering? Higher lateral grip or less? Is it an issue with how the steering feels?

Handling is all of these things and more. Not dissing anyone, just trying to tease out the stuff that might shed some light on this. Honestly, my experiences in the GXP/RedLine have been pretty positive, and I think it tends to handle a bit better than the base cars (stock) that I have driven. I can drive the handful I have at higher speeds, with more confidence, than any base car on RSAs.

Bird, this stuff is for you too. Try and explain as exactly as possible, what you are feeling. If anyone wants categorical thought starters, I can drop them in when I log back on tomorrow, but think of it in separate categories: how does the car feel when you FIRST turn the wheel? When you try and carve a steady corner? When you wiggle the steering wheel back and forth?

[Krazed Kanary]

Originally Posted by SolsticeMan Which would you trust, a caster derived from steering the front wheels left to right and trying to identify hundredths of a degree change in camber, ignoring the effect of the suspension geometry, and having an outdated lookup table, subject to the possibility of not having the brakes properly locked when measuring it... ...or a digital angle gage with a direct measurement of tightly controlled, machined holes in an aluminum knuckle? This inclinometer can be checked just like a bubble level, and used on all four corners (yep, the same instrument). maybe it's just me, but I'll take the ability to measure it directly every time, TYVM. I had a local alignment shop (Belle Tire, no details on location ) that had ZERO idea that rear caster was even an adjustable measurement when I was helping someone set up their Solstice. (If you read this, you're very welcome, thanks for letting me snoop underneath at the same time... ) When I got the alignment shop to borrow a caster gage from a local dealership, the difference between the 'top of the line laser alignment hunter machine derived caster' and using the caster gage was quite staggering and disappointing. We ain't talking hundreths or tenths, we're talking differences of over 3/4 degrees.

Really? you used the electronic caster gauge to measure and set the front caster??? Where did you get the correct offset angle for the front from? GM doesn't publish it because they do not want you setting the front caster that way. I now know what it is because we set the front caster with the Hunter machine and then checked it with the gauge and could read the difference (the offset angle) Fact is tho caster angle difference of +- a degree much less a hundreth of a degree, will not change the handling characteristics enough for even the best driver to notice. But our front and rear were not set to spec from the factory even checking the rear with the digital gauge. I had to get the dealership service manager to go look for the gauge he didn't even know they had it, and then teach the tech how to use it properly, it hadn't been out of the box before.
I talked to the GM engineers while they were testing the (non existant) GXP ZOK about the rear caster and they said they tested it from one extreme to the other of the adjustment range and could not detect any affect on the handling. It's just there because they used the same hubs and suspension members front and back.

[birdliver]

Sm,
Categorical thought starters might be helpful. Snow melting would be helpful for conducting a few runs with those thoughts in mind, too.
For now, just a brief ramble. After a few weeks of driving the GXP initially, I shook off the initial denial I was suffering from regarding mainly, the car's handling in turns. I kept telling myself initially that the new power might be overwhelming me (It was a huge change, obviously) or the tire selection could still be wrong etc., but I finally felt after going back and forth driving the N/A a few times that I had become familiar enough with the GXP to suspect that some characteristic of the new car was responsible for it not at least equaling what I was getting from the base car. I didn't notice individual things that felt wrong, but I was clearly no longer tracking through turns like I was on rails and I wasn't getting back the info that the base car was providing and so I felt less confident and the GXP felt less predictible in the turns. Nothing in particular felt different or wrong that I could put a finger on. Included in the "not tracking/no go cart" thing was that it had been replaced with a bit of roll (no way in the base car) and a feeling of less control that I didn't get at all in the other car either. I still don't know if the less communication idea is tires but LV is making me think maybe not, unless other solutions prove better than his tires or mine (I'm still OEM), I hope so. In terms of shedding some light on the subject, if someone with the capacity, time and place could conduct some comparisons between the two cars maybe some determinations could be made and some solutions provided.

[Krazed Kanary]

I'm getting really curious as to why several here have said they don't think the GXP handles as well as the BASE Soli. I have not driven a base "in anger" but so far I think the GXP is an awesome handling car on sticky tires which is the way it was designed to be driven. I really don't care how well it handles on the street tho, especially on those Flintstone Rockhards it comes with. Body roll??? Not compared to a fully prepped Miata, this thing has some HUGE swaybars. Turn-in? Nearly instantanious with the right alignment.
First time we drove it we nailed nearly every slalom cone with the front fender.
We are still working at finding the cornering limits of the car.
The power is awesome as well. Then again a thoroughbred race horse is not going to feel as comfortable and under control as an old plow horse to a novice rider.
A number of testers have made the handling comparison between the two cars already, it's called 60' slalom times, and the GXP eats the base alive (even on the OEM tires)!
I'd bet GM chose those tires (and definitely the alignment) primarily to keep unskilled drivers alive.
Should untrained drivers buy sports cars? In practical terms yes, otherwise the manufacturers wouldn't build them for us, in personal opinion no, or at least they shouldn't try to push it's performance envelope on the street without proper training. The ZO6 for example should come with mandatory driving school, it's a lethal weapon in the hands of a yahoo. Same goes for the Elise and several others. If you really want true Sports Car experience, come on out to an autocross or track time trials. I sure would like to see a few more GXP's out there running so we could truely evaluate and wring out it's potential, we have only just begun.
Will GM listen to the average buyer and make changes? Yes about such things as better cup holders, power seat lifts, and door lock switches etc. About increasing it's handling ability on the street, I really doubt it if their legal dept has any say in the matter, they are walking a very thin line already. Sorry if I offend anyone, but I tell the truth as I see it. If you really think you are such a skilled driver, why don't you prove it to everyone where it counts rather to a teenager in a fartcan equipped Civic at the stoplight? I would love to have a go against you.
Have you tried turning off the traction control and ESC? It is quite intrusive and hampers the handling (for good reason?).
But if you try it on the street you are on your own, I take no responsibility for the results.