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Discussion Starter · #1 · (Edited)
9-5 Suspension: Inherent Problems & Solutions for Racing & Sport Driving

Our car is certainly a nice sport sedan. The thing that is missing from our car compared to other "sportier" RWD sedans is a good chassis setup. (Body flex & Sloppy suspension)

So, after threadjacking VWAlex's thread on spring rate inquiry (sorry!) , I thought that it may be time for a overall suspension problems discussion thread on our 9-5. I would think that some of discussion here will benefit other non-racing members too, since we have a lot of unexplored option on upgrading our components.

Half way through writing this post, I realized something. Before talking about alignment specs, hardwares, driving techniques to yeild better laptimes, fundamental suspension improvement must come first for settings to mean anything. While the suspension setup may be correct stationary, it would become completely different once suspension sees some load with sloppy bushings.

Front suspension:
1.Subframe bushings: VERY IMPORTANT.
06~ cobra models is reported to have "90% stiffer subframe bushings" than ~05 models. Do we all remember the subframe brace that kept on breaking? Unlike NG900s, we do not particularly need a subframe brace. Our subframe is already on a pretty stiff side, and if we feel like installing one, the brace mounting design should be limited to subframe itself. IT MUST NOT eliminate the subframe-to-body play, which is due to subframe bushings.

I had a chance to inspect the subframe on a friend's 05 Aero with 70k miles. Just like mine, it had significant amount of vertical and some lateral movement FROM THE SUBFRAME BUSHINGS. These play was mostly limited to right bushings, probably due to the way torque is exerted onto the subframe as it is trying to turn against the ground. (hence engine movement when car is in gear.) . Who knows how much lateral movement these bushes may allow with 1G of force on 3700lbs car?

What is mostly going to be affected from mooshy subframe bushings are just soft steering input coupled with odd noise-vibration-harshness. Nonetheless, this is going to be a very important component for an overall driving experience improvement.

Almost missed: Our subframe bushings are CRUCIAL for minimizing the torque steer as well as WHEEL HOP! the 05 aero friend's wheel hop is GONE-GONE after he changed out the subframe bushes.

Maybe we can get some custom ones made as a groupbuy? For those who liked the subframe brace that broke like a clockwork, this would be the definitive replacement. (Nick? :D I know you have been thinking about this! But due to difficult installation procedure, demand might be an issue?)

2. Spring Rates + Stiffer Shocks.

3. Retaining suspension alignment under load (lateral/vertical):
Pretty much the only flexing component that at front are the big and small bushings in the control arm. I think powerflex bushings are available for both, but front suspension don't seem to be that much of problem in this regard.

4. Swaybar Bushings:
I remember from a post on Rennlist that mushy swaybar bushings (primarily from aging) may actually decrease the swaybar strength by 40~60%. Powerflex swaybar bushings are available for cure in this regards.


Rear suspension:
1. Retaining Camber- whether it's positive or negative:
- Our rear camber seem to change significantly under load due to rubber bushing flex. This is not just limited to lateral load, but also vertical movement from loading luggage and stuff. Engineers who designed suspension on our car must have factored additional weight causing camber change into the design; sagging bushings must be the cause of our rear camber problem.
Rear camber correction shim alone is not "the fix" for excessive rear negative camber problem.

Camber migration can be this bad under significant lateral load, in this case having shifted from -2 deg to wayyy positive:
(By "Dasmopar" from SRTforums)



Closer shot:
http://www.gcsrts.com/srts-admin/pictures/leftrearrollover.jpg

2. Retaining Rear toe: I suspect similar bushings those cause unstable camber cause toe migration issues.

With rear suspension, there are so many bushings in our rear suspension that can go bad, unlike the front.
From this pic:


Suspects are:
1. Subframe bushings #2 & 3
2. Torque rod (control arm) bushing, #17
3. Torque rod mount, #18
4. Maybe #7 and #15 bushings those go into two cross stays.

Otherwise, we can do stiffer springs & shocks just like the front for the rear.

As for Chassis Stiffening: (body flex solution)
1. Strut tower bar: one that -pts sell has some great reviews. This may fit for a good group buy as well, (Nick? :p)

2. Some kind of chassis that bolts to spots under the car.

3. Cross-Bar in trunk?

Please share your experiences with certain suspension component renewal (bushings) and fitting sport suspensions! It would be a big help for improving our car on overall!
 

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#17 and #15 upper in the rear suspension pic are ALWAYS bad. Powerflex makes the #17. When #15 goes bad camber goes way negative. At least #15 is pretty cheap.
 

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What is the difference in -01 and 02-up front spindle?

I don't think chassis flex is really an issue at this point. Everything else is so soft and most of us are still running on very small not so sticky rubber.

I plan on investigating on the rear bushing as the snap oversteer gives very little warning and can give some goosebumps when it happens at triple digit speeds. Keeping the toe on check when under load could probably make the oversteer much more previsible.
 

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Discussion Starter · #4 ·
What is the difference in -01 and 02-up front spindle?

I don't think chassis flex is really an issue at this point. Everything else is so soft and most of us are still running on very small not so sticky rubber.

I plan on investigating on the rear bushing as the snap oversteer gives very little warning and can give some goosebumps when it happens at triple digit speeds. Keeping the toe on check when under load could probably make the oversteer much more previsible.
oo ya I forgot about snap oversteer. My car with newer rear arm bushings (#15's, both arms) still has some snap oversteer. Like on highway offramp, it'd sometimes suffer from sudden under-over. With 9-5s being relatively long wheelbased FWD, it's not all that difficult to control, but the slip angle can get PRETTY BIG!

This usually seems to happen when there is a gradual, long-duration load in one direction- like on highway on ramps or long sweeping turns. Although not certain, I think this may be related with unstable feeling I get from the back when going over bumps. (It feels like I got suspension travel-dependant rear steering lol)

I am gonna try out the big bushings (#17) from powerflex and see if this "rear steering :cheesy:" kinda feeling can be eliminated.

As for 02+ knuckles, I think it sticks out less and has a better design somehow, as some people says? Most obvious differnece is the wheel hub (wheel bearing carrier) design, as 02~ use sealed units. ~01 ones use press-to-fit wheel bearings integrated in the hub.
 

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oo ya I forgot about snap oversteer. My car with newer rear arm bushings (#15's, both arms) still has some snap oversteer. Like on highway offramp, it'd sometimes suffer from sudden under-over. With 9-5s being relatively long wheelbased FWD, it's not all that difficult to control, but the slip angle can get PRETTY BIG!

This usually seems to happen when there is a gradual, long-duration load in one direction- like on highway on ramps or long sweeping turns. Although not certain, I think this may be related with unstable feeling I get from the back when going over bumps. (It feels like I got suspension travel-dependant rear steering lol)

I am gonna try out the big bushings (#17) from powerflex and see if this "rear steering :cheesy:" kinda feeling can be eliminated.

As for 02+ knuckles, I think it sticks out less and has a better design somehow, as some people says? Most obvious differnece is the wheel hub (wheel bearing carrier) design, as 02~ use sealed units. ~01 ones use press-to-fit wheel bearings integrated in the hub.
Think it would be be worth it to switch to the latter unit.
 

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And yeah while entertaining at times (people around here where thinking my 9-5 was RWD because of the angle) a bit more previsible behavior would be faster and more fun.
 

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As someone that has installed Bilstein HD's, SAS swaybars, new subframe bushings, and Powerflex trailing arm bushings, MY biggest issue is with body flex in the rear half of the car. I think that a rear chassis brace could do big things for the car. However, the reason I bought a wagon is for maximum utility/ability to carry lots of stuff. I'm afraid that any effective bracing system would limit my ability to use my wagon to its full potential.

Example of rear brace:



Example in an 850 wagon:

 

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I would like to know (factually, not speculation) what is actually stiffer on the 06 and later models from the 05.

I find the steering input and road holding to be far superior on the newer 9-5's and would LOVE to be able to get that sort of feel and response out of my 05.

Thoughts?
I just had a look through the EPC and found all of the bushings were the same except for the rear ones on the front subframe. :roll:
 

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I would like to know (factually, not speculation) what is actually stiffer on the 06 and later models from the 05.

I find the steering input and road holding to be far superior on the newer 9-5's and would LOVE to be able to get that sort of feel and response out of my 05.

Thoughts?
I just had a look through the EPC and found all of the bushings were the same except for the rear ones on the front subframe. :roll:

Other than the rear bushings on the front sub frame (and I find it hard to believe 2 little bushing could make that much difference - and mine need to be replaced btw), there is no mention of different parts (other than struts, shocks, and springs).

I have gone through all of the parts, both on-line and with a dealer and so far, the only difference I can find is the rear bushings in the front sub frame ... which btw, our favourite on-line store lists as being the same part. :eek:
 

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Discussion Starter · #10 · (Edited)
Ok, something I noticed today:

Sagging rear suspension:
I just removed 130lbs of luggage from trunk I often haul around (tools and other stuff) and gained 1 1/4" ~ 1 1/2" of static ride height from the rear. With the luggage out, the car has a full tank of gas, other fluids and maybe 10 lbs of misc. items.
This is on 02~ Aero suspension! Stock Aero springs IMO are relatively stiff so its stiffness should really not be an issue. So I am wondering how much the shocks can contribute to our ride height. While shocks are NOT supposed to put any downward / upward static force like the spring does, some people on different forums even reported better rear tire wear. Considering there is no difference in spring perch weld location, can shocks be responsible for sagging rear suspension?

The truth of matter is, I have 132k miles and STILL HAVE original shocks! The car's front wants to take off like an airplane on acceleration. I am guessing it's really time for shocks.

SO I am thinking I'll leave the stock springs in (uncut), replace shocks with Koni Yellows for the front, and get Billy sports for the rear :cool: and report:
1. How the car feels in everyday setting
2. Autocross impression & time improvement
3. Camber & ride height Difference
4. Wheel hop improvement prior to new front subframe bushing installation
5. Torque steer characteristic change
6. lastly- longitudinal (front-rear pitch, not side by side) pitch upon acceleration

I am going to do the rear shocks first, then do the fronts. I'll report how stock front + Bilstein sport rears compare to Koni front + billy rear setup. Then, I'll proceed to replace some rear bushings and see how those changes vehicle characteristics. I will be using the above rubric.

Any comments / suggestions are welcome. If you can think of something to be looked at in addition / in more detail to the above rubric, please comment.

Alex.

PS- Any input on front shocks? Bilstein Sport Vs Koni Yellows? (no Koni FSD, btw)

EDIT: I called friend with 04 9-5 Aero w/ like 40k miles and he says he gets similar sagging problem as I do. Hmm.
 

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Discussion Starter · #11 ·
Other than the rear bushings on the front sub frame (and I find it hard to believe 2 little bushing could make that much difference - and mine need to be replaced btw), there is no mention of different parts (other than struts, shocks, and springs).

I have gone through all of the parts, both on-line and with a dealer and so far, the only difference I can find is the rear bushings in the front sub frame ... which btw, our favourite on-line store lists as being the same part. :eek:
Would it be possible for you to post the part number for the subframe bushings before and after revision?
 

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Would it be possible for you to post the part number for the subframe bushings before and after revision?

It would ... once I get the new style in, I will do that as well as post my impressions of the bushings themselves.
Of course, the real test will come after installation ... it's a good thing the originals need to be replaced. ;)
 

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Discussion Starter · #13 · (Edited)
Update!

HI everyone, I am back from autorcrossing for two weeks in a row. I am putting down very good times in stock class (G Stock). Regardless, I am still slower than a god-like driven H-Stock Mazda 3 with R-Comps by 2 Seconds. I would have been able to put down similar times as his if I didn't get too greedy and hit three cones on the last run :roll:

My current setup is -2.7 or -2.9 deg of camber up front, 1.5mm toe-out on each wheel (3mm total toe-out) with 225/45/17 Direzza Z1 Star Specs on 17x7 ET42 Rims. (BTW, 17x7 are NOT ENOUGH FOR 225s!!!!!!) I run stock everything for autox except for Forge DV, which replaced the broken OEM DV. (I like OEM DV better, boost onset seem to be smoother with it, and sometimes I hear compressor stalls with Forge DV....)

Once in positioned mid-speed corners, like long sweeper, the car handles greatly. Also does slaloms admirably, but there is too much weight transfer that occur in between cones (and it does so slowly :( ) The camber setup I had was too much that I was hurting acceleration significantly (and some braking) but I was able to fix this to some extent by really straightening teh steering and applying power gently.

Also, there is too much ultimate roll in corner on front, which makes the camber to run positive with McPherson suspension geometry.
But then, I am gonna stay in stock class, so my options are limited to:
1. front sway bar (which will hurt acceleration with open diff)
2. Stiffer shocks for the front (won't do a squat for ultimate amount of roll once stabilized in corner.. will help with slalom for sure)
3. Less overall stroke (shorter dampers? will this blow out the damper?)

If not staying in stock class:
1. LSD
2. Stiffer springs instead of stiffer sway bar
3. ?

As of now, chassis rigitidy do not seem to be the problem, and the rear suspension with Bilstein Sport dampers are doing great. The rear feels much more stable during weight transfer.

Before next autocross, I am gonna set my car to -2.2deg of camber (VWAlex- suggestion?) and change out subframe bushings. We'll see how that goes.


BY THE WAY 06~ Front Subframe bushings (2x Front & 2x Rear ones, NOT 2x middle ones) are MUCH stiffer than ~05 bushings! Can anyone confirm that 06~ones fits in stock subframe? Dealer said no, but I can't see any difference in subframe bushing design. THIS, is what probably makes so much difference between ~05 and 06~ car handling difference.

///Trying to pioneer worn-out 9-5 handling///

 

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Before next autocross, I am gonna set my car to -2.2deg of camber (VWAlex- suggestion?) and change out subframe bushings. We'll see how that goes.


BY THE WAY 06~ Front Subframe bushings (2x Front & 2x Rear ones, NOT 2x middle ones) are MUCH stiffer than ~05 bushings! Can anyone confirm that 06~ones fits in stock subframe? Dealer said no, but I can't see any difference in subframe bushing design. THIS, is what probably makes so much difference between ~05 and 06~ car handling difference.

///Trying to pioneer worn-out 9-5 handling///

Sorry for the delay, haven't had much time to come on here (or anywhere for that matter) in the past few weeks.

As you found out, 2.9deg is too much for a sticky street tire like the star specs. It is more suited for R-Comps.

The way I usually align my cars with street tires is 2-2.3deg camber in the front, zero toe. In the rear especially since this is an understeering platform I would go around 1.5deg camber and sligth toe out.

Hope this helps
 

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BTW I tryed a Koni Yellow and Eibach equipped 9-5, the shocks are good but the springs are WAY too soft for any type of spirited driving so the search is still on...
 

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BY THE WAY 06~ Front Subframe bushings (2x Front & 2x Rear ones, NOT 2x middle ones) are MUCH stiffer than ~05 bushings! Can anyone confirm that 06~ones fits in stock subframe? Dealer said no, but I can't see any difference in subframe bushing design. THIS, is what probably makes so much difference between ~05 and 06~ car handling difference.

///Trying to pioneer worn-out 9-5 handling///

It is actually only the rears that are different.
The front and mid bushings are the same throughout the MY ranges.

The rears will fit.
I ordered 2 in for my car (to be installed when time and money allows).
They are identical in size.
The difference is in the bushing itself.
The 06 ones are solid whereas the 05 and older are not (hense where the extra stiffness comes from).
 

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Rear shock input

My personal experience is that the factory rear shocks are exhausted due to age by 100K miles. This is based on highway miles only and does not include any autocrossing or track days. At 272K miles my car now is riding on its third set of replacement rear shocks, its fourth set overall.

The factory shocks are gas charged whereas many/all of the aftermarket rear shocks are not gas charged - even the sporty brand name shocks. Loss of this gas will result in poor shock response and contribute to a saggy butt (car, not driver).

Use of non gas charged shocks, without use of stiffer springs too, may also contribute to drooping rear end of a loaded car.
 

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Discussion Starter · #18 · (Edited)
Thank you for your response, VWAlex:cheesy::cheesy:, I will try the following setup this weekend:
Front: -2.2 Deg Camber, Zero Toe
Rear: Stock Camber (without anything loaded, it's around -1.6deg) and slight toe-out (Aiming for 2mm (1/16") total toe-out)

Thanks SaabScott, I bought all six of subframe bushings:lol:. I think you are misinformed on that only rear two subframe busings are different. It's the other way around- The front (towards headlight) & middle bushings are of new design, while the rear two (by flex plate) are of an older design.

The part # are:
12762090 x 4 - These are NEW design. These bushings have solid core, unlike the previous 5233382 which had bit of hollow core. As you said, it would fit to the front & middle positions.

5231808 x2 - These are older design and fits to the REAR portion of the subframe by the flex plate.

I will post pics soon for these bushings.

Edit: PICS
Left bushings with white case are Rear bushings (5231808) and Right are the new design front & middle bushings (12762090)


12762090 Bushings:



5231808 rear bushings:



And MI-Roger,

you are probably correct about the gas pressure shocks and ride height relation. For the record, Bilstein HD & Sport struts/shocks are gas pressurized shocks. Konis, on the other hand, are not I think. In reality though, gas shocks should only contribute very little to our rear ride height problem.

Reduced ride height imo should be addressed by either new springs (unlikely-) or use of spring rubbers (search google for this) in case of heavy luggage loading.

Hope this helps everyone. Thanks again for contributing a lot to the forum. Saves so much hassle for all members who would eventually get these problems, including myself.
 

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Thank you for your response, VWAlex:cheesy::cheesy:, I will try the following setup this weekend:
Front: -2.2 Deg Camber, Zero Toe
Rear: Stock Camber (without anything loaded, it's around -1.6deg) and slight toe-out (Aiming for 2mm (1/16") total toe-out)
Any feedback on the alignement?

BTW I just got a set a Koni yellows and 600lbs 60mm I.D. springs for the front and 700lbs 60mm I.D. for the rear. I will start machining the rest of the parts to make a proper coilover setup and maybe get the koni revalved (kinda sucks to spend that money on brand new shock and take em apart rigth away though so I will try with konis valving first). Any interest in me machining more than one set of those parts?
 

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How much money are you talking for the whole setup?
 
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