Understeer Reduction

[Imp558]

You're biased, so was I. Take a look at the air ride in a 96 SSEI in alldata

[RobertISaar]

found a TSB from August/2000 while looking at the 96 SSEI stuff.... lists a few of the cars that got interdasting suspensions.

 

89-92 Allante (Speed-Dependant Damping)

91 Eldorado/Seville (Computer Command Ride)

92-93 Eldorado/Seville (Speed Sensitive Suspension)

91-93 Deville (Computer Command Ride)

94-95 Deville (Speed Sensitive Suspension)

92-93 Achieva (Computer Command Ride)

92-94 Skylark (Computer Command Ride)

93-96 Park Avenue (Computer Command Ride)

91-95 98 (Computer Command Ride)

94-99 Bonneville (Computer Command Ride)

 

I know that isn't all of them GM had released up until that point(northstar cars aren't listed, neither are corvettes), but it covers a decent range of applications.

 

but for the Bonneville stuff: in 96 at least, there were a few different suspension options, including an airbag based rear leveling setup, but the CCR setup is far more interesting. appears to adjust shock valving at all 4 corners using a motor inside of the strut.

 

the Road Sensing Suspension setup used on the Northstar car seems like the CCR setup on steroids... 20mS reaction times(instead of the up to ~5 seconds of CCR), variable control of the damper motors instead of the sport/tour 2-position dampers(which have a nominal impedance of 2 ohms, instead of the 20+ in the CCR setups), closed loop control of basically everything....

 

I'd probably be happy with CCR-like stuff.

[jman093]

It's been awhile since I've raced a w, but I remember my 96 GTP being fairly neutral as far as under/over steering goes. It at least had enough oversteer for me to spin it on course a couple of times. You have the 20mm bar, obviously the 22mm from a 95 Z34/LTZ or from addco is going to be stiffer, but not spending money for 2mm is understandable. I would, however, replace the outer bushings for the bar with polyurethane.

 

It's always said that increasing front roll stiffness increases understeer. This is technically true, but we need so much help with roll, that any increase in front roll stiffness seems to have the opposite effect, likely due to the tires rolling over less on the sidewall. So I'd be trying to stiffen up here as well. You said you have a 30mm bar. There is a 34mm bar available, but the 34mm bar is definitely hollow, and the 30mm bar appears to be solid. I'm not really sure which is stiffer, but the 30mm one weighs about 50% more than the 34mm one. The 30mm one is always listed as FE1 and the 34mm as FE3/F41, but I have a feeling the FE1 is actually slightly stiffer. I want to make a jig to test them. Whichever bar one has, I replace all four bushings with polyurethane for increased stiffness.

 

Other areas for improvement is alignment. Anything you can do to increase positive caster and negative front camber will increase front end traction. Especially the negative camber. Unfortunately this is difficult to do with the stupid effing one piece knuckle/strut assembly. It requires grinding slots either in the cradle for the lower control arm bolts, or the strut tower for the strut mount bolts. I did the former on my GTP. Polyurethane control arm bushings also help. I had them in the GTP.

 

And toeing out the rear should tend to make it oversteer more, although if IIRC, spec is already zero toe in/out on the rear of w's, which is very uncommon. Vehicles almost always call for some toe in, so you would have to actually have total toe out in the rear for improvement over stock.

 

Lastly don't forget about tires. Everything else is essentially chasing wind compared to the rubber on the ground.

[55trucker]

Back in the 70's when I was in my 20's much of my spare time was used up by reading articles on suspension tuning (back then in the family we had a couple of emulated BRE 510 Datsuns that were heavily modified for road racing...Paul Newman was our hero),

 

there were two guru's back then who literally wrote the book on GM suspension tuning...

 

one was Dick Guldstrand & the other was Herb Adams, these two guys were heavily influential on the suspension modifications to the Corvettes & the F-body Firebirds & Camaros.

 

If you want worthwhile reading info on what to do to setup your car then read up on both their opinions, the methodology still applies today, it's time well spent.

 

http://www.hotrod.com/how-to/chassis-suspension/0607phr-car-handling-tech/

 

http://www.motoiq.com/MagazineArticles/articleType/CategoryView/categoryId/120/Ultimate-Suspension-Guide.aspx

[GnatGoSplat]

i could be wrong, but it seems like an air system would take way too long to react to situations other than keeping the front and rear level...

 

that, and wouldn't "stiffening" the springs via more pressure cause ride height to go up with it? or am I thinking about that incorrectly? I'm basing that statement off of the air shocks that I've played with.

 

I think most OEM air systems probably are used more for leveling and keeping the car flatter in turns, despite the "active air suspension" label they give them.

You can get fast bags though, appropriately named "fast bags".

 

I would guess that more air would both stiffen and increase ride height, although if the air pressure is actively increased on individual wheels when the height sensor for that while detects height drop and decreases air pressure as soon as it detects height increase, I'd think it could work as a true active suspension and keep the car level in turns if the response time is quick enough.

I think most truly fully active suspensions (at least OEM) do use hydraulics instead like Mercedes Active Body Control.

 

Then there are also some cars like BMW and Lexus that have active sway bars.  I'm guessing the motors increase the torsional spring load on the sway bar based on input from sensors.  Don't really know though.

[George]

It seems I remember in its simplest terms, the stiffest end of the car slides first. It was alway recommended if you couldn't put larger sway bars on both front and rear at the same time to put the front on first as understeer (front pushing) is easier to safely control than oversteer (rear sliding around). If that holds true leave the front sway bar stock and add a larger rear sway bar or put in stiffer rear springs or add more air pressure to the rear tires.

 

The 34mm front sway bar on my '94 Cutlass vert is solid.

 

 

Sent from my iPhone using Tapatalk

[RobertISaar]

so, I have my front sway bar off now, noticed that the surface the bushings ride on for the subframe connection is noticeably smaller than the area around it.... is that normal for a 30mm front bar? weighing it, it is without a doubt a solid bar, so a small loss in diameter there isn't super concerning, but when I pulled those bushings off, there appeared to be a ring of compacted rust inside the bushing near ~3mm thick, I'm aware of using iron oxide as a polishing agent, but I don't know if this is just part of the manufacturing process?

[jman093]

so, I have my front sway bar off now, noticed that the surface the bushings ride on for the subframe connection is noticeably smaller than the area around it.... is that normal for a 30mm front bar? weighing it, it is without a doubt a solid bar, so a small loss in diameter there isn't super concerning, but when I pulled those bushings off, there appeared to be a ring of compacted rust inside the bushing near ~3mm thick, I'm aware of using iron oxide as a polishing agent, but I don't know if this is just part of the manufacturing process?

 

 

No, not normal. I have 30 and 34 bars sitting right next to my computer here. They are a uniform thickness until it necking down on the ends.

[RobertISaar]

huh... rust inside of rubber will do quite the number to a piece of steel then.... the bushed sections of the bar were down to ~28mm after removing some surface rust. there is some out-of-round with them due to the split bushing design, but the majority of it is 28mm now.

[RobertISaar]

quickly looked at the 91GP's front end, Ben put a 34mm bar on it, along with greasable inner and outer bushings(I assume poly, they feel far stiffer than any rubber bushings I've felt). can't tell what is in the control arms yet, that will have to wait for the car to be on the lift to find out. can't really get under the rear end yet either, so hard to say what's back there. I imagine it's going to be the largest 1st gen bar, which is something like 14mm?

[Imp558]

Damn you Robert, I never noticed my understeer until you started this thread. Now it bugs me.

[RobertISaar]

it's not incredibly bad with your average W, but it does feel unnecessary to have the front end plow so much in a fast corner.

[pshojo]

I must have missed something. I picked up two sway bars from monte/lumina and seems that they are wider than my  4 door cutlass.  Does this make sense? Is there difference with the 4 door and 2 door?

 

If i could post a picture i would. I can only get the pic down to 67kb, where max is 64kb. SOOO frustrating!!

 

Either way, looks like i have 2 of these, probably be going up for sale shortly.

[RobertISaar]

rear bars are somewhat different on a 1.5 vs a 1. fronts should be identical.

[pshojo]

so the 1.5 are different from the gen 1. i shouldn't use them? if i knew they would align i'd use them.

https://www.facebook.com/groups/214957548532535/permalink/1168609479833999/?comment_id=1168621103166170&offset=0&total_comments=3&notif_t=group_comment

[GnatGoSplat]

The 1.5 rears are about an inch too wide for 1st gen or something like that if I recall correctly.  You might look up old posts by Ken, I remember he tried them and found them too wide.

[Turbocharged400sbc]

the 1.5 cars are the second gen style coil spring mcpherson in back with the early frontend

[jman093]

Yeah, gen 1.5 bars are wider than gen 1. Twice I've put bigger gen 1.5 bars on a gen 1, but both cars had all 4 adjustable lateral links allowing me to move the track width out a little bit to make room. I imagine it's possible to cram them in a gen 1 with the stock lateral links, but it will rub like mad on the shock.

[Imp558]

the 1.5 cars are the second gen style coil spring mcpherson in back with the early frontend

I thought my Regal was a 1.5,it's got a mono in back.

[GnatGoSplat]

Nope, 95+ Luminas and 95-99 Montes are the only 1.5 gens.

[Imp558]

I've always wondered how close the early suspension from the eighties was to bolting in the back

[GnatGoSplat]

Suspension from an 88 would bolt right into a 1st gen 96.  Only thing that changed were the brake calipers.

[pshojo]

The Olds 88 would bolt directly into Wbody Gen1? Really? Are the calipers larger?

[55trucker]

^ I'm sure that Shawn was referring to an '88 W body platform car and not the H body platform...(Olds Delta, Bonneville, LeSabre), completely different platforms and underpinnings.

[GnatGoSplat]

Yep, that's what I meant.