Understeer Reduction

[RobertISaar]

W-bodies being W-bodies, understeer is obviously going to occur with any stock setup.

 

What can be done to get closer to a neutral-handling car and drawbacks to each method? info specific to each gen is fine, but I'm most curious about 1/1.5 cars for obvious reasons.

 

from what I'm seeing, starting with a stiffer rear swaybar is cheap/easy, but would a stiffer front bar offset it? help it?

 

poly control arm bushings also look like a fairly cheap option with no apparent drawbacks(other than perhaps installation)?

 

alignment settings look like they can be played with a bit before having a serious effect on tire life?

 

for a 1.5 car, shorter springs front and rear(with a probably increase in spring rate) obviously exist, but is lowering suspension travel and increasing the spring rate on both ends going to help/hurt? 1 have the same front springs available, the leafs springs have a couple of factory options, but even those are getting tough to find, so rear coilovers may be getting done out of necessity soon in the future in the event of a worn/broken/insufficient spring.

 

am I missing any of the major options beyond replacing old bushings with new rubber or poly? I get the feeling that playing with front/rear tire pressure could have some decent results, but it seems like it would just be skewed towards making the rear slide around via less traction rather than trying to distribute lateral forces more evenly from front to rear.

[l67ss]

Actually a stiffee rear bar will INCREASE understear. Im running shorter stiffer springs, heavier front and rear sway bars along with a fast ratio rack. I actually wanna increase understeer

[RobertISaar]

I've noticed you post that before..... but everyone else who has gone with a stiffer rear bar has reported the opposite, I don't know what to think of that, if you have some combination of factors that no one else has reported on?

 

I can't see anyone wanting to increase understeer in a W.... they're not quite boatlike with refusal to rotate the front around in a fast turn, but they're not too incredibly far off in "comfort" trim levels either. the 88 New Yorker does that to a rather extreme degree and not only is it annoying, it feels somewhat like a safety issue as well, fast wheel changes result in either a refusal to change direction or a noticeably laggy response, requiring overcorrection and then when it catches up, you're sawing the wheel back the other way.

 

not that I'm looking to make a track car out of a ~170HP 3400lb FWD grocery accumulator, but something more responsive/predictable is what I'm aiming for. the LQ1(with eventual LZ4 power?) GP, things can get a bit more nuts.

[l67ss]

Reason most people dont report more understeer is they have the terminalogy backward. Understeer is a tendancy to try to go straight when trying to turn and oversteer is a tendancy for the rear to break loose

[Imp558]

Back when we were kids my best friend and I built a '79 Lesabre, the rear had a lot of squat at launch so we lifted the rear to get a better trajectory on the radius arms and it began to oversteer due to the resulting caster adjustment.

[RobertISaar]

measured my existing swaybars on the MC today, I appear to have a 30mm front and 20mm rear. so, in terms of swaybars, I only really have 1 stiffer option that I'm aware of, but I think there are 28, 32 and 34mm front bars to choose from? my bushings appear to be pretty damn sloppy, so those are getting replaced at a minimum.

 

I wouldn't think caster would have nearly as much effect on steering feel as camber does, but suspension stuff is still voodoo to me.

[Imp558]

Imagine the car riding somewhat on the front of the tires, that resulted in some very quick steering, it was kind of cool

[l67ss]

If your stock bar is 20mm its been swapped out. Monte ls had 15mm stock

[55trucker]

Depending on the type of tire you're using on the car they can have one of the biggest affects on handling, a low cost *S* or *T* general purpose rated tire won't handle as well as a better quality *H* or *V* rated performance tire.

 

Anything you do to make the rear end more reactive will reduce the plowing (understeer) at the front..... a larger anti-roll bar, more negative camber on the wheels, higher tires pressures, lowering the rear end to lower the center of gravity and lessen the 65/30 front to rear..all these will affect the front end response.

 

At the front end to reduce understeer dial in more negative camber, harder springs to lessen dive, keep the anti-roll as it is but make use of the poly bushings.

 

By increasing the negative camber at the front you're keeping more of the tire face in contact with the road surface when cornering which increases response, lessening the tire trying to *roll over* on the sidewall which induces understeer, 

 

 try first just picking up some alignment shims for the front end, the factory camber setting is close to +.80 degree which is an extremely *safe* setting which induces plowing on the front end. Even reducing the front camber to -.25 will make a noticeable change to how the front end responds (this where my front end is...1 degree shim), I've made no other changes where bushings are concerned at the front end as of yet. The rear end camber factory setting is +.10 to + .5 degree, I reset mine to -.25 as well when I changed the shocks to reduce the rollover effect under spirited cornering. 

 

here are a few links to ebay where you can pick up some of the alignment shims    ........there are more of the same there as well,

 

this is a cheap and easy place to start your project, after installing them do some driving, if you like what you feel begin to make changes elsewhere

 

 

http://www.ebay.com/itm/Northstar-45-7005-2-GM-W-Body-Front-Camber-Shims-1-2-Degree-FREE-SHIP-/130794106077?hash=item1e73efacdd&vxp=mtr

 

http://www.ebay.com/itm/Northstar-45-7009-2-GM-W-Body-Front-Camber-Shims-1-Degree-FREE-SHIP-NEW-/130794119512?hash=item1e73efe158&vxp=mtr

 

http://www.ebay.com/itm/Northstar-45-7007-2-GM-W-Body-Front-Camber-Shims-3-4-Degree-FREE-SHIP-/121009166475?hash=item1c2cb5588b&vxp=mtr

[RobertISaar]

If your stock bar is 20mm its been swapped out. Monte ls had 15mm stock

 

highly unlikely considering how much of the past of this car I have knowledge of. Alldata also indicates that a 95 monte LS should have a 10242079 rear bar, which was what the tag on it stated it was. measured it anyways to confirm, but a 95 LS should be a 20mm rear bar. 95 Z34 is a 22mm unit with a 10248629 part number. 96 is the same. 97 shows the Z34 as receiving the 20mm unit now, with LS receiving a 10288583 bar, that's a 15mm unit. 98 and 99 are setup the same as well.

 

looking up the lumina numbers as well, same trends.

 

with 1.5gen stuff, 95 and 96 got larger bars for whatever suspension option was used compared to the 97-99/01 cars.

[RobertISaar]

Depending on the type of tire you're using on the car they can have one of the biggest affects on handling, a low cost *S* or *T* general purpose rated tire won't handle as well as a better quality *H* or *V* rated performance tire.

 

I went somewhat cheap on the summer tires since I hadn't planned on making it a super long-term vehicle, but it has gone that way. not Chinese-market cheap, General Altimax RT, T-rated. I didn't stick with a stock size(205/70-15), went wider and lower with 215/60-15. if one of my suspicions is correct, they'll be getting mounted on some aluminum 15x7 wheels that should bump up the track width a bit.

 

Anything you do to make the rear end more reactive will reduce the plowing (understeer) at the front..... a larger anti-roll bar, more negative camber on the wheels, higher tires pressures, lowering the rear end to lower the center of gravity and lessen the 65/30 front to rear..all these will affect the front end response.

 

let's see.... I can go up one size on the rear roll bar, the stock rear camber spec of +.1 for a 95 1.5 was intended to be bumped closer to -.5, stock front camber spec of +.7 was intended to be moved toward a neutral 0, tire pressures could be run up to 44PSI, beyond what sag has occurred and the shorter tires, I can't get away with lowering the car any further, there is now a lot more weight in the rear than what would have been present from the factory... 1/8" plate steel isn't light.

 

At the front end to reduce understeer dial in more negative camber, harder springs to lessen dive, keep the anti-roll as it is but make use of the poly bushings.

 

By increasing the negative camber at the front you're keeping more of the tire face in contact with the road surface when cornering which increases response, lessening the tire trying to *roll over* on the sidewall which induces understeer, 

 

 try first just picking up some alignment shims for the front end, the factory camber setting is close to +.80 degree which is an extremely *safe* setting which induces plowing on the front end. Even reducing the front camber to -.25 will make a noticeable change to how the front end responds (this where my front end is...1 degree shim), I've made no other changes where bushings are concerned at the front end as of yet. The rear end camber factory setting is +.10 to + .5 degree, I reset mine to -.25 as well when I changed the shocks to reduce the rollover effect under spirited cornering. 

 

I see my plans weren't too far off base, but shims don't seem necessary if slotting the tower per GM's procedure would be sufficient for the front. i'll need to take some measurements to see what kind of slot would be necessary assuming the current position is exactly where it should be.

 

here are a few links to ebay where you can pick up some of the alignment shims    ........there are more of the same there as well,

 

this is a cheap and easy place to start your project, after installing them do some driving, if you like what you feel begin to make changes elsewhere

 

 

http://www.ebay.com/itm/Northstar-45-7005-2-GM-W-Body-Front-Camber-Shims-1-2-Degree-FREE-SHIP-/130794106077?hash=item1e73efacdd&vxp=mtr

 

http://www.ebay.com/itm/Northstar-45-7009-2-GM-W-Body-Front-Camber-Shims-1-Degree-FREE-SHIP-NEW-/130794119512?hash=item1e73efe158&vxp=mtr

 

http://www.ebay.com/itm/Northstar-45-7007-2-GM-W-Body-Front-Camber-Shims-3-4-Degree-FREE-SHIP-/121009166475?hash=item1c2cb5588b&vxp=mtr

[l67ss]

Actually a larger front bar will reduce plowing

[RobertISaar]

i imagine it would.... less body roll and all.

[55trucker]

 

 

 

I see my plans weren't too far off base, but shims don't seem necessary if slotting the tower per GM's procedure would be sufficient for the front. i'll need to take some measurements to see what kind of slot would be necessary assuming the current position is exactly where it should be.

Keep in mind that if you drop the car you will naturally induce more negative camber as the top of the strut will lean in moreso, how much depends on the amount of drop, so the shims do come in handy to correct any over induced negative camber,

 

To find what each increment of 1 degree equals.....

 

find the circumference of the wheel/tire by.........the diameter of the tire times 3.14 (pi)

divide that figure by 360

the # you get will be what each degree equals in a decimal of an inch

convert that decimal to fractions of an inch

 

example.. the wheel/tires diameter on my car are 26.2"  26.2" diameter tire divided by 360 = .0727"  which equals a little less than a 5/64 of an inch at the top of the tire for each degree of camber movement

[vipmiller803]

What about strut tower braces? Those supposedly reduce boatyness too...

[RobertISaar]

the front strut tower bar on the MC is probably sufficient for 2 cars... it's like 1.5" round tubing(fairly thick walls as well) and slightly rubs the underside of the hood. nothing on the rear though, I have a set of RSTB brackets from Matt but I was planning on using them for the 91SE.... maybe i'll get another set and use these for the MC.

[vipmiller803]

So not stock I take it?

 

I thought about getting strut tower bars but got worried that they might produce a tail happy effect in the snow. Of course they are easily removable for seasonal use.

[GnatGoSplat]

Much bigger rear sway bar greatly increased the risk of oversteer for me.  One time I steered quickly to avoid a log in the road and the rear end flew out and I ended up doing almost a 360.

[RobertISaar]

So not stock I take it?

 

I thought about getting strut tower bars but got worried that they might produce a tail happy effect in the snow. Of course they are easily removable for seasonal use.

 

was bored, equipped with an arc welder, made monster bar for both the MC and 90GP(I imagine it's still on it if the newest owner hasn't taken it to the scrapyard yet) that day. it certainly took some floppiness out of the front when I put it on.

 

Much bigger rear sway bar greatly increased the risk of oversteer for me.  One time I steered quickly to avoid a log in the road and the rear end flew out and I ended up doing almost a 360.

 

I assume with a 1st gen rear end? the spring itself seems to do a decent job of acting as a sway bar on its own, which is why the 1st gens got tiny(or no) bars compared to 1.5/later cars with rear coils. I've only got one option for a larger rear though with the 95-96 FE1 bar being used on 97-99 FE3 cars, I'm not sure what to think.... it's too bad nobody has probably driven equally fresh/equipped 95/96 cars back to back with a 97-99 car to compare.

[rich_e777]

I noticed a reduction after installing a Z34 front sway bar with ES bushings, a bit more once the STB`s went on. My gauge was I-65`s Harding Place exit which has a nice open two lane loop and low traffic at times. 60ish is about as fast as I`m willing to push it on the current tires and suspension components. Mostly factory,    ...mostly.

 

Whatcha trying to do?

[RobertISaar]

Whatcha trying to do?

achieve a higher lateral grip threshold without losing too much predictability(or crossing over from understeer to oversteer in a corner while maintaining speed/acceleration situation, oversteering while turning and braking is always going to be an issue with so little weight in the rear and a lot of nose diving due to braking).

 

it's too bad there isn't a clear-cut way to adapt some active suspension into a w-body, even just the front to prevent weight from transferring out of the rear end while braking, that alone would do wonders without having to go with an otherwise really stiff front.

[GnatGoSplat]

I assume with a 1st gen rear end? the spring itself seems to do a decent job of acting as a sway bar on its own, which is why the 1st gens got tiny(or no) bars compared to 1.5/later cars with rear coils. I've only got one option for a larger rear though with the 95-96 FE1 bar being used on 97-99 FE3 cars, I'm not sure what to think.... it's too bad nobody has probably driven equally fresh/equipped 95/96 cars back to back with a 97-99 car to compare.

 

Yep.  Big (7/8") rear sway bar in place of an 11mm one on the rear of a 1st gen makes a HUGE difference.  Almost dangerous if the tires aren't up to snuff.  Just had some skinny 225/60R16 all seasons at the time.  Hasn't been a problem with 245/45R18 speed rated Michelins.

 

it's too bad there isn't a clear-cut way to adapt some active suspension into a w-body, even just the front to prevent weight from transferring out of the rear end while braking, that alone would do wonders without having to go with an otherwise really stiff front.

 

Active suspension would be very cool, but end up costing many times the value of a W-body.

[RobertISaar]

I'm trying to find GM applications to possibly adapt stuff from, a 99 Seville has electronic front struts.... for about $600 per side. not entirely an active suspension from a modern viewpoint, but perhaps some kind of direction to look towards. rear air assist stuff exists on a lot of applications, but not really useful in this situation.

[GnatGoSplat]

The magneride stuff might be the easiest to find, but it just controls damping, doesn't it?  You might be able to adapt generic strut bags and use electronically controlled valves, compressor, and sensors connected to a custom microcontroller running some custom code to control them.  Someone once posted links to an active air ride kit, I'm sure it was pretty pricey but if you assemble it yourself, might be a lot cheaper.

 

I was actually rather impressed with the active air suspension the Audi A8L we test drove.  Felt firm, but comfortable.  Quite flat in corners.  The car felt a lot smaller and more nimble than a W-body to drive, but it's a lot bigger (or at least it looked a ton bigger on the inside).

[RobertISaar]

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.