Rear toe and bumpsteer question.

[Ultimate 85]

Is the rear toe adjustment necessary (or as important) on the rear drive wheels as it on the front wheels? I see all this talk about bumpsteer being shitty on the 84-87 cars when they're pushed to their handling limits and starting wondering about some of the kits available to eliminate the toe out characteristics under load. Is eliminating bump steer from the rear as simple as fabbing up a set of control arms where the rear of the knuckle is tied off to the back of the control arm and on the same plane rather than way the hell back on the cradle with a tie rod? Anyway, I hope this isn't confusing and I don't sound like a total :knob:

:blah5:

[notyourmomma]

It is critical to make sure the rear is adjusted so that the tires are toed in at the same angle on both sides relative to the body panels, or the car will dog-track. Rear toe in should be 1/16th with stock wheels, 1/8th with larger wheels and at least one degree of negative camber. A cam bolt replacing the lower adjustment bolt on the rear strut allows for camber adjustment. GM engineer and racer Herb Adams recommended two degrees of camber for racing but not for the street. Too much camber can induce excessive bump steer so it’s best to be conservative in alignment settings for the street. The rear control arms are super easy to remove and for about $30 you can put polyurethane in the rears and stiffen them up.

[Kohburn]

problem with tieing the control rod into the lower control arm is that you still get flex in the bushings and that would allow toe change with accel and braking..

personally i am considering the RCC kit - its simple and basicly just moves the pivot out all but eliminating the bumpstear except when you get airborn

[eHoward]

You want to think about that.

I stopped reading the rest of what you wrote after I read it.

It is critical to make sure the rear is adjusted so that the tires are toed in at the same angle on both sides relative to the body panels, or the car will dog-track.

[The Dark Side of Will]

It is critical to make sure the rear is adjusted so that the tires are toed in at the same angle on both sides relative to the body panels, or the car will dog-track. Rear toe in should be 1/16th with stock wheels, 1/8th with larger wheels and at least one degree of negative camber. A cam bolt replacing the lower adjustment bolt on the rear strut allows for camber adjustment. GM engineer and racer Herb Adams recommended two degrees of camber for racing but not for the street. Too much camber can induce excessive bump steer so it’s best to be conservative in alignment settings for the street. The rear control arms are super easy to remove and for about $30 you can put polyurethane in the rears and stiffen them up.

Ummm... Toe is measured in degrees relative to the CL of the car. Only plier mechanics measure toe in inches. I guarantee you that your body panels are not parallel to your car's centerline.
Cam bolts not required as the camber is fully adjustable FROM THE FACTORY. Cam bolts just make it a little easier.
With stiff suspension, you gain more from more camber than you lose to bump steer. I run -1.75 in the rear on the street and I get even tire wear...

[notyourmomma]

You want to think about that.
I stopped reading the rest of what you wrote after I read it.

It is critical to make sure the rear is adjusted so that the tires are toed in at the same angle on both sides relative to the body panels, or the car will dog-track.

I guess you've never had a garage 'align' your car and tell you that it can't be 'truly' aligned because the car was 'bent' when I knew better. I have had a Ford pickup truck that definately the panels didn't line up with the wheels. I guessed they didn't pull the car in straight to get the alignment right. The alignment was supposedly 'correct' except a straightedge would touch farther up on one side panel than the other (I'm still referring to toe not camber) the handling was not good and made me think Fieros were crap and dangerous to own. Until someone suggested I have it checked at a different garage and they caught the problem. They pointed out that the toe was correct when you compared the two rear wheels to each other but not to the car. I can't say for sure what kind of shortcut they were trying to pull but it made me pretty angry, especially when I 'make it easier' for them by doing things like putting in adjustable cam bolts. I pay for four-wheel alignments now intstead of just a front or back. I only had the rears done because I had rebuilt the rear suspension (and lowered it).
You in case you missed it, rear toe is important. Camber addresses the bumpsteer issue, but if you enjoy feeling the car squirm in strange ways, ingnore getting the toe in done properly.

[The Dark Side of Will]

I guess you've never had a garage 'align' your car and tell you that it can't be 'truly' aligned because the car was 'bent' when I knew better. I have had a Ford pickup truck that definately the panels didn't line up with the wheels. I guessed they didn't pull the car in straight to get the alignment right. The alignment was supposedly 'correct' except a straightedge would touch farther up on one side panel than the other (I'm still referring to toe not camber) the handling was not good and made me think Fieros were crap and dangerous to own. Until someone suggested I have it checked at a different garage and they caught the problem. They pointed out that the toe was correct when you compared the two rear wheels to each other but not to the car.

I've had garages tell me pretty dumb things. I bought a lifetime alignment at Firestone and on one of the occasions when I brought it in to try different setting, the kid forgot to tighten the left lower camber bolt. The car would hold its camber adjustment until I bent it into a hard right hand turn, then the LR tire would go to extreme positive camber and the back end would break loose. I was not pleased. When I brought the car back to have this issue fixed, the kid of course swore up and down that he'd tightened everything... then told me that he didn't know why it acted that way because the upper bolt is the one that holds the adjustment... Ummm... riiiiiiiiight.

So anyway, what did you expect them to align on a vehicle with solid rear axle? F150's use leafsprings, right?

I can't say for sure what kind of shortcut they were trying to pull but it made me pretty angry, especially when I 'make it easier' for them by doing things like putting in adjustable cam bolts. I pay for four-wheel alignments now intstead of just a front or back. I only had the rears done because I had rebuilt the rear suspension (and lowered it).

Well that was your fault for trying to cheap out of doing things the right way.

You in case you missed it, rear toe is important. Camber addresses the bumpsteer issue, but if you enjoy feeling the car squirm in strange ways, ingnore getting the toe in done properly.

The squirmy feeling is bumpsteer. Rear toe just causes changes in rear grip and changes the handling balance of the car.

[notyourmomma]

I've had garages tell me pretty dumb things. I bought a lifetime alignment at Firestone and on one of the occasions when I brought it in to try different setting, the kid forgot to tighten the left lower camber bolt. The car would hold its camber adjustment until I bent it into a hard right hand turn, then the LR tire would go to extreme positive camber and the back end would break loose. I was not pleased. When I brought the car back to have this issue fixed, the kid of course swore up and down that he'd tightened everything... then told me that he didn't know why it acted that way because the upper bolt is the one that holds the adjustment... Ummm... riiiiiiiiight.

I 'make it easier' for them by doing things like putting in adjustable cam bolts. I pay for four-wheel alignments now intstead of just a front or back. I only had the rears done because I had rebuilt the rear suspension (and lowered it).

Well that was your fault for trying to cheap out of doing things the right way.

You in case you missed it, rear toe is important. Camber addresses the bumpsteer issue, but if you enjoy feeling the car squirm in strange ways, ingnore getting the toe in done properly.

The squirmy feeling is bumpsteer. Rear toe just causes changes in rear grip and changes the handling balance of the car.

I guess the squirming description is too generic... Your description of the camber flopping around would be really scary. I thought bumpsteer would be a little too abrupt to be described as 'squirm' since I can correct a 'squirm' better than I can correct a 'bump' during driving.

---> But getting back to the original post, I'd still say YES getting the correct alignment FRONT and BACK IS important. Correct rear alignment will help minimize bumpsteer. I said MINIMIZE not eliminate. Bumpsteer is a sudden change in geometry and the Fiero has rubber bushings in the rear a-arms being the assembly from basically a front drive car with the 'tierods' anchored to the chassis up and down motion is going to change toe through the arc of suspension travel. I'm aware that the RCC kit moves the pivot point out to minimize the degree of arc through 'normal' range of travel and is probably the most cost effective way to 'fix' the early suspension from that perspective. What happens that the RCC kit doesn't address is that the a-arms can twist on the bushings and have been doing so since the first turn the car took umpteen years ago and are likely worn out by now. Hitting the brakes, accelerating and cornering are causing them to gyrate in all directions. You don't notice this in front drive cars because the cabin follows the suspension and it doesn't effect the ride or handling as noticeably as when you put it out back and the rear wants to do some creative direction finding of its own.

[The Dark Side of Will]

Bump steer isn't sudden. It's present all the time, just in varying degrees.
Worn out bushings are a different problem. I run UHMW control arm bushings and aluminum cradle mounts without complaint. I have an RCC kit, but I'm not impressed with it. It makes the sweet spot sweeter, but more narrow. It gets out of its sweet spot quickly when the car is lowered.
Controlling suspension motion controls bump steer. Hard bushings, still springs and stiff shocks will dramatically reduce the effects of bad suspension geometry... although a suspension with better geometry will always be a better suspension.

[eHoward]

May I recommend reading this: http://www.amazon.com/exec/obidos/tg/de ... s&n=507846

before giving us definitions of suspension terms.

Bumpsteer is a sudden change in geometry

[The Dark Side of Will]

Good suggestion. Guided research is much more productive than not knowing which way to go.

[notyourmomma]

May I recommend reading this: http://www.amazon.com/exec/obidos/tg/de ... s&n=507846

before giving us definitions of suspension terms.

Bumpsteer is a sudden change in geometry

Oh damn I've been caught quoting Herb Adams in an article he wrote specifically about the 87 Fiero he prepared for Firehawk Series racing. My bad.

[Ultimate 85]

So regardless of where you anchor the rear portion of the knuckle you will still get a bumpsteer effect because of the rubber control arm bushings flexing? Would solid steel control arm bushings need their own special set of bearings & eliminate the metal sleeves that go on with rubber & urethane bushings?

[Kohburn]

So regardless of where you anchor the rear portion of the knuckle you will still get a bumpsteer effect because of the rubber control arm bushings flexing? Would solid steel control arm bushings need their own special set of bearings & eliminate the metal sleeves that go on with rubber & urethane bushings?

no thats only if you tried mounting it to the arm itself

if you change the tierod pivots placement to the same plane as the lower control arm with the inner joint on the same axis as the lower control arms bushings but not attached to the lca, then it would eliminate it

the majority of what people complain about fiero handling or call bumpstear is just plain old worn out components int he suspension.

[notyourmomma]

So regardless of where you anchor the rear portion of the knuckle you will still get a bumpsteer effect because of the rubber control arm bushings flexing? Would solid steel control arm bushings need their own special set of bearings & eliminate the metal sleeves that go on with rubber & urethane bushings?

What Herb Adams (the guy first listed in the link that was provided above) discovered was that you could minimize it with solid bushings but you wouldn't completley eliminate it. He used to market aircraft-quality monoball bearings and sleeves that replaced the rubber bushings in the rear a-arms. They were marketed through Moroso, but last time I checked they were no longer available. Keep in mind they had to be disassembled and re-lubed every six months. Well, that's what Matt Adams, Herb's son told me over the phone a couple years ago. I suppose a creative person could duplicate them, but I'd wonder if something else would give in the control arm? Poly is a cheap, more effective substitute for that kit and is going to flex a whole heck of a lot less than any rubber GM offered. Gerald Stvorik http://www.8shark.com/8shark.html knows something about this and makes Ultra High Molecular Weight bushings that would be even stiffer, not squeak and he claims last longer than poly. They cost about three times as much as poly, but he also sells these sway bar endlinks that use a ball-and-socket design that reduce steering effort that look really nice among some other racing accessories. Herb Adams (if you haven't heard, he was a GM engineer and race car driver as well as published author on Chassis Engineering) also made replacement sway bars for the Fiero but he made larger rear diameters than front. Great if you like to throttle steer more than brake steer, but dangerous for the street IMO. Race track is safer than the street if you ask me. Chances are good (as said above) rear suspension is in need of rebuilding. The rear is a lot simpler than the front I have found. Like I related above. I had rebuilt the front, got the car four wheel aligned and decided to do the back suspension completely and ran into a slight problem. I posted that little bit of info as a caution. I wonder if what really happened was what Will experienced... didn't tighten the lower strut mount cam bolt when I took it back. You'll know when a car dogtracks, you'll feel like you have to turn slightly to the right or left as you are going straight. Older Novas had a habit of doing that.
Anyway, I'm offering this info as a help, not to come off as some ultra-cool, uber-suave race car driver. I put in Gerald's link. You'll find him ranked in the San Fransisco area SCCA. If I'm not clear, I'm sure these other folk will set me straight with glee.

[Indy]

...but he also sells these sway bar endlinks that use a ball-and-socket design that reduce steering effort that look really nice among some other racing accessories.

Time for some setting straight... :lamer:

[eHoward]

That doesn't make it any less wrong.

May I recommend reading this: http://www.amazon.com/exec/obidos/tg/de ... s&n=507846

before giving us definitions of suspension terms.

Bumpsteer is a sudden change in geometry

Oh damn I've been caught quoting Herb Adams in an article he wrote specifically about the 87 Fiero he prepared for Firehawk Series racing. My bad.

[The Dark Side of Will]

Poly v UHMW:
Polyurethane is NOT a good bushing material. It's used for bushings because it's cheap and easy to make bushings from it. Polyurethane is a sticky plastic and binds. That's why poly bushings creak and squeek and need to be greased.

UHMW is a slippery plastic and does not bind the suspension. It has excellent wear properties and is stiffer than poly. However, it's much more difficult to make bushings from it as it must be machined rather than poured.

[Ultimate 85]

How well does Delrin (spelling?) hold up as a bushing material, there's a couple vendors selling them in bushing kits for control arms and mounts. Supposedly stiff stuff but I read elsewhere that it fatigues and deteriotates rather quickly (never used the stuff, don't even know if this is true or not)

[The Dark Side of Will]

UHMW is pretty much UHMW.
Delrin is a trade name and there are lots of variations on it.
I tried some in my car's front suspension, but I have no idea what kind it was (just a bar of plastic in the materials shelf in the machine shop back at VT). I had to sand a good bit of it off the center sleeves in order to reuse them with the XL UHMW bushings that are in the car now.

I made UHMW rear bushings at the same time I made Delrin front bushings, and they're holding up just fine, after the Delrin bushings needed to be replaced.