for 200 mph aerodynamics are crucial for stability (well anything over about 80mph it makes a difference but the faster you go the mroe important it is)

I'm wondering about welded/bolted custom knuckles that used a bolt on bearing assembly like the rear wheel bearings (or better yet the heavier duty ones from a newer gm fwd car) - could even be made to have an adjustable kingpin angle and tie-rod arm length..

quote Originally posted by R Runner: BTW.... Did we really ever answer the original thread question?

Not directly, but I think the original questions were answered. We just dove into the fun part - How?!?!?

quote $20k... to turn a stock fiero into something supercar worthy... 0-60 in 3.0 seconds... 0-100 in 6... 0-100-0 in 10 1. Can it be done?

Straight-line goals are possible, but a true "supercar" is sooo much more, and will take so much more ($$$) to do correctly.

quote 2. Can it be done without modifying the exterior so much that it doesn't look like a fiero anymore?

Yup

Now back to that "how-to" part...

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Todd Perkins - the member formerly known as "perkidelic"
todd's hot rods

for the how to:

engine choices are many, and will depend on each persons personal prefference for low end grunt or high end scream..

transmission - the pontiac drag car got into the 9's with a 4speed tranny with dog gearing - the gears are still available.. but i've never heard of anyone breaking a 4speed other than the pre-85 ones with the weaker case.. so i'm going with the standard v6 4speed tranny

brakes - couple good options.. i'm going the 11.25" vented brake route

suspension - rear i'll be doing coilovers, bumpstear eliminator, poly bushings, solid mount cradle.. possibly a knuckle adaptor to allow 10" wide tires later if power requires
- front i'm up for more discussion on how to make the pre-88's handle better, kingpin angles, control arm length and angle etc..

body - lowered - modified nose and hood scoop to allow air out from under hood -- I believe thats all that is necessary

Here's my take on the front suspension... talked about it other places, too

Street Dreams steel or aluminum lowering knuckles. Match these with HIGH offset wheels to get the steering offset down to basically zero. Use Held upper coil over mounts and upper control arms with RCC lower coil over arms. The Held upper mounts are bolt-in, while the RCC mounts require cutting. The RCC lower arms are castor-adjustable, while the Held lower arms are not. The control arms can be had in custom lengths to make up for the large increase in wheel offset and put the wheels/tire back where they should be in terms of track width and fender fit.

Add some anti-dive blocks into that mix and you'll have just about the best bolt-together setup that can be put into a Fiero. After that, it's just a matter of tuning--alignment settings (castor, camber, toe), spring rates (free selection with coil-overs), shock settings (double adjustables, right?)...

quote Originally posted by Will: Street Dreams steel or aluminum lowering knuckles. . The control arms can be had in custom lengths to make up for the large increase in wheel offset and put the wheels/tire back where they should be in terms of track width and fender fit. Add some anti-dive blocks into that mix and you'll have just about the best bolt-together setup that can be put into a Fiero. After that, it's just a matter of tuning--alignment settings (castor, camber, toe), spring rates (free selection with coil-overs), shock settings (double adjustables, right?)...

what about custom knuckles using a bolt on hub rather than using a huge offset rim which is hard to find

What's more cost effective?

I'd like a knuckle with bolt-on hubs, and intend to eventually do something about getting it made, but that will be quite a while.

quote Originally posted by Will: What's more cost effective? I'd like a knuckle with bolt-on hubs, and intend to eventually do something about getting it made, but that will be quite a while.

I dunno - the street dreams set is what.. 800$? I'd rather file down a solid block of aluminum, but there is no reason nuckles couldn't be made from multiple parts bolted and/or welded together to make it cheaper than a solid CNC peice, plus it could be adjustable in multiple respects

I hope Paul can get that software working and find some time to see what Will's combination looks like in terms of geometry. I am really curious to see what the stock setup is capable of. The reduced scrub should be a benefit - period. The longer arms swinging on stock pick-up points, and with a stock ball joint height, will change things - hopefully for the better.

The other thing I am curious about is the castor. Will, have you ever determined how many degrees the crossmember would have to be rotated to eliminate the pro-dive geometry? Do you have a guess as to how much castor can be dialed back in with the RCC lower arms?

As for cost effectiveness... I will probably be able to get C5 knuckles, with some kind of hub, for less than the Street Dreams knuckles. I am pretty sure I can get my crossmember and arms done for close to the price of the Held and/or RCC arms and coil-over mount. Coil-overs - same price. So, I don't think I will actually be spending any, or much, more than the incremental route. The disadvantage of course, is that my setup probably won't fit under a stock Fiero. Even if the track width is approximately the same, I am sure the upper arm mounts would dictate some sheetmetal work - because of the taller ball joint height.

I wish we all had the money to just go for it. It would be interesting to watch these different methods unfold, simultaneously, and compare the pros and cons of each. Would be good for the Fiero community. Maybe we can go out and sing do-wop on street corners to raise the cash.

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Todd Perkins - the member formerly known as "perkidelic"
todd's hot rods

I would like to offer my take on Will's suggested front suspension tweaks. This is my opinion only so take it for what it's worth.
1. New wheels required. Because of the special offset these will most likely have to be custom made. That means a set of four.
2. Coil-overs required. This will limit suspension travel and require stiffer spring and shock rates to stay off the bump-stops.
3. By increasing the length of both upper and lower a-arms the same amount, camber gain will be made slightly worse.
4. You haven't addressed steering rate. I think most would like to see quicker steering.
5. Way too much money required for the gain, and the changes must be done as a package to have effect.

Now a little background of 12 degree spindles. Back in the day, most late model front ends were camaro derived. Even when the switch was made to tubular clips the same basic geometry was used. (This is why Sweet, Appleton, etc. rack and pinions are 18 1/4 inch eye to eye, as that resulted in acceptable bump with the camaro a-arm pick-up points). Spindle inclination with the Camaro-derived suspension was in the 6 1/2 to 7 1/2 degree range. Latter the switch was made to strut ffront ends, at which point 10 degree spindles were used. Most pavement late models today are using 10 degree spindles. Recently some of the fast guys have started using 12 degree spindles which are giving a little lower lap times. Why? I don't know. It's all a compromise. What Will said is true about losing additional camber on corner entry. But it's also adding a little wedge and could be compensated for with a little more caster. I do know that the tire only needs 100% of its available grip only around the apex of a turn. Late models are limited in wheel offsets to what will clear the brakes and have a lot of offset between the spindle king-pin axis and the hub face. I have no argument with Will about keeping the king-pin angle as low as possible, but as I said It's all a compromise and maybe enough can be gained from my suggestions to justify the cost of the components. Again, I suggested a fabricated spindle with more king-pin angle and shorter steering arms, an extended lower a-arm, harder bushings and a 50/50 shock. By lengthening only the lower a-arm, camber gain is increased slightly, which may off-set the loss from increased king-pin angle and again, additonal caster could be used. I am going to have to disagree with Will about anti-dive. Removing it will require increased spring/shock rates to stay off the bump stops. Again, these are my opinions only.

quote Originally posted by gusshotrods: ...I am going to have to disagree with Will about anti-dive. Removing it will require increased spring/shock rates to stay off the bump stops...

quote Originally posted by Will: ...The Fiero suspension has a few glaring faults...at the front: steering kickback from excessive scrub radius and pro-dive geometry...

Will's position is that the 84-87 front suspension has pro-dive geometry, which is what he is trying to eliminate.

I would have to agree with most of your opinions though.

The late models you speak of are stock cars right? Aren't they left turn oval cars? I am just asking that, to ask you if you think the same methodology would work on road courses, slaloms, and back roads? I thought there was a considerable difference in theory for the two types of racing.

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Todd Perkins - the member formerly known as "perkidelic"
todd's hot rods

Stock suspension has anti-dive.

quote Originally posted by Kohburn: I dunno - the street dreams set is what.. 800$? I'd rather file down a solid block of aluminum, but there is no reason nuckles couldn't be made from multiple parts bolted and/or welded together to make it cheaper than a solid CNC peice, plus it could be adjustable in multiple respects

To duplicate the functionality of the Street Dreams knuckles, since they have 4 bolt patterns, you'd need $800 in hubs alone.

Now, I think that cartridge hubs are a better solution, but the project did not develop that way. (I designed the hub used with that setup, so I have a little "protecting my baby" to do... )

I have the beginnings of a bearing seat design to accept multiple bearings and a list of bearings to use (for all except the 5x4.5" pattern). I'm open to suggestions on how to design the knuckle we both want. I can think of how to make it both ride-height- and overall-height-adjustable. Bolt on steering arms can vary steering rate. There even ought to be ways to give the knuckle adjustable camber/kingpin depending on application. I could prolly come up with those given a little time. Let's get to work.

Will: Are you thinking heim or a tie rod end for the steering arm connection? If a heim is used you could use a slotted hole in the steering arms which would allow fine adjustments of steering ratio. I'm not sure how familiar you are with circle track stuff but if you look at the left side steering arms on circle track spindles most have a slotted hole with serrated plates to hold the adjustment. Just fyi if you were not aware of it.

quote Originally posted by gusshotrod: I would like to offer my take on Will's suggested front suspension tweaks. This is my opinion only so take it for what it's worth.

All productive opinions are welcome here.

quote 1. New wheels required. Because of the special offset these will most likely have to be custom made. That means a set of four.

You want to use stock wheels? I was planning on spending $2000 or so on custom three piece wheels anyway. For the rears I want 17x10-51... try finding that size in an elegant 5 spoke design, let alone 5x100mm pattern... Getting 17x8-7x for the fronts is part of the same package.

quote 2. Coil-overs required. This will limit suspension travel and require stiffer spring and shock rates to stay off the bump-stops.

Do the coil overs have less suspension travel than stock? My suspension will be at stock ride height and should have all the stock travel. I will be using lowering knuckles to drop the front of the car.

quote 3. By increasing the length of both upper and lower a-arms the same amount, camber gain will be made slightly worse.

true. It was never very good to start with, though. There's enough adjustability in the Fiero suspension, and even more when modified, to get enough static camber to make up for this...

quote 4. You haven't addressed steering rate. I think most would like to see quicker steering.

No, I haven't. I don't think that's very hard, though. A steering quickener box could be used. Sweet, the company that made the fast rack for the original Indy pace car could make a fast rack to fit the Fiero housing. An important design attribute that was unfortunately left out of the Street Dreams knuckles was a second tie rod mounting point that would give them a shorter steering arm than stock. I will modify my knuckles to have this, and talk to Ross about implementing that design aspect in future production runs.

quote 5. Way too much money required for the gain, and the changes must be done as a package to have effect.

Well... to the front, sort of. The knuckles could be bought, followed by wheels, followed by suspension arms/coil overs, so they don't have to be all at once, but there are a few large chunks.

quote Now a little background of 12 degree spindles. Back in the day, most late model front ends were camaro derived. Even when the switch was made to tubular clips the same basic geometry was used. (This is why Sweet, Appleton, etc. rack and pinions are 18 1/4 inch eye to eye, as that resulted in acceptable bump with the camaro a-arm pick-up points). Spindle inclination with the Camaro-derived suspension was in the 6 1/2 to 7 1/2 degree range. Latter the switch was made to strut ffront ends, at which point 10 degree spindles were used. Most pavement late models today are using 10 degree spindles. Recently some of the fast guys have started using 12 degree spindles which are giving a little lower lap times. Why? I don't know. It's all a compromise. What Will said is true about losing additional camber on corner entry. But it's also adding a little wedge and could be compensated for with a little more caster. I do know that the tire only needs 100% of its available grip only around the apex of a turn. Late models are limited in wheel offsets to what will clear the brakes and have a lot of offset between the spindle king-pin axis and the hub face. I have no argument with Will about keeping the king-pin angle as low as possible, but as I said It's all a compromise and maybe enough can be gained from my suggestions to justify the cost of the components. Again, I suggested a fabricated spindle with more king-pin angle and shorter steering arms, an extended lower a-arm, harder bushings and a 50/50 shock. By lengthening only the lower a-arm, camber gain is increased slightly, which may off-set the loss from increased king-pin angle and again, additonal caster could be used. I am going to have to disagree with Will about anti-dive. Removing it will require increased spring/shock rates to stay off the bump stops. Again, these are my opinions only.

Ahh... I see where you're coming from now.
So when using a Macpherson strut type front suspension, going to 12 degrees of kingpin improves lap times over 10 degrees of kingpin. I'll buy that for a dollar. The steeper kingpin angle gives the strut suspension a better camber curve AND a more tightly defined roll center.
I was thinking of an SLA setup in which high kingpin angle and differing control arm lengths lead to poor roll center behaviour.
I don't think that additional castor is a good idea. Castor determines the amount of contact patch feel and feedback. Too much castor overwhelms the reduction in steering effort when the front contact patches start to slide. '88 Fieros have MUCH better feedback in this regard than early cars. That's what I aim to correct with high offset wheels.

quote Stock suspension has anti-dive.

I'm going to have to disagree with you on this one. The stock Fiero suspension has PRO-dive. The rear pivot of the upper arm is lower than the front pivot, sure enough, BUT, the rear pivot of the lower arm is lower than the front pivot of the lower arm. The two pivot axes are roughly parallel and are both tilted back. This lowers the side view instant center and results in pro-dive geometry. Just correcting the pro-dive and giving the car neutral dive geometry will result in less brake dive with the same spring rates, and no bad interactions with cornering loads.

About the anti-dive thing. You are most likely right. I have the rear mounts of the lower arms cut off on the cradle I was looking at. I assumed the lower arms would be somewhat level. I think we are on the same page concerning anti-dive. Sorry for the confusion.

Oh yeah... something I've been meaning to mention for a little while...
Bump steer is, of course, the bane of good suspension tuning, the cause of much consternation, and the object of much thoughtful design. However, that I have seen, not much elegant design has been applied to bump steer. The natural solution for dealing with it occured to me some time ago, but until recently I had never seen that solution implemented. The old Jaguar XJ front suspension (from the original Series 1's, 2's and 3's, when a Jaguar was a Jaguar and not a very nice Ford...) is the only suspension I've ever seen implement things this way... They lowered the steering rack until it was in the plane of the lower control arms. The center distance on the inner tie rod ends is the same as the center distance between inner lower control arm pivots. The tie rods are the same lengths as the control arms. If well built, the setup has NO BUMP STEER, with almost no design effort given to not having bump steer. There IS a bump steer adjustment, but it is only to compensate for British chassis building, which was less than precise...

On second thought, the 4th Gen F-body front suspension might be done this way as well...

About the bump steer thing, all late model stock car clips are built this way.

[This message has been edited by gusshotrod (edited 01-05-2005).]

quote Originally posted by Will: I'm going to have to disagree with you on this one. The stock Fiero suspension has PRO-dive. The rear pivot of the upper arm is lower than the front pivot, sure enough, BUT, the rear pivot of the lower arm is lower than the front pivot of the lower arm. The two pivot axes are roughly parallel and are both tilted back. This lowers the side view instant center and results in pro-dive geometry. Just correcting the pro-dive and giving the car neutral dive geometry will result in less brake dive with the same spring rates, and no bad interactions with cornering loads.

so then raising the rear pivot of the lower control arm (or lowering the front pivot) to be parrallel to the road surface would result in a more neutral / anti-dive setup? with minimal other affects to the suspension geometry..

[This message has been edited by Kohburn (edited 01-05-2005).]

quote Originally posted by gusshotrod: About the bump steer thing, all late model stock car clips are built this way.

That's good. Somebody's thinking.

quote Originally posted by Will: That's good. Somebody's thinking.

essentially same as how i plan to fix the rear end bumpstear

quote Originally posted by Kohburn: so then raising the rear pivot of the lower control arm (or lowering the front pivot) to be parrallel to the road surface would result in a more neutral / anti-dive setup? with minimal other affects to the suspension geometry..

It has to do with where the side view instant center is. Since the pivot axes are parallel, the side view instant center is at infinite distance. The tilt of the suspension puts the line going to it sloping down as it goes back. Where this line intersects the plane of the car's CG defines the car's dive characteristics. Since it intersects below ground, the car has pro-dive. Tilting the suspension forward until the pivots were level would fix this.
The pro-dive of the front suspension combined with the pro-squat of the rear suspension put the car's pitch center well below ground level, which is why the Fiero pitches so much on acceleration and braking. Now that I think about it, fixing this pitch behaviour ABSOLUTELY MUST be done before even attempting to reach 200 mph. Aerodynamic loading is VERY sensitive to pitch attitude.

quote Originally posted by Will: Gonna keep the ball joint?

no - but i'll have to make an adaptor for the knuckle to lower the arm pivot to the same plane as the LCA without it hitting the inside of the rim

quote Originally posted by Kohburn: I understand what will was saying about shimming the cross member now - but personally i don't want to make any part of the car lower..

Anti-dive blocks won't make any part of the car lower. They will effectively raise the chassis on the suspension. I don't know exactly how thick they'd need to be, but I will probably stop at 1". I'll have 2" lowering knuckles plus 1" anti-dive blocks, for 1" overall lowering on the front, which I think is about right.

quote it looks like drilling a lower mounting hole on the lower front pivot and possibly also raise the rear pivot slightly.. how many degrees do we need to rotate the lower control arm forward to fix the dive?

I'd rather keep the pivot axes parallel. There are fewer other compromises that way. Also, to prevent the control arm geometry from getting worse than it is, you need to NOT move the LCA inner pivots away from the UCA inner pivots. This leaves moving the LCA inner rear pivot relative to the crossmember as the only real option.

Before Bill Gates and Steve Jobs took over the world, I would imagine that they actually used pencils, paper, and a drafting board to plot suspension geometry. I am so curious about this that I am almost ready to try it. It's gonna be a while before I can afford the Pro Trends software, but I am decent at mechanical drawing, hmmm..

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Todd Perkins - the member formerly known as "perkidelic"
todd's hot rods

quote Originally posted by Will: Anti-dive blocks won't make any part of the car lower. They will effectively raise the chassis on the suspension. I don't know exactly how thick they'd need to be, but I will probably stop at 1". I'll have 2" lowering knuckles plus 1" anti-dive blocks, for 1" overall lowering on the front, which I think is about right.

well for the same amount of chassis lowering that'd make the cross member 1" closer to the ground.. and since I preffer a 1.5-2" lowering that makes groudn clearance tight..

quote Originally posted by Will: I'd rather keep the pivot axes parallel. There are fewer other compromises that way. Also, to prevent the control arm geometry from getting worse than it is, you need to NOT move the LCA inner pivots away from the UCA inner pivots. This leaves moving the LCA inner rear pivot relative to the crossmember as the only real option.

parallel or slightyl anti-dive is what I was thinking..

any thoughs on the distance between the baljoints? (which by itself doesn't mean much but what it would equate to is the lower arm being parallel to the ground at rest and the upper arm being angled up more changing how the camber changes throughout suspension travel)

How much lower do you want the car? Do you want the chassis itself low, or do you want the wheels to fill the wheel houses better? I find that a combination of moderate lowering and moderate increase of tire diameter looks best to my eye. A lot of lowered Fieros look silly, IMO because they use small diameter tires. The wheel house gap ends up nice and tight on the top, but much wider on the front and rear edges of the tire. I find that less lowering with a moderate amount of increase in tire OD fills the wheel house up better and gives a wheel house gap that's much more even all the way around.

In general, the height of pivots has a larger affect on camber and roll center stability than lateral location. Yes, raising the UBJ somewhat will improve camber characteristics, but I don't remember what it does to roll center characteristics. I'd think that would raise the roll center, which is something that we don't want to do on the front of the car. I don't have time right now to break out my software, and I'd like to update my models, now that I have lots of loose suspension parts to examine.

my front tire size is 225/45/17 - essentially the same as a 215/60/15 (and also a 265/40/17) as it sits on the 84 SE there is about a 4" wheel gap up top

if raising the UBJ raises the roll center I'd like to lower it enough to cancel that out
i'm mostly concerned with handling - then apearance, since I have body mods planned we gap could potentially be adjusted

This thread is awesome guys, I wish I could add to it, but you have gone a bit over my head as far as tech goes. Along with possibly pushing the Fiero to it's limits, I would like to think that this thread is coming up with some new answers to some old problems.

quote Originally posted by Kohburn: my front tire size is 225/45/17 - essentially the same as a 215/60/15 (and also a 265/40/17) as it sits on the 84 SE there is about a 4" wheel gap up top if raising the UBJ raises the roll center I'd like to lower it enough to cancel that out i'm mostly concerned with handling - then apearance, since I have body mods planned we gap could potentially be adjusted

I've currently got 225/50-16's (essentially the same size as your 225/45-17's) and I think those are a bit small. I will eventually be running 225/50-17's and I think that will be about right.

quote Originally posted by gusshotrod: If you are talking about the natural period of the suspension it can be tuned or whatever speed/wheelbase required. This is done to prevent the car occillating in the pitch direction. This is a pretty neglected facet of race tuning and can easily seen if you know what you're looking for. Most of the tuning is in the aero for cars going 200 mph. The center of pressure needs to be behind the cg for stability. Most cars run at Bonneville are interested in low drag. Moving the center of pressure rearward can increase drag. The other issue with Bonneville cars is a lack of aero balance from front to rear that again would require increased drag to fix. Some of the ways to move the center of pressure to the rear of the car is with large side fences on spoilers, adding fins to the rear, or with rear wings/spoilers. A good example of this is the Porsche 917 that ran in the Can-am series. When Porsche first brought this over it wasn't that fast. Penske/Donahue redesigned the thing adding a lot of drag in the process and ended up with an unbeatable race car. Take a look at that car before and after and you'll see what I mean.

Keep in mind too that saltflat cars go for Zero lift or down force (which you said) to reduce the drag. The weight of the car is the only thing that is holding the tires to the ground. With the increased areodynamics (like a large rear wing, nose air dam, side skirts, flat underside panels, etc.) a short wheel base car can do just fine at the higher speeds.

Didn't mean to repeat anyone here. Been out of town on business..... just catching up.

Paul

quote Originally posted by Will: ...I will eventually be running 225/50-17's and I think that will be about right.

Isn't the the overall diameter of your current tire size an inch larger than stock? I have the same size (225/50-16) on my car right now and it is an inch bigger than the 215/60-14's or the 225/50-15's I had on it previously.

If so, your ultimate combination will be at the original ride height. Down two inches from lowering knuckles, back up one inch from pro-dive elimination shims, up another inch from increased overall tire diameter (as compared to stock).

My car is lowered about three inches right now and the wheels fit beautifully inside the stock wells IMO. Can barely squeeze a finger between the top of the front tire and the fender lip. Of course, I don't have stock inner fenders to worry about, and eventually the bodywork will be all custom to fit around the new suspension.

Final note: it is a challenge to drive on Ohio/PA public roads this low but I like it. Feels like a go kart! You just can't whiz in and out of parking lots and driveways like a normal car, but I am not trying to build a "normal" car

Paul - this is no time for business we got playing to do

Todd

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Todd Perkins - the member formerly known as "perkidelic"
todd's hot rods