WIll: What I was saying is that there wasn't any room to raise the inner pick up points unless the trans was also raised. Also, Chapman never built a grand prix car with struts.

quote Originally posted by toddshotrods: Two A complete "from scratch" front design that will bolt to the front of any Fiero with nothing more than minor modifications. Of course some things like knuckles would likely be pre-existing parts from some other vehicle. Tires will fit under the fenders. Goals = great geometry, great driving experience, great numbers. More expensive but more rewarding for the true performance junkie that doesn't want to alter the look of the car. Six New cradle with strut suspension as gusshotrod has done, and Will has planned, which will address geometry and provide best solution without radically transforming car. Complement to "Two".

I don't even think it needs a "from scratch" design to be a pretty dam nice front suspension.
Start with Street Dreams aluminum knuckles. This gives stronger bearings and multiple hub bolt circles, as well as dropping 4# of unsprung weight per corner. Pick a wheel with a VERY high offset to reduce steering offset, provide good feedback, and reduce kickback. The extreme offset will narrow the track width by approx 1" per side. Order RCC lower coil over arms and Held upper arms and upper coil over mounts, both with +1" per side track width change. The Held upper mounts bolt in, while the RCC lower arms are adjustable for castor. There you have it... fully adjustable suspension with free selection of spring rates and shock damping, aluminum knuckles and whatever brakes will fit stock Fiero knuckles. Combine the stiffer springs with anti-dive blocks I outlined above and you have a very nice front suspension that bolts together. You've picked from the best that's available on the market and built the best that can be bolted together.

On the rear, things get more complicated. When the Citation front end was transplanted, the anti-dive geometry was retained. In the rear, this anti-dive turns into pro-squat. To get rid of this, the rear of the cradle must be lowered. On the original Indy pace car, this was done by putting spacers between the rear cradle bushings and the chassis. Presumably the cradle bushings were also poly or solid. However, this alters top-side clearances, which can get pretty critical on some engine swaps (especially certain DOHC V8's...). So what I envision to deal with pro-dive is a set of eccentric front cradle bushings combined with sloped rear cradle bushings. These will be used to raise the front of the cradle while lowering the rear, but in such a way as to rotate around the top of the engine. This will move the axle forward somewhat, which will have to compromised by the reduction in pro-squat. If the last little bit of pro-squat can't be dealt with, a small spacer could be added above the rear cradle bushing.

The next fault of the rear suspension is bumpsteer. There are various solutionson the market, like the RCC kit and the Held kit. The RCC kit is in my opinion a bandaid, and a poorly engineered one at that. The Held kit is well engineered solution to what Held perceived as the problem. I perceive the problem differently. The WHOLE SUSPENSION is part of the problem. The lateral separation of forward control arm pivots is greater than the lateral separation of rear control arm pivots. This means that the pivot axle of the control arms are not parallel. This plays havoc with trying to develop a bumpsteer kit. The solution to this is a bolt- or weld- in bracket that moves the rear pivot of the control arm out (and maybe down some to help fight pro-dive) to get it coaxial with the front pivot and get the two pivot axes parallel. Once that's done, an H-arm and new knuckle could be designed to provide zero bump steer characteristics, along with larger bearings, brakes and bolt circles.

However, it's not quite that easy. In order to use an H-arm, the control arm pivot axis will have to be perpendicular to the strut. Since the suspension was implemented retaining its pro-squat, it also likely retains it's castor. The top of the strut would have to be moved forward, or the attachment point of the strut to the hub carrier moved back to get to zero castor, which will allow zero pro-squat (or zero anti-squat, or just neutral squat geometry). I don't forsee this being a problem, as the top of the strut can be moved three inches, as can the bottom of the strut. A three inch move at one end would change castor by over 7 degrees, which should be MORE than enough.
Once all that has been done... voila, a VERY nice strut suspension with minimal cutting/welding of chassis metal.

quote Originally posted by Will: I don't even think it needs a "from scratch" design to be a pretty dam nice front suspension. Start with Street Dreams aluminum knuckles. This gives stronger bearings and multiple hub bolt circles, as well as dropping 4# of unsprung weight per corner. Pick a wheel with a VERY high offset to reduce steering offset, provide good feedback, and reduce kickback. The extreme offset will narrow the track width by approx 1" per side. Order RCC lower coil over arms and Held upper arms and upper coil over mounts, both with +1" per side track width change. The Held upper mounts bolt in, while the RCC lower arms are adjustable for castor. There you have it... fully adjustable suspension with free selection of spring rates and shock damping, aluminum knuckles and whatever brakes will fit stock Fiero knuckles. Combine the stiffer springs with anti-dive blocks I outlined above and you have a very nice front suspension that bolts together. You've picked from the best that's available on the market and built the best that can be bolted together. On the rear, things get more complicated. When the Citation front end was transplanted, the anti-dive geometry was retained. In the rear, this anti-dive turns into pro-squat. To get rid of this, the rear of the cradle must be lowered. On the original Indy pace car, this was done by putting spacers between the rear cradle bushings and the chassis. Presumably the cradle bushings were also poly or solid. However, this alters top-side clearances, which can get pretty critical on some engine swaps (especially certain DOHC V8's...). So what I envision to deal with pro-dive is a set of eccentric front cradle bushings combined with sloped rear cradle bushings. These will be used to raise the front of the cradle while lowering the rear, but in such a way as to rotate around the top of the engine. This will move the axle forward somewhat, which will have to compromised by the reduction in pro-squat. If the last little bit of pro-squat can't be dealt with, a small spacer could be added above the rear cradle bushing. The next fault of the rear suspension is bumpsteer. There are various solutionson the market, like the RCC kit and the Held kit. The RCC kit is in my opinion a bandaid, and a poorly engineered one at that. The Held kit is well engineered solution to what Held perceived as the problem. I perceive the problem differently. The WHOLE SUSPENSION is part of the problem. The lateral separation of forward control arm pivots is greater than the lateral separation of rear control arm pivots. This means that the pivot axle of the control arms are not parallel. This plays havoc with trying to develop a bumpsteer kit. The solution to this is a bolt- or weld- in bracket that moves the rear pivot of the control arm out (and maybe down some to help fight pro-dive) to get it coaxial with the front pivot and get the two pivot axes parallel. Once that's done, an H-arm and new knuckle could be designed to provide zero bump steer characteristics, along with larger bearings, brakes and bolt circles. However, it's not quite that easy. In order to use an H-arm, the control arm pivot axis will have to be perpendicular to the strut. Since the suspension was implemented retaining its pro-squat, it also likely retains it's castor. The top of the strut would have to be moved forward, or the attachment point of the strut to the hub carrier moved back to get to zero castor, which will allow zero pro-squat (or zero anti-squat, or just neutral squat geometry). I don't forsee this being a problem, as the top of the strut can be moved three inches, as can the bottom of the strut. A three inch move at one end would change castor by over 7 degrees, which should be MORE than enough. Once all that has been done... voila, a VERY nice strut suspension with minimal cutting/welding of chassis metal.

Will.......

Obviously you have given this a lot of detailed thought. Tomorrow I'll call the company (Performance Trends) to get the code so I can use it on my newer computer. I would like to plug in some numbers and move stuff around. That will help me visualize what your proposed changes are and we can look at the result to the wheel.... plot camber curves, dive, squat, etc. and see just what it affects. I would love to have a nodal analysis program to analyize the tortional stiffness on the cradle and figure (more than intuition) the best bang for the buck stiffening mods. Once we knew that we could see how much it affected the wheel loads and that would pretty much cover it.

Does the Held upper arm help move the upper ball joint rearward? It seems like unless this is done there may not be enough adjustment in the RCC component to get the caster more positive.

One thing that may help us is to define where we want the caster curves to be, overall positon of the wheel, etc. That being known, the changes proposed can be evaluated as well as the optimum geometry determined. Then we can see how easy it would be to make it a "bolt in" piece. ....... its getting late... brain shutting down.... must sleep.....

Paul

Sounds like a good start to some basic procedures to transform the ordinary everyday Fiero into a thoroughbred sports car. The only thing I beg to differ on is Will offered this is a solution to objectives "Two" and "Six" but this actually addresses "One" and "Five".

quote One Best incremental enhancements to the most common 84-87 front suspension... Same crossmember, same arms, just revised geometry... The point is, all the currently available bolt-ons should work with option "one". Goal = performance on par with or exceeding the 88 setup. Five Incremental mods to 84-87 rear strut suspension. Altered pick-up points, etc. Complement to "One".

I think your train of thought on this is excellent Will. If the numbers confirm your theory, there will be a nice path for Fiero nuts to follow that can be done in stages, as time and budget allow - excellent.

The only thing I don't understand is why you seem to be opposed to creating new designs, as a next step. If my goal was supercar performance with the original styling I would gladly fork over the bucks for custom front and rear suspensions. With 10K+ members I am convinced that there are some like-minded people out there wishing and waiting for objectives "Two" and "Six". I was actually planning on the "wide track" top-o-dee-line Held front suspension setup when I first came here. Then I started hearing conflicting opinions about whether or not the geometry was what I expected. That led me into this whole mind-numbing pursuit

One system simmering, three to go...

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

[This message has been edited by toddshotrods (edited 12-31-2004).]

I'm after best bang for the buck... The Fiero is a nice platform, but it can only go so far. In trying to make it something it isn't, you wind up with a lot of work and not much Fiero.

If you're going to build everything from scratch, why bother with the stock Fiero shape? was it really that good? I think it could stand to have the front wheels pushed forward about 5 inches, among other things...

When I build a car from scratch, it will probably be some sort of open wheel A-mod autocross type vehicle that would put any street car to shame in terms of performance...

Don't overlook the impact that small improvements can make. For instance, how much would the Fiero driving experience be improved with a set of pedals that could be heel-toed? a telescoping steering column? For me a $0.50 block of wood on the gas pedal and a $20 junk yard Caddy steering column to move the wheel closer could have a large effect on how enjoyable the Fiero is.

I just think that the Fiero can be brought to a large fraction of the performance of any supercar out there, at least in terms of the suspension, for a relatively small outlay of cash and work. If you absolutely have to have a Fiero that kicks everything's butt, you can go further, but the cost/return curve turns up sharply...
I go fast for a hobby. If you're in the business of building custom cars, go for it.

Man, this is good! I had trouble sleeping last night because two years of planning and searching is finally beginning to jell into something I can live with. My plans are still not set in stone, but process of elmination has led me back to a certain combination everytime. Since a street vehicle is basically a rolling set of compromises, and there is really no such thing as a "perfect" street vehicle, it's all about priorities. I figured out what the characteristics of the vehicle itself had to be to meet my goals and expectations, then started figuring out which combinations of parts could fit within that package.

My front suspension will follow objective:

quote Three The ultimate front suspension that can be adapted to the space frame. May require extensive mods and possible a wide body to cover the tires. No compromises in the design except maybe what can fit on or around the stock main frame rails, transaxle, engine, etc. Other less critical items may need to be moved. Goal = supercar performance, no excuses.

For this I am planning on a mandrel-bent rectangular tube crossmember, moly upper and lower tubular arms, C5 knuckles with C4 hubs, race type adjustable sway bar, Woodward steering rack. The desired geometry will dictate the width from hub-to-hub, and the offset on the wheels.

For the rear I have to create objective:

Nine
Tubular cradle designed specifically for transverse-mounted V8 and my custom suspension. Moly LCA's, and aluminum knuckles (W-body???) with C4 hubs, race type adjustable sway bar. I may have to compromise a bit here on geometry because it has to balance the car (relative to the front). I should have plenty of room to come up with something decent though.

What I love about Fieros is I can develop the whole car, with all of this in mind and bolt all the expensive stuff on as I can afford it. I can even drive a finished looking car while I save my pennies for the good stuff! If I need to do some cutting and welding, I can pull all the bodywork off, go crazy on the chassis, splash some paint on it, hang the bodywork, and go have fun again!

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

[This message has been edited by toddshotrods (edited 12-31-2004).]

You guys are making me drool and I have only read 1 page. I wish this thread would have started back when I was building my fiero. ok back to reading the other 2 pages

quote Originally posted by Will: For me a $0.50 block of wood on the gas pedal and a $20 junk yard Caddy steering column to move the wheel closer could have a large effect on how enjoyable the Fiero is.

Just out of curiousity, i had a friend who's dad put a block of wood on the pedals, which, the only reason that i know of that he did that was because of his height. Just out of curiousity, how tall are you?

to stay on topic, not that i can add much, but would there be any benefit to doing something like helds tubular front suspension? They may or may not have the best geometry on their design, but does that piece save any weight? or would it not be worth it? Also, if you do design a suspension, and i think i asked this earlier, but haven't seen a response, would it work with an 87 or older fiero?

quote Originally posted by toddshotrods: C5 knuckles with C4 hubs

??? Typo?
Why that combo. They have different bolt patterns, you realize...

quote Tubular cradle designed specifically for transverse-mounted V8 and my custom suspension. Moly LCA's, and aluminum knuckles (W-body???) with C4 hubs, race type adjustable sway bar. I may have to compromise a bit here on geometry because it has to balance the car (relative to the front). I should have plenty of room to come up with something decent though.

Might want to wait until you see what I come up with... Prolly going to be more "universal" than you want, but the cradle I envsion will have mounts for all popular engine swaps, even a bolt in member to pick up the proper mount locations on a Chevy, suspension pickups for '88 suspension... stock and corrected pickups for early suspension... etc.

As far as aluminum hub carriers go, I don't think the W-body is really the best choice. I'm in the process of designing a replacement fabbed aluminum hub carrier based on the '88 Fiero unit. We'll see what I can get into it, but I should be able to fit mounting locations for early style, '88, and F/W-body brakes.

SLA... maybe.

[This message has been edited by Will (edited 12-31-2004).]

quote Originally posted by Will: ??? Typo? Why that combo. They have different bolt patterns, you realize...

Maybe I have the combination wrong. I have notes on it somewhere but am too lazy to dig 'em up right now. Then again, I may have been planning on having some machine work done.

quote Might want to wait until you see what I come up with... suspension pickups for '88 suspension... stock and corrected pickups for early suspension... etc.

I will definitely be interested in seeing your cradle. The biggest reason I was planning on a custom piece is that my car will be pretty wide and the geometry will likely be different. We have some of the same basic plans though - eliminating pro-squat, making the LCA mounts parallel to the longitudinal chassis center line, raised roll center, etc. But then, I got all that from you in the "Porsche-ish potential" thread

quote As far as aluminum hub carriers go, I don't think the W-body is really the best choice. I'm in the process of designing a replacement fabbed aluminum hub carrier based on the '88 Fiero unit...

That's why I put three question marks on W-body. I just figured I will be able to find a suitable factory knuckle or have a pair made. Important thing to me was figuring out the basic configuration for my rear suspension. Maybe your design will work for my project, and be ready by the time I need it.

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

I'd like to offer my take on improving the early front suspension. I would start with fabricated spindles with 12 degrees kingpin inclination and a two inch drop. This would allow an extended lower a-arm which would increase camber gain. The increased spindle inclintation would reduce/eliminate scrub. The fabricated spindle would also allow a shorter steering arm to increase steering rate. As far as anti-dive, my experience tells me some amount is a neccessary evil. Athough it causes caster change during suspension movement, the benifits are a softer spring rate and suspension movement not being used up under braking, and a better transition from braking to acceleration. A good 50/50 shock and stiffer bushings and you're good to go.

It's the transition from braking to cornering where anti-dive causes problems. It loads up the suspension and effectively changes the suspension tuning when the driver is on the brakes... not all that great for consistent handling.

12 degrees?!?! that seems like a HUGE amount of kingpin angle...

The big reason the early cars have the scrub radius issues that they do is that the hub flange is soooo far from the kingpin axis. Look at the hub carriers on an '88 suspension... the hub flange is MUCH closer to the kingpin axis on those knuckles.

12 degrees of kingpin angle will give you good stability and on-center feel, but I think it will compromise cornering a lot. It'll overwhelm your castor and you'll lose camber on the outside tire as you turn (camber on outside tire will go positive).

If you fab a knuckle, concentrate on getting the hub flange as close to the kingpin axis as possible, since that will let you run less kingpin inclination, yet still have good steering geometry. That's why Audi's and 2G DSM's have two lower ball joints and two lower a-arms... they were designing a "virtual" kingpin so that they could get the scrub radius down...

Longer lower A-arm doesn't necessarily mean better camber... it can, but it also tends to make a LOT of tradeoffs in roll-center behaviour with control arms that have significantly different lengths.

12" knuckle height... the taller you make a knuckle, the more you have to move the upper ball joint relative to the lower to get camber gain...
In general, if your focus is anti-dive, you can get more anti-dive with less castor change using a tall knuckle. That's why a lot of passenger cars today (Z32 300ZX, 4th Gen F-body, 2G DSM's, etc) have tall knuckles. However, cars in which camber is important (Corvettes, Ferarris, Vipers) have shorter knuckles. With the limited space under a Fiero for suspension pieces, I think it's better to use a shorter knuckle, because it's easier to fit the control arms that will give that knuckle good camber gain. The stock knuckle height is about 8" from ball joint to ball joint, and I wouldn't want it to be much taller than that.

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

If you're transitioning from braking to cornering you ain't doing it right. The problem area that lack of anti-dive causes is the transition from braking to accel during cornering. The front end unloads and washes out. There are a lot of racers changing to 12 degree spindles out here with good results but what you say is true about less offset being better. I do think that the fiero could use more camber gain and couldn't see any other way using the stock crossmember.

Too much to think about, gotta take a break from this - I'll talk to you guys next year

Happy New Year Speed Junkies!!!

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

Here's something I haven't seen anyone else do. These are some bolt-on steering arms I made for 88 spindles. There might be a market for something like this if they were designed to speed up the steering rate. These were used on a custom front suspension for a fiero I made using a Sweet rack.

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

That's cool. Quite a few older cars had bolt on steering arms, now that I think about it... Could probably do something like that for the early spindles with a bit of work
One thing I regret not thinking about when I was working with Street Dreams on the aluminum knuckles was adding a second tie rod attachment closer to the kingpin than the first.
Next time I get in touch with them about brake brackets, I'll have to mention it for future runs of their knuckles...

Measuring mine, the distance from the kingpin to the tierod hole is about 4 5/8"... drilling a new hole 1" inboard would quicken the steering by 28%, reducing the steering from 3 turns lock-to-lock to 2.35 turns lock-to-lock. Moving it an inch and a half would reduce it all the way to 2 turns lock-to-lock... Hmm...
Have to be careful about exactly where it went, so as not to screw up the ackerman angle...

What kind of bump-steer issues might that create? I don't think it would be a problem, but once every few years I'm wrong about something...

Now what's the reasoning behind going to a 12 degree knuckle? I can see that it would give good on center feel and might give good feedback in high speed corners, but I'm also pretty sure it would make the car understeer in really tight turns (like autocrosses... Do you want a supercar that gets beaten by Miatas in parking lots? )

Anti dive...
Can't get away from weight transfer... However, good suspension tuning and tire selection helps a lot. Going with much wider tires in the rear mitigates a lot of the Fiero's worst handling traits. As long as the tires are matched to the weight distribution, you're going to have a pretty good compromise. It can't be perfect both ways...

Camber change/roll center...
The way I've usually seen it work is that improving camber performance raises the roll center... but because the Fiero centroid axis is pretty low in front, we don't want to raise the roll center in the front, just in the rear.

A couple quick questions for anyone planning to build a Fiero or Fiero-related supercar - Will, gusshotrod, and Paul please answer

1) How do you intend to use your car after the supercar goals have been met?

2) What led you to reach for this goal in the first place?

Just trying to add some more perspective to the things that are posted here.

In my case,
(1)
> My car will be a marketing tool for my business
> It will be raced in select grudge type events
> I am gonna drive it, drive it, drive it

(2)
> I love competition
> I have always had a preference for the most exotic things in life (vehicles and otherwise). Not even so much for the "wow factor" with other people - but more for what they do for me personally, from a purely artistic perspective.
> I have always wanted to drive a supercar on public roads

edited for typos and other errors
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Todd Perkins - the member formerly known as "perkidelic"
todd's hot rods

[This message has been edited by toddshotrods (edited 01-02-2005).]

quote Originally posted by toddshotrods: In my case, (1) > My car will be the "flagship" marketing tool for my business > It will be raced in select grudge type events > I have always wanted to drive an exotic car on public roads (2) > I love competition > I have always had a preference for the most exotic things in life (vehicles and otherwise). Not even so much for the "wow factor" with other people - but more for what they do for me personally, from a purely artistic perspective.

(1) I plan on doing some racing with my car, maybe autocross, or preferably, some kind of road course racing.
It won't be a daily driver, but this will be something that I'll want to drive on a frequent basis, at least 2-4 times a week.
I also want something that will have the feel I am looking for, I don't want to take a corner and halfway through have that, "o crap!" feeling that a fiero can tend to give.

(2) I like cornering, otherwise I wouldn't have bought the fiero
I like competition as well, but it's still more about me and my wanting of tearing up some corners.

I edited my original post after cooguyfish quoted me because it was late when I first answered my own question and I had things a little out of order - nothing screwy is going on around here though

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

I want my car to do everything well, but I don't want to pay a mint or spend five years building it (oops, too late...)
I like to surprise people, especially with ingenuity/creativity
I like to share what I've designed/made (which means that it has to be shareable, and easy to install... not like a 100% custom car)
I like to thrash...

A quick question for the fabricators...what thickness/type of steel would be suitable for making a crossmember?
I was thinking of 3/16" thick square tube. I believe stock is a little less than that thickness(sure feels like tin foil). Any advice?

My crossmember is bent(wondered why I could never align the driver's side). I'm not going for supercar handling, I'm installing air bags and I'm thinking that anything I can make would be stronger than the stock one. It's either that or weld stuff onto a stock one.

[This message has been edited by Joe Torma (edited 01-03-2005).]

will - about changing the LCA pivots on the cradle.. people have mentioned using the grandam/grandprix? cradle in the fiero after welding on front mounting wings to go to the fieros front cradle mounts.. does that cradle share the anti-dive/prosquat characteristic with the fiero cradle, and if not would this be an easier way to change that aspect of the fiero suspension...

quote Originally posted by Joe Torma: A quick question for the fabricators...what thickness/type of steel would be suitable for making a crossmember? I was thinking of 3/16" thick square tube...

Wow, that's pretty thick stuff! For comparison, on 2x3 or 2x4" rectangular tube frames:

.083" wall is lightweight for racing
.120" wall is considered heavy duty for street type applications

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

quote Originally posted by Kohburn: will - about changing the LCA pivots on the cradle.. people have mentioned using the grandam/grandprix? cradle in the fiero after welding on front mounting wings to go to the fieros front cradle mounts.. does that cradle share the anti-dive/prosquat characteristic with the fiero cradle, and if not would this be an easier way to change that aspect of the fiero suspension...

The W-body cradle probably has the anti-dive geometry as installed in the W-body. The thing I don't understand about the Fiero cradle is this: they weren't reusing the X-body cradle exactly... there was a bit of redesign involved. Why couldn't that redesign have included rotating the cradle just enough to get rid of the pro-squat? Seems like that would have been cake considering what they were doing...
So as installed in the GP, I'm sure there is anti-dive/pro-squat. However, installing it in the Fiero, I'm sure you could rotate it to get rid of that...

What would be accomplished in using the Grand Am/Prix cradle? Would the LCA pick-up points be parallel to the longitudinal center line? Or is this the aluminum cradle that was mentioned before? Just trying to understand what would be gained in swapping in a different cradle.

Another question:
What do you guys think about the 93.4" wheelbase at or above 200mph? I read this article on an MR2 (94.5" wb) that went slightly over 200 at Bonneville. It was apparently enough of a challenge that an experienced land speed driver was needed for the record runs.
http://www.bobnorwood.com/The%20Fastest%20Little%20Sports%20Car%20in%20Utah.htm

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

in a straight line at high speeds mid engine is a disadvantage so is a short wheel base

mid engine design to pull the polar moment closer to the cg along with a short wheel base is designed to turn easily..
high speed are better with more mass, longer wheel base and a front engine -- think arrow...

quote Originally posted by toddshotrods: Wow, that's pretty thick stuff! For comparison, on 2x3 or 2x4" rectangular tube frames: .083" wall is lightweight for racing .120" wall is considered heavy duty for street type applications

Too thick huh? I do think the stock is made out of tin foil though. Probably why mine is bent!
Thanks for the info.

quote Originally posted by Joe Torma: Too thick huh? I do think the stock is made out of tin foil though. Probably why mine is bent! Thanks for the info.

I took my last 86SE for a 10foot drop off the road into the woods and it bent the cross member - but i was able to get it within spec with slotted upper ball joints.. it takes a lot of abuse to bend it

quote Originally posted by toddshotrods: What would be accomplished in using the Grand Am/Prix cradle? Would the LCA pick-up points be parallel to the longitudinal center line? Or is this the aluminum cradle that was mentioned before? Just trying to understand what would be gained in swapping in a different cradle. Another question: What do you guys think about the 93.4" wheelbase at or above 200mph? I read this article on an MR2 (94.5" wb) that went slightly over 200 at Bonneville. It was apparently enough of a challenge that an experienced land speed driver was needed for the record runs. http://www.bobnorwood.com/The%20Fastest%20Little%20Sports%20Car%20in%20Utah.htm

The car was a challenge the first time because they ditched the rear anti-roll bar. Somebody didn't have the best grasp of vehicle dynamics...
They put the roll bar back on for the second season and the car was MUCH more tractible.

I think the W-body cradle is desired because it's aluminum. I'm all about tweaking what the Fiero has, but I think that even I'd rather build exactly what I want from scratch than try to pack something else that isn't exactly what I want into the car...

Yeah, I am familiar with the considerations of our mid-engine/rear-drive, short wheelbase that make it more favorable for handling (especially tight road course type venues). I also saw where they mistakenly discarded the MR2's anti-roll bar and figured out it was needed.

I am more curious about the effects of the short wheelbase itself. All things being equal, from what I understand, the advantage of a longer wheelbase for straight-line stability is that the front wheels have a better opportunity to recover before the rear wheels encounter what "upset" the front suspension.

So, I was just wondering what your thoughts were on the 93.5" wheelbase itself at 200mph or beyond.

The Porsche 911 platform has an even shorter 92.5" wheelbase and has been in that range. The production 959 (same chassis) was spec'd at 197mph for top speed. I'm pretty sure I have read accounts of 911's at Bonneville in the 200mph range, but can't remember where right now. I've haven't come across any complaints about instability at these speeds with such a short wb. Am I just not looking hard enough, or is the short wheelbase itself not such an important consideration at 200mph. The 911 has a pretty high CG and is basically an arrow flying backwards.

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

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.

Thanks gusshotrod. That seems to be doable, and most importantly in ways that can be specifically implemented just for top speed runs. Then the car can be returned to "normal" afterwards.

In the end, I will probably end up with a longer (than stock) wheelbase but I wanted to see what's possible with the shorty. The same priniciples can be used with a slightly longer wheelbase for increased stability, so the knowledge gained won't be wasted.

Original

Penske/Donohue

On the subject of wheelbase and top speed - 2300mm (90.55") Top speeds 200-220mph.

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

[This message has been edited by toddshotrods (edited 01-04-2005).]

My take on how wheelbase really affects high speed stability is basic levers..

on a short wheel base if the wheel hits a bump or moves to the side it disturbes the cars mass much more than when the wheels are farther from the CG..

kinda like changing the stearing ratio of the car.. quick ratio a small twitch will turn more than on a slow ratio ..

quote Originally posted by gusshotrod: There are a lot of racers changing to 12 degree spindles out here with good results but what you say is true about less offset being better.

I'd like to hear more about the 12 degree knuckles. Hope I didn't come across wrong by being too opinionated or disagreeing with you.

quote Originally posted by Will: 911 has a high CG? ...

Could be wrong, and I will admit I was just quoting what I read. I should have noted that that was supposed to be in comparison to much lower sports cars, i.e. Ferrari and Lamborghini. It was an article on the Porsche 959. They were trying to give both objective and subjective performance evaluation of the car as a competitor to the current offerings from the two Italian makers. The high CG comment came when discussing its handling characteristics.

I don't wanna get too far into the wheelbase/straight-line issue because going around corners is more relevant to this discussion. I know it is possible to do reasonably safely, because it has been done more than a few times with wheelbases close to ours. I just wanted your opinions, to see if there were any major considerations that should be designed into the car for 200mph. Like most other things, it seems to be more an issue of tuning.

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

[This message has been edited by toddshotrods (edited 01-04-2005).]