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Thanks Dean,

I really appreciate all of the time you are putting into this. I have a dedicated autocross third gen that I run in CP and I believe I will find this info usefull. Looks like right now the most important part for me to get will be dropped spindles from part 1.

Again Thanks Dean, This should be made sticky

That's it for now... darn!

Mike

Dean you must be a engineer, your attention to detail is amazing....


aligment question, on a stock ride height 91 formula, what aligment specs do you recommend that give best tracking and handling.

could anybody make this and his previous thread into one and make it sticky ?? i will be needing all this info when prepearing my car into drift and it will be easier to find all this useful information

best regards

x2 on they should both get a Sticky.

Im in the process of making them part 1 and 2 into webpage info.

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This should definitely be a sticky... I'm reading all this info and trying to comprehend this knowledge! It's so complicated man... I appreciate the time you put into this Vetruck! I'm also contemplating getting 2" dropped spindles from Racecraft to lower the car rather than lowering springs! I'm also gonna buy everything adjustable as well.

Thank you!

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In response to the chassis part... I have installed both MAC (like the alstons) and the SPOHN (outer) frame connectors... I first installed the MAC ones and the car DID handle better, but with the spohn ones it feels more boxed and more like the rear follows the front in the corner... There's literally no flex anymore.

pic
This one has SFC's welded in, but is it the one you want?

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Wow that is an amazing pic of the underneath of our cars.. thnx!

update??

suscribed

What about the other braces I've seen on your car? Care to explain those or how different parts of the chasis move when under strain. Example: how do the strut towers move/flex when you turn or go over a bump? I know I've read about the mods to your STB and how an adjustable wonderbar helps due to the preload you can put on the front frame horns. Can you go in depth about that kind of stuff? I could try to explain it, but I'm sure you could do it better.

Mike

Probably the best introductory book to this stuff I've seen, even if you sometimes have to connect the dots for yourself. Got mine when it sold for $5 new and I still refer to it.


I hate to just post "subscribing" if I can write something at least remotely useful to somebody.


Norm

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Unless/until it buckles, a round tube IS more efficient at carrying torsional loads, at least in terms of the stress distribution being uniform. And it's more stable in terms of retaining its cross section shape when loaded that way. I don't think anybody questions these things, either over on FRRAX a couple of years ago or at any of the other places where this topic has surfaced. [V6RSR, right?]

But BY ITSELF, a small-diameter thinwall round tube (think 2"/11 ga and smaller) does not add much torsional stiffness to the chassis (think 10%, just to get an idea). It needs to work with the rest of the chassis structure, and it's here that the picture about which shape is better gets a little cloudy. Questions like how much torsion vs how much bending come up. It very well may come down to "ease of fabrication" eventually counting for more than shaving off the last few ounces per foot.

No, I wouldn't use a sharp-cornered extrusion in any structural automotive application either. That's just asking for trouble.


Norm

Moved to new thread

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moved to new thread

< moved to http://www.thirdgen.org/techboard/su...-ultimate.html (I moved the Post from Ultimate suspension part II Need some suspension help with push) >



Norm

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So, is this all you would do for additional chassis bracing in the average street car?
Now, what if we took it a step further and added a roll bar/cage? Where would you tie into for mounting points and how much would you add? Basically, at what point does the added weight/complexity of the cage outweigh it's structural benefits?

Also, separate question but still on topic, would you do anything differently for a t-top vs a hardtop car? Any idea how much the t-top guys are giving up in chassis stiffness? Or is it minor enough not to matter, especially if properly braced?

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So you don't feel that even properly caged and braced a t-top chassis is still no good?
Wouldn't the proper amount of cage triangulation make up for the loss of a full roof?
Or at that point does the extra weight added offset any gains?

And for the record, I do have a hardtop car. Just trying to further explore the topic of chassis stifness and how it relates to handling.

I have a t-top car and it handles great... Subframe connectors added on will make the chassis very stiff, I have two frame connectors and can say it's stiffer than most hardtops. This just means added weight but you still get the benefit of a stiff chassis so i don't think t-top cars really are that much worse in the handling department as long as the chassis is properly braced and things are done to keep the weight down.... Two sets of frame connectors probably weighs around 40lbs (20lbs each). You can offset that easily by installing 4th gen seats which are approx. 40 less than 3rd gen seats.. AND the seats sit higher than the frame connectors so you would actually be adding weight lower than the roll center where it counts and removing where it's useless (above the roll center).

Also, I know you can't do this for drag racing (I don't think) but taking off the t-tops and putting them in the t-top bag over the rear wheels adds traction and the weight is lower there as well. So, t-tops are not that bad for handling but do require more to stiffen the chassis and keep weight down than a hard top.

MY 0.02$!

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Obviously the hardtop car will have the stiffest chassis. Not at all what I was getting at. I was basically looking for input in this thread on chassis bracing as to what you would do if you were prepping a t top chassis. And what, if anything, you would do differently vs a hardtop car?

I ask because around here t top cars are much more plentiful as donors than hardtop ones and thougt it would be interesting to hear from someone who is obviously knowledgable what they would do if starting with such a platform.
As to why, why not if you're building a max effort street car. Some people like to take the t tops out for a nice cruise every now and then but still like to get the most they can out of their vehicle.
Just thought it would be interesting to discuss. Didn't think I'd get a why bother answer.
And yes, the last t top f body I caged I did tie the main hoop into the center of the roof and also tied the sides of the cage into the sail panels. I too have seen the cage flex separate from the rest of a car. That particular one had a 700 rwhp twin turbo 383 so I did all I could to strengthen the t top chassis.

I've done plenty on dragstrip and all out street cars so I have knowledge and experience in what I'm talking about. Im just now starting to get into setting up a car for open track use. Hence why I was looking to have a discussion with someone who is into handling and how chassis stiffening could/should be applied to the different chassis we have available in our platform.

In short, yes we all realize a hardtop is better. But, if you really need to have t tops, in your opinion, what extra steps should you take in relation to chassis bracing. Chassis bracing was the original point of the thread so it seems like a relevant question to me.

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Is this something you could quickly illustrate? I can't picture what you mean.

The added stiffness from SFCs that you feel in your seat is not necessarily the stiffness that helps tune the handling the most efficiently. What you're really after is torsional stiffness, and that pretty much ends up having a 3-D solution. Things like wide, deep sills or a boxed tunnel is ons possibility. A proper space frame is another. A platform with deep diagonal bracing yet another. The OE coupe/hardtop is more or less a space frame, with the roof rails and windshield/hatch headers being part of this. Cut the roof rails out and replace them with a single strip down the middle of the roof and the load paths are now nowhere near straight, and the structure simply can't be as rigid without being lots heavier.

I think that sometimes, class rules regarding cage design and attachment are intentionally written to keep cages from being too good at adding stiffness. Trying to walk the fine line between having a chassis that's production-based vs something that's nearly a pure scratch-built tube frame (silhouette) car.


Norm

Thank you. I understand what you are saying about why it's not ideal. Just wondering what steps you would take for those that have to have them.
When jacking would you go to the outermost edges of the unibody or the corners where the suspension mounts? And, what specifically would you measure, how much lift it takes before you see it elsewhere in the car? I get what you are saying, just trying to be clear on how to check for it.

On another note, but also to do with chassis bracing/stifness, what about seam welding all of the unibody rails to the floorpan? Worthwhile or no?

Ok I understand now, thank you.

Concerning the welding the floor pan to the unibody rails, what about re-inforcing the steering box mount? That is an issue many 3rd genners have and could probably make the steering better or less prone to breakage.

answered allready

Vetruck. Wow, and I thought I had a good bead on suspension!! For some reason (subject matter, writing style, or I'm less tired) part 2 seemed to make more sense/more relevant than part 1. Not a knock, just maybe the difference between largely theoretical vs practical. Thank you for putting all this together, as I think I took out 2 things that are immediately applicable to my car, then I have a question that should be general enough to help the audience.

I have recently (in car's miles, not time) put on the LS1 front brake kit (from Ed Miller, I think his screen name is ebMiller), then swapped in an LS1 and T56 (originally L98/700R4). Since I have been driving it a lot in the last 1-2 months, I have noticed that the car wanders a LOT, has very poor habits when it comes to following 'truck ruts' etc. For example, level road with straight and curvy bits, it will go where I want it to just fine. As soon as the road becomes uneven (undulating as opposed to bumpy) it will try and change lanes, go from one side of the lane to the other, necessitating large corrections in steering from me to keep going in the intended direction/lane. From what I was able to glean from what was posted, this is possibly (probably?) due to scrub radius? - Note, at this point I have my doubts that the alignment is any good.. Also from what I understand from this post, I will need to use the Intrax "camber kit" to help eliminate this problem. I can do the alignment myself, so the attention to detail has 1 less layer of communication to get messed up in

Second thing I took from this is I may end up keeping my stock k-member. I don't think I had ever read/heard about the K-member bracing the front control arms, though it makes perfect sense. I was wondering why you had left that out from part 1, even though you had referenced spohn's a-arms. I had been on the verge of ordering the whole set up. Or at least saving up for it.

Last thing, using my car as an example, though I'm sure there are plenty out others out there in a similar position, what would be your order of operations for updating/upgrading the suspension/chassis? Here is what I think I'm understanding:

Chassis-
STB (3pt)
SFC
(already have the 'Wonder Bar)
Rear A-arm brace

Suspension-
New struts/shocks (current ones worn)
2" drop spindles (hadn't heard of these for 3rd gens until now)
Intrax "camber kit"
tuning

Sorry if I rambled, or if this should go in it's own thread, bit tired right now. Some of this is new stuff to me and I'm trying to make sure I am understanding things right. Any suggestions would be great for quality struts, but I realize that is a more preference thing, so I left it out. Would you mind PMing me? Again thanks for the info, always nice to find someone who knows what they are talking about.

If your front ride height changed, your camber and toe are likely off. Caster will also change slightly, but assuming that the nose went up that would add a little more positive caster and tend to make the car more directionally stable rather than less so.


Norm

That makes a lot of sense, and looking at the tire wear would support that with feathering on the shoulders starting to appear. With the drop spindles, the suspension settings won't change much, will they, like if lowering springs were used? So in effect, dropping so much weight from the nose made the camber situation worse, as I think, the settings are almost maxed out already judging by where the bolts are on the strut tower.

Good point and something more to think about for the guys doing LS1 swaps.