Anyone know of any good references/books to start learning about suspensions? I saw an interesting book the other day but it was more focused on Indy car type suspensions.

 

Muddied the waters, eh? Well, hmmm, I thought we were having a discussion about bump steer and its effect on handling performance. Do you agree, disagree or not understand what I’m saying? Don’t get me wrong, I know what you have done to your car and I respect your expertise and knowledge. I’m not trying to start a war. It seemed to me that discussing theory would be relevant to the topic. You don’t seem to want to discuss theory beyond the straight-line drive assumptions. I have already agreed that that is a good basis and I’m trying to expand the depth of the discussion. What 427V8 suggested is exactly what I’m talking about, measuring the toe change as the wheel is turned.

As for hard numbers, our tie rods have a total length of approximately 17.25”, center to center. The tie rod brackets mounting holes are 12.4” on center. This compares to the stock system of 15.3 and 16.25 respectively. Additionally, our outer tie rod pivot points can be lowered .7”. I don’t have a comparison with the upper mounting location but perhaps I can get something in a little while. Let me also say that (repeating your statement, Norval) each car needs to be measured and adjusted to its needs. While the goal may be zero bump steer through out the entire suspension travel many times that isn’t possible. So the curve then should be tuned to minimize bump steer in the operating range. This is my point. The numbers that you have given are a good direction to go (and I would encourage those willing to do the mods to do so) but others following them will not necessarily get the same results because yours has been measured and optimized for your car (i.e. yours has been tuned to your operating range). Yes they will see an improvement but another car will have a different operating range, bushing and frame compliance and different a-arm geometry. We are taking tenths and thousands of inches here so a seemingly little difference is actually a big difference.

Also, while I am concerned about looking bad in the eyes of others that is not my primary goal here. I was trying to answer a few questions and add to and expand the conversation so we could have a good, lively and informative discussion. We seem to have the lively part. I figured that Norval would be a good participant since he seems to spend a lot of time working these kinds of problems. Additionally, we are continually improving our products and discussions like this can shake out some good ideas.

427V8, the problem with publishing specs are the very problems that I’ve brought up, they are dependent on a host of variables that are beyond our control and that are usually different. What we measure on our car most likely wont be what you measure on yours.

Sorry for the strange, double post. Wrong login.

 

Let's all agree that BS is a factor in our C-3 suspensions and that this is discussion or debate and nothing else.

The idea is that to correct BS it requires redesign (as Norval has done) or replacement and/or redesign as Steeroids has done of our tie rod systems. Both attempt to create a beter C-3,different methods, same goal.

IMHO there are also the corrections needed in the A-arms to allow additional caster and more camber adjustment. Then coordinate the tie rod points of movement to curtail toe.

I understand that there is only so much that can be accomplished with alterations of our C-3s without ripping the front suspension out and starting from scratch so I am.

I have in essence started to replace my whole system with the VBP mono-spring upper and lower poly bushing tubular a-arm front suspension which allows up to 5 degrees more positive castor and more camber adjustment as well. They have a relocated ball-joint mount and the off-set cross-shafts to provide this. Bilstein Shocks and then the 2002 Jeep Grand Cherokee 12:1 high effort power steering box. While we are visiting the front let's add the Hydraboost to push the brake pads as well.

Then addressing BS further by using an extended set of front spindles, a modified drag-link such as Norvals to allow the longer tie-rods that attach on top of the present location and 3.1" inward( Norvals Specs and may need to be adjusted to usage). Gulstrand blocks on the modified steering arms to lower the other tie rod end, a VBP 1 1/4" front sway bar kit and last a spreader bar to help restrict chassis flex.

I too like the soft spring approach to handling. This was one of the ideas of the mono fiberglass spring that ride height is adjustable while using a low spring rate. I believe that limiting the motion of suspension travel with high rate spriings defeats the purpose of suspension travel that allows the tire to follow the roads surface.

Suspension restriction that allows the wheel to lose contact with the road is not a positive thing and then at the re-contact point with the surface it may also create a loss of control or darting as does BS toe so then there is no accomplishment anyway.

I looked at steeroids and I looked at other methods of changing the front guidence system. I decided to stay with the conventional steeriing box but upgraded from the 1954 style steering and slave set-up to the much improved Jeep box and altered manual relay rod for my car.

I think I will be able to see what works on mine by plotting toe with a laser through system travel with the spring tension removed on this set-up.

I'm not an engineer, and never claimed to be, several here are engineers and I think a couple are actually versed in front suspensions in the C-2 section. Hey Norval invite those guys up here and see if they can give good supported direction to a modified new and improved front suspension for us.

Norval, I wish do you would invest in the 17" wheels and a set of good tires with the Bilstein shocks. You may be surprised at what the out come would be with these changes.

Does anyone have any information on a measured increase from going from 15" wheels and high profile tires to a 17 or 18 inch low profile tire and wheel? Then add in the Bilsteins. seems like I read an article sometime back on this.

Another question I have is what effect does front tire/wheel width have on steering at high speed? I believe this to be a factor also to good road handling.

Where's Twin Turbo? he's good on this.

Norval, I lost your other address during the LuvWorm computer crash. Jim

 

Well said, PROSOUTH.

 

Pro, I know full well this reply is somewhat silly in that I can't really give you a total recall of the situation....BUT when I bought my car the entire mechanical underpinnings were bone stock original, and tired...after about 130k miles or so....car being about 23 years old then....what wasn't worn out was definately dried out and driven that way......

so I drove the car a bit, examined everything as before , when I bought it...and decided to replace everything at once...so therefore I have NO factual idea of comparison from a clean stock car to my modded up version...
and in fact that was a mistake..maybe...

the springs I feel now should have remained stock, not that I"m going to change them now....

the heavy sway bars were a bad decision ride quality wise....

be as it may over the suspension changes....I feel the largest improvements for the car were obviously the wheels and tires, followed by the rack/pinion steering, now Jim Shea would say the recirc ball setup should have just as good an input as the rack/pinion setup...but that is not my experience....but then again, my experience is NOT directly A-B comparison, and certainly no numbers to back it up....I will say one thing though...for sure the highway tracking is much better, bump steer be damned, and the quicker ratio steering is very welcome in a vette....it is supposed to be 'sports car' .....

also in fact of MY histor with mods on a Lemans/GTO chassis some years ago, the useage of another recirc ball box and built in power assist may in fact BE a better setup...but that leaves all the changes Norval is doing to the drag link/tie rods....

I would love to be an un-harried GM engineer.....

so would us all......

GENE

 

Eric,
I now understand from you the range of adjustability and from Norval how to take measurements.
So, how do I adjust your system to approach 0 toe? Lengthen tie rods? or shorten? Or lower outer tie rod end? or?
I have the VB front monospring that has been lowered.

 

Speed Direct,
Yea I suppose it would be a little scary, maybe even misleading to publish specs like that, besides no one besides Norval, Gene TT and maybe me would care about it!

Cook;
I just bought a book called "Stock car Setup Secerets" it looks pretty good so far...

Gene,
I must have the same hobby as you do. I drove the wifeys Saturn to work today and was paying attention to it over bumps ( lots of road construction) the car is as straight as an arrow, completely predictable. the steering wheel never even wiggles.

My Dodge Caravan however flops around like a fish on these same bumps, lots of correction needed to keep the dang thing pointed down the road.

Wanna bet that it's all related to bump steer?

 

Thanks! :cheers:

I agree with you on the Caravan. The road I live on was destroyed when the old folks home decided to add a massive addition. If you aren't paying attention some of the dips and bumps (at 15 mph) will rip the wheel out of your hands.

 

Here I been a car guy for decades now, and over the years have hot rodded many a car, now don't laugh but the old B body cars of the 60-70's, and the A body Lemans/GTO cars too...and never even heard of bump steer being any issue mentioned EVER for ride/handling...mods or anything else...just not mentioned...don't ever remember the wheels changing toe when jacking it up either....could be olde tymers disease, but don't think so....

at any rate, only now in the last what near 2 years has it been an issue, and only on this vette...I somehow find it amazing about all the criticisms of the stock design....I did a LOT of suspension mods, and steering/brake mods on the last GTO/Lemans, but never crossed bump steer as an issue...

GENE

 

Well you know how it goes Gene, The problem doesn't really exist untill someone invents it. then we all have to go out and fix it! :banghead:

:jester

 

Ive been reading a new book, mentioned above...

Surpriseingly they have a website :steering:
And sell software...

But most importantly they have links to articles about suspension design

Oh Here it is -> http://www.racingsoftware.com/

 

I was kind of eyeballing this discussion from the side line, afraid it would turn ugly and people would get burned here. :)
The recirculating ball setup can be as good as rack and pinion, bimmers and mercs have used them well into the 90's (Merc is still on the SLK), the only BIG difference is the design of their box. They have oversized bearings that will hold the shafs very tight, no play there. The play in those parts is where most of the steering problems come from. Norval has addressed that by machining spec'ced bushings. His box must be really tight.

Now, my question is. How can the steeroids system be adjusted? As i see it you have the option of either placing the tie rods over or under the steering knuckle, which of the 2 works best? (I would guess under) Then the inner position is fixed unless you build yourself a new bracket. I don't see how this is adjustable.

About the bilstein shocks, they're great shocks, I tried them. I also tried the koni adjustable ones and I must say, I like the koni's better. I know they're expensive over there. I got mine cheap (they're made here). Maybe I can find a good cheap source for those.. who knows.

As for me, I'm still looking for a front steer ETO rack, ETO is suited for double a-arms much more than a CTO rack and I want to have front steer to eliminate some problematic areas (like the need for a big complex bend in the steering input) and it would give much more clearance under the engine.

Only problem w. the ETO rack.. the rack must have the proper pivot-pivot width and must be mounted on the exact correct height for bump steer to be eliminated.

 

Well it's about time TT!

So tell me why is an ETO rack better for A-Arm suspensions?
I understand why front steer is better...

 

Why would front steer be any better, sounds like old tall tale to me....
shouldn't be any differance, other than chassis design.....

I know in circle track/dirt cars they use both a manual and power steering verision of a rack that measures only about 18 inches long, or so...and has a throw of about 6 inches and it's a pretty stout piece.....guys down the road from me showed me on on a dirt car....now it's really small compared to most of the commonly available stock ones....

GENE

 

front steer or rear steer doesn't really matter that much, in the C3 the rear steering rack necessitates the complicated input shaft setup using the flaming river type joint.

The ETO rack is better suited becayse of the short tie rods, if you select the proper length rack you can place it in the proper plane so that you have 0 bump steer. The same can be done with a CTO rack but the plate on which you mount the struts would have to be very wide. In that case placing them as far near center would be a simpeler (and probably better) solution (this is done to minimize the angle change over suspension travel), the wide bracket will induce flexing problems.

Here's the pic:


With the ETO pivot placed at where the yellow line intersects with the green one and the tie rod exactly parrallel with the lower arm is what you want for 0 bump steer.

Gene, are those circle track racks ETO and front steer? If so, it could be one of those sweet manuf. racks. they are all about 16-18" long and they're about the correct length of what we would need for a front steer setup. I have looked at their rack list but the list was somewhat confusing. Will have to look at it again.

Marck

 

Gene, are those circle track racks ETO and front steer? If so, it could be one of those sweet manuf. racks. they are all about 16-18" long and they're about the correct length of what we would need for a front steer setup. I have looked at their rack list but the list was somewhat confusing. Will have to look at it again.

Marck[/QUOTE]


Marck, yes, as I recall I think Sweet if the company....seems it's a recollection anyway....and yes, they did have a rear steer rack available...
thing is the input is also more toward the car centerline, so even with our engines on the pass side there, we still have a HUGE header clearance problem....
unless we come up with a ceramic bearing to we can pass the steering shaft through the header pipes....

:D :D

GENE

 

I don't have headers :D I have lots of room on the side of the engiine:



I won't have a heat problem where you guys have headers, my heat problem area is close to the firewall.

 

.I took a course in college on vehicle suspension. It covered simulated modeling with transfer functions and more calculus than anyone really wants to do. I'll sell you the book for $100, its really a deal given a paid $150 for the stupid thing. :lol: I used to think chassis were boring but after buying a vette and replacing nearly every suspension component under it, I kinda like that stuff now

 

nitro, wht is th name of the book?

everyone,
in the above book, they say that it is most important to minimise bs in the turn, cause that when it's critical, hmmm

here is a quote;
"If you cannot get zero bump steer in both static and dynamic locations, where do you want the car to have zero bump steer? Take a wild guess. Down the straightaway where you don't really need it or in the turns where you are right on the ragged edge of disaster, and running side by side with a guy who's never brought a race car home in one piece before."

He also says that bump steer is very new, just a couple of years, and that many people still don't understand it's importance. And this guy is talking about race car chassis builders.

So believe it or not this is cutting edge technology aparently.

 

The book was called Dynamic Systems and Controls published by Kettering University. Another book was called Vehicle Dynamics but I'm not sure who the publisher was. I don't remember too much about bump steer (of course maybe that was one of the days I skipped :lol: ) Anyway they both have a lot of good info on yaw rate, oversteer/us, response modeling, and that sort of stuff. I would recommend this book to anyone who has trouble sleeping. :sleep: :D