Ideal Geometry

[ccracin]

Well as I have been ready on this site over the past years it seems a large portion of the debate has to do with front end packages. Sub-frames, control arms, spindles, etc. etc. Alot of companies have great marketing practices but never really provide actual data. Others do. So here is my question. What would everyone consider the ideal suspension geometry to be? This is assuming we aren't worried about track width (with in reason) or frame rail width (again we still have to have an engine up front for this exercise). The ride height would have to be reasonable. I guess ideal is also different for different needs. So lets say we break it down to 3 separate areas. Street, Open Track, Auto Cross. I'm really hoping to see some of the heavy hitter chassis guys respond. I love looking at the dynamics of all this. I have read all the standard fair as well as magazine articles. They all tell you how to measure bump steer, ackerman, roll center, etc. But very very few of them actually recommend specs. Some things I would like to see:

Roll center location and migration specs. in dive and roll
Roll center to center of gravity relationship
Caster
Camber
Camber gain per inch of travel
Caster gain per inch of travel
Ackerman for a given steering input
Bump steer ( amount of toe in or out per unit travel)
King Pin angle
Scrub radius
Anti-dive
Ideal amount of body roll to design for at max lateral-g

Have I missed anything or am I full of SH...... on one of the items I listed?

Don't disappoint me folks! :bow: :lateral:

[ccracin]

What's up, no opinions?

[chevyIIpost]

Bump.............. Would love to hear some opinions and debates. This thread/topic is wide open...................:question:

[novanutcase]

I think the reason no one has really responded is:

a) This is such a wide open question that any answer would be both wrong and right.

b) A lot of these guys would be giving away their hard earned secrets. That would be like asking Smokey Yunick how he got his motors to work so well!:lol:

John

[ccracin]

I think the reason no one has really responded is

a) This is such a wide open question that any answer would be both wrong and right.

b) A lot of these guys would be giving away their hard earned secrets. That would be like asking Smokey Yunick how he got his motors to work so well!:lol:


John

Hey John,

Thanks for the reply. I agree about it being wide open. That basically is the point. Folks can say why they believe what they are posting is IDEAL! I don' t agree with the secret part. I'm asking for the final readings. In my mind it is like asking Smokey for his opinion on the ideal torque & hp curve for a road course. I'm not asking how to get the curves. Does that make any sense?

Later,

[pro-tour79]

your questions can't realy be answered because those values are different for different vehicles, there is no "one best" and most importantly is the driver's confidance in the seat is what makes a car handle well.

[ccracin]

your questions can't realy be answered because those values are different for different vehicles, there is no "one best" and most importantly is the driver's confidance in the seat is what makes a car handle well.

Good suspension geometry is not different for different vehicles per say. My question was for what folks would call ideal without the confines of a particular body style. This comes down to physics and dynamics. The way a suspension system works has nothing to do with what sheet metal is wrapped around it. (Except for how that sheet metal affects weight and balance) So to clear this up a bit more. Lets just say we are all able to build a tube chassis ACME Hot Rod (Think Old Road Runner Cartoons Here!) What would the ideal front geometry be for the 3 areas I listed in the first post? Oh and to some degree I agree with driver skill and confidence, but a confident driver does not make say...........an old Willys Jeep handle "WELL" at Road Atlanta or on an autocross course. :lol: But I get your point.

[ccracin]

Maybe I should get this started. These are all guesses on my part to get this going. I am by no means an expert, obviously based on me asking the question. :) At least these numbers may garner a B... Sh.. or Yeah that will work. Lets see if we can keep this going.

Street
Roll Center location Static +4"
Roll Center Migration In Roll <1" / Degree of Roll
Roll Center Height in Dive and Lift <= The Amount of Dive or Lift
Roll Center to Center of Gravity relationship Short as Possible ** This one is somewhat dependent on the vehicle.
Caster +4 Deg.
Camber -1 Deg
Camber gain per inch of travel 1/2 Deg More Neg. / Inch of Travel
Caster gain per inch of travel 1/4 Deg More Pos. / Inch of Travel
Toe 1/16" In
Ackerman for a given steering input 2 Deg. Per 20 Deg. Of Steering
Bump steer ( amount of toe in or out per unit travel) .015 / Inch Of Travel
King Pin angle 8 Deg.
Scrub radius 1" - 3"
Anti-dive 3 Deg.
Ideal amount of body roll to design for at max lateral-g 3 Deg.

Track
Roll Center location Static +3"
Roll Center Migration In Roll <.75" / Degree of Roll
Roll Center Height in Dive and Lift <= The Amount of Dive or Lift
Roll Center to Center of Gravity relationship Short as Possible ** This one is somewhat dependent on the vehicle.
Caster +5 Deg.
Camber -2.5 Deg
Camber gain per inch of travel 3/4 Deg More Neg. / Inch of Travel
Caster gain per inch of travel 1/4 Deg More Pos. / Inch of Travel
Toe 1/16" In
Ackerman for a given steering input 1 Deg. Per 20 Deg. Of Steering
Bump steer ( amount of toe in or out per unit travel) .015 / Inch Of Travel
King Pin angle 8 Deg.
Scrub radius 0"-1"
Anti-dive 4.5 Deg.
Ideal amount of body roll to design for at max lateral-g 2 Deg.

Auto - X
Roll Center location Static +3"
Roll Center Migration In Roll <.75" / Degree of Roll
Roll Center Height in Dive and Lift <= The Amount of Dive or Lift
Roll Center to Center of Gravity relationship Short as Possible ** This one is somewhat dependent on the vehicle.
Caster +2 Deg.
Camber -3 Deg
Camber gain per inch of travel 1/2 Deg More Neg. / Inch of Travel
Caster gain per inch of travel 1/4 Deg More Pos. / Inch of Travel
Toe 1/16" In
Ackerman for a given steering input 2 Deg. Per 20 Deg. Of Steering
Bump steer ( amount of toe in or out per unit travel) .015 / Inch Of Travel
King Pin angle 8 Deg.
Scrub radius 0"-1"
Anti-dive 4.5 Deg.
Ideal amount of body roll to design for at max lateral-g <2 Deg.

[chevyIIpost]

I would venture to say that anyone on this site understands that there is not going to be One correct answer to each item listed. But there has to be a narrow range of good and a much wider range of bad to the list of items mentioned that started this thread.

Roll center location and migration specs. in dive and roll
Roll center to center of gravity relationship
Caster
Camber
Camber gain per inch of travel
Caster gain per inch of travel
Ackerman for a given steering input
Bump steer ( amount of toe in or out per unit travel)
King Pin angle
Scrub radius
Anti-dive
Ideal amount of body roll to design for at max lateral-g

And even if that range is wide than the discusson and opinions that will follow will be interesting and may educate and enlighten. This is a black magic area to most beginners and as you learn more about suspension design and function you will realise that it is less black magic but requires a whole lot of knowlege and understanding of a very dynamic system. So I hope some of you more educated suspension guys will lift the magic spell and throw out your opinions and points of veiw for the rest of us to learn form.

That Acme Road Atlanta Car could go from having a 1969 camaro front clip and be upgraded to a C6 set up and we discuss what changed and/or improved as a result. :question:

[ccracin]

Thanks for helping with this Ted. You are definitely catching what I am pitching. :thumbsup: This thread is meant to educate us all as the discussion builds. Hopefully we will get some takers.

[Silver69Camaro]

I'll bite. I actually have no problem sharing our data, because somebody can't really just take the numbers and copy it. If you could, you wouldn't need us because you clearly have the knowledge and know-how to be doing it yourself. Trying to copy the whole package is very difficult. Anyway, I've shared this information before on and off topic.

Anyway, per your listings:
Roll Center location Static: +1.9"
Roll Center Migration In Roll: 0.258" / Degree of Roll
Roll Center Height in Dive and Lift: 1 to 1 ratio
Caster: +6 Deg.
Camber: -0.5 Deg (Street alignment, but adjustable to stupid amounts)
Camber gain per inch of travel: 0.6+ Deg Neg. / Inch of Travel
Caster gain per inch of travel: 0.5+ Deg Pos. / Inch of Travel
Toe: Up to end user
Ackerman for a given steering input: 1 Deg. Per 20 Deg. Of Steering
Bump steer: .014 / Inch Of Travel
King Pin angle: 9.2 Deg.
Anti-dive: 6.5 Deg.
Ideal amount of body roll to design for at max lateral-g: Rougly 2 to 3. I wont give the exact answer here.

We also have exact models of C6 suspension parts that allow us to accurately locate pivot points and ball joints. No dial calipers and measuring tapes here.

Like everyone has said before, this is a system that we believe works best for these vehicles. We have lots of time under our belt to give us priceless experience and know-how.

[ccracin]

Matt,

Thanks very much for jumping in. You are one of the "Heavy Hitters" I was hoping would jump in. Just to be clear again, I am not trying to garner anyone's secrets to copy their product. That's I why I say "ideal", knowing that compromises have to be made sometimes for packaging. If you didn't have to package it in an F, A, G ..........body, would you be looking for something else to make it better? I give you great respect for publishing "actual" numbers for your products. In fact I already had great respect for your products, enough that I used your stuff on our project and did not try to re-invent the wheel. Anyway, back on task. If the numbers you posted are for your street set-up, what tweeks would you recommend for high speed track days and lower speed auto-x stuff? Thanks again Matt, you and the rest of the Morrison team are top notch.:hail:

later,

[Silver69Camaro]

Thanks for the kind words.

The only things I would change are simple alignment basics; camber and toe. I generally try not to increase caster (doesn't really need much more anyway), because it raises the outer tie rod pivot location and can increase bumpsteer. Not much, but it's there.

For camber, obviously that depends on your tires. The camber gain is fairly aggressive in this suspension, so 0.75 to 1.5 degrees is all you need (static) unless if the tires spec more. Toe is fun to play with, and I like to have slight toe out, as little as possible. Works very well.

We also carry a line of stuff to "fine tune" our suspension. Solid rack mount bushings, adjustable flow steering pumps, custom rack torsion bars, etc.

[XcYZ]

Awesome info, Matt. Thanks for posting.



We also carry a line of stuff to "fine tune" our suspension. Solid rack mount bushings, adjustable flow steering pumps, custom rack torsion bars, etc.

Solid rack mount bushings... is there much of a demand for those? I'd guess you have seat time in cars with them, what do you think of that setup?

[ccracin]

I agree with Scott. What are your driving impressions? Since I have your front end components I am wandering if these parts would be beneficial to our project. Although I should probably get the thing on the road before this is important. I bet they don't do a bit of good for a truck on jack stands!:lol:

Let's hear from some other people too. What does everyone else have to say?

[pro-tour79]

From what I get from the question " ideal geometry" is specific settings, the sheet metal around the chassis does not matter, but what does matter is weight, weight bias, CG, wheel base and track width, roll axis, and all of this in turn affects the settings, and driver feel, and spring, and sway bar rates.
but some items can be answered with "as little as possible" such as roll center migration, bump steer.
It is important to keep all that in mind.

[ccracin]

From what I get from the question " ideal geometry" is specific settings, the sheet metal around the chassis does not matter, but what does matter is weight, weight bias, CG, wheel base and track width, roll axis, and all of this in turn affects the settings, and driver feel, and spring, and sway bar rates.
but some items can be answered with "as little as possible" such as roll center migration, bump steer.
It is important to keep all that in mind.

You bring up some very good points. This kind of information is what I was hoping for from this thread. I talk to people all the time at local shows and cruises. They talk about improving the handling of their cars but have no idea what it takes to do that. They don't even know what questions to ask. They only know what they see in ads and from marketing wizards. The "average Joe" has never heard the terms Matt, You, and myself are throwing around here. If someone is going to spend thousands of dollars to upgrade their car or truck (we can't forget the trucks:unibrow: ) they should actually get an upgrade rather than some pretty tubular control arms that don't do anything but be tubular. Don't anybody get upset that sells tubular control arms! They have a place, but I just thought an open discussion about these principals would help alot of people.

As I said after your first reply, the sheet metal doesn't matter other than for weight and balance. I would argue however that if you look at the hierarchy of what systems to resolve first, the mechanical geometry of the front end should be considered first. This is only my opinion, hence why I brought it up first.

You have to take one system at a time and evaluate it. When you have what you believe is a good solution then you evaluate it against the other systems. If changes have to be made, then repeat the process. This is why some of these parts cost what they do. Quality vendors take the time and spend the money to evaluate these systems so they can educate you as you move along. Others spend the money on marketing alone. Hopefully this discussion will help figure out which is which for yourself.

Track width in an "ideal world" would be much wider than is practical in street cars. That is why I said earlier 'ideal" within reason. Wheelbase comes into play in my mind when you start evaluating both ends of the vehicle with regard to weight bias, balance, and evaluating the roll axis along with the rear suspension system.

It has been my experience that evaluating each end of the vehicle independently and then working to balance the 2 gets you closer faster than jumping back and forth. Any thoughts?

Anyway, thanks for the continued input pro-tour79. This is getting good. I threw out enough of my opinions, so lets see if anyone jumps in to tell me what is wrong with the way I do things. If anyone agrees let us know and hopefully we'll get some more good info.

Later,

[Silver69Camaro]

From what I get from the question " ideal geometry" is specific settings, the sheet metal around the chassis does not matter....


I totally agree with you, but you have to take "marketability" in mind. I absolutely love our Musclecar chassis, where sheetmetal truely does not matter...it all gets cut out and suspension function takes top priority.

BUT...if we had a "bolt-on" front clip for first gens that required cutting, we couldn't sell it. There is a fine balance between packaging and suspension optimization that is probably the hardest part about my job. For instance, my first instinct was to make the Camaro front clip hub track width about 62" wide, quite a bit wider than stock, but I had to bring it down to 60.5" in order for most guys to find a wheel that would fit. This increased bumpsteer from .001" to .014", which thankfully isn't a big deal.

[Silver69Camaro]

Solid rack mount bushings... is there much of a demand for those? I'd guess you have seat time in cars with them, what do you think of that setup?

I like them alot. Granted the AGR urethane bushings are pretty hard, these lock the rack housing to the crossmember via male and female chamfers on the mating surfaces. You do get more road feel, but to my surprise, I don't feel more vibrations through the steering wheel. When a front tire loads and unloads, you can feel it in the wheel and allows you to understand what the car is doing. For the price, I consider it a good upgrade. Combine that with the KRC power steering pump, you've got a steering feel that is absolutely wonderful.

There are downsides. If you hit a pothole large enough to ruin a wheel, there is a greater chance the rack will be hurt as well. Considering the scrub on these cars is pretty low, I don't worry about it.

[ccracin]

Thanks Matt. When we get our project on the rode, we'll see how it feels. Because in the true sense our project might not really see anything more than spirited street action, the urethane mounts may be the ticket. Thanks again for the info.

[parsonsj]

I occasionally dabble in design (consulting only) for folks who want to build their own suspensions. I've been working on one that uses C5 components. Those numbers look something like this:

Roll Center location Static: +2.0"
Roll Center Migration In Roll: 0.62" / Degree of Roll
Roll Center Height in Dive and Lift: just about 1 to 1
Caster: ~8 Deg.
Caster gain per inch of travel: 0.5+ Deg Pos. / Inch of Travel
Camber: -1 Deg (adjustable to whatever)
Camber gain per inch of travel: 0.9+ Deg Neg. / Inch of Travel
Toe: whatever
Bump steer: less than .005 for up 1.5" dive, .010 for up to 1" lift, .020 for 2"
King Pin angle: 9.9 Deg.
Anti-dive: 23%

As Matt mentioned, the hardest part of the whole design is the packaging: finding workable racks, getting the engine in the car with the rack, figuring out how to get a workable sway bar, and, in general, making sure none of the parts hit each other as the front suspension moves.

jp

[parsonsj]

My rack in II Much is solid mounted. I don't notice it being any different than my wife's Mazda or my big-ass Duramax in terms of vibration or other annoying behaviors.

jp

[ccracin]

Thanks John. Since you do some design work, what are your thoughts on the process of designing suspension system? I threw some things out in an earlier post as to logical steps in mapping out a suspension system. Where do you jump into the water? I think your opinion will be valuable to alot of people. Do you agree that once you get the best geometry on the front end that can be packaged properly for the vehicle that you can tailor the rest around this starting point? Did that make sense?:( Anyway, I hope it did.

Thanks Again,

[parsonsj]

Do you agree that once you get the best geometry on the front end that can be packaged properly for the vehicle that you can tailor the rest around this starting point? Did that make sense?Sorry, but not really. What do you mean by "the rest"?

jp

[chevyIIpost]

They talk about improving the handling of their cars but have no idea what it takes to do that. They don't even know what questions to ask. They only know what they see in ads and from marketing wizards. The "average Joe" has never heard the terms Matt, You, and myself are throwing around here. If someone is going to spend thousands of dollars to upgrade their car or truck (we can't forget the trucks:unibrow: ) they should actually get an upgrade rather than some pretty tubular control arms that don't do anything but be tubular. Don't anybody get upset that sells tubular control arms! They have a place, but I just thought an open discussion about these principals would help alot of people.

Chad, this is the exact road I have travel over the last 5 years. My original thoughts where for a S-10 pickup suspension but I didn't want a salvage yard car. I went to the school of "Hard knox$" with a Jim Meyer set up because I had no clue what questions to ask let alone what the correct answers might be. I read and learned some after this purchase and found that what I had welded in my car had bad bump steer, only a couple of degrees of caster, a bad camber curve, no anti dive to speak of, and poor ackerman, etc. Basicly a street rod suspension for 40 Ford. I am now finishing up another learning process on a c5/c6 set up that has great specs and should do the job very well. Now I know enough to get in trouble when on my own but I can at least ask good tough questions and sort through the posers and the real doers. It just cost me $$ and time to learn this.:rolleyes: I would hope this thread could help others avoid this long painful process.

[ccracin]

Sorry, but not really. What do you mean by "the rest"?

jp

Sorry John,

What I mean is what process would you follow to design a complete chassis? I personally start with what wheels and tires will be on the car. Then I do the front end. Then the rear, weight & balance etc. I guess I'm just looking for some rules of thumb to help people evaluate what to look at. Hopefully that helps. I started this thread on front ends, because it is an area that people spend alot of money on and can sometimes take a bath doing it.

Thanks,

[chevyIIpost]

All suspensions have some bump steer the attempt is to minimized it as much as possible. But with the bumpsteer that is left, if you have a choice, do you want it toe out or toe in during bump steer?:question:

[Silver69Camaro]

All suspensions have some bump steer the attempt is to minimized it as much as possible. But with the bumpsteer that is left, if you have a choice, do you want it toe out or toe in during bump steer?:question:

Doesn't matter (for the most part). What you want is for the correct steering in a full cornering situation (body roll), corner exit (body roll + rear squat/front lift) and corner entry (body roll + front dive/rear lift). You also want to consider what it does on acceleration and braking.

[parsonsj]

Oh, ok, I think I understand now.

Sure: wheels and tires first. Without that, you don't know anything.

Then begin iteration:
1. ride height
2. track width
3. front suspension
4. rear suspension
5. Go to 1.

After that, you've got (in loose order) steering linkage, drivetrain, pedal linkage, seat, a/c, exhaust, cage, floors, trunk, wheel wells, firewall, radiator, etc.

jp

[Silver69Camaro]

Chad,
I know you didn't ask me but I pretty much set the wheels and tires last.

For some reason, people always want to build a car around an existing set of wheels, a back seat, and a fuel tank. None of those should matter. You should never limit yourself to a specific backspace, but obviously you need to keep it reasonable so a manufacturer can actually produce the product (this is what JP is referring to). But here's what I do:

1. Build front suspension first; have ride height, approx. tire diameter and ride height, and CG location.
2. Build rear suspension to accomodate front suspension for solid axles; if IRS is used, build front and rear suspensions together.
3. Repeat, because the first design never works the way you thought.

But first and foremost, you need to be realistic about what suspension properties you want. 99% of the people here want the appeal of a race car, but don't actually want to drive one. If it is a true street car, even with some moderate autocross or lapping, don't get overboard with caster and camber gain; and choosing a suspension frequency "race car" high will make it terrible to drive on real roads. Be realistic.

[parsonsj]

If it is a true street car, even with some moderate autocross or lapping, don't get overboard with caster and camber gain; and choosing a suspension frequency "race car" high will make it terrible to drive on real roads. Be realistic.Amen. Double Amen. Sing it to the heavens, my brotha!!!

Race car suspensions aren't really that enjoyable on the street. No doubt it's cool to take freeway off-ramps at triple their rated speed, but the rest of the time a twitchy, tire-wearing, bone-rattling, NVH on steriods ride will just annoy and tire you out.

Make your shocks adjustable, keep your caster and camber at reasonable levels, don't go for too-quick steering, and use bushings with some compliance.

jp

[parsonsj]

For some reason, people always want to build a car around an existing set of wheelsYou're right: it's all about making sure the suspension will fit inside the car body. Reasonable choices here make the rest go much better.

jp

ps. And Matt, it was your boss who taught me to choose the wheels and tires first. Art wouldn't make me a chassis until I spec'ed the wheels. :cheers:

[ccracin]

Guys,

This is exactly what I was hoping for. I have seen the need for this type of info, but didn't know how to go about extracting it. I feel like a lawyer here, asking all these leading questions. :lol: I figured if I could get some recognized people in the industry to speak up it would have more credibility than some nobody spouting off.

Matt,

When I said I picked wheels and tires first, I meant for diameter. Then i choose my ride height. It looks like we all tend to agree on this point.

I also agree with issues dealing with driving a race car on the street. When people get it, most don't like it. I guess that is why they call them "Race" cars and "Street" cars. I guarantee I would not want to drive a car that rode like my circle track cars on the street for very long.

Later,

[Silver69Camaro]

ps. And Matt, it was your boss who taught me to choose the wheels and tires first. Art wouldn't make me a chassis until I spec'ed the wheels. :cheers:

Yeah, wheels and tires need to be picked when doing our chassis or else we don't know how wide to set the rear clip or what hub track width to use. But when designing a suspension from scratch, only a range of wheel sizes and backspacing is needed...instead of designing the suspension around an existing set, which only puts limitations on the design and will more likely be less than optimum.

Heh, who does Art think he is, anyway? (just kidding!)

[novanutcase]

I'm going to tiptoe through here and make a suggestion.

Why not try and separate both types of suspension? Street and Race. I think this will help focus a lot of questions that everyone would like to hear the answers to within that specific genre. Maybe pick a model of car for street that is typical and run through the process of setting it up. A camaro maybe? :unibrow: Same for a race car although in that case you're not really limited by packaging constraints other than whatever the rulebooks limit you too.

John

[ccracin]

I'm going to tiptoe through here and make a suggestion.

Why not try and separate both types of suspension? Street and Race. I think this will help focus a lot of questions that everyone would like to hear the answers to within that specific genre. Maybe pick a model of car for street that is typical and run through the process of setting it up. A camaro maybe? :unibrow: Same for a race car although in that case you're not really limited by packaging constraints other than whatever the rulebooks limit you too.

John

Sweet! I'm game. John, that's why you get the big bucks. You're an idea man!:hail:

We don't even have to say "Camaro". We could just give a jump off point.

I'll throw this out to what you guys think.

Front Tire diameter: 25.5"
Rear Tire diameter: 26"

Front Track Width: 60"
Rear Track Width: 61"

Wheel Base: 108"

Start here and indicate whether you are setting up a street car or a race car. If this doesn't work, where should we start?

[parsonsj]

Sure ... this could be fun.

But we need more contraints: wheel diameter? what kind of spindle? base chassis? engine placement?

jp

[ccracin]

Sure ... this could be fun.

But we need more contraints: wheel diameter? what kind of spindle? base chassis? engine placement?

jp

Constraints...we don't need no stinking constraints! Sorry I couldn't resist.:P

I would say for the race car, you choose with regard to all of those.

For a street car, how about:

18" Wheels

You choose the spindle. That is part of the magic, right? Anyway this seems to be an area of great debate lately.

Custom Chassis with the track width and wheel base i mentioned above. With these dimensions it should be close to alot of cars guys on this site are working on. Right or wrong I don't think in most cases it is cost effective to modify a stock chassis to the extent that some do. JMO

Front Engine. Hmmmmmm how to explain placement. For the street it would have to fit in an engine bay with in reason.

These are just suggestions on my part to keep this going. I am open to any suggestions.

[novanutcase]

Constraints...we don't need no stinking constraints! Sorry I couldn't resist.:P

I would say for the race car, you choose with regard to all of those.

For a street car, how about:

18" Wheels

You choose the spindle. That is part of the magic, right? Anyway this seems to be an area of great debate lately.

Custom Chassis with the track width and wheel base i mentioned above. With these dimensions it should be close to alot of cars guys on this site are working on. Right or wrong I don't think in most cases it is cost effective to modify a stock chassis to the extent that some do. JMO

Front Engine. Hmmmmmm how to explain placement. For the street it would have to fit in an engine bay with in reason.

These are just suggestions on my part to keep this going. I am open to any suggestions.

There ya go!

I'm sure a lot of guys that don't really understand what a street type suspension is made of will get some great info from this thread. I see a lot of guys setting up race suspensions that will, more than likely, never see the track. This thread can help them differentiate what is considered best for street and what is considered best for race or any mix thereof!:thumbsup:

I would think that setting up a race suspension would be easier since most of the components and setups are pretty tried and true for the most part but seeing all these great race parts a lot of times many people get mesmerized by the allure of the part not realizing that for their application it would be better to use something more geared for the street.

I know I'll be reading posts from Matt, John and whoever else chimes in(Norm Peterson, Where are you?!?) VERY CAREFULLY and absorbing as much as I can.:yes:

John

BTW thanks for your advice on the fire suppresion system. I don't think I ever really thanked you for your advice!

[fasterpatrick]

Very good thread guys, but all I have to add is been there done that. If you what to find a geometry nirvana give up. I spent six months studying countless chassis design books and geometry articles for every type of car imaginable. My head hurt for weeks afterword. What I came up with is a untested compromise of every thing I absorbed. Sorry there are no numbers to give out did not use them. If you want to design a suspension system start at the corners and work inward at ride height, thats the best way I found.
I'll be watching,
http://www.clubcobra.com/photopost/data/500/IM000697.JPG
http://www.clubcobra.com/photopost/data/500/IM000684.JPG
http://www.clubcobra.com/photopost/data/500/IM000729_Small_.JPG
http://www.clubcobra.com/photopost/data/500/IM000721_Small_.JPG
Patrick

[ccracin]

BTW thanks for your advice on the fire suppresion system. I don't think I ever really thanked you for your advice!

No problem John. Just happy to help. It's not often you can give personal experience with something like a fire system. I hope my experiences in that are are done and I hope all you ever have to do is wax the bottle!

[ccracin]

Very good thread guys, but all I have to add is been there done that. If you what to find a geometry nirvana give up. I spent six months studying countless chassis design books and geometry articles for every type of car imaginable. My head hurt for weeks afterword. What I came up with is a untested compromise of every thing I absorbed. Sorry there are no numbers to give out did not use them. If you want to design a suspension system start at the corners and work inward at ride height, thats the best way I found.
I'll be watching,
Patrick

Patrick,

Awesome build.. The Cobra has been on my "Want To Build" list for a long time. I'll be subscribed to your thread.

I know exactly where you are coming from. I have read and researched for a long time. The Holy Grail is obviously not out there or everyone would have the same setup already. I was hoping to extract some information to help the folks that are caught up in the marketing wars and really don't even know where to start looking to develop the headache we have all had. But after a couple asprin and some time, this suspension thing is alot of fun. It is very satisfying to have conceived and built a chassis that meets or exceeds your personal goals for it.

Later,

[chevyIIpost]

Bump Bump

[ccracin]

Sorry Ted, I am a bit under the weather. I am hoping to keep this going. I hope Matt, JP and others are working on some ideas. I am going to take a stab as well, but frankly until I kick this bug I'm just not up to it. Hopefully some others will jump in.:lateral:

Later,

[ironworks]

Not that I have any more info then the next guy these are some things that I take into account when setting up some of these suspension numbers.

1. Overall tire height
2. Widest Track width possible with given tire height and ride height of
vehicle, The fender over hang, or how much the tire tucks affects this.
3. Desired Suspension design to be used Mustang II or corvette, ETC
4. Physical contraints of the car, size of car, spindle vs desired rim size.
5. Avaliblity of rack and pinion for proposed narrowed suspension geometry
or will you have to do a custom width rack.
6. If your building you suspenion to an already avalible rack width then more then likely you will have to adjust your suspension track width to optimise. We do this in Solidworks. You must also take into consideration the steering arm height of the spindles and how that rack location will affect engine mounting and Engine dampener clearance.
7. After you have figure out all these different issues, you must decide what specs can and would like to have in your suspension. Do you want a high roll center or a low? What kind of camber gain are you looking for? The length of the upper control arm determines this along with the static angle it is mounted at.
Roll center, upper control arm to lower control arm ratio, instant center, anti-dive, scrub radius, and an million other things that all affect each other. If your using alot of stock parts things like ackerman and King pin inclination and overall spindle height are already determined.




Then once you think you have it all figured out, you find out the suspension will not droop enough to get the back tires out so back to the drawing board so you don't have to drop the rear trans axle to get a tire off.


Interesting thread but my head hurts.

[Beach Cruiser]

I'll Chime in with my .02, I went through this whole exercise a year or so ago, reading everything I could read and asking everyone I could ask. There is no Ideal, just a mixed bag of trade off's. 1st trade off is that you got to get the motor in between there somewhere, second the wheels and tires can't stick outside the fenders (in our version of the sport anyway)

I started with the wheel's and tires I wanted to run, 17x9.5 Z06 wheels. Second was the overal width of the track so I won't rub the fenders. I knew I wanted to run stock Corvette (C5) parts, so the spindles and control arm dimensions were fixed. But to get this config under the front of my camaro it ended up being about 5" narrower than the stock vette geometry. So I had to go back to the drawing board and refigure all the geometry with the new track. I ended up with the roll center about 1.5" above ground. From there I tried to optimize camber gain and minimize bump steer. The Rack location is the hardest part, With some help from Matt at AME we came up with a solution to lower the mounting points on the control arms and get the rack low enough to clear the engine. I also set my engine back about 1.5 inches so that the rack sits in the "sweet" spot behind the balencer and in front of the pan. Every 1/4" helps.

Everything on my suspension is adjustable, lower control arms, upper control arms, tie rod mounts ect... I havn't driven the car yet so I can't give you any real world feedback, But I will say that My Daily Driver Trans AM that I auto x with is a handful on the street in full auto X trim. There are to many inperfections in the road, it wants to dart off in any number of directions and rides like a brick. After every event I dial back down the shocks to a softer setting to make it bearable.

My Two cents, hope it helps.

[Silver69Camaro]

6. If your building you suspenion to an already avalible rack width then more then likely you will have to adjust your suspension track width to optimise. We do this in Solidworks.


Just curious, why not use a program like WinGEO? Solidworks can be very cumbersome for assemblies like that.

[ccracin]

Just curious, why not use a program like WinGEO? Solidworks can be very cumbersome for assemblies like that.

Roger,

I use and love Solidworks as well, but I agree with Matt. I use specific software that just crunches the geometry numbers. Much quicker to do "What Ifs" IMO. What's your motivation on this one? I'd like to hear you wrote some cool Macro that you are willing to share to automate this process in Solidworks.:_paranoid

[ccracin]

7. After you have figure out all these different issues, you must decide what specs can and would like to have in your suspension. Do you want a high roll center or a low? What kind of camber gain are you looking for? The length of the upper control arm determines this along with the static angle it is mounted at.
Roll center, upper control arm to lower control arm ratio, instant center, anti-dive, scrub radius, and an million other things that all affect each other. If your using alot of stock parts things like ackerman and King pin inclination and overall spindle height are already determined.

Interesting thread but my head hurts.

The initial base for this thread was to try and answer some of these questions or at least give folks some legitimate targets. Alot of guys can choose alot of parts and put them together, but have no idea what the end target should look like. I think we are turning on some light bulbs with regard to this stuff.

Your complete post just gave alot of information that I guarantee guys that spent thousands of dollars on parts never even considered.

My head hurts too, literally I'm still sick! Crap.

Thanks for jumping in Roger, your thoughts are well respected around here.

[ccracin]

I'll Chime in with my .02, I went through this whole exercise a year or so ago, reading everything I could read and asking everyone I could ask. There is no Ideal, just a mixed bag of trade off's. 1st trade off is that you got to get the motor in between there somewhere, second the wheels and tires can't stick outside the fenders (in our version of the sport anyway)

I started with the wheel's and tires I wanted to run, 17x9.5 Z06 wheels. Second was the overal width of the track so I won't rub the fenders. I knew I wanted to run stock Corvette (C5) parts, so the spindles and control arm dimensions were fixed. But to get this config under the front of my camaro it ended up being about 5" narrower than the stock vette geometry. So I had to go back to the drawing board and refigure all the geometry with the new track. I ended up with the roll center about 1.5" above ground. From there I tried to optimize camber gain and minimize bump steer. The Rack location is the hardest part, With some help from Matt at AME we came up with a solution to lower the mounting points on the control arms and get the rack low enough to clear the engine. I also set my engine back about 1.5 inches so that the rack sits in the "sweet" spot behind the balencer and in front of the pan. Every 1/4" helps.

Everything on my suspension is adjustable, lower control arms, upper control arms, tie rod mounts ect... I havn't driven the car yet so I can't give you any real world feedback, But I will say that My Daily Driver Trans AM that I auto x with is a handful on the street in full auto X trim. There are to many inperfections in the road, it wants to dart off in any number of directions and rides like a brick. After every event I dial back down the shocks to a softer setting to make it bearable.

My Two cents, hope it helps.

Thanks for jumping in. You just solidified some points made earlier. Most people get wide eyed at all these trick race parts and just have to have them. What they don't realize is they may be building the most untamed, kidney busting street car they ever saw. It is no fun. Where I live in South Western PA, the roads are terrible. We are the pothole capital of the country! I have a friend with a tire shop, he just told me last month he replaced 3 factory wheels on SUVs because the owners hit a pothole and bent or broke the wheel. Imagine driving your race car into one of those!

Anyway thanks for the input, this just adds more credibility to what is being said in this thread.

Later,

[ironworks]

Just curious, why not use a program like WinGEO? Solidworks can be very cumbersome for assemblies like that.

I use Solidworks because I have it and can turn the design in Soildworks into plates to machine out to make different crossmembers for suspension. I realize that there are better programs for suspension, but it all boils down to numbers. I don't need the program to tell me what the instant center is, I know the point where the upper and lower control arms intersect is the instant center and solidworks well tell me that number.


There were guys haulin ass with kick ass suspensions that they drew on the floor with chaulk. Todays modern suspensions have just be refined to the point that they test and tested. Computers just make that easier and quicker. You still have to be 2% smarter then the program your using.

[ccracin]

There were guys haulin ass with kick ass suspensions that they drew on the floor with chaulk. Todays modern suspensions have just be refined to the point that they test and tested. Computers just make that easier and quicker. You still have to be 2% smarter then the program your using.

I still have a piece chalk in the tool box! Don't forget the string! You hit the nail on the head, it is just quicker. 2% smarter, I quit! :lol:

Later,

[ironworks]

The initial base for this thread was to try and answer some of these questions or at least give folks some legitimate targets. Alot of guys can choose alot of parts and put them together, but have no idea what the end target should look like. I think we are turning on some light bulbs with regard to this stuff.

Your complete post just gave alot of information that I guarantee guys that spent thousands of dollars on parts never even considered.

My head hurts too, literally I'm still sick! Crap.

Thanks for jumping in Roger, your thoughts are well respected around here.

As far as respected, I don't know about that, we are just lucky and might have common sense which is not so common any more.


I have a 1946 Packard that a customer brought in a while ago that we are going to have to build a complete custom suspension for. No C6 stuff with trans axles, just a 5.3liter LS engine with 4L60E. It will have updated rear leaf springs in the rear. But the front suspension is almost impossible to get parts for and who would want to use it any ways, the steering in those days did not return to center and and was not built to do much over 55mph, maybe. I have looked at using the stock pick up points and build new control arms to those since we lowered the ride height the geometry would be Descent. But the crossmember curves forward to clear the old straight 8 flat head engine. Now I started with the tires he wants to run ( Caddy wire wheels) which have a 28" diameter in the front with the tires. But the wheels only come in a 5 on 5" bolt pattern. So that limits the avalible spindle and brake options real quick. Wilwood had a 13 kit with 5 on 5" pattern with their Pro spindle but those would not clear or even work with a 15" wire. So
I got a set of 98 chevy truck spindles for 100 bucks from the junk yard. They have 5 on 5" pattern stock. I'm working on figuring on the ride height of the chassis and will set the spinldes at the spindle height of the desired tires at the rough track width I'm looking for. Then I will set up the rack at the height the spindle's steering arms. I will then figure out a good upper control arm length and ratio to the bottom to optimise bumpsteer with the standard 24" center AGR rack.

I'm not trying to make a super corner carver Packard, but there is no front suspension kit on the market that I found that will suit my needs so we will build it. Same theory just not as high tech I suppose.

take it for what it's worth, probably not much

Rodger

[chevyIIpost]

Cool! Thanxs guys for the input. How about some plus or minus ranges for general guidelines in the street performance range.

Camber gain per inch..................

Static caster..................

Roll center height.................

Bump steer................

Ackerman.............

Anti dive %..................

How about some software recommendations?

Where do you guys source specs from for stock components?

Which stock components do you like to work with? I will assume C5/C6 as one option that works well?

Which after market components or sources do you guys like? (ARG, Maval/Unisteer, Stock car products)?

Who is will to do consulting work in this area for a fee?

[novanutcase]

Numbers?:)

John

[ccracin]

Numbers?:)

John

I second the motion! I'm finally free from the bug that held me down and am trying to do some work on this. But, what I think the numbers should be are not what people want. Where are you suspension guru guys? Please don't stop the enlightenment! :D

[novanutcase]

I second the motion! I'm finally free from the bug that held me down and am trying to do some work on this. But, what I think the numbers should be are not what people want. Where are you suspension guru guys? Please don't stop the enlightenment! :D

YEAH! Don't stop!

We're still trying to take the pebble from your hand!:lol:

http://i56.photobucket.com/albums/g170/novanutcase/kungfuwhenpebble.jpg

John

[Silver69Camaro]

I'd love to provide a "general" list of specs, but I can't really. I have to do that on a case-by-case basis.

You could say the specifications I listed previously works for vehicles similar to a well-prepared first-gen Camaro. I wouldn't stick it on a Chevelle or a '55 Chev if you wanted the best of performance. But honestly, you could put it on most vehicles and just swap springs and ARBs to match the new vehicle.