so im turning my iroc into a 90% solo car with the occasional street cruise to the local hangout, as well as being able to drive it to and from events (mostly solo II autocross whatever you want to call it)

My engine puts me in street modified under SCCA rules, so basically i can do whatever the heck i want with the rest of the chassis.

So here's the question, if you could build your dream handling third gen, any suspension mods go, what would you do.

Doing some research on here for the fronts i ended up deciding on weight jacks. I'm still not sure if that was the right way to go, simply because that design is basically for using in street prepared and having "stock" suspension to go with a more or less stock car.

The only other option as i could tell was to go with coil overs, and the issue with that is only being able to run a 245 tire in the front. I'm no expert but pretty sure my car is going to handle better with 10" front wheels and weight jacks then stock rubber and coil overs.

now i'm a little confused with the weight jacks because jay the camaro tech at ground control said you cant use weight jacks with aftermarket a-arms. I'm hoping he was thinking about coil over style arms as i dont see what the issue with a tubular a-arm with the stock spring perch would be, especially as the adjustment ring is barely wider then the spring.

i need to replace my k-member anyways (its got a good dent in it) so i'm hoping to go with the racecraft tubular k-member and a-arms if i can run my weight jacks with them.

that and some J&M strut mounts more or less sums it up for the front. the back is going to be a standard full tubular adjustable, spherical rod end setup.

If you could build your dream race car camaro, what suspension would you use. street mod has virtually no suspension rules as long as its based on the stock chassis so go nuts.

 

the weight jacks spring and the stock springs are 5.5" wide, they will fit as long as there is a standard spring pearch in the a-arms

 

thanks for reading my whole post! wow do i ramble sometime lmao

ya i called for clarification today and was told that what he meant wasn't that they wont work but that he wouldnt say that they will work based on the fact they were designed on the stock piece and doesnt want to put himself in the position where he gets people calling him saying the part doesnt work with some random aftermarket a-arm.

i'm going to be ordering a whole racecraft front end tomorrow. sweeet.

 

I have been out of SM for a few years now so I might be wrong but I think a tubular K-member might be illegal in SM. I thought you where pretty limited to SP suspension rules but pretty open on the drivetrain.


Personally I would go with the weight jacks with springs in the stock location, coilovers won't make it any faster.

 

I personally think putting weight jacks ontop A-arms is rediculous. By doing so, one is adding a tremendous amount of unsprung weight and reducing the ride ratio.

The ultimate in handling is trying to get a car up to a range of 4:1-5:1 ratio sprung to unsprung weight so as not to unsettle the chassis over road imperfections. This is done Via use of exotic very expensive lightweight suspension componants.

I am very fond of corner weights- and the best wqy to do this I have seen ONCE on a third gen where someone on here took the time to pull the motor and insatll weight jacks intot he top cans of the chassis with the adjuster screws coming up through the subframe in the engine bay. This makes the weight jacks sprung weight, not unsprung.

Then, Lightweight control arms (Leave the factory Kmember, its solid), lightweight struts (Can't beat Varistrut Aluminum double adjustables), shave the spindles like I did on mine, aluminum hubs (I had GlobalWest G-body roadrace hubs), aluminum tierods, Monoballs (Lighter than balljoints, and have adjustments for rollcenters), Aluminum calipers and rotor hats, lightweight lugnuts (Titanium) anf you have a very light weight expensive front suspension package.

 

I agree about Putting weight jacks in the A-arms. They can be put in the K-member with the engine and K-member in the car. I just got some standard 1" weight jacks that come with a large hex nut from a circle track supplier, and a 1 1/8" hole saw to drill thru the subframe and top of the K-member. It actually drilled easier then I thought it would. The fun part was trying to weld the nuts in the bottom of the K-member while laying on my back, Maybe I should say not so fun part. Total Cost was less then $80.00.

I wish I could afford some lightweight suspension parts.

 

Two words AIR BAGS!!!!!!!

 

Before you buy anything take a look at what we have to offer. I have a k member for any engine combination that you have plus we offer a arms with or without spring pockets. Both can withstand the abuse of the road coarse or a daily driver. Here is a link to our site. Take a look and if you have any questions please give me a call.

http://www.bmrfabrication.com/F3.htm

 

I'm pretty sure the ground control weight jacks fit in the upper spring mount in the k-member and the threaded portion is adjusted from a hole in the bottom of the a-arm.

Your assumption about "as long as its based on the stock chassis" is fairly correct however replacing the k-member isn't legal as are rod-end LCA's. A-arms would be ok if you stayed with stock strut mounts but you can only do one or the other.

That said, as long as your not planning on being competitive with the car at a divisional or national level nobody is going to care. Just make local competitors aware that you are not 100% legal and they probably won't care. What you've described so far would put you in C-prepared with converted GT1 cars at the extreme end of the spectrum. At a national level a third gen car is not going to be competitive in either class so just go out and have fun.

I've been setting my car up for track days, so autox legality has been a secondary concern. Locally I'll run SM or street tire open class. If for some reason its fast enough to give some of the legal SM cars a run for the money I'll run CP instead, or take off the illegal parts. That said I'm going to be suprised if my GTA is ever faster than my little four banger on street tires...

In terms of ideal setup the cars going to get most of its improvements from increasing your tire to weight ratio (more tire, less weight) and an aggressive alignment. Setting up the suspension to handle better after that is just icing on the cake. IMO the weight savings for aftermarket k-member and a-arms aren't significan't enough to them worthwhile if your just starting out on the suspension.

Use Delalums in the front LCA's, get the camber plates if you can't get the camber/caster #'s your tires want, increase the spring rates all around (stay around from off the shelf lowering springs!) and lower the car some in the process, get koni yellows at a minimum unless you can afford better. After you've got the basics covered then I'd stop modding and decide if you want to run SM or CP or if you want to just do as you like and run locally.

 

YUP, thats how they go in/adjust. It still is unsprung weight though, 1-2LB per side, not too bad

 

I'm clearing out a few sets of front and rear springs that might be of use, including brand new 800# Hypercoil fronts, used 225# Hypercoil rears, and used 175# Blue Coil rears. Check the classifieds if interested.

 

the adjuster is on top of the spring, how is that unsprung?

 

If the adjuster is just 'sitting' atop the spring and not welded or bolted to the upper can then it is weighting the suspension with gravity just as the weight of the spring is doing.

However! the unit has no motion since it is just sitting atop and being forced into place not to move so there is no polar motion weight in reversal movement of suspension travel. Thing of it as the portion of a-arm that mounts right next to the chassis around the bolt holes- that metal on the A-arm is still considered unsprung weight even though it does not affect polar movement. When calculated, it will be unsprung weight calculated to 0% but still unsprung because it has potential to drop loose of the chassis even though it is above the spring.
Its a little technicallity in the scenerio, but consider it 'sprung weight' because it will start being labeled unsprung but will calculate out as a final outcome of sprung weight.

I hope that explination was not too silly- buts its the truth.

Dean

 

A final note, you just need to reduce the weight of the componants that move up and down in the suspension.

Take you arm and extend it out sideways. Your hand is the tire, your armpit is the chassis bolt of the a-arm (the pivot point). Now move your hand up and down 2 feet with arm extended out sideways- then do it now holding a 2 lb weight- it takes much more effort to sloww the up direction and move back downwards, and visa versa. This is polar movement of the suspension. The higher the unsprung weight of the suspension the more upward polar movement weight of the lever assembly the further the inertia of suspension travel- THUS the more it will compress energy raising the chassis unsettling the ride. The lighter the assembly the quickler and easier it goes up and back down to follow the road inperfections, the smoother the chassis stays.

It is all leverage and weights. So now- tqake that same arm extended with 2lb weight and bend the elbow 90* so the upper half of the arm is pointing forwad cutting the polar distance in half (hand and elbow now basically the same distance from armpit)and move that same weight up and down (like doing the funky chicken). Result? well, the polar weight is about the same with the arm shorted but 2lbs heavier as it is the arm extended with no weight added. This is leverage. Less leverage can have more weight in polar movement.

Those big fat tires everyone wants to run with those big fat wheels...well, they are heavy along the lever of unsprung weight. And if your footprint accross that wider thread pattern is not making flat contact throughout articulation when the lever moves, you have just further hurt yourself in handling by adding wider tires.

Everything is relative. Some alot more than most people think. Its why so many peoples cars ride "harsh" in their words.

My car was firm wih reduced body roll and chassis movement, but never would I have described it as harsh. Its all how things are engineered with weights and leverage.

 

i've been so busy getting the car stripped and the engine bay prep'd for paint i forgot all about this thread.

i have so many questions and there is a ton of good information already in this thread but i need to do a bit of research so i'm not just asking stupid questions (for instance dont have a good understanding as to why different types of suspension change what counts as sprung and unsprung weight?)

it'll be a couple days but i'll be back to this.

Also didnt realize that the k-member puts me in a prepared class, from the bit of reading i had done i thought it would be fine for SM. The car will just be an autocross toy for now so if i do get competitive with it then i will worry about making it legal. I have no track experience so the current setup should be fine for me to learn how to drive, because as i'm learning with my bike there are few things that make you realize how much you suck at something, as being around people who are semi-pro at it.

 

okay i read bout half the post and since you said "what would you do to the suspension", i had to answer.

complete tubular front end. air bags all around. 10" wheel on front and back. go to spohn, say i want panhard bar, torque arm, tranny Xmember, STRONG sub frame connectors, and poly bushings. get a 12 bolt rear with the torque arm mount. think id be done there. everything under the car would be BRAND new and last me another 20 years.

 

Any SCCA Solo category with "Street" in its name is heavily restricted as far as basic chassis modifications go.

It's at the 'Prepared' level where the freedom to tinker with the chassis really begins. And that means that you can do LOTS more things besides just replacing the stock K-member. CP is actually a pretty good place to be if you've got a few folks playing there. There isn't nearly as much worry that some little tweak or other will make you illegal for the class.


Norm

 

Even in CP, if you have an aftermarket K-member you will be running a 10% weight penalty because it is then considered a tube frame car Yeah really dosen't make much sense.

There is a lot of freedom in chassis design though and really a fun place to play. If your smart enough You can design your own SLA front suspension and Move suspension mounting points as long as you keep the stock K-member. You can even modify that K-member how you see fit but you just can't replace it. Properly set up, Front struts seem to do just fine though.

Prepared is still a place for stock chassied cars, what I call tub cars. Even though Tube framed cars are allowed in CP(with a weight penalty) some of the higher level competitors kinda frown on them and think they should go into Modified.

 

We do not use SCCA rules in Canada.

I have 16x10 race rims for sale, only 12lbs.

 

I agree, the last thing I want is to be racing against a converted GT1 car with a solid roller 4.3L to make up for the weight break, but still making insane horsepower. Besides the LCA relocators, LCA's and PHB my car is legal for SM and locally there alway somebody running the class although no serious cars. There is a certain MSE car in CP that I haven't seen this year that I could run against. I was at the KC National Tour, I understand if he takes his time getting back.