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Come in and check out my auto-x/road course suspension plans

2994 Views 41 Replies 12 Participants Last post by  yellow73sb, 
hosspowerinc
Ok well this is my first post on this forum after months of lurking. I give up! Seems all the brains have moved over here and thats just fine with me!

Well I just finished welding and gusseting my frame and its time to focus on the suspension. My goal is to have a street car that is a weekend warrior at the parking lot auto-x and the occasional run at the local track.

What I have now is 550# front springs, 360# rear spring, poly bushings, spreader bar, steeriods style rack, and rebuilt suspension(trailing arms, spindles, bushings, and ball joints). As for the reset of my combo. I have a 77 thats getting a 500hp Ls6 and a tremec 5 speed. I will be doing a 6 point roll bar and running 285/35/18 rear tires and 255/45/17 fronts.

Lets start with the front end. I will most likely be cutting 1/2 coil off the 550s putting them around 600#. Im thinking of a set of (speedway?) adjustable upper a-arms. I know TT has these and a few others but are they worth the trouble and cost? It would be great to dial in a lot of caster and camber but is there any benefit of these over stock strength wise? I feel the lower control arm will be fine for my application. With the front sway bar Im thinking something on the lines of 1 1/8 or 1 1/4. Opinions on this would be welcomed.

As for the rear end, this is what Ive really been thinking about. What should I do about the rear toe change? I know VB&P has the smart struts (which I can build quite frankly) but it also gets rid of the camber gain. Can someone help me with ideas on this? I really dont think a 6 link is the answer and I havent seen too much pop up on the forum on this subject. Aside from that, I doubt I will need a rear sway bar but possibly a small 3/8 or 1/2 if I have too much understeer. Also, would a dual mount rear spring setup be of any benefit? I dont see how it would but thought Id ask.

Ill combine the last 2 as shocks and brakes. I have a hydroboost unit ready to go and am pretty sure I will be going with wilwood dynalites on all 4 corners with stock rotors. Has anyone made there own brackets for these? Id like to fab my own up if they are pretty easy. The shocks I would like to know more about. I hear koni's are the way to go but Id like some direction on that. If there as some just as good that dont cost as much, Id like to know.

In summary-

Adjustable upper arms.... yes or no?
What size front sway bar?
Do my spring rates seem satisfactory?
What do I do about the rear suspension geometry?
What are the best shocks?

A few pics of my frame progress






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Turbo84
Looks like you're on the right track with your initial suspension choices. Once you get it running again you can always tweak the values and settings if needed. I ended up doing that a couple times. I'm currently running 550 fronts and a 420 rear (the 360 was a bit too soft for me), and I like the way it handles, given the limitations of the stock C3 geometry. I'm running a BB, so my frontend weight is is a bit more, and I'm using a 1 1/8 inch front bar, and no rear bar due to the stiff rear spring. I fabricated caliper brackets for my Dynalites, but these brackets fit the C4 suspension I put on my spare frame, so I guess I can't offer up any patterns there. The gusseting additions look good. I'm trying to brace and stiffen up my frame also while it's convenient to do so.
Nice job. Keep the pictures coming.
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SMYDA
I have to compliment you on your welds, being (in your post under "Projects")
it looks like your using a 110v Hobart welder on a frame. Nothing wrong with
a Hobart. I prefer a 220v welder (easier penetration).

Keep up the good work. :thumbsup:
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Turbo84
SMYDA said:
I have to compliment you on your welds, being (in your post under "Projects")
it looks like your using a 110v Hobart welder on a frame. Nothing wrong with
a Hobart. I prefer a 220v welder (easier penetration).

Keep up the good work. :thumbsup:
Click to expand...
Okay, I give up. How are you determining what welder he is using? (Not being sarcastic, just darn curious.)
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SMYDA
Turbo84 said:
Okay, I give up. How are you determining what welder he is using? (Not being sarcastic, just darn curious.)
Click to expand...
:D
I'm psychic.............J/K :rolling:


I boo booed, I said, "(in your post under "Projects")" when it was actually
in his post under "Pics of your C3".
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hosspowerinc
Thanks for the complements. Yes I am using a hobart handler 140. I have it set on 90 amps and it works very well. I started it out at 140 amps No need to go to 220v when that one gets the job done! It would be nice for the duty cycle though. This one is only 20% at 90 and 8% at 140.
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T
hosspowerinc said:
and running 285/35/18 rear tires and 255/45/17 fronts.
Click to expand...

I don't know if you are going to be happy with the way the car handles with skinny 255 tires. i would try and get something bigger on even if you have to trim the leading edge of the wheelwell.
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hosspowerinc
Good to know. 255 was my street size to be able to turn lock to lock but I could have another set for the track. Your running 275s arent you?
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T
hosspowerinc said:
Good to know. 255 was my street size to be able to turn lock to lock but I could have another set for the track. Your running 275s arent you?
Click to expand...
Yes, 275/40/17 all around and its not enough. I'm limited by a 9" rim.

I'd like to get 10" and go to a 315 all around.
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TwinTurbo
why did you weld on the a arm bolt threaded block thing? If you strip it out you've got a big problem.
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hosspowerinc
It looked like a pretty weak spot for the lower arm to mount. As far as stripping it out, as long as they arent crossthreaded in I dont see how that could happen. I was more worried about the frame cracking and the block getting torn off than anything else. A doubt that can happen now:D .

Anyone have any advise as far as my suspension questions go? Doesnt seems like too many people actually race their cars.....
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big2bird
TwinTurbo said:
a arm bolt threaded block thing
Click to expand...
So that's what it is called.:rolling:
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8
I'm getting ready to do some auto X and some 1/8 mile drags... Nothing beyond casual...

The biggest problem I felt the car had was a flexi flyer frame. In my Motorcycle Racing days that was the ugly.... You can go to stiff in a MC but I dont think you can get the frame to stiff in a C3.

I Just got done putting dynalites on the rear and superlite 4's on the front. It was was easier to by the brakets for $100/axle from Keith 'cause you get the brakelines and fittings with them. I have a CNC plasma cutter and a CNC Mill. If you can afford the time make your own brackets. there were so many other parts that needed making that I couldn't buy...

I've built a 6 link with an eye to going to a floating piviot and toe control rods in the future...

I have the bike for real track work :lookinup: :lookinup:
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gkull
hosspowerinc said:
What I have now is 550# front springs, 360# rear spring, poly bushings, spreader bar, steeriods style rack, and rebuilt suspension(trailing arms, spindles, bushings, and ball joints). As for the reset of my combo. I have a 77 thats getting a 500hp Ls6 and a tremec 5 speed. I will be doing a 6 point roll bar and running 285/35/18 rear tires and 255/45/17 fronts.




In summary-

Adjustable upper arms.... yes or no?
What size front sway bar?
Do my spring rates seem satisfactory?
What do I do about the rear suspension geometry?
What are the best shocks?
Click to expand...
I don't have adjustable a-arms. But I do manage to set mine at 5 degrees caster.

I have 550 front springs with a light front end. They are already an inch shorter and I would mount them first before cutting. The fenders might rub on a shorter spring with 255/45/17's I have those tires on the front also

I have the 1 1/8th front and 3/4 rear

Smart struts are a must as is a 420+ pound year spring.

Some of the racing C-3's use the front mono spring.

I ran a recent RR event and used a 720# RF and a 625# LF

I boiled out 500 degree Valvoline brake fluid Dot 4 is something like 420 degree. Wilwood sells 580 degree and I got 600 degree racing stuff and I'm adding 3 inch air duct lines with machined stock calipers using piston insulators.

C-3's need lots of diet and at least a 6 point with 10 inch front and 12 inch rear slicks to really race. If you are going to a bigger motor forget about trying street tires.
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TwinTurbo
84rzv500r said:
I've built a 6 link with an eye to going to a floating piviot and toe control rods in the future...
Click to expand...
Ahhhh :thumbsup:

BTW, I have adjustable a arms, coil overs all round, rear double a arm irs....and so on. never driven the car though in current state...all theory and ideas.
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hosspowerinc
Alright finally some real info:partyon:

I guess Ill hold off on the upper a arms. 5* is what I was going for and if I cant get it, I can upgrade them with relative ease. I will be making some form of smart struts and will keep my spring rates for now until I get everything together and running and on the track. I will pick up a 1 1/8" front sway bar too and hold off on the rear.

What shocks are you guys running?
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gkull
For smart struts I have the poly ends. As soon as they show some ware I'm replacing them with steel ball ends.

My 420+ pound rear spring is a custom unit that holds the half shafts nearly Parrallel to the ground. With big spring/shocks/sway/smart struts you are limiting the verticle movement of the rear wheels. So you are not inducing big toe and camber changes.

I can dial in @.60 neg camber and end up with a nearly identical temp across the face of my rear 315 or slick tires.

If you are going for a late model injected motor skip little 350 ci like the LS6. Big inches and a 5 speed is how to get around a track fast
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T
TwinTurbo said:
why did you weld on the a arm bolt threaded block thing? If you strip it out you've got a big problem.
Click to expand...
It was really good that he did that. We've seen several pictures of the frame ripping away in that very area. Thats probably the weakest point on the frame. If he strips it out he just drills it out for a bolt and nut. No big deal at all.

What did you end up doing in this area?


Gkull, I thought we decided that smart struts are not an advantage for going around corners, since you want as much neg camber gain in compression as you can get. The looseness of the whole system is a problem. I dialed in a ton of rear camber last time i was out and the picts show no camber at all or even positive in the corner. This concerns me. I've even questioned redvetracr about his avatar where it looks like his rear wheel is going positive, but he ignored me as usual.

The other thing that surprises me that you (Gkull) run skinny 255s on front. But then mention that to get serious you need really big tires. I think that's a no brainer we can all agree on. It's a matter of deciding to flair the fenders.

My cheapo RCSI adjustable shocks from Mid America are working well for me. I think its important for a street car to have them so you can dial down the brualness.

As far as the rear ride height problems we all have, i've cut the spring and modified the mounting system. I plan to put a 80-82 aluminum rear in one of these days. I will mount it as high up in the frame as possible so that will help with the over-arched springs that everybody makes now days.

Not enough power is my biggest problem right now as the wrx's, stangs, yada yada yada pass me like i'm standing still.
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turtlevette said:
It was really good that he did that. We've seen several pictures of the frame ripping away in that very area. Thats probably the weakest point on the frame. If he strips it out he just drills it out for a bolt and nut. No big deal at all.

What did you end up doing in this area?


Gkull, I thought we decided that smart struts are not an advantage for going around corners, since you want as much neg camber gain in compression as you can get. The looseness of the whole system is a problem. I dialed in a ton of rear camber last time i was out and the picts show no camber at all or even positive in the corner. This concerns me. I've even questioned redvetracr about his avatar where it looks like his rear wheel is going positive, but he ignored me as usual.

The other thing that surprises me that you (Gkull) run skinny 255s on front. But then mention that to get serious you need really big tires. I think that's a no brainer we can all agree on. It's a matter of deciding to flair the fenders.

My cheapo adjustable shocks are working well for me. I think its important for a street car to have them so you can dial down the brualness.

I
Click to expand...
:agree:
I was going to say that I don't see any benefits from the smart struts also



Also to the OP if you want adjustable circle track shocks find the ones for a 70-81 camaro. The fronts are the same as ours.
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hosspowerinc
When I say smart struts all I mean is a heim jointed adjustable strut rod. When I lower the car I will weld up the original mounting bracket an redrill the holes for optimal camber gain. Anyone know what that is? Maybe something in degrees per inch? I agree that the VB&P product is for drag racing only. I just wish I could get rid of the toe change in the rear without a 6 link:rolleyes:
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