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Discussion Starter · #1 ·
Hey Marck,

I know you are very knowledgable with the suspension of our C3's and would like some advice on improving certain things.

Is there a way to build some sort of rear suspension that gives better control of the toe change it has. I was personally thinking of putting in a link at the rear of the TA with pivot points at the same distance and with the link parallel to the half shaft... However the front of the TA (which i'm going to mount with the Johnny Joint as you suggested) keeps bottering me.

Or does it need something like the Guldstrand, with 2 rods attached at the bottom and 2 in the front.

Next in the past i experienced some problems relating to bump steer. Is there anyway to resolve this, different position of the steering arms, higher spindle (can this be safely done btw)...

I would like to change something for the better. I do not want to race, but I want to stay on the road and have a car that won't steer itsself in difficult situations.
What I certainly do not want to do is spend a fortune and cut my car completly up.

Have you got any suggestions. I've been reading through a lott of treads but I seem to get lost in all the suggestions and different opinions.

Maybe some others will get some ideas to.

Thanks

Yves
 

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Stick with off the shelf solutions.... :thumbsup:

Call me crazy but I dont get how you guys are experiencing ill manners in a C3 on the street in the US if the car is properly set up stock and with no worn parts...

If you push it past the street you're gonna come across some warts the first and foremost is the flexy-flier frame.

You may chage the feel but without baselines, testing, and development time you'll likely
not know if it's really getting better...

:cheers:
 

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Discussion Starter · #5 ·
Stick with off the shelf solutions.... :thumbsup:

Call me crazy but I dont get how you guys are experiencing ill manners in a C3 on the street in the US if the car is properly set up stock and with no worn parts...

If you push it past the street you're gonna come across some warts the first and foremost is the flexy-flier frame.

You may chage the feel but without baselines, testing, and development time you'll likely
not know if it's really getting better...

:cheers:
That's why i'm asking guys who did this before...

I did experience some akward handling problem before when i drove mine. This was probably bump steer related. It wasn't at high performance driving, just giving it some gas in a bend in the route, while hitting a pot hole at the same time...
 

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That's why i'm asking guys who did this before...

I did experience some akward handling problem before when i drove mine. This was probably bump steer related. It wasn't at high performance driving, just giving it some gas in a bend in the route, while hitting a pot hole at the same time...
Years ago I was driving a ~5000 lbs '67 Grand Prix down a country road....out pops a damn COW, when I hit my brakes and horn the cow turn sideways/parallel to the car....took out the whole left side of the car....

to you can say I suffered from Bump Stear......so I purposely mis spell it that way...bump stear.....

:thud: :WTF :cheers:
 

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Yves,

I'm not TT, but I do have an idea (based on homework, not opinion) about a couple of your questions, and if/when he chimes in you can see if I've got this right...

I've been looking into this same question a bit, and it appears the addition of a separate upper link freeing up the half-shafts from that duty would make no difference in toe-steer control as long as the stub axle assembly is still linked via the original single point trailing arm arrangement, which precludes the use of a proper toe link (that's the function of that extra lower strut on Guldstrand's 5-bar).

In order to isolate the stub axle assembly from that TA's influence on toe-steer and allow use of a toe-link, any trailing link(s) must have joints at both ends, and that requires additional links to keep the assembly from just flopping around. This can be done with a triangulated trailing link or dual trailing links, either arrangement having joints at all points. The more desirable of the two is the dual links, which allow anti-dive geometry to be tuned. Going to upper and lower A-arms would eliminate trailing links altogether, but that would be quite a job on the C3. Short of that, those dual trailing links and dual lower struts you see in Guldstrand's 5-bar appear to be necessary.

Below is a pic of Greenwood's answer. It appears there are dual upper attachment points, indicating the complete elimination of trailing links, essentially creating an upper control arm. Note two lower links, one serving as the camber strut and the other a toe-link.



Getting your steering links located properly to minimize bump steer is pretty much taken care of with bump steer blocks. I believe the rack-and-pinion setup also addresses this, but there have been some complaints about Steeroids mount flexing. Maybe Marck has a solution for that issue. ??

FWIW, I hope that helps...

Charlie :cheers:
 

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that photo is the lower arm and the upright of a greenwood double a arm IRS. The imsa wide body guy here has something like that. The lower arms are not a camber strut and toe link, they are simplyt an A arm. The toe is set with the rear rod on the upper arm, it's not in the pic. The attachment point on the upright IS visible, it's the one on the rear. The a arm itself mounts to the forward mount (the tip of the "triangle")

I build something very similar, I have a double a arm IRS w/ adjustable toe links.

Belgian, what do you want and how do you want to achieve it? Buy or fabricate? How much are you willing to spend, how "into" suspension stuff are you? If you don't want to go knee deep into it, just set the rear w/ neg. toe and make sure you set it so that the halfshaft is piinting DOWN outboard, certainly not up or level. This way you will go toe toe in on bump, in the other cases you will toe out which is a distaster!

Here's my double a arm IRS, it's a notch above the 5 bar/ 6 link combo I built and previously sh!tcanned because I decided to do it like this:



 

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that photo is the lower arm and the upright of a greenwood double a arm IRS. The imsa wide body guy here has something like that. The lower arms are not a camber strut and toe link, they are simplyt an A arm. The toe is set with the rear rod on the upper arm, it's not in the pic. The attachment point on the upright IS visible, it's the one on the rear. The a arm itself mounts to the forward mount (the tip of the "triangle")

I build something very similar, I have a double a arm IRS w/ adjustable toe links.

Belgian, what do you want and how do you want to achieve it? Buy or fabricate? How much are you willing to spend, how "into" suspension stuff are you? If you don't want to go knee deep into it, just set the rear w/ neg. toe and make sure you set it so that the halfshaft is piinting DOWN outboard, certainly not up or level. This way you will go toe toe in on bump, in the other cases you will toe out which is a distaster!

Here's my double a arm IRS, it's a notch above the 5 bar/ 6 link combo I built and previously sh!tcanned because I decided to do it like this:



I'm gonna get cracking on those parts... wont take long... I see they are missing from the drawing :surprised :D


:thumbsup:
 

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Discussion Starter · #15 ·
That double A-arm design will be superior to all that is there, but it involves a lott of refabricating, welding up etc. This would be fine if going all the way.

This is basically not how far I want to go. Don't mind fabricating and welding some, but in my opinion it should somehow still be possible to go back in needed and it needs to stay "fairly simple" if you know what i mean.

I don't want it to be absolutly "perfect", just something that keeps things better in control and prevent unwanted toe changes for example. I know that camber gain will be far from perfect, but if it would be, i would also have to use different tires, frame reinforcing etc etc.
I do not just want to buy bolt on, since I see some things that do not get me where i want...(just my .02$) plus imo they are way to expensive for me (despite I agree that they spent a lott of development on it)

I experienced some erratic handling when i drove mine in the past, and although the car was far from restored, not all of the problems were purely related to worn out parts.

As far what my knowledge goes, well i do know what all the angles mean on a suspension, i can measure them and i know how they interact. From the suspension design point of view, what I know i learned from Adams' book.

Maybe what i'm asking is not possible, but then i would like to know that too, since i then i want to stop thinking about improving things and concentrate on other things on the car that need finishing. :huh:
 

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the only way to be able to control toe and be able to go back to stock is to use a greenwood or guldstrand type 5 bar;. You can still go back to rtailing arms with those setups.

Here's what I had built, it's missing the toe control links and the upper rods in those pics. Never finished that. The toe control links were kind of a PITA to do on the 80-82 diff because of the batwing. Well, they were easy to do if you use a c4 center pivot mount but I wanted them perfect in geometry w/ the halfshafts, that requires a large mounting plate.





The P shaped brackets bolt to a set of mounts welded to th frame and the forward part is inserted into the spring pocket and uses the trailing arm bolt.



The large notch in the frame is there because i used 3/4 rod ends and large bolts, you could just use 5/8 and narrow the bracket (mine has big misalignment spacers because I wanted to widen the rear suspension), it'll all fit into the frame pocket then.
 

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no, it uses a rear toe control rod (not in pic). I have the models but no pics hosted anywhere of it. It's not as easy as it looks, you have to get the stuff placed perfectly or it won't work worth a damn.
 

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that photo is the lower arm and the upright of a greenwood double a arm IRS. The imsa wide body guy here has something like that. The lower arms are not a camber strut and toe link, they are simplyt an A arm. The toe is set with the rear rod on the upper arm, it's not in the pic. The attachment point on the upright IS visible, it's the one on the rear. The a arm itself mounts to the forward mount (the tip of the "triangle")...
Appreciate the corrections/clarification. I haven't seen the complete Greenwood setup, so I had made some deductions based on what I could see of it, as the copy that accompanied that pic I found was pretty thin on info, but I knew the stock TA's didn't go with it. :cheers:
 
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