I have a '69 Conv. with the F41 special purpose suspension. Everything is original and my rear struts' bushings are going.
I've looked at Van Steel's adjustable stuts along with thinking stock replacements would suffice.
Any opinions what I should install this winter?
Thanks, Rog

 

If you're interested in originality and the car will align properly by just using the eccentric adjusters (which it should) then you should probably replace them with OEM-type replacements. The adjustable ones do offer more camber adjustment than the fixed ones, and the ones with solid Heim ends will hold a camber setting better than the rubber-bushed kind, but again the OEM replacements are perfectly all right if you want to keep everything original-looking.

 

I vote for the factory replacements. As the strut moves up and down, it also twists. The rubber bushings accomodate that just fine. To go to solid joints is just overkill, on a street car. IMHO.
Also, on most C2 and C3 diffs, there is often quite a bit of end play in the driveshaft yokes, occuring as the posi clutch pack wears. If you don't address both at the same time, you are putting lipstick on a pig. IMHO.

 

Thanks for the feedback guys. gcusmano...I've replaced my driveshaft, are you suggesting I replace my posi clutch pack when I replace the struts with the OEM style? (which I will do based on your comments)

 

If you want to spend a bunch of cash go ahead with the fully adjustable aftermaket replacement units, they will work fine, but are simply overkill... Replacement of the strut rod bushings with factory style replacements is fine. I recommend however that you do use polyurethane replacements available from several sources. In my opinion there is no point on old style rubber bushings being used anymore. The poly units are a much more durable design.

There is a valid point made about checking the play in the diff side yokes, but that doesn't have to happen simply as a necessity of putting new bushings in your strut rods. Not to mention which, you'll be faced with the necessity of totally disassembling your differential, which will result in pretty much a total overhaul of the unit... Not trivial or cheap. If you gotta, you gotta, but if it ain't broke, don't fix it....

Good luck

 

Poly bushings are the worst possible choice for any joint that requires 3D movement like strut rods or trailing arms.

 

I know I'll get flamed by those that have used adjustable length struts, but here goes.

There is a very specific reason the engineers made those struts a fixed length and adjusted camber by moving the pivot point.

The design of the rear suspension (and the front) is what is known as a long arm/short arm design. The upper control arm (driveshaft on the rear) is shorter than the lower control arm (strut). The reason for this is to prevent the tire from moving toward the centreline of the vehicle as it moves through it's travel causing a loss of traction and tire scrubbing. Because the upper outer end moves in a tighter arc than the lower the top of the tire moves inwards more than the lower causing the bottom of the tire to pivot outward and stay in it's track.

The ratio of the lengths of the two arms is critical. By changing the length of the lower arm you defeat this designed in correction.

Now you may want to do that if the car is going to be used differently than the engineers envisioned, like on a raceway, but you need to know how to perform the geometric calculations to assure you are getting the effect you are looking for (and you need to know what effect it is you want. There is more to handling than camber).

If you are unable to get the correct amount of camber you want to find the reason and correct that. I can assure you it won't be because the strut changed length. Changing the strut length to get your camber is just trading one problem for another.

Steve g

 

While I agree with your views on the geometry, I don't see how it applies here.
When using the oem adjustment cam, you are in effect moving the lower upright mount either in or out which is exactly the same thing as shortening or lengthening an adjustable strut. Keep in mind that the increase in the distance from the inner mount to the outer mount is relatively slight in both cases.

BTW, I made my own heim joint adjustables for around a 100 bucks using high quality moly/kevlar joints with seals added and off the shelf tubes. Much improved ride control, and no more harsh than oem.

 

Actually, the amount of variation typical with adjustable length camber struts induces fairly minimal changes to the IC's and RC's inherent to the C2/C3 rear suspension, especially when compared to that resultant from relocating the height of the inner camber struts (a useful chassis tuning tool), or even those from ride height changes for that matter.

FWIW, it has been my experience that the eccentrics simply don't hold their adjustments under heavy loads, and so suggest replacing them with camber lock plates for any serious performance application. Also, IMCO heim-jointed struts are the best way to eliminate compliant camber strut bushings. For those whose priority is stock appearance and/or ride comfort, this is all moot anyway. My $.02

TSW

 

WOW! Mike and I agree for once. Buy replacement bushings and R&R the rotten old ones. The early strut rods work really well when rebuilt. I used them to win a Corvette Council autocross championship in 2004. Just make sure you have the correct early struts (74 and earlier.)

 

Google long arm/short arm or unequal length arm suspension for some diagrams. There is a big difference between moving the pivot point and lengthening/shortening the arm. It's all about the arc that the outer end of the control arm travels. If you move the pivot in or out the outer end draws exactly the same arc traveling up and down (the radius is unchanged). If you lengthen the strut this radius now forms a larger circle and a more open arc. Shortening it creates a smaller circle and a tighter arc (think length of radius and size of circle). A broader arc means that the the outer end moves inward less and a shorter radius moves it in more.

The broader arc means the bottom of the wheel moves inwards less than it did previously. The length of the upper control arm stays the same. By design the upper control arm is shorter and as such moves the top of the tire in more than the arc of the lower moves the bottom in. The difference in these two arcs was carefully designed so that as the suspension moves through it's travel (because it moves in an arc it moves toward the vehicle centreline) the top of the tire moving inward more than the bottom causes the bottom of the tire to "pivot" outward and stay in it's track.
While I agree that the change is very little, unless you know what that change is, it's a crapshoot. Keep in mind that the difference between the lengths of the 2 arms is not that great to begin with and any change you make would be looked at not as a percentage of the length of the strut, but rather as a % of the difference. A quarter inch on a 24" strut might not seem like much, but if the design difference between the two lengths is only 4", .25 inches becomes significant.

Steve g

 

I fully understand the concept, but again, given the specs of the suspension, I doubt you are lengthening the arm more than 1/4" at extremes and it would be a crap shoot as to whether the eccentric or heim method is advantageous or detrimental. The travel is so short that it is barely an arc.
It would be interesting to see a travel superimposed, given the same camber settings. I doubt you would even see a difference in camber change.

BTW, on a Pantera the camber is adjusted by actually shortening the upper control arm.

 

I'm always a little skeptical when it's suggested that the design engineering was not necessary. The change you make by altering the length may not be very much, but it is moving it away from the optimum.

My point was/is that altering the length of the strut is not doing the same thing as changing the pivot point and unless you've done all the calculations as to what effect it has,the outcome is anyone's guess. And it's highly unlikely it's an improvement over design. And if you're trying to correct a camber issue you still haven't solved the problem.

The arc may seem to you to be pretty small, but it creates enough inward travel that it lead to the development of the unequal arm back in the 30's. I don't know why Pantera adjust by changing arm length, but look at the thousands of cars built since the 1930's using the unequal arm and pivot point adjustment is the norm.

Nuff said on my part.

Steve g

 

Good onya for the homemade strutrods! but, I disagree with your analysis. Think of a pendulum. When you move its pivot point (down in this case) the arc itself remains unchanged while changing where the arc occurs.

If you change the length of the pendulum, you change its arc: longer = wider, shorter = narrower. While the center of the arc will now be where you adjusted it to, the farther away from center the pendulum swings, the farther away from the original arc the new arc will be.

Given this, if you change the length of a strut rud, you do indeed change the shape of its arc; whereas if you move it's pivot point, you merely move where the arc takes place and not the shape of the arc. Another way of "seeing" it, is to think in extreme. Move the pivot point out 1' and make the arc, then make the rod 1' longer and make the arc... see?

I have adjustable strut rods. After working on this car enough, I have come to the opinion that much of the engineering placed cost and the ability of a union factory worker to cobble the parts together well ahead of optimal design. I may have somehow slightly upset my geometry, but IMO, those little camber bolts and stamped steel strut rods are crap.

 

I also made my own heim joint rods, and I felt it improved the handling noticeably. Steve's comments may be accurate with respect to geometry, but I can tell you from experience that my car drives better with the camber bolts replaced with plates that center the thru-bolt in the slot, and camber adjustments made by changing the rod length. This is a mod that many, many guys have made, and the reviews are almost all positive. The benefit comes from the rod ends, so if someone were still hung up on the rod length, there's nothing stopping 'em from setting up the heim joint rods to the exact same length as the stockers, locking them down, and continuing to use the cam bolts to set camber...

 

Steve, while I respect the point you're attempting to make, and while anyone having even an elemental grasp of geometry should understand how changing the length of a radius changes an arc, I'm afraid your apparently blanket assertion that anything other than the General's original design specs are necessarily less than optimum is simply incorrect. Many a C2/C3 (particularly the C2) can benefit from altering the IC's and RC's from stock (especially if shod with modern tires), and the easiest way to go about that in the rear suspension is to relocate the inner camber strut height; a significantly more radical alteration than the relatively minor strut length adjustments being debated.

Not saying the factory engineers didn't know what they were doing, but Zora himself admitted the C2/C3 OE suspension was somewhat of a budget-driven compromise. And, when you get right down to it, even among one or the other of the generations sharing our layout, there just isn't a one-size-fits-all optimum setup for each and every individual vehicle and application. Besides, with compliant rubber camber strut bushings the geometry isn't exactly fixed anyway, tho some rules require them.

Not flaming you, just trying to shed some extra light here.

 

Wow, thank you all. Some serious talent in this forum, which is why I feel fortunate to be able to tap into it. Better than talking at swap meets in the olddays!!
I'm happy SolidLT1 and Mike agree. I'm going that way.
My car has 63,000 miles on it and all of the original suspension parts except for the shocks. I'm very happy with the ride quality given it's a 43 year old car! I drive it hard...mostly in a straight line though because I couldn't live with myself if I lost it pushing hard in a corner or ramp. I'll challenge Ferrari's up to 130...the thread on what it takes to go 150 was awesome...Rog
FWIW - putting an aluminum radiator in this winter too.

 

Heim joints, Spreader bar, Bilstein shocks, 460 # front springs & 330 # rear spring is the way to go, if you are driving on the streets. Have a great one. Gene

 

Mark your calendars folks, it may never happen again.

 

January 27, 2012!