VB&P Smart Struts

[Kid Vette]

I've been thinking about Smart Struts. These lower the inner pivot points of the strut rods. And, I'm not sure, but they may also move the pivot points out towards the wheels as well. Anybody knows if that is correct?

Also I think the 2 effects of the SS is reducing the negative camber gain in jounce and to lower the roll center. Is this considered good things for general handling (no drag racing)?

Does anybody have experience using SS with a 80-82 rear end?

I know Greenwood recommended lowering the pivot points by 1/2"; Herb Adams never mentioned it. I'm pretty ignorant on all this suspension stuff and I'm too lazy to learn. I just want to know if this is a worthwhile mod.

 

[Twin_Turbo]

I would NOT use them. The poly bushings are hard and they will not let the strut rods articulate without flexing the whole bushing and possible the brackets. Also 80-82 has offset rods, not straight so the welded smart strut poly rod ends won't even work. Get some spherical ends and some seals it boots and luibe them, seal up and install. Never a prob again and free articulation

 

[mrvette]

I would NOT use them. The poly bushings are hard and they will not let the strut rods articulate without flexing the whole bushing and possible the brackets. Also 80-82 has offset rods, not straight so the welded smart strut poly rod ends won't even work. Get some spherical ends and some seals it boots and luibe them, seal up and install. Never a prob again and free articulation

I have some SS on my '72 vert, been there for years now, needing a 3rd set of bushings.....AS I RECALL, someone told me the rubber bushings from a 80-82 shark struts would fit the VBP SS I have, thinking of trying them this go around.....anyone know what rubber bushing would work good??

:crutches:

 

[Kid Vette]

I'm not really asking about the struts themselves; I plan to use some rods w/spherical ends like you suggest TT. I'm wondering about the bracket that attaches to the diff and relocates the inner strut pivot. Does this change in geometry make sense for street/autocross?

VB&P offers brackets for the 80-82 diff. Does anybody have experience with these?

1980-96 Smart Strut Bracket w/cams

 

[Twin_Turbo]

Oh the bracket, lowering it will reduce camber gain, depending on how roll stuff your car is it could be done but I would not be surprised if you actually need more camber gain to counteract roll reducing contact patch.

If anything you want a bracket with NO cams and a 1/2" minmum bolt or even better a 5/8th for the heim end. You will adjust it with a sleeve, not a cam.

Also, those are C4 brackets..they DO fit, the original bracket is a 1 piece design. You could source some off a junker C4 for the cheap.... I don't have an original 80-82 bracket anymore to compare but I think the pos. on the C4 ones was higher uop than the C3 one.

 

[68/70Vette]

I have the struts sold by Tom's on both my 68 and 70. First of all he uses a modified stock strut rod differential bracket. The bracket mounting holes for the attaching bolts are accurate on the stock GM bracket. The VBP bracket holes are larger in diameter allowing the possibility of the bracket shifting back and forth. Tom's cuts off and re-welds the ends of the bracket so that the strut rods are parallel to the half shafts...which is what you want...the stock strut rods were not parallel. Next, Tom's strut rods have heim joints to avoid twisting whereas strut rods with bushings have a twisting torquing problem.
........................

Tom's strut rods with the heim joints attach to the shock mount bracket at the bottom of the spindle bearing housing forks. He supplies some spacers for both sides of the heim joints. I found his spacers to be about 0.020 inches too big. Had to grind them down. Not a big deal, but just tedious.

 

[MYBAD79]

I lowered the inner mounting location and now I have pretty much no camber gain ( also have upper strut rods) ... I cannot complain.... I have not done any real testing though. I still have another bracket so I could raise the inner mounting point back to the stock location and see how it compares, but then again I have made so many changes that it is difficult to really get a clear picture..... with the 315-35-17 tires I don't know that I really notice a less than optimal contact patch of the tire.... even if only 75% of that tire makes contact, that's still more rubber on the road than most others.... lol

 

[Kid Vette]

OK, I understand that you may want to reduce camber gain especially if you are using low profile tires with less sidewall deflection. Greenwood says reducing the camber gain "results in better rear tire wear". Has anybody seen a difference in rear tire wear with the Smart Strut bracket? I guess you would see less wear on the inside tread?

Nobody has touched on lowering the roll center. Why would you want to do this? My understanding is that will increase body roll, right? Greenwood is pretty vague on the benefits of doing this change. He just says it will "hold the road better in constant turns".

I was hoping somebody would have some direct experience using the Smart Strut bracket (especially for the 80-82 diff) that could give me real world results.

 

[Twin_Turbo]

I have the struts sold by Tom's on both my 68 and 70. First of all he uses a modified stock strut rod differential bracket. The bracket mounting holes for the attaching bolts are accurate on the stock GM bracket. The VBP bracket holes are larger in diameter allowing the possibility of the bracket shifting back and forth. Tom's cuts off and re-welds the ends of the bracket so that the strut rods are parallel to the half shafts...which is what you want...the stock strut rods were not parallel. Next, Tom's strut rods have heim joints to avoid twisting whereas strut rods with bushings have a twisting torquing problem.
........................

Tom's strut rods with the heim joints attach to the shock mount bracket at the bottom of the spindle bearing housing forks. He supplies some spacers for both sides of the heim joints. I found his spacers to be about 0.020 inches too big. Had to grind them down. Not a big deal, but just tedious.

for drag racing you want them parallel but not for road race, parallel takes out a lot of the camber curve. You only retain what's left because of the unequal length of the 2 members

 

[BBShark]

OK, I understand that you may want to reduce camber gain especially if you are using low profile tires with less sidewall deflection. Greenwood says reducing the camber gain "results in better rear tire wear". Has anybody seen a difference in rear tire wear with the Smart Strut bracket? I guess you would see less wear on the inside tread?

Nobody has touched on lowering the roll center. Why would you want to do this? My understanding is that will increase body roll, right? Greenwood is pretty vague on the benefits of doing this change. He just says it will "hold the road better in constant turns".

I was hoping somebody would have some direct experience using the Smart Strut bracket (especially for the 80-82 diff) that could give me real world results.

Reducing camber gain is probably the primary benifit. A C3 has horrible camber curve through suspension travel. Moving the strut bracket down 1/2" probably does not make enough difference in roll center height to make a noticable difference.

 

[Kid Vette]

Somebody over at CF posted the numbers on the camber gain using the various settings of the Smart Struts. I took those numbers and created a graph. I added the camber curve for the '63 to '67 Vette bracket. As Greenwood mentioned in his article, they redesigned the brackets for '68; lowering the pivot points. I got the numbers for the '63-'67 from the camber gain graph in the SAE paper in the Downloads section here.



A couple things jumped out at me. The various settings of the SS don't change it that much but there was a big jump when they made the bracket change in '68.

Here's a couple pics from the SAE paper that illustrate the concept.





I found a very good explanation of the whole concept over at DC by a very wise man, "The bracket is not just for drag racing, however the reduction in camber gain is a bit much, especially on a stockish car. The stock camber curve is a little bit on the high side but more importantly, the geometry has a too high roll center and therefore a jacking effect. Lowering the inner pivots lowers the roll center, which is a good thing. However, since it also reduces the camber gain you always want to combine this with making your car more roll resistant/stiff. This should be the 1st goal, getting the car to roll as little as possible and then you can lower the roll center to eliminate jacking and alter the camber curve. The jacking problem is also there because you're stuck with the halfshaft as the upper member, the lower rod is the only variable you have to alter the camber characteristics, a 6 link can change that however you'd need telescopic shafts, otherwise you'd end up with something that has to work with the stock shaft in place but floated, to eliminate excessive stub movement you really can't change anything radical unless you change both rods at the same time and keep the IC in compliance with the halfshaft (or close)
Of course, when you significantly lower the car that lowers the roll center also, lower it a lot (slammed) and the differential position comes into play, positive toe changes and all that. It's compromises all over the board. I do agree that the smart strut bracket lowers the pivots way too much, especially since most of these cars roll more than the camber gain those give (they do still allow camber gain as the halfshaft is still shorter giving a trapezoid, only if the rods are equal length to the halfshaft will it give a parallelogram)"

Think I'll buy the bracket and try it at its highest setting which should be a 1/2" drop from stock. :thumbs: