TSW
sounds fine
lowering D to 1" will make my 1/2 shafts almost level to the ground i think... but i'm going to increase the rear toe-in from 1/4" to 3/8" and so partially offset the toe-steer issue.Anyway it's easy to test the car with D= 1" and 1,5" so I'll see which gives a better feeling.
Also I want to try to disconnect the OEM rear sway bar and see what happens

Unfortunately my car is a compromise in respect to chassis : not that stiff, not that low...etc. trying to get the best into the limits. Intriguing anyway this suspension's brainstorming...

 

No pictures. I used 1/8th inch bar stock and welded it to the inner side of the a-arm channel where the vertical bolts attach the a-arm to the frame.

Here is some other ideas

http://forums.corvetteforum.com/c3-t...arge-pics.html

 

This may be sacrilege to question Chev Power but by my measurements the vertical distance between the outer u-joint center and outer strut pivot is about 6.75 in. The vertical distance between the inner pivots with the standard bracket is about 5 in. The Chev Power seems to indicate adjusting height with longer spring bolts to achieve the specified D height of 1.25. This method would put the inner u-joint about 0.5 inch below the outer in conflict with the Greenwood recommened Plus 0.5 in to control toe out. It would seem that to keep the inner u-joint 0.5 above the outer for toe control and have a 1.25 D height the inner pivot point on the bracket should be about 1 in below the stock location. Which is about the drop Skunk Works said the smart strut bracket would provide.

 

Raising the diff, as mentioned in the Chevy Power book, serves to correct the half-shaft angle problem presented when lowering, yielding additinal margin in the geometry. For anyone doing this, don't forget your pinion angle.

 

I thought I could figure it out but I am not catching on. Could someone explain what z and d height are.

 

Here is an extra camber plate, made from 1/2" alum. bar stock. CNC machined, grade 8 bolts, stainless steel washers. I was worried about bottoming out in the rear (1 1/4 length would have been better than 1 1/2" bolts but I couldn't find them. Instead I used a lock washer on each). $50 shipped anywhere in the continental US. Please PM.

 

 

Factory trim (ride) heights vary from model to model, and some years have more elaborate schedules than others (i.e. '69). As you can see on the '74 AIM page posted by petes74ttop there are four specs given. Z and D are the important ones for suspension geometry, and aren't affected nearly as much as are J and K (or any other height referenced to the body) by non-OEM tire sizes. FWIW, below is a link to the Chevy Power book Corvette Chassis section (C3), in which you'll find the IMSA GT / SCCA Trans-Am competition ride heights we're talking about.

http://www.corvettefaq.com/c3/ChevyPower.pdf

 

Thanks, I have to move the AIM to a lower shelf so I can get to easier and more often.

Tom

 

Very good info!

 

Raising the diff will help the CG but since the strut rod bracket is attached to the diff it will also be raised. Chev Power (at least my old, old edition) only recommends welding a single hole plate over the camber adjusting slot, no spacer, no modified bracket. With these conditions the relationship of the inner u-joint and the inner strut rod pivots remain unchanged. The only way to achive the recommended D height with the outer pivots location fixed by the tire diameter is to lower the inner pivots which results in an inner u-joint about 1/2 inch below the outer. Not a desireable setting for controling toe out. What I am saying is Chev Power, as written, gives bad advice. Now you can burn me at the stake.

This post is about the Smart Strut bracket and how to use it. The vertical slots in the Smart Strut bracket allow adjustment of the D height by changing the relationship between the inner u-joint and the lower strut rod pivot point. The additional degree of freedom built into the bracket allows the inner u-joint to be located above the outer and also achive a 1.25 in D height. As Skunk Works said a plate with a hole in the center of the slot comes very close to delivering a 1.25 D height.

 

If you're goal is to lower the car (stance) to achieve the "look" or lower CG then its worth raising the diff to keep proper Half-shaft geometry.
You just have to know that you are limiting wheel travel. I would think your strut rod bracket should be raised then to keep the current geometry. So your strut rod would not change in relation to its mounting to the diff.

 

I appreciate this is a few years old but thought i'd share anyway

I did both, raised the diff and got smart struts, not perfect but good enough. the car handles very well

[IMG][/IMG]

 

Unless straight line acceleration at the strip is your only priority, you really should dial your SS inner links back up to the top of the "inclination" slot. That would put them back to only ~1/2" lower than are their stock heights, which is where John Greenwood rightly recommends and where IMCO they should remain as the default adjustment in lieu of actual test results proving otherwise for a given set of circumstances.

 

Thanks for the info Skunk, I've had the car on the road since the pic, it's just hard to find the time for proper testing what with it pi**ing down with rain the whole time

The car is light years better than it was.

I really need some double adjustable shocks to dial the car properly but they'll have to wait.

So the idea is not to get the lower arm and half shaft level then?

Cheers

 

you have to have the 1/2 shaft angled down externally. to do this you should raise the rear of car

i solved the toe steer issue adding a lot of rear toe-in and stiffening as much as possible the rear suspension to avoid excessive body roll

i use a 7 leaf steel spring ( which is stiffer than your composite) and qa1 single adjust shock setted quite stiff. i suggest qa1 because are really easy and fun to tune...just turn the ****

 

I had the car really low and have gradually raised it up over time, it's at a nice height now, just need the QA1's which i'll get when I pass through on my way to Aus at Xmas.

I have adjustable Spax's on the car at the moment but double adjustable is what i'm after.

It's compromise between stance and geometry hence why it's not perfect but good enough for a fast road car, oddly the only racing I do with the car is drag racing even though it's set up as a circuit racer

 

So my, uneducated, initial thought when I looked at the picture of aaronscorvette was it was perfect, half shafts and struts in parallel, guess that proves I need to do some reading. My 68 will be for the SO and will never see the track unless you consider a high speed pass through the Walmart parking lot the track . So we're saying the struts and half shafts should have some down angle for a street car? Pic of my 68, unweighted, on the jack stands waiting for the body to be dropped back on.!

 

Correct, yes the axles should point down so that they're level when the car squats.

My picture was to illustrate trying to get the axle and lower arm level, my goal was to get the ride height I wanted and engineer the suspension to suit i.e the cut down bump stops, this mod provides another 3/4" suspension travel without any rubbing, moving the diff up gets the shafts straighter and smart struts allow things to line up easier.

It's as good as it'll get and a damn sight better than it was with the standard setup, I can really throw the car around now and get it to 95% of it's cornering capability

Next up is a roll cage to stiffen that floppy frame.

 

Here's the modded cross member

[IMG][/IMG]