I meant to post it in the bumpsteer thread oops.

Norval/TT and other people this is basically what your explaining. The 1 inch line represents the suspension travel. The lines connecting to it represent the tie rods. The 2 inch long tie rods have 28* change while the 4 inch tie rods have 15 * in change. Is this correct?

 

What you are doing is trying to minimize bumpsteer by taking out the angularity effect out of the tie rods, this means placing them as close to each other in the center of the steering rack so that during suspension movement the angularity effect is less and the resulting horizontal length change of the tie rods is minimized.

This is a way to do it but you won't get it perfect. There IS a way to get it perfect and that's by using the suspension gemetry and having the tie rod angled so that it's in tune with the 2 control arms, like a trapezoid with fixed lengths..it can move freely without binding up.

Here's how to do it:



Look at this picture, it's all about extending the ball joint to cross shaft lines, where they cross you have your instantaneous center, then from there go to the steering arm. Where all this intersects the line between the 2 cross shafts is where the tie rod end should be, the angle can be fine tuned by spacing the steering arm side. It will be difficult and time consuming to do but you should be able to get it very close to ideal, that sure makes fine tuning easier later on (w/ bumpsteer measurements) I did all that with the entire front clip off the car, much easier that way and I know you won't be able to do that.

What they call "alternate" position is where the tie rod will roughly be, slightly lower than the lower control arm.

Where it says line 2 you see the inner pivot for the tie rod, THAT'S where the hole in your rack's center plate should be. I know you spoke to Norvalwilhelm about this, look at his pics, that's exactly the position of the eye on his center link, he modified the stock one to reposition the mounting hole.

Don't worry about line 1, it's purely theoretical, there's no way the line will be in the same plane as the 2 balljoitns since the steering arm is further back and you have to accout for the ackerman geometry putting the steering arm hole slightly further inboard from the spinde steering axis.

 

Yes! Now I comprehend it! Thanks to you both.....

John

 

Chris-
Back to your old question about spring height--I finally got a chance to root through some milk crates and found my old ones. 1973 L48 (yellow SBC coupe): 16" high, 5" diameter; according to VBP, rated 293# although I seem to recall reading somewhere else they were rated 250#.

John

 

Now this has gotten me thinking again.....Never quite understood the idea of the geometry of unequal length A-arms. Why not use equal length A-arms? Camber change would be removed and it would be easier to get all the steering and suspension components into line with matching pivot points. Seems to me that would remove bumpsteer, if the tie rod was parallel with A-arms and equal length too.There would be a change in track width but is that a serious enough issue alone? Do we want the camber change to account for frame plane change from body roll? I know I'm missing something here, and I'm very curious now to understand this.
"Inquiring minds want to know."

John

 

JPhil, you answered your own question. In fact you do want a change in camber as the suspension travels to counteract body roll. So you want to gain negative camber in bump. Ideally it would only happen when you were cornering but that is impossible from a geometry aspect. For best tire grip you actually want to have negative camber (absolute measurement) on the outside wheel. Often times you can have 1 deg neg camber (static) but in a turn the body rolls 2 deg so you wind up with 1 deg positive camber on the outside wheel.

 

Right or wrong? Right! Too much to think about, I am concentrating on taking weight out of the car because it is as low as it can go with just about every go fast cornering piece known to the Corvette. I have even been buying the center drilled bolts from Coleman for non-critical areas. There was a racing team in the past that paid their crew for every pound that they removed.

 

I also worked at removing every pound possible. The front vacuum tube alone lost 20 pounds. I pulled about 50 pounds out of the front end with drilling everything, acid dipping alot of the parts and just plain leaving alot of parts off.

 

Do you ever hear any whistling when driving from all the holes? (Probably not over the wine of the blower and the 3inch exhaust.) How did you decide where and how big to drill the holes?

 

No I have never heard a whistle while driving but like you said the blower has it's own whine. The exhaust also has a healthy sound.
As for hole size and layout I just layout any pattern I want and drill until it looks right. It takes hours but I watch the pounds drop off. I have a accurate counter scale and weigh everything before, during and after.
Recently I was porting my intake and weighed some of the cuttings comming off and got 3 pounds of chips from the internal passages alone