Norval, you are saying in the other thread, the stock setup is that if the wheel goes up from an at rest position, the top of the wheel tilts OUT?? how in hell is that possible with an unequal length top/bottom A arm length?? top HAS to some IN, same as if it was extending on the travel...

IF what you say is true, that would mean old Zora blew it?? NO??? ca't hardly beleive that....so much so, I'd have to pull my springs and check that out....I find it very hard to beleive...

GENE

 

Norval is right about the camber gain. Zora didn't blow it, he was just limited by his days technology, and the weak link was the tire. If the top of the tire came in as desired (and they new at the time that was the way to go) then there was so much lateral force on the bottom of the tire due to a maximized contact patch, that the bead would seperate from the rim. Not good for a production car. I have heard that the race cars had custom made spindles from the factory to correct this, but it seems mostly to be a rumor. Be nice if a real racer would chime in on this, as this is (after tires) the absolute worst aspect of our front suspension.

Chris

 

71R, you saying that a 75-78 series tire will roll the steel beed off the rim??? is the to came in as we want??? I say BS, someone have to show me that...I"D say it worse if the top leaned outward, now THAT would roll the bead off maybe...sorta like cornering on a flat tire...but if the tip rolled inward the way we think it should...and I can't see any way it wouldn't... that tire is planted good and solid....I can see at some point maybe the skidding would be more likely to happen as the tread squirms around and the tire slides sideways due to sidewall flex...but off the rim??? sorry can't see that happening.....

GENE

 

When you go around a corner the stock setup gains POSITIVE camber on the ourside tire. You are turning hard to the left and the passenger tire goes into POSITIVE camber. This rolls the tire under the car.
You want the wheel to go into NEGATIVE camber pushing the tire out at the bottom and pushing down harder on the contact patch, not try to roll the tire off the rim.
If you are running fast and want to turn LEFT hard you stick your right foot out front and push off hard to the left. Your leg has gained NEGATIVE camber.
Try making that same turn hard to the LEFT but stick you hip out and push the leg under yourself. See what happens the ankle takes a beating, could break it. You just acheived POSITIVE camber. Hurts the angle?????? YOur tire feels the same way.
A extende spindle turns the positive camber into negative camber. A 2 inch longer spindle would do the trick.
What happende to our suspension experts. Please chime in.

 

Norval, I hear and totally understand what you are saying, but number 1, I ca't beleive an unequal length A arm suspension is capable of acting the way you describe, and number two, that Zora would have done that design...makes NO sense on two scores.....

I guess I have to jack up the damn car and pull the springs, and play around with the suspension...to prove it to myself , self.....

GENE

 

Hi guys!

This is a sketch of what I think it is happening. the left side show the suspension at rest and the right side is making a left turn.
This at least demonstrates that gaining positive camber is possible with unequal length arms. Now we just need to look and see what we got...



P.S.: I DO hope that this is NOT what happens. What I don't really understand is how the spindle affect this? Maybe my translation knowledge isn't all that hot though and the spindle is not the part that the wheelbearing goes around on and I'm misinterpreting here...

Prost!:cheers:

Stefan


[Modified by Stefan69, 2:07 PM 5/7/2003]

 

Yes, this is indeed the problem area and it's part of what makes our cars feel so in-direct when cornering (that combined w/ a 20+ year old & worn steering setup)

Another way to fix it would be a shorter upper control arm but the stock upper arm already is fairly short. One could also mount the cross shaft lower on the frame ear or get some seriously short arms and mount them on the outside of the frame, just like a C4. All these will put the irc lower and closer to the center of the car and the camber change would be negative.

That pic is indeed what is happening.


[Modified by Twin_Turbo, 1:08 PM 5/7/2003]

 

Here's a good example of a remedy for the problem.





notice the position of the upper arms, then look at the stock situation (remember, there's no load on the suspension but still, look at where the liens are going, not toward each otehr, the RC is on the OUTSIDE of the car -> pos. camber change)

 

Great pix TT, man that is looking AWESOME !!!!

 

the guy w/ the modified front suspension (upper pics) has VB&P arms, I think stock spindles I tihnk and mini ball joints (he redrilled the upper amrs for them).

I will contact him and ask some more about this, it caught my eye when I saw this.

 

Yep, thats the problem. Even with a load on the suspension and the a-arms are a lot more parallel than that pictures suggests, the roll center and camber gain are based on 1950's tire technology. Ideally, the lower A arm would be parallel to the ground and the upper would be much higher on the out side than the inside, resulting in negative camber gain. As it is, we have positive gain because as I said, it was common for the tire bead to be pulled off the rim. Steel belts. Bias ply. Super tall sidewalls. Back in the day you could change a car tire with a crow bar (I did this once or twice, it wasn't easy, but it was possible). Try that today!

Thanks for those pics by the way. Those really help clear up what is going on.

Chris

 

Twin Turbo Those pictures illistrate it perfectly. The inner pivot point on the upper A arms must be lower then the outer ball joint of the lines never intersect.
Great pictures.

 

So a TALLER spindle would fix the problem? Or of course moving the upper a-arms lower on the frame. Ooops. There's no frame there...

:cheers:

Stefan

 

I contacted the owner of this car, the spindles are stock, he used coleman joints on the upper and lower arms.

 

TTurbo, THANK YOU, NOW I see it....sometimes it takes a :smash: :smash: upside the head to see it,...of course if the upper arm and lower arms are not level or equally so...the dynamics of the system would change...and that would also be affected by ride height....lovely...

OK, back to the drawing boards for me, anyway....so much easier to see it with a naked chassis....

thanks again....

GENE

 

OK, When are we placing the order for the Custom spindles and is this a group purchase? How much will they cost.

Wonder how many would have to be sold to make them up? If they can make drop spindels, why can't we get some made up too?

Would they need to have a drop of an inch or so also to maintain lower control arm angle?

Could a new spindle cure some bump-steer problems if it was designed to?

If I can't get them, I guess I will get Bubba to make a set of spacers for mine. How thick should they be?

Anyone think of anything else for the wish list?

Found this on the net

" A new front suspension system was designed by Don Alexander and Sheldon Tackett to optimize Project Sidewinder performance for its dual roles as a great handling street/road race sport truck and as a Bonneville record setter. The new suspension uses unequal length A-arms and coil-over springs/shocks. By using coil-over springs/shocks with threaded spring collars for ride height adjustment, the Sidewinder can easily be raised or lowered for specific needs at Bonneville, the drag strip or the street. Motorsports suspension experts, the Progress Group®, provided the coil-overs and springs.


During the Bonneville speed runs, it was necessary to get the front of the Sidewinder very low to minimize frontal drag and reduce the amount of air that gets under the front of the truck at speed. Ideally, the chin spoiler on the Sidewinder is “kissing” the salt at full speed. While the threaded coil-over springs/shocks provide several inches of ride height adjustment, dropped front spindles were also required to get the Dakota down to the desired height while keeping acceptable front end suspension geometry. As no acceptable dropped spindles were readily available, Sheldon Tackett machined two blank Stock Car Products® spindles designed for NASCAR Busch Grand National stock car racing applications. Tubular steel upper and lower control arms were fabricated to provide extra strength and to accommodate the dropped spindles. Heavy-duty Chrysler screw-in balljoints are used top and bottom. Oil-impregnated bronze bushings provide deflection-free A-arm movement. The suspension pickup points were also modified to reduce camber gain during suspension movement. Snubbers from a ’02 Chevy Suburban attached to the lower control arms limit upward travel of the front suspension, while frame mounted rubber snubbers limit the downward travel."

Is this a start? Jim :smash:


[Modified by PROSOUTH, 10:19 PM 5/7/2003]

 

Jim, I think Norval took about 3-4 posts to hammer home that we need to extend the TOP of the spindle, effectively, by getting longer stems on the ball joints, not just raising the arm position...have to raise the top PIVOT CENTER, not just the controll arm angle....


GENE

 

What we need is to make the spindle longer so that the balljoint on the upper arm is in a plane ABOVE the cross shaft, only THEN will the lines you draw through them (and lower arm) meet inside or just outside the opposite side of the suspension. Dropping the suspension will put the wheel center higher on the spindle, which makes the roll center sit higher above the ground.

As for bump steer, bump steer is caused by different geometry between the steering linkage and the control arms and stereing knuckle on the spindle.

The best way to get 0 bump steer is to get one of those racks w/ end steer (rods on the ourside that move, not the whole rack) and placing it parralel to the lower arm and withing the vertical plane of the pivots and ball joints (see green lines in next draing) only THEN will the steering shafts "effective" legth to the steering knuckle be the same throughout suspension travel.

The steering rod will be the yellow lines, it does not matter if you place it above, below or in front of the lower arm, as long as it's parallel.



Notice the spindles and hubs are on backwards in these pics (steering knuckle facing front) I tried to just place the knuckle to the front but that does not fit, I however don't like trailing brake calipers, it just looks funny. Also, there's an interference problem w/ the sway bar there.. damn damn :)

I'll do some more work on this, front steering is much easier because you won't have oil pan clearance issues and you won't need a messy steering input shaft setup w/ all kinds of universal joints in there.

Greg P used S10 spindles and he has front steer. I don't know if those spindles are taller than ours (he used dropped ones) and the bracket for the caliper is a part of the spindle.

Marck

 

.... :confused: is this discussion dead all of a sudden? it was just getting good :crazy:

 

I'm still trying to digest it! :lurk: