Road / Track Suspension Discussion

 

Actually, the hacked lower arm doesnt affect the geometry, only ride height/spring length, and whatever ride height change may do to geometry.  Pivot points are all in their same location (again, except for height change).

Can you explain us laymen what your trying to do ?

Sounds interesting to me.   I would like to understand what your changing about the suspension geometry to improve...I surmise its to improve cornering, but not exactly sure how...and what its improving.  It sounds like your trying to change the car's suspension center...to improve the alignment under heavy side loading?   I was looking at the upper and lower arm lines relative to the bump steer only...but in doing so it struck me as odd that the upper A arm angled down instead of up from the frame to the ball joint.   I guess your fixing this a different way rather than lengthening the spindle...or somehow getting the A-arm to point up vs down...

and is there enough range on the ball joint before it binds to do this under full compression?

Thanks in advance.    I'm just a mere Padawan.   I work with pictures and crayons ;-)

 

Now put the car back together and drive around a left hand curve.  As the car rolls to the right, the right wheel goes up into the fender and the left wheel moves out of the fender.  The tops of both tires move to the right.  The bottoms of the tires are now tilted away from the inside of the curve and the car is now riding on the outside edge of the outside tire and the inside edge of the inside tire.  This is detrimental to grip.

 

Optimised road race suspensions are designed to have a negative camber gain (not positive) when the wheel goes up and a positive camber gain when the wheel goes down.  This is so that the tires tilt against the curve (towards the left, on a right hand curve) and as the car leans and the tires deform, they stay flatter on the road.  This is great for front end grip, compaired to the description above. 

 

I measured all of my pick-up points, and plotted them in auto-cad.  Then I plotted the arcs that the upper and lower arms make, and re-adjusted the angle of the spindle to match the p/u points.  I had an idea how much camber change I was looking for.  I tinkered around w/ those points to see what was possible in the confines of the frame, to improve the geometry.  At first, I was trying to duplicate the "Shelby Drop", by trying to move the upper control arm inner points, down.  But that involved alot of cutting and welding, because of the attachment method and frame design.  At some point, I looked at the lower arm.  I rolled under the car and saw that there was just enough space above the lower arm to be able to move that inner point up, without interfering with the frame.  Combining the moving of the lower inner pivot up 1 1/2" with lowering the car 3", I will have .5 deg negative camber gain when the wheel goes up 1", and .42 deg positive camber gain when the wheel goes down 1", which is very good on a street aplication (some race cars have up to 1 deg per inch).

 

Yes, the upper are will be pointing up, and the lower will be just about level.  Ball joint bind shouldn't be a problem.

 

Btw, there is too much of a good thing.  Too much gain starts turning the suspension, virtually, into one similar to the ford truck front twin i beam or the early vw rear swing arm suspension.

 

But that works if your lowering/cutting the springs down 3"...Correct?

 

Lowering 3" puts the arms in the right relative stationary position...but how does that impact the remaining suspension travel?   I can see that the upper arm isn't the issue; its the lower arm before it hits the frame.    I haven't looked at any of this, but it seems like there may be a couple inches of upward travel left?

 

I'm glad to see that its calculated using Autocad or something equivalent.   I can't wait to see your results.   I'm wondering if at some point its better off replacing the lower arm with an aftermarket unit.   That will also leave plenty of room to use a splined sway bar in the front without those trailing links.

 

I like your ideas here...  

Thanks for splaining

 

-John

 

I may actually go back to the little 3/4" front sway bar.  Changing the suspension also changes the roll center (the axis that the car rotates around when it leans).  Stock is 4 1/2" BELOW the ground,  "adjusted" will be 2" above ground, which changes (quite a bit) the amount of torque that's applied to the suspension by the weight of the car.  Combined with a front spring rate of about 750 lbs, I may not need the big 1 1/8" bar.  Stiffer isn't always better.  It will be trial and error though.

 

Street.  With my tallish tires, there shouldnt be a bottoming problem.  The roads are pretty smooth around here (north of Atlanta, Ga).  Stiffer springs help.

what size tires are you planning??

 

that way the spring wont have a chance of falling out of place on full extension

Sounds like we are thinking of similar tires and suspension setups....

except your going stiffer springs with smaller sway bars where I'm thinking of bigger sway bars with softer springs.   I'm thinking 1 3/8" front with 7/8" rear sway bars with 700lbs/in front springs(may lower) and about 210-220 lbs/in rear springs.

What about shocks?    

Right now...I'm all over the map with everything.   First I have to decide the ride height... I would like to lower it 2-3" like your doing but I hate hitting man hole covers that stick up and speed bumps like I'm 4 wheel'n through a parking lot bottoming out rocking on a speed bump.

 

 

Example. 

Both of my Cougars have full poly bushings, larger bars, etc. 

I initially bought Bilsteins P71 spec'd to run with the 17s and OEM small block springs under a big block. Brutal, IMO, for new england roads. Felt needlessly stiff over bumps.

Same shocks against OEM size 225 75 15 tires, car felt 'perfect' for what it was. I ended up moving the Bilstein's to the '77 with the OEM wheels. I feel I could abuse this car like a police officer beats on a Crown Vic hopping curbs and the car would be fine (not that I would)

Instead I now run Motorcraft P71 spec shocks with the 17s, and it feels MUCH better, more balanced. Springs are PST springs for a 72-79, that were supposed to drop the car 1". They didn't, so the previous owner heated them until it settled. (I am normally not a fan of this, but it worked, so much so I used these springs in 'my' car).

Ride quality was a concern for me.

 

 

Why not graft in a 2003+ Crown Vic front suspension?   I has aftermarket support, springs, shocks, etc and a front steer rack.

 

I believe the frame rails for this year Crown vic outside to outside is 34" ...I think the torino is 37-38"...

 

Just something I stumbled on.

-John

 

Is that a 4 bolt ball joint?