Thread: IFS alignment, best way to...

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This site has been a god send for me. The amount of information and help I have gotten is truely outstanding, thank you all.

I have gotten into the new front end and it turned out to be a little more crusty than I thought so I have completely dis-assembled it and am in the process of bead blasting and painting it. I am also going to put all new bushings and ball joints in it while I have it apart. Parts will be here monday and I will have it all cleaned and painted tomorrow so I will be ready in a couple days. Thanks again everyone, I feel like I have done a dozen of these now!

Thanks for all the info, Tech.

Techinspector,
I'm not much on tech talk, I'm just a see and do kind of guy. I take things apart and put them back together that's how I accomplish things. When it comes to calculating the physical aspect of something using protractors, mathematics and such, I'm no good at that. I look at the over all picture and when it doesn't look good using my eye I get out the tape measure. I took measurements from an existing frame with aftermarket Mustang II suspension and the upper & lower control arms had parallel 5 degree angles. The thing that didn't look right to me was the tie rods on the rack were not parallel to the ground so I made sure mine were.

Are you saying I've made a boo boo on my front suspension with regard to dive, instant center, etc., that my car is not going to react well under braking ?
What about handling characteristics in everyday driving ? Or is it that you're seeing an optical illusion in the photo with regards to the upper & lower arms not looking parallel to each other and the ground. Both control arms are indeed parallel with each other as the measurement between the ball joints and the measurement between the frame mounts are the same. I placed a jack under the front crossmember and without the air bags installed I moved the car up and down through it's suspension travel and I saw no variation in the perpendicular of the wheels.

WITHOUT AIR BAGS

WITH AIR BAGS

So Tech, what was the final result of giving up some ackerman to achive 0 bumpsteer? Do you feel that there is no noticable effect to the driving of the car? If to do it again, would you do it the same way?

As I breath a sign of relief I must confess, it was my first attempt at building my own frame and I had no idea what I was doing. I figured if I took enough measurements and used cardboard templates for all my angles and as long as I think it through and double check my measurements I should fair pretty good. And as luck had it, it turned out better then I expected.

Same thinking applied in the chopping of the roof, which was also a first for me. I thought long and hard to over come the curve rear glass dilema. Because the glass is tempered it could not be cut. At first I thought I'd build a pocket in the lower part of the window frame to set the glass down into. By doing this I'd still be able to lower the roof. Then one day the light blub came on, I realized if I remove the window frame entirely from the roof, chop the roof and then weld the frame back in, the glass would appear to be smaller. I was right, once the frame was back in the chopped roof, it blended in very well with the smaller front and side windows.

Now if I can just work out the hydraulic tilt front clip, the remote door poppers, the Lincoln Town Car trunk actuator, electric windows, frenched side pipes, revolving hidden license plate, etc, etc, etc.....................

Thanks tech, you have been a great help. As soon as my new bushings and ball joints arrive the party begins here. I may check out one of those Carrol Smith books. Any one you may suggest in particular?

Your doing a great job Bulletnose, car is looking awesome. That lincoln actuator you mentioned, is that just for the latch or does it lift the trunk lid?

Thanks again Tech, I will order up one of those pronto. This is one of the few things I have never attempted before and you have helped put my mind at ease. I am looking forward to getting to it.

Originally posted by techinspector1
bulletnose, it's interesting to note that you designed the suspension to preclude an instant center by angling the upper and lower arms at the same angle. I did the same thing on mine, except that both upper and lower arms are parallel with the ground, meaning that the actual dive in the car will be determined by the front spring rate. I didn't like the idea of a constantly-changing caster, which is what you get with arms that are laid in at different angles. With a heavy car such as a production bodied car, anti-dive is helpful, but if you have very little weight on the front as in my car (115" wheelbase, motor set back 17" as measured from the front spindle centerline to the nearest spark plug hole), it's not such a big deal.

For those of you who don't understand anti-dive, it is calculated by dividing the distance from the ground of the instant center of the control arms by the distance from the ground of the center of gravity of the car. Let's do a for-instance. The center of gravity height of the car is roughly at the camshaft height of the motor. My cam is 20" off the ground. Now, let's say that you lay the lower arm in level with the ground and it is 8" off the ground. Now you lay the upper arm in at whatever angle you think you want, lets say 2 degrees. Looking at the side of the car, run an imaginary line through the lower control arm bushings toward the back of the car. Now run an imaginary line through the upper control arm bushings toward the back of the car. In this case, the instant center is going to be at 8" above the ground regardless of the angle of the upper arm, because the lower arm is parallel with the ground and the upper arm line will intersect it at some point behind the center of gravity. Divide 8" by 20" and you get .40 or 40% anti-dive. You can angle the arms to get any anti-dive figure you want, even over 100% by angling the upper and lower arms down in the front, thus projecting the instant center above the center of gravity. I suspect you'd have a fairly evil-handling car if you did, but it can be done. Heck, by having over 100%, you could make the nose of the car RISE on braking. I suspect this 5 degree angle that everyone is talking about on the upper arms came directly from the Mustang II car that someone laid an angle finder on and said, hey, if it works for Ford, it'll work for me.

Dave, my setup has absolutely zero bumpsteer through 9 inches of travel (4 1/2" bump, 4 1/2" droop). I've set up fixtures and checked it with a dial indicator several times and even had a fabricator buddy come by the house to verify it. Of course, I had to give up some things to get it, 100% Ackerman being the most important. I have SOME Ackerman in the car as a natural function of the way a front suspension works. This car is an experiment on wheels. Normally, to gain Ackerman, you would draw a line from the center of the rear axle, through the lower balljoint centerline and extend that line out to the centerline of the tie rod hole in the steering arm. This will give 100% positive Ackerman. As you move your steering arm tie rod hole further inboard, you reduce Ackerman. Some race cars have even experimented with negative Ackerman, having the imaginary line drawn through the steering arm tie rod hole and the centerline of the lower balljoint laying somewhere outside the car!!! I capitulated to neutral Ackerman for the sake of zero bumpsteer. With the centerline of the inner tie rod joint (where it connects to the rack) exactly in line with the inner control arm bushings on the lower arm, I fabricated my steering arm hole to be at the same position as the centerline of the lower balljoint. This means that the tie rod and the lower control arm are exactly the same length and operate on the exact same pivot centers. To make this work, I fabricated the lower arm bushings 17" wide on centers, so that the tie rods run behind the front lower control arm bushings. In other works, starting at the front of the frame, the front lower control arm bushing is first, then the tie rod, then the rear lower control arm bushing. This is the only way I could figure to have absolutely zero bumpsteer. The car isn't on the road yet, so I have no idea of the transient handling characteristics. I'm just hoping for the best. That's the kind of guy I am, a hot rodder at heart, try it and see how it works. Am I babbling here?? I hope some of this makes sense to you guys.

Techinspector,
Thanks for the info! This is what I was asking on some of my threads earlier. Somebody is creating and testing own ideas and sharing the experience!
Unfortunately I have to read everything several times because of my translation. The inches vs. millimeters doesn't help either. Still a lot of new ideas that raises more questions in me.
drawings would help too.

Does anybody know any easy to use Windows programs to test the ideas?
I've got a demo version of the Front Suspension Geometry Pro. It is easy to use but you cannot do anything with the Demo version. Should I buy the full version or is there a better one available?
http://www.auto-ware.com/software/asgp/asgp.htm

- Jani -

Originally posted by brickman
I am getting ready to put my pinto ifs under my '48, I preped the frame today. As far as I know, you would level the frame front and rear. Center the spindle in the fender well(Pre-Marked), making sure that the center of the spindle is the same distance up or down from the top of the frame on both sides. Then cross measure from the inside rear corners where the new ifs meets the frame and the rear inside corners of the frame.

If I am doing this wrong or am missing an important step some help from you all would be most appreciated.

I am really excited to get on with this part of the construction and get the chasis rolling again....Thanks all.

I purchesed a heidts crossmember and a mustang II tubular suspension, they came with rack extenders to help prevent bumpsteer. All is now up and running and all is working fine. I set up the upper and lower a arms with a piece of all thread and welded T for the shock area and adjust for horizontal to the ground a arms and to my surprise when the engin and trans was in it sat near perfect. Ed ke6bnl

You said you adjusted to the ground Ed ke6bnl? What did you mean by that? You set up so the bottom a-arm was parralell to the ground w/out the engine in? Just a little puzzled?

Streets, thanks for the positive comment.

Brickman, the trunk actuator I'm referring to is the latch. You've probably seen one work, you close the lid gently on the first lock and then the actuator kicks in and draws the lid down locking it into the closed position. I'm also thinking of a screw actuator that lifts the lid up after the electric unlock button has been pressed.

Was also thinking of using screw actuators instead of hydraulics on my tilt front clip, eliminating all that hose. The actuators in the closed position will lock the clip firmly down on the rubber cone stays.

As it stands today, I'm going to have so many gadgits on this buggy I'll need to run an extra battery and a large amp alternator.

opps!

Thanks Tech, I'm doing ok! With all the help, this is going to be a breeze. I am not going to get to worried about ride hieght with the engine in, it should equal itself out. I finished painting the a-arms and springs this morning, the spindles are already done. Love Small Blocks new bead blaster! I have the bushings and ball joints on the way from Southern rods and then the party starts. Getting the bushing's out I guess is a drill the old out and press the new in.

I am stuck with a manual steering Rack & pinion so it should be interesting steering the car.