Thread: front end set up opinions

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Hey guys, I have a motor mocked up in the Ranchero and and wondering about a few things. This car has to handle GREAT on the big end, it should be a fast one. I'm using Heidt's A-Arms on the front with 2"drop spindles (forged spindles). With the lowers set parrallel to the ground, what does the angle of the top A-Arm contriute to handling and stability. I will of course be cranking in some anti-dive on the upper mounts, and about 5 degrees of caster to get a bit more high speed stability. Bump steer and caster should be my main considerations for stability, right??? Oh yeah, haven't decided on the coilovers yet, either a pair of Aldan's with adjustable dampening on the shock, or a pair of Carrer'a just recently acquired from Blykins.

On the rear I am thinking of using a triangulated 4 bar set up with adjustable top mounts (like a circle burner late model) as well as a Watt's linkage to control movement. I know the Watt's linkage is probably not necessary with a triangulated 4 bar, but I like the idea of added lateral control.

The front and rear will have stabilizers. I'm considering a torsion bar setup with adjustable links because sliding in a different rate and size bar should add to the tunablity of the chassis???

Any thoughts or comments from the chassis guru's would be appreciated.

bump

Hello Dave, while I'm no chassis expert I would think you would want the uppers parrelel like the lowers, what would happen is thru bump you would gain or lose caster depending on wich way ya angled the upper arm,we usta do that on purpose with the big block modifieds to help load the right front wheel on corner entry but on a street car I would think ya would want everything to stay on an even keel.......

"what would happen is thru bump you would gain or lose caster depending on wich way ya angled the upper arm"

Yep, that's one of the characteristics of using anti-dive. The more you angle the rear of the upper control arm down, the more anti-dive you build into the car and the more the caster goes positive on bump under braking.

In the other plane, angling the upper control arm so that the ball joint end of it is higher than the bushing mount end will contribute to more or less camber gain, something you shouldn't be concerned about unless you're gonna road race the Ranchero. Camber gain will keep the tire tread parallel with the road surface and prevent the outside tire from rolling over onto the sidewall. On the T, I designed in 3 1/2 degrees of camber gain at full bump by angling the upper arm where I wanted it.

You will have little control over bumpsteer if you have used a MII crossmember fabricated by someone else. The rack mounts where it mounts and that's it in relation to the control arms and steering arms/spindles. Again, on the T, I mounted the rack so that I could remove or add shims to move the rack vertically by about 1/2" total either up or down to minimize bumpsteer.

Dave, there is so much involved in drag racing suspension that I suggest you lean on the experts. I learned quite a lot from Dave Morgan in his book "Doorslammers" and suggest it as good material for anyone who'll be setting up a drag suspension. Here's a link to the book and a video by Dave which I haven't seen, but will soon (cause I just found it looking for stuff for you)
http://www.ssapubl.com/index.cfm?do=list&categoryid=9

I also stumbled across some software that you might find interesting....
http://www.performancetrends.com/4link.htm

Thanks Tech, it is a MII suspension, but I am building my own mounts for the upper arms. The arms are also 3/4" narrower than stock, which I'm sure will also effect the geometry. The Ranchero has got to be able to handle, also. Maybe not road racing, but at least a fun drive down the
Valley Road !!! (lots of curves and hills). I know if I can make it handle good on the street, going staight down the dragstrip should be a cake walk. I know it's tough to build dual purpose into a car, usually involves too many comprimises.

How about the stabilizer bar idea??? My thought is when it's time to head to the dragstrip I could just remove the front one and possibly preload the rear, similar to what Pro Z is running on the Maro....

Thanks for the help and the good advice

Dave, if you're doing the placement of the upper control arms, then you're basically at Step One of designing your own IFS geometry. I know you are no newcomer to this and have a great deal of knowledge, but if you haven't designed the whole thing from scratch before, I'd advise at least reading Carroll Smith before you go any further. I read every suspension book I could get my hands on and nobody brought it together for me like Smith did. In my humble opinion, Tune To Win and Prepare To Win should be minimum required reading before tackling a project like yours.

Among other things, you must know how to set the instantaneous center, roll center, roll couple distribution, side scrub, camber gain, anti-dive, etc., etc. and Smith will lay it all out for you.

Thanks Tech, I've got the book around here somewhere. Must be time to get it out and do some more reading. The shorter control arms had me thrown off a bit, but I mocked up some pieces and put the trusty caster/camber gauge on and got the specs to come in.

Thanks for the reminder on Smith's book, think I'll go do some reading and verify that this thing is going to work correctly.

Severson; Did you ever finish the power windows with the new tracks you told me about? Still haven't figured out what to do for my windows and tracks yet. Not trying to steal your thread just curious and need some good ideas on this problem for my 65 Ranchero. Thanks


~ Vegas ~

Haven't made it to the windows yet, today I got some hood hinges built (now the Ranchero hood is hinged in the front) and studied my chassis books for getting the suspension to do what I want it to do. I usually use the kit that Dakota Digital sells, good quality stuff for windows, locks, and of course digital gauges.

Dave,

Some good info on MII suspensions.

http://www.heidts.com/heiford.htm

http://www.heidts.com/heisinfo.htm#bump

The attached photo shows the MII setup I used on my A-bone. It's not set up like Heidt's recommendation. I had to compromise to get it under my fenders.

However, I never noticed any problems with steering. The darn thing ran like a slot car. It may have worked because of the relatively short suspension travel.

I'm not recommending this - just showing what I did.

The shorter travel definitely makes dialing in the bump steer a lot easier!! Thanks for the links, copied them. Hope I can get the slot car handling, setting the engine back quite aways to improve the weight distribution and going through all the information on the geometry I can find. Tech reminded me to get my books out and study. So many years of installing the "store bought" IFS set ups does tend to make one lazy and forgetful, like I really needed any help on forgetting more!!!!!

Would you have a pic of the same front end from the front of the car??? Curious to see where the tie rods ended up. Thanks.

Dave,

I have a couple of photos of the front, but I didn't document this car very well. These photos were taken before the body was installed and the chassis fully loaded. The wheels are turned, so it's difficult to get a good view of how everything lines up.

After the final setup, the tie rods were pretty near parallel with the bottom A-arm, and the tie rod / A-arm pivot points were pretty close.

Here's another photo. Obviously the upper A-arm is significantly different from the ideal MII design. However, like I said, with limited travel, it worked. The engine setback and resultant weight distribution helped also.

The front suspension on this car may be a bit out of line according to the Ford MII design, but it's set up a lot closer than many high-end cars I see in the magazines today. Some of those guys realy butcher it up in order to get what they call "a great stance."

I know what you mean on giving up ride for stance!! I'm greedy, I want to have both of them right!!! Thanks for the pics of the front view.

By the way, that was based on a Progressive Automotive kit. I believe they were one of the first (if not THE first) kits available.