MII Directional Stability

It looks like your tie rods are not parrell with a arms.
I think if you put 1 deg caster it will bring them closer.
The tie in should be with tape measure.

 

Ok. I'm pretty convinced that I have geometry close enough. I raised the front end about 2" from where it was. The over boost thing could be a factor.

How/where do I check pressure and how do I lower it?

 

In picture 1 is the car sitting on the level with the suspension at rest? If that is the case the left hand tie rod "looks" like its going up hill and the right hand one going down. Is the rack level in the frame? Doesn't look it by picture 1 of 6. Check out the distance between the rack bushing and the mounting point on the frame.

 

No. They are symmetrical and the rack is level.

 

The MII should be about 1 degs pos caster.This is set with car level.The way i see it with more caster you are raising your tie rod up where it should be level.With the caster at 1 deg should make it more parrelle.This may help but looks like your rack is to low and raised would make level.What happening is when a arm goes up and down your wheel are going in and out.
By being parllral the movement is less.Also the dropped spindle may made to high,But I think the rack is to low.

 

Can anyone tell me from the pictures if I have a 74-78 power rack or a 79-93?

 

For what its worth it looks like the 91 Mustang rack I have in my car. The hard lines and bosses on the rack are the same as mine, but then I don't know if the Mustang II rack looks much different.

 

Caster is used to counter-act the king-pin inclination .
Without caster king-pin inclination will cause the wheels to flop over into positive camber if turned either direction, so the king pin is laid back [ caster ] to counter-act this on the outside wheel. Positive camber is quite desirable on the inside wheel.
The side affect of caster is the vehicle will alway want to straighten up the steering [ but also feels heavier ]

That can be an optical illusion, you actually need to draw crosses on the centers of the ball joints and tape string on them to see [ remove the rack boot ]
The tie rods need to be parallel with the lower A-Arm only if it is at the same height, but if you do it this way the tie-rod also needs to be the same length [ this is the easiest method ]

The drag link [ or rack ] can be wider in the center than the inner pivots of the lower A-Arm if it is front steer allowing for ackerman [ narrower for rear steer ] but try and keep the tie-rods the same length

Too do it correctly you need to string up an find the instant center , but keeping it level with the lower A-Arm is easiest [ here is 3 examples plagiarized from our lovely internet ]
Note the first example allows for ackerman on a rear steer car [ tie-rods behind ]


Also Toe-in and Negative Camber are not very good "bedpartners" you shouldn't have both so set the Toe to Zero [ easier than setting camber ] or set the camber to zero.
Negative camber causes the 2 front wheels to drive towards each other like to "cones" [ called camber thrust ] so you actually need toe-out to counteract this.

Toe-out is quite unstable on rough surfaces and is often confused with bump steer [so set it to zero ]
Most modern A-Arm front suspension has shorter upper A-Arms so that negative camber is induced dynamically so you could safely use Zero Camber [and some toe-in ]

The only reason race cars run 2-3 degrees negative is to keep the outside wheel at about 1/2 degree negative camber at extreme bodyroll [ high G's ]

​

 

In looking at your pics this maybe way out but,I wonder if the tie rod lever on dropped spindle was bent up and giving clearance for the wheels.
Checking around I don,t think location of rack is problem.

 

Sounds like a pressure problem.

 

By the time I drive to Nashville and back, I believe I will have decided if it is a pump problem or not. There is nothing bent or screwed up in thisnfront end tha I can determine. It just drives a little squirrelly and I was trying to get it sorted out before I hit the road. Unfortunately, I've had to be out of town during the week and I just haven't been able to get it done. Thanks for all the inputs and suggestions.

 

A couple years ago I had bought a 56 F100 with MII and PS. It was a white knuckle drive home and was really darty. All component were brand new and it was a fresh installation. It was set-up with about 2Deg caster. I cranked it up to five and it settled right down. Had I kept it I think I would have taken the PS out, or at least changed the valving.

Hope you get it sorted out!

 

I just got home and looked at the front end again. There is nothing awry. The ps pump is Tuff Stuff pump and they offer them of MII systems, so I assume it is right. Unfortunately, I can't easily read the number, so I will wait until next week to verify that it is a low pressure model......but I'll bet it is.

 

I was looking at my setup with stock spindles and did some measureing.
From the lower ball joint boss center to center tie rod boss center is 1 1/2inches.
You may want to check that.

 

Well, after driving 400 miles, it's apparent that the steering is simply too quick off center. If you movemthemsteering wheel a degree or two, it starts turning...quickly. If a cross wind hits you and you try to correct, you'd better have good nerves and both hands on the wheel. I've gotta slow this thing down or get a manual rack. Life is too short too live in terror. The car tracks straight on a flat, smooth stretch.

 

My Stude was just like that, could run straight road hands off. Soon as you touched the wheel, say to over take someone, it just darted , waaay too touchy.
Even after putting the shims in pump there was no noticeable improvement. I never tried the adjustable valve tho.

I went manual, much nicer, just a little harder to turn, in the low speed stuff.

 

On my old front end I would drive with one finger it was so light until I shimmed the GM pump.

 

I'm tellin' ya, the magic formula is a manual rack and a stock sized wheel. My former girlfriend is 4 11" and about 98lbs and drove the hell out of the Plymouth with it set up like that with no problem... Unless you count the burnout tht got away from her at the upscale shopping center that took out the valet stand...

 

How big is stock wheel?
I think a bigger wheel would help my car, but you know you gotta be cool.

 

Most cars up 'till the mid fifties had a wheel about 17 or 18" I just walked out and measured a '40 deluxe wheel and it was 17". The smaller the wheel, the less leverage the driver can exert on it. That's when power steering came in, 'bout the mid fifties as cars got heavier and steering wheels got smaller. A smaller wheel also quickens the steering response too. A larger wheel slows it a bit.

Tons of guys set Mustang II front ends up under even mid weight cars like mine with power because "they want the wife to be able to drive it". She just proved to me that it wasn't a big deal to drive my car without, 'cause she was about as small a person as you could get and still reach the pedals.

 

Hahahaha! Well, it's funny now.

I'm loving this thread Rock. A ton of brain trust chiming in on something an awful lot of us have a real interest in. Feeling a lot better about my manual rack now . . .

 

Physics 101. Classic equation is Torque = Force X Length of lever arm.

Duh, that's why we all have those really long screwdrivers and such.

 

That only applies if you are using them as Pry Bars

And love the avatar from the Europe 72 album cover

 

The "Ice Cream Kid" by Stanley Mouse.

And the Dead's finest album.

So . . . longer handle to break the nut does not translate to longer handle to break the screw . . . funny how you hear what you want to hear and see what you want to see.

I'm sure you're right, but I sure have been fooling myself

 

I've heard too many stories of power R/P that were too touchy. I have a manual rack now in my '46 pickup, and would like to go to power. Two possible fixes...

A company called Unisteer tells me they can supply a rack and pump that are matched, and would not have these problems.

Or...

Heidts sells a by-pass valve that goes in line. They claim by adjusting this valve, you can dial back the pressure until it feels right, without damaging the pump.

Anyone tried either of these?

 

Oh , and manual racks don't leak.

 

Word!

 

I have a question, not trying to hijack.
Is rack supposed to be in a staight line, from tie rod end to tie rod end?
Or set either backwards or forwards any?

 

How much is "slightly outside", really, not trying to be funny.

 

Rockable, measure the toe in with a tape as close as you can. The center seam in your tire is close enough for an estimate. What you are describing is excessive toe in. If you are to measure and you have more than 1/8" narrower in the front than the back, then that would be the cause of all this.

I would even go an 1/8 toe out just to see if it's an alignment issue or a pump pressure issue. My experience is telling me alignment is the culprit.


Johnod, there are formulas to figure these things out. But to dumb it down, to a quip the inner tie rod socket lies in a plane between the upper and lower control arm pivots. There are always caveats but for the sake of what we are dealing with right now, the inner socket is slightly wider than the inner mounts of the lower control arm.