Tech: Alignment for modified Mustang II front suspension

@ekimneirbo , the V you refer to, are you suggesting OP get the Ackermann closer to correct?

 

Yes.

I have no idea how to do that right now. But I’ll look at it when the weather makes garage time possible again.

 

Yes.............

 

Depending on whether the steering arms are made onto the spindles or bolt in place, I would guess either a spacer or heat and bend. A string from the spindle to the center of the rear end would probably show you how much movement is needed. The point on the rear end where the lines converge would be the centerline of the rear axles.

 

Kanter and P-S-T offer suspension/steering components. 'Rare parts' I've always thought of as a broker.
Their pricing seems to have an added 1 or 0 compared to others.

I think we box ourselves into thinking such devices are complex unobtanium for the regular joe.

Bumpsteer Gauge

Two Franklins + shipping and****embly you can have your own.

Oooooooo...
The problem with bumpsteer is, you usually don't know you have bumpsteer.

Driving down the road hit a bump you won't notice. It's when things get serious and the car doesnt go where its been directed might indicate a bumpsteer issue. But there are plenty of cars from the factory that have bumpsteer on purpose.

As for ackerman...
No street car(sedan) has, or really should have, 100% Ackerman. On paper it may seem nice, initially, wheels stay on proper congruent arcs of travel. However in the real world, the inside tire will be unloaded at speed, using it to help rotate the car safely is a different matter.

100% ackerman at speed gets sketchy, the car becomes very sensitive, sure the tires are pointing in the same directions for congruent arcs of travel but this does not mean stable, fast or both. Bump(roll) steer can be used to change toe and thus steering angle kinmatically.

Take a look at some fast race cars, they will have visible anti-Ackerman

But most of this conversation is theoretical until the car is weighed(driver + 1/2 tank fuel), bump steer checked, some math is done... after fixing any worn or broken parts of course.

The increased tierod length without increasing control arm lengths(not track width) will cause toe out in roll for both tires in droop and bump.

Does this mean it's a problem?
Unknown at the moment.

What is the suspension motion of the MII?
What is the typical MII front tire wear?
And what were the intentions of the MII suspension engineers at Ford in the 70's?

Your typical mass produced sedan, including muscle and pony, will have various suspension motions that may seem 'wrong' without understanding the motions as a whole for a given vehicle.

I'm still of the opinion that the tires are partailly to blame. Undersized, hard bricks, not David's fault... under inflated... maybe David's fault.

Most weird or undesirable suspension motions are to keep the vehicle stable and keep the average owner/operator from putiing the car into an uncontrolled situation during normal driving.

 

Back in the 1980s, when a Mustang II front end was used in an early Chevy with a stock Mustang II crossmember the springs interfered with the frame. It was typical to widen the crossmember 2" to clear the springs to the frame. To do this we used a Mustang II rack with Fox Mustang tie rod ends. There was no big effect on bump steer.

As far as length and mounting a Mustang II rack and a Fox body Mustang rack are interchangeable if you use offset mounting bushings in the Fox Mustang rack.

You might get in touch with Welders Series welderseries.company.site they make wider kits for the Mustang II front end and might have some suggestions

 

I have done a few of these early Chebbies , installed with OEM Muustang 2 crossmembers . I basically notched the outside of the Chevy top hat frame and raised the crossmember up to where it needed to be and welded it in place adding gussets as needed . One thing that was very important to installing the crossmember was keeping it level with the floor or ground at the ride height you want . I had it down to a science . I did 3 different cars for the same owner . I would take them to be aligned to factory Ford specs , and return the finished product , not one handling or tire wear issue . The strut rods were tough to mount until I determined make a bracket and bolt it , rather than weld to the thin frame material .

 

Sorry for the delay in getting this thread up to date. It took longer than expected to get everything done.

First, I rebuilt the front suspension with all new bushings, ball joints, wheel bearings and seals.



And, of course, ran in to difficulties. The Delphi lower bushings I ordered from Rock Auto didn’t fit. They’re .10” too small diameter. RA replaced them, no charge, which caused a delay waiting for shipping, and now I have two sets of bushings that don’t fit. RA refunded, and I re-ordered and got the Dorman bushings. Those fit fine.

The upper and lower bushings were destroyed to remove them (hole saw), so I can’t say if they were worn out. But the strut rod bushings were definitely hammered:




While waiting on shipping, I painted the arms and strut rods. A friend with a press helped install the new bushings.



The alignment shop has a backlog, so it was a couple weeks before I could get in. Meanwhile, I did a string and tape measure alignment to get it driveable.



At this point, I still had the same steering wheel vibration, but the car did seem to be less rattled by bridge expansion joints and railroad crossings.

I ran the tyres up to 40 PSI, with no change.

Once the alignment shop could get me in, I got:


The slight left/right difference was recommended for road crown compensation. I think I should have gone with more caster, but that’s going to have to be ok for now.

This also did not resolve the steering wheel vibration.

Last stop was tyres. As you can see, these were worn out, and I believe worn unevenly from poor alignment. The Optivo tread pattern is NLA, so now I have a pair of Hankook Kinergy ST H735.

After getting these installed, the vibration is gone.

I’m running 40 PSI in the front now. These new tyres are max 50 PSI, so I may run them up to 45 or 50, see what happens.

 

Why such high tire pressure? It seems 30 to 35 psi is more common and would give a softer ride.

Your work, although it took awhile, should provide years and miles of service.

 

here's an old guy test to make sure you don't eat a set of tires,..

run your hand across the top of the tread .... back and forth.. it should feel smooth going both ways... if your hand feels a sharp edge going in and a smooth edge going out the alignment is starting to eat up the tires..

 

I would agree that 40 is pretty darn high. Make a few chalk marks across the tread and go around the block. If it's worn evenly across the whole face, okay. But I have a feeling it's going to be scuffed off in the center and not so much at the edges, even though Radials "don't grow".
I may get better MPG, but ride harsher and not grip as well, along with that tire wear.

 

another thing with the Mll.... cutting coils or too soft of a spring makes the ride height up past center.....you can check this with the spring out to get ride height...put a rim on and cycle the suspension up and down and watch for neg camber.. if the lower arm is past center every bump puts it in to neg camber.... that starts getting worse as it scrubs the inner tire tread.. and tires end up looking like yours...the other thing is the adjustment slide bolts... put too much weight on the front and they will slide..

 

tire pressure is relative to carrying weight, as is the tire max pressure on the side wall... lets say the tire says max load 2200 lbs @ 50 psi so x 2 = 4400 lbs x 2 8800 lbs.... go to the truck stop and weight each axel... weight shows 2000 front axel and 1800 rear axel... tire man. have a chart.... lets say it says 35 psi will carry 1500 x2 =3000... sooo... you need the weight you will carry on the tires to get correct tire and air pressure

 

Tire pressure with new radials can be changed(grossly) without affecting tread wear much.
These are not like bias plies where the whole carcass is a uniform reinforced donut balloon.
Sidewalls are much softer and even with the high falutin big wheels even those rubber band tires can have more cushion than an old huge sidewall BP.
There's a reason older cars have very long and low lb/in rated springs.

But most important is how the vehicle is driven.
Tire tread will tattle and adjustments can be made to net more even wear.

 

It’s now the end of hot rod driving season here in Illinois. If all goes well, I’ll mess with the pressures some more next year when driving season returns.