Tech: Alignment for modified Mustang II front suspension

Under my 37 Chevy is a real Mustang II front suspension. The donor from back in the day:



From what I can find, the stock width of a MII is about 56”. So I’m assuming that alignment and tracking are all based on that track width.

Mine was modified. First, there’s a 1 1/2” wide patch here:



Second, the ECI brakes kit was used to convert to GM rotors.

https://ecihotrodbrakes.com/mustang_pinto_discbrake_conversions

GM (4-3/4") Bolt Circle - uses 69-72 Chevelle, 69-74 Nova rotor and caliper (or GM equivalents)

MOVES EACH WHEEL OUT APPROX. 3/4"

So that’s another 1 1/2” added to the track width. When I put a tape measure across the rotors, I get 59”



With that as background, I’m getting steering wheel vibration/shake/shimmy when going around bends in the road at speed. This doesn’t happen with low speed, turning corners. It’s 50-60 MPH highway bends and long sweeps. It doesn’t happen straight ahead, only once the steering wheel goes off centre.

Also, uneven wear on the inside edges:




Could the 3” of additional track width be responsible for this? Or is there enough designed in tolerance in an MII to handle this modification?

The other possibility is that the bushings are shot. I don’t know how old they are, it’s possible that they’re from that Ford in the picture when it left the factory. I’m planning a suspension rebuild for spring when I can get out to the garage again.

 

I would check the front end and tires for wear and make sure the toe is correct. Those things will cause your vibrations.

 

When you go to an alignment shop, they will lift the car and inspect for worn or bent components. Better to be proactive and DIY and repair before going.

Most are set up with a modern, computerized unit. Same as the parts store, they need to enter YMM to start. What happens after that is the tech and their knowledge.
What is adjusted is camber, caster and toe. They will also get something that is called Steering Axis Inclination. This is used to check for bent hard parts and frame straightness.It will also measure thrust, which is the rear axle to frame. Remember those old Ford pickups that would dog track going down the road? It should also check Ackerman, which might be affected by your mods.
The tech should have a good idea what to set the car to without the machine's suggestions. The corporate store with low advertised price employing the fresh tech school grad isn't going to have the experience. The old local shop with the older person who has been under the rack for a couple decades will.

Inside tire wear can be a lower ride height, common in rods, which affects camber, the camber itself or worn components. If old parts were found and replaced, the tires will also need to be replaced for best results on the shake.

I could give some generic setting numbers, but trust the tech under the car or go to one you do trust. They know the local conditions (road crown, etc.) and is ultimately responsible for the end result.

 

Tires have uneven wear. I’ll get new ones in the spring. Toe was correct at the last alignment, a couple of years ago. Will need an alignment after the front suspension gets put back together with new bushings.

It’s the change in track width that I’m wondering about. Is 3” change in track width significant? Or no big deal?

 

Last time, we went with YMM of the donor. That may or may not be close enough, but YMM of the car (37 Chevy, no longer with knee action front end, not at stock ride height, no longer enclosed driveline rear and) is certainly wrong.

I have a decent local shop, they don’t assume a non stock ride can’t be aligned like the local chain places.

I’ve never seen an alignment that included addressing the different turning radii of the front wheels, because that’s not something that would normally change. Maybe with commonplace use of wheel spacers and weird offsets now, it is more common than it used to be to run a non stock track width.

It’s possible that I’m overthinking this.

Would you be concerned by a 3” increase in front track width?

 

Track alone will not affect camber, caster or toe.
The wheel/tire is still going to lean in a bit, tilt back on axis and be slightly in from parallel even 10 feet apart!
It will increase leverage on the bushings, springs, ball joints and wheel bearings with the ground contact moved out. Should be within limits, providing it's not much heavier or much wider.
It will also change the scrub radius, which any offset out wheel would do. This would be felt in increased effort at rest, since the tire is pivoting outside the point where the 2 ball joints are aligned and pointing at the ground. For you with the discs spacing out, more like the middle.

The Ackerman I mentioned is all part of the geometry between the axis shown and the steering linkage. It should still point the wheels in the correct direction, but it might be affected due to that scrub radius. This is not a concern because almost every car design does not hold the same steering angle thru the full suspension sweep. This can be seen by the efforts some racers go through to get as little change as possible.
There are books written on this stuff. You could over think this and educate yourself in great detail. I'd suggest rodder style and bolting it together and giving it a try. You can also ask the alignment tech, but unless you measure each point and run it through a computer program to compare results, it's probably going to be a guess too.

 

Looking at the tires, your primary issue is underinflation. Those tires are wallowing on the rims.

Radials are sensitive to Psi, these tires show underinflation, when this occurs even with spot on alignment and settings any slight deviation will be exascerbated.

On radials look at the center blocking rows, they should wear square. Outer blocks can wear unevenly due to driving style/route type.

I don't recall how agressive the Ackerman is on MII.
When you widen an existing suspension(no other changes than width), this changes the ackerman to be less agressive which the makes the car understeer.

If changing the inner pivot point location of the lower control arm, this also creates a change in bump/roll steer with the car. Since you can not readily change the pivot point location of the inner tie rods. You would need a longer(wider) rack in the R&P, or a wider matching rack.

MII has a modern negative camber curve. IIRC every inch of compression = -1° camber gain.
Worn suspension bushings will allow lots of movement under load.
If the chattering is during cornering load on the outside loaded wheel it could be a worn BJ, bushings, loose bj nuts, worn outer tie rod or inner tie rod, or worn rack bushings.

I'd start with inflating the tires to a higher pressure and having the alignment checked while you sit in the drivers seat.

Lowering tire pressure on a radial for comfort is not the best. Radial tire sidewalls, not stiff like Bias-Ply, can vary in ride harshness. Most modern sidewalls are supple compared to radials from a decade ago. Lower or higher pressures don't affect ride quality like it used to.

On a radial street car, especially with smaller/narrower radial tires, don't be afraid to try out the tire pressure into the 40s, if the tire can handle it even 50psi can decrease tire wear while maintaing good grip and cornering.

If there is no obvious bushing wear, increase your tire pressure 5psi, go for a ride and see if there is a marked improvement. Rinse repeat. Just make sure not to over inflate your tires(look for the max(cold) rating of the tire.

 

I bought an aftermarket cradle that was 2" wider than stock (formerly Horton Hot Rods and now Welder Series out of Ontario Canada). I used the factory upper and lower control arms but instead of the factory lower strut rod, I used an aftermarket item that bolted in place of the strut rod, essentially turning the factory lower control arm into an a-arm (pictured below). Going off memory, I used wider Ford Fairmont tie rod ends on the factory manual rack & pinion to make up for the added width. I also used a kit that allowed the use of GM 4 3/4 rotors but don't know if that affected the overall width.

I put a lot of miles on that combo and never had any tire wear issues so I would suggest that the widening of your factory crossmember is not to blame as long as you are still able to align the front end. As for alignment, I did it with the help of my father in-law, using a original Ford manual for specs and the father in-laws alignment tools.

 

If I remember right, aftermarket kits that were wider than stock came with rack extenders to keep the pivot points of the rack in the same relationship with the suspension pivot points. This would not include the extra offset of the brake kit.

Gary

 

My aftermarket cradle was 2" wider and did not use rack extenders, it used slightly longer tie rod ends from a Fairmont. I understand that not widening the rack itself is not technically the best solution (on paper) but I can say that it did work flawlessly for many miles.

This was not my solution, it is what the manufacturer of the wider cradle/crossmember said should be done and what I did.

 

Just curious....why did you widen the MII suspension to begin with? Wasn't it the same as the Shivel-lay ?
6sally6

 

I have had the best service out of Mustang II front ends by increasing the caster to about 4 degrees, and reducing the toe in to 1/16" or less. This is with rear struts, front struts, A frames, or strut eliminators on stock width or widened crossmember.
One thing to remember is that this front end was designed for bias ply tires so the stock setting seldom work. Also with rear struts the toe in increases as the car rolls down the road. I have used factory crossmembers, widened factory crossmember, Progressive crossmembers, Weedeater crossmembers, Welder Series crossmembers, , Fatman crossmembers, home made crossmembers, tall spindles, GM spindles, Horizon rear steer racks, Fox body racks, Thunderbird racks they all work about the same if you get them tuned right.

 

I’m running the tires at 32 PSI. Max cold PSI is 35, IIRC.

The steering rack is manual, it and the inner tie rod ends are a couple of years old. I had worn inner tie rods, which are NLA for the manual rack as a separate item. Had to replace the rack, which comes with inner tie rods.

The outer tie rods are not MII. They’re longer, making up the difference in the stretched crossmember. I see a reference to Fairmont tie rods being g longer in another post, so that could be what they are.

Having no idea how old the rubber bushings are, I figure they’re probably due for replacement. It’s possible that it’s just wear and tear, and some new parts and an alignment are all I need.

If the only expected change from widening the suspension is an increased tendency to understeer, then that’s no big deal. I’m not expecting autocross steering here.

 

I didn’t. Bought the car with it this way.

I assume it was done to better the track width and wheel position in the fenders where they wanted.

 

There are a few differences between 71 Pinto and 74 MII. Pinto was bias ply, by the time of MII the car had radials and a diffeent weight. Ford has never left a given chassis alone, unless you have the numbers in front of you it can be hard to see. Big parts may be the same, but mounts and angles can be slightly different. And probably unknowns from Ford, at this stage, would be shock valving and bushing durometer. These minor changes can greatly affect handling. I would not be surprised if Ford alignment specs for a 74 MII are different from a 78 MII.

Try bumping up the pressure to 35 and see how the car handles and how the tires wear.
What make/model/size/age are the tires.

Inner tierods are shared with the later 80s Mustang.
There are two types, the Ford built and the Thompson(TRW) racks. Thats the difference, at the top of my head I forget what the diffeence is.

Most likely, Pinto/MII outers are stubby.

Old bushings that are checking and crumbling will need to be replaced, inactivity of the bushing is what will kill a rubber bushing.

 

Just to toss another thing to consider/watch out for, Ford did the TRX mess in there too, which probably has another set of parts.
https://www.roadandtrack.com/car-culture/a46076617/michelin-trx-metric-tires-infamous/

 

TRX was used on the Fox Chassis 79-84 Mustangs, not the MII, and the posted tread pattern is definetly not TRX.

Found a set for cheap and slapped them on my Fairmont. Considerably better than the stock 14" blubber, and tighter than any 15" wrapped 10 hole/phone dials from the eighties. Ended up selling to an overly enthusiastic TRX Mustang owner 100 miles later.

TRX was designed to fail as it would never gain traction(hyuck hyuck) in the mass market. Only die hard TRX enthusiasts in the Mustang, Peugeot 505, and the poor Ferrari 308 guys would ever keep that going. The unique tread pattern was totally different, but it was cheapend by its use on common BFG T/A.

Back to MII suspension woes and such.

 

Yes, but you mentioned later M words and the Fairmont, the first fox. Ford then seemed to feel the customer was the beta tester and made a lot of strange variations. Just wanted to warn a fox isn't always the same!

 

Tires are Hankook Optimo H724. P195/75R4. Installed June 2017, at 69,435, today they’re at 98,824 miles.

The inner tie rods I could get were all the same. They are apparently for the power rack. They’re the right length for the manual rack, but the thread size is wrong. I can’t find my notes on it to get the details, only that I bought several sets from several suppliers that claimed that they would fit, only to find that they don’t. I even tracked down the manufacturer and called them, and they confirmed that their tie rods are only for the power rack. I don’t know who is making the ones that come with the manual rack, but that was the only way I could get them.

If they’re the same as 80s Mustang, that would be nice to know. I don’t expect to wear out the rack, but I could see needing tie rods again some day.

 

It bugged me not being able to find my notes, so I looked for inner tie rod end info. I think the difference I ran in to is that all of the available rods I could find in 2017 were for the power rack, and have a 15/16”-20 thread on the rack end. See Delphi TA2209 for one example.

The rods I need, for the manual rack, are 1”-20 threaded. I found a web site purporting to have the manual rods available, but the price is “internal database error”, so this may not be completely reliable. I just know that the available rods would not thread on to the manual rack.

The later Mustang rods appear to be the same as the power rack rods, with the 15/16”-20 thread.

 

This is a guess on my part, but may be some food for thought.
Widening Track
"It increases the front scrub radius, which leads to more steering effort. Having a wider track also affects the steering feel and kickback. With more scrub radius, there’s more kickback, meaning your steering will be more sensitive to directional changes every time it hits a pothole." (That was an internet quote)

The video below discusses the Ackerman Principle. Here is my best guess.

When the track is widened, the front wheels now need to follow a different path than they did originally, so the amount the wheels turn needs to be different. Possibly a longer or shorter tie rod arm will correct the amount each wheel turns in relation to the other.Again, my best guess.

www.bing.com/videos/riverview/relatedvideo?q=What%20does%20changing%20track%20width%20do%20to%20the%20steering&mid=DE42FA9151F28DDDF1CEDE42FA9151F28DDDF1CE&ajaxhist=0

 

Well that answers one problem.
Optimo whitewalls are probably one of the best looking ~1" whitewalls, very crisp and do not discolor like others, pretty durable as well.

That's the only compliment they get.

Rated 500 A B speed rated S(112mph) these tires tend to be on the skinny side when it comes to tread width. Those 195s are more like 175s . You stated 35psi max, last pair I had were 44psi max.
Problem is the tread is narrower than it should, imo these tires are easily over driven which causes them to heat up and wear excessively. IIRC these tires have a 75,000 mile warranty, you'll use it.

195/75R14 is now a hard to find P tire size, especially if you want a whitewall. Plenty in LT. If you can switch to 205/70R14 that would open up a lot more P tire options. Don't knock the generic tire brands, some of them are pretty good especially for the price point.

What I was thinking of Ford vs TRW was with power steering racks. There is a difference with threads, but it has to do with hydraulic lines. For whatever reason the TRW PS racks use a different thread for the hoses. They both use the same inner tie rods, which are different from manual racks.

Manual racks were made by Cam Gear Ltd of England. They ceased operations in '83, which would explain why Fords last year of a manual rack in a Mustang was '84.

Flaming River, afaik, is the only company that currently sells new inner tie rods for Ford manual racks.
Unlike the PS racks, the manual rack is drilled and tapped. Requiring this style of inner tie rod...

A stock replacement rack is ~400, these inner tierods are ~80 each. I understand why some folks balk at simply trying to replace the inners and just replace the whole rack. If you've never done it, it can feel sketchy to do. But it is a simple enough job.

For anyone wondering,
'Why not simply put a PS rack in a MS housing?'
Can't.
PS rack is a larger diameter to allow piston area for the hydraulic fluid to push on. Since a manual rack doesnt need or have piston area there is no provision for it.

 

I’m running the black side out, don’t care about them having whitewalls. Not stuck on the size, or brand. These are what the tire shop recommended (a friend owns the shop). I could be wrong on the max pressure, but it’s cold out right now and I’m not going out to check. I’m not thrilled with their wet performance, they tend to slide easily in any rain or wet pavement.

On the tie rods, the Flaming River ones are completely wrong for what I was looking for.

The power rack inner tie rods are like these:



The manual rack tie rods look the same:






But note the thread difference on the rack side. Close, but not the same. I’m not sure that this Rare Parts place exists, and actually has these in stock. I didn’t find them when I was looking for them when I needed tie rods to actually fit the rack I had.

Even if they do exist, a whole new rack with rods from Rock Auto is less than just the rods.

 

That’s basically what I’m getting at. The suspension is designed for a track width, and to have the wheels each follow the correct path through a turn.

Theoretically, changing the track width is going to put the wheels outside the designed path. That could be why I’m getting chatter on long sweeping turns at speed.

In the real world, is a 3” change in track width enough to actually matter?

 

Based on the drawings below, I would guess "yes". They will at least provide you with some food for thought. The Ackerman diagram is for a straight axle, but I think the idea of V line passing thru the steering arms is what may be causing your issue. Again, purely a guess on my part, but I think this is where I would experiment first.

Don't know why the picture posted twice. But if you think about the straight axle cars, they get bump steer and other issues just from small variations when trying to set them up properly.

 

@MAD MIKE Good info. I agree that a fresh set of something without the panache of the top tier tires is better than 5 or 10 year old super stuff. Tires age and the tech grows!
@ekimneirbo I am having that happen too. In my case, the mouse is getting worn, causing double clicks. Easy enough to edit one out. Highlight and delete.

 

Have I got this right? The crossmember has been widened by 3" but the steering rack remains as previously, with lengthened arms making up the difference? That being the case the intersection of the inner pivots will be out of whack so bump steer will be an issue. Given that bump steer is toe change arising from suspension movement, besides possible I'll effects on handling I'd suspect tire wear could be an issue too?

By coincidence I recently saw a YouTube vid of an alignment on an outlaw street racer. The interesting thing was the alignment rig that also checked bumpsteer by raising the front of the car with the measuring equipment working in real time. Never seen that before! Didn't know it existed!

Chris

 

Perfect............Thanks a lot.

 

The crossmember is widened 1 1/2”. The disc brake kit moves the wheels out an additional 1 1/2”. So the track width is 3” wider than a stock M2.

For Ackerman purposes, the pivot points are moved 1 1/2”.

The other 1 1/2” is scrub radius. Steering effort is fine, so I’m not concerned about scrub.

There might be some bump steer, but not enough that it has been a problem.

Really the only thing that I’m concerned with is the chatter vibration on long sweeping turns at speed.

 

Thats what I was trying to get at. With the wheels moved out wider, the V line going thru the spindle arms will put the intersecting point behind your rear wheels. That is going to affect how the front wheels track. They will not be in sync with the rear wheels and the amount of turn will be wrong. I would think that the steering arms need to move inward till the V lines return to the original intersection point. Again, just my opinion..........