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Calling all alignment experts

4K views 34 replies 9 participants last post by  Huskinhano 
#1 ·
I took the advice from last year and got the Longacre alignment tool for measuring caster and camber. Now that its warm here in the NE I got a chance to try it out. This is a '66 Mustang that seems to wander a bit above 55 MPH on the highway. I leveled the car the best I could using a level spot I have in my garage and with a set of home made turn plates, so I'm pretty sure the starting point was a level car (took me 3 hours to level it). The first question I have with the measurement process is they don't seem to be as repeatable as I thought they would be and were as much as 1/4 degree - maybe that is within the margin of error. Anyway, here are the results:

RF - Camber ~ -3/4 degree, Caster ~ +1 1/8 deg to +1 1/4 deg
LF - Camber ~ -1 degree, Caster ~ +1 1/4 deg to +1 1/2 deg

So what numbers should I shoot for and the million dollar question is given the above, what changes should be made on the RF and LF sides on each of the upper A frame bolts to achieve the above. I don't know what shims are in there now so this is more a question of what deltas to make to what is already there. That's where the alignment experts come in:nerd:
 
#3 ·
No Arning drop done or planned at this time. Just trying to get set to the right specs with original setup. I did find my notes on what shims are current in place:
RF: rear bolt - Two 1/8" shims = 1/4" total
front bolt - Three 1/8" shims = 3/8" total

LF: rear bolt - Two 1/8" shims + one 1/32" shim = 9/32" total
front bolt - Two 1/8" shims + one 1/32" shim = 9/32" total

So given what was measured in my first post, the exercise for the alignment wizards is to figure to what needs to be changed to get closer to spec.
Thanks for any inputs.
 
#5 ·
Thanks. I still don't get the shim stuff. Given what you posted for specs how does that translate into what shims should be added or subtracted to current set up? Determining what shims to add/subtract and how this mutually affects caster and camber has me somewhat confused on how to calculate the change to get to those new specs on the first try.
 
#6 ·
Add shims under the front bolt and/or remove shims at the rear to increase positive caster.
Adding shims under either the front or rear bolt will increase positive camber.

So....

RF: rear bolt - Two 1/8" shims = 1/4" total (Remove these two)
front bolt - Three 1/8" shims = 3/8" total (Add 1/8" shim)

LF: rear bolt - Two 1/8" shims + one 1/32" shim = 9/32" total (Remove the two 1/8" shims & replace with a 1/32" shim)
front bolt - Two 1/8" shims + one 1/32" shim = 9/32" total (Add one 1/8" shim and one 1/32" shim)

Adjust toe-IN to 1/8".
 
#8 ·
Not if you want to obtain any significant caster angles. I think the real concern, here, is stress on the bolts and the shock tower as they pass through at an angle due to the difference in washer stack thickness. Over the years I've seen many a Ford AND GM with quite a difference between front and rear bolts. Finding a thick 1/2" washer and milling one side so it resembles a wedge and installing it under the control arm mounting nut would see to be the appropriate "fix", but I don't believe it to be necessary. I think, if I were to venture a guess, that there are darn few '65-66 Mustangs out there with a sixteenth, or less, difference between bolts.
 
#9 ·
Do i have this right? - For the RF example where the caster is currently +1.25 degree

RF: rear bolt - Two 1/8" shims = 1/4" total (Remove these two)
front bolt - Three 1/8" shims = 3/8" total (Add 1/8" shim)

By doing the above (net change is adding 3/8 inch to front bolt), the new caster angle will then be:
+3/8" change = +12/32" @ 0.5 degree per 1/32" = +6 degree change + original 1.25 degrees = 7.25 degrees caster when done
 
#10 ·
Get the Ford shop manual. It spells out exactly how much a shims is worth and how to adjust and center the steering wheel with toe adjustments. Off the top of my head I believe a 1/32" shims on one control arm stud will change caster by 1/2°. A 1/16" shim on both control arm studs will effect camber by 1/3° degree.

If you don't have this info, it's going to be very frustrating and time consuming. Use black plastic 3 mil contractor garbage bags folded up under the tires. This will allow the tires to float on the floor and keep the suspension unloaded from the tires sidewalls. Once you understand what's going on it should go a lot quicker.
 
#13 · (Edited)
Speaking my opinion and not as an expert I would say you want to stay in the 3-5 range ideally. When you're at zero caster when you turn the wheel, you're pivoting on one spot only. As you add caster your tilting the spindle back and as you turn the tire your actually climbing the outside of the tire and lifting the weight of the front end of the car. The more caster, the more weight and the less leverage you have to lift the weight. It's that weight that keeps the tires straight. The more caster the quicker the turn in when you turn the wheels. My opinion on the amount of caster to run is what feels best to you. On the low end of the caster it will be easier for parking if you do a lot of parallel parking or U turns. I have 4° and like it. I think about trying 3°. I think you'll be happiest with 3-4 range. Keep in mind with the shims as you add a shim for caster, you're adding a small amount of positive camber too. You can offset by splitting the difference. Instead of a 1/16" shims on one stud, add 1/32" to one stud and remove 1/32" to the other. You will get your caster but not effect camber.

At the end of the day I think mechanical limits are going to decide and I think that is exactly what the Shelby specs are. I don't feel they are some magical, ideal setting just a compromise between caster and camber on these cars in stock form. That's why I built my car with a camber kit, adjustable struts and control arms. You seem to be really interested in making the car drive well. I truly think you're doing yourself a big disservice in not doing the Arning drop. It will totally transform the car along with some caster as you have planned.
 
#16 ·
These are the things you're looking at with really big positive caster
numbers.... from the obvious to the not-so-obvious. (SLA suspension)
- Increased steering effort
- Center of gravity is affected
- Caster shake/instability/wobble
- Increased tire scrub
- Car feels unsettled and squirrely at very high speed (faster than
you should be going around the public)

Seems like I'm missing 1 or 2 as well.
Your positive caster numbers would have to be pretty big though to
see these issues, particularly those at the bottom of the list.

Some of the Fox Mustang racers would run like 8 degrees on McP strut.

ex-Global West GM
1991-1995
 
#17 ·
GT289, you being in CA I'm certain you and Mike Maier have crossed paths. Maybe a couple different schools of thought on this subject, but a few weeks ago, I visited Mike's shop and he took me for a ride in a customer's '65/'66 FB he had literally just finished installing his MOD1 front/rear/steering kit. If I remember correctly, his initial settings were something like -1 or -2 camber, +7 caster, 1/8" toe in. He hadn't dialed the car in yet so it had a little scrub on the left rear. However, the car was extremely nimble and very stable at speed. He could littlerally point the car on entry with one finger on the wheel and the car just went, set, and smoothly transitioned through a turn. Quite the opposite of what you suggest. Again, I'm sure there are several schools of thought on these items, that's just what I experienced in this car with that setup.
 
#19 ·
I spoke to Mike last at the Knottsberry show. When he was working with
his Dad in Hayward we used to occasionally sell them parts. They liked
our subframes until they came out with their current design, I seem to
recall. (maybe our MC bars too, the 90's was awhile ago)

What you're seeing is different setup for different arm geometry would be
my guess. You know it's different because of the static camber numbers.
They generally ran more negative numbers. The high caster numbers do
affect the static camber you're able to achieve. He's doing something else
too, 7 positive caster is a crapload on SLA.
(maybe different SAI through a different spindle?)

You can search the internet and get some pretty good direction on the
various topics, including this gem I found at CornerCarvers.......
"Finally, large amounts of caster and scrub radius can in some cases produce
really disagreeable behavior in the steering, in the form of various types of
oscillation. Any runout in the tires or pulsation in the brakes will be felt more
in the steering. I have had clients running large caster settings on stock cars
report steering shimmy at lower speeds."

The relationship between camber and caster involves trigonometry. All the
math in the world will say something obviously but HOW DOES IT DRIVE?
You'd get the basic design from math but then have to trial and error it
to make it drive well....... Mike obviously spent some time doing just that.

ex-Global West GM
1991-1995
 
#18 ·
Lots of different input here, all good info. When I originally started this thread the whole camber/caster shim thing was something of a mystery but now that there has been lots of responses and I did study the shop manual I think I now understand whats going on. My original complaint was the car not being all that stable over 55 mph. There is no abnormal play in any of the suspension linkages so I'm assuming the ~+1 deg caster might have something to do with it. I will try something in the mid +3 degree range first and see how that goes now that you all have convinced me I can do this myself in my garage with the Longacre tool and several home made accessories.
 
#20 ·
Not trying to hijack the thread but what would you suggest for alignment specs on mostly street driven 67 Mustang with Arning drop and manual steering with 265/50/15 tires all around.
I just bought a Fastrax alignment tool and will be my first attempt on doing my alignment myself.
 
#21 · (Edited)
Something in the -.5 Camber with +2 to +3 degrees of Caster and 1/8" total toe. Install a 1/16" shim in the front bolt of the upper control arm on each side. This will give you a little more Caster without having to pull the lower control arm as far forward with the strut rod. I would not get crazy with the Caster with that wide of a front tire.
 
#22 ·
Ok, back to the '66 Mustang. I'm ready to change the shims around based on the measurements made and the corrections added in. I jacked the car up with the jack under the lower control arms and put jack stands under the front frame rails back where they extend from under the front seat. With the jack then removed from under the LCA I discovered that I cannot get at the UCA bolt heads since the UCA is now fully in its lowest position. So I'm assuming I have to jack the car back up from under the LCA so that the spring is now compressed sort of like in its normal driving position and the bolt heads now accessible. The question is - if I now loosen the nuts on the other side of the shock tower am I supposed to pry the UCA out enough to loosen up the existing shims and make room for the new shims? It seems like there is going to be a lot of pressure on those bolts now that the spring is compressed. I'll wait to hear before proceeding. Thanks for many inputs.
 
#28 ·
I would say Shaun's come preadjusted for 3*. When I put his suspension in I used a level against the lower arm and marked the floor with the stock struts. When I ut the adjustable struts in I adjusted them so the level was in the same spot. In theory the adjustable struts were the same length as the stock. When I measured caster, I had 3* on one side and 3.5* on the other. I adjusted the 3* to 3.5*. Currently I run 4* but I would 3* would be fine.
 
#29 ·
Making progress on my alignment experience. I now have the shims in for the first iteration. It was a real trip loosening the two UCA nuts on each side of the shock tower. The car has the thermactor exhaust stuff so there is not a lot of room to get a wrench down there however I managed. The best I can do is get a 12" long 3/4" box wrench on the nuts however there is not much room to swing the wrench when tightening. So what do you folks do to torque a nut to spec if there is no way to get a torque wrench on the nut?
 
#34 ·
Update - after adding a total of 1/8" shim change on both sides to increase caster (-1/16" on rear UCA bolt and +1/16 change on front bolt) the caster changed from approx. +1.25 degree to +2.5 on both sides. The spec implied that a total 1/8" change should have increased caster by 2 degrees (0.5 degree for each 1/32" change) so I was hoping for something in the 3 degree range however I got a little more than half that change. I adjusted toe to 1/8" using the fishing line method (well it was dental floss not fishing line but that's all I had). I took the car out for a test and it was 100% better above 60 MPH now - no constant left/right correction needed to keep going straight. And to boot the car now has no tartar between its teeth.
 
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