High Speed Shake & Rear Susp. Alignment

AKimball92

AKimball92

True Classic
I attempted to do a cruise last weekend but as soon as I got onto the interstate and up to speed the car began to shake. Badly Shake!!!

I have done suspension work on the car, front and rear. I did not align it prior. It tracked straight so I spent my time elsewhere. After this I went to do a string alignment and noticed front right tie rod jam nut was loose and too much toe inward. 🤦‍♂️ String alignment to about .75" outboard of the front edge of the rear wheel and torqued down helped a bit. Very slight pull to the right so slight adjustments needed still, maybe a quarter/half turn after a very straight entrance to the garage.

Hit the interstate and the shake isn't as bad and now I feel the shake come from the rear as well.

Can someone help in identifying "proper" string alignment for the rear? Pics below show two different values. Severely sorry for the upsidedown pics. I ensured the phone was right-side up for being sideways. Its correct in the files and media viewer on the computer. 🤬 (this happened last time)
IMG-0830.JPG IMG-0831.JPG

If the alignment doesn't fix it I will take the wheels for another balance. Two were done by someone I trust, the man who does the wheels and alignments for Ford Performance. The shop hand that did the first two didn't know the wheels were directional with the standard Federal V tread design...
 
The string method is the same front and rear. Same strings.

Basically the string method is a box around the car, at the front and rear there is a bar with the strings running from bar to bar at the same distance apart on each bar (at least 6” wider than front and rear track of the car). The strings are set so that the distance from the center of the wheel to the string are equal on the front axle and then the same (but likely different dimension) at the rear wheels. The strings need to be set so they are at the CL of the axle above the ground. The best situation is when the bars are suspended directly from the car so if you need to move the car the strings relation ship doesn’t change

Toe is measured from the string to a landmark on the front or rear of the wheel or tire (you just need to be consistent, I choose a feature on the tread near the centerline of the tire) and then to the same landmark at the rear of the tire. The difference between the two measurements is 1/2 of the intended toe. Same for the wheel on the other side. Same process for the rear. I use a set of calipers or a metric steel rule to measure with and use monofilament for the string to make measurement easier and more consistent.

The difficulty with an X is it is so blasted low so getting to the adjustment (particularly at the front) is difficult. The other issue you get into is settling the suspension between adjustments and not disturbing the strings.

I have considered making a platform for each wheel elevating the car to make it easier to reach the tie rods with aligament plates. Hard to justify when I rarely need to adjust my alignment.

I designed a set of additive printed parts to take standard square aluminum tubing to suspend the tubes from the car but haven’t printed them yet. I will try and dig the file up.

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One Pair Aluminum Turntable Wheel Alignment 360° Rotating Turn Plate Table 4 Ton | eBay

The plate holds up to 2 ton each. Capacity: 2 ton each. Table Rotation: 360° Degree. Table Height: 47mm. WARNING: This product contains progesterone, a chemical known to the State of California to cause cancer.
www.ebay.com
3142E696-A20B-4162-82F8-026348A17D4A.jpeg


Bernice’s set up is the thing to die for, look for her post on what is the absolutely right way on how to do this.
 
From some yeas ago. The entire set up is portable. We take it to the track, set it up, do testing, tweak the car..
It's always a trade-off. This was the LeMons car from the white-red polka dot days, and yes it's all adjustable.


LeMons X1:9 on chassis rig.JPG



Strings at Ferrari F1.
Ferrari_String Aling.jpg



Bernice
 
Start with zero toe in the front, slightly toe in on the rear. If you're measuring at the wheel's rim, try about 0.050" to 0.100" toe in rear.
Get the toe set wrong, it will destroy the tires.

Oh, toe must be adjusted with the tires on turn plates (could be as simple as two sheet of steel with grease between them, crude but sort of ok) or some device that allows the tire-wheel to move with the adjustment. If the toe adjustment is done with the tire on the ground, loading the tire by adjustment will NOT produce a toe setting that is anywhere near as measured due to the elasticity of the tire. Be aware if the wheel is bent or have a non-uniform surface for measurement, it will affect the toe measurement.


Bernice
 
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Andrew, if you were using the rear wheels to set the string, it won't work unless the rear wheels are at zero toe which they probably aren't. If you have rear toe in then string lines set off those wheels will form two strings verging towards each other. I have always wondered what the reference points are to set the strings parallel to the body on an X. Are the bottom pinch welds on the rockers parallel?
 
First, its important to note that a severe shake isn't caused by an alignment issue. Shake is typically caused by loose, worn, bent or otherwise damaged parts. Any part (ball joint, tie rod end, control arm bushing, wheel bearing, etc...) that is used to control/locate the upright, if loose or worn will enhance a vibration or shake as it will allow the oscillating frequency more amplitude. Therefore, the first thing to do is carefully inspect all of the suspension components to identify any slop and fix that first. Also check the hub and wheels for runout, and the wheels for balance.

Another note on X1/9 alignments. For street alignments I NEVER recommend zero toe. Both the car and the tires want the slight preload that comes from a touch of toe (either in or out). I setup my street cars with 1/8th inch toe in on both ends.

The Hub Stands that Bernice posted above are very nice. I like them, especially for doing a base setup. Hub stands and Smart Strings are very popular for use at the track to do racecar alignments. I like the hub stands because they allow easy access to the adjusters (especially on my car, which are hard to reach) but they take longer to setup than the smart strings.

I should write a book about DIY alignments. Its not easy to setup that first time and there is so much bad information out there on alignments.

When setting up the strings you need to ensure that you have reference points at both ends of the string anchors. That is the strings need to be parallel and to achieve that actually takes some effort. I have marked a reference "square" on the floor of my garage for easy setup. To setup the strings they should be the two sides should be the same length and (as noted parallel). To verify this measure the cross distances between the ends. Of course that's not easy to do with the car in the way. Once you have the strings parallel measure the distance to the center of the spindle, not the wheel. You want that measurement to be consistent on both sides. Note that the car's track is not identical F/R so that must be accounted for. Now you have the strings setup and you can take your toe measurements.

If you base your string positions off the car you are making a BIG assumption per the string's position and you'll get all of your alignment specs wrong.

Its also important to note that the wheels of your car are likely NOT where they are supposed to be relative to the body and each other. This is due to manufacturing tolerances, bushing wear, rear control arm shims, caster shims, etc... You can take measurements to determine if the wheels are square and where they are relative to each other and the body. It takes time and effort but if you want a good alignment (on racecars this is critical) its worth the effort.

The turn plates posted above are very nice. I use similar plates often but in my own garage I use a pair of floor tiles with a layer of grease between them. They work perfectly. You can do a lot with them if you think about it. I use them to square the car between the strings, jacking and repositioning if needed. They do a nice job of allowing the suspension to settle too. I can even use them to take measurements to calculate caster.

SAM_3431.JPG


SAM_3432.JPG


SAM_3433.JPG


SAM_3434.JPG
 
BTW, the string supports for that set up is made using two 1" dia, 0.083" wall, 2024 T3 aluminum seamless tubes. These are precision cut to length with grooves at 1" intervals on both ends for the string to locate on. The grooves are made on a lathe to assure groove spacing tolerance is no more than 0.003" difference between each groove with both alignment tubes matching to 0.003". It is crucial both tubes match as the rectangle you're doing alignment with must be accurate and precise.


Bernice
 
Several years ago I saw a neat "DIY" alignment setup while traveling through Europe (I enjoy stopping at local automotive businesses to see what's going on in other parts of the world). The basic principle is the same as a string alignment, but instead of strings it uses laser pointers. There were little "placards" or cards attached to each of the four wheel centers for the laser beams to hit. The grids on the cards were calibrated to allow quick measurements. Lasers point not only front to rear but also side to side to get it all square. This enables complete alignment (caster, camber, toe) of all four wheels without a lot of setup changes. Is it a perfect solution? Perhaps not, I'm sure there is still some room for error compared to other systems. But for a home alignment on a street car that is not a daily driver (e.g. a play toy), it is likely much better than what most alignment shops will do (at least in my experience*).

When I returned from my trip I did a lot of research on the system I saw. Turns out there were a couple of very similar ones available in Europe but nothing like it in the US. Unfortunately they were expensive and shipping killed it. So I set about designing my own version, taking what I felt to be the best aspects of each one. For the most part it is something I could make myself very inexpensively. In fact it could be produced and sold for under $100. However to be as accurate as possible a couple of the components should be done by a proper machinist. I found a guy that was interested in making the full system and producing them for us to market. However he never followed through. I've since seen a much cruder system that has a few of the same elements as my design (I believe the same guy was involved in that one). Unfortunately it has several design flaws and would not be very accurate, and the selling price is ridiculous for what it is.

This is something I still think about building, but these days I have no interest in producing them for the market. If anyone with a machine shop is interested in making the needed components for it I'll happily share the plans.

*Funny alignment shop story. When I was deeply involved with my full time career plus running three other part time businesses I would take my cars to local shops for some routine services. One car needed an alignment so I dropped it off at a shop specializing solely in alignment work. Several hours later they contacted me to come pick up my car and charged a rather high sum for the work, handing me a spec sheet showing the before and after settings. The next few days I noticed the handling still wasn't right. So I took it to another alignment shop. Turns out the settings were still EXACTLY the same as the "before" settings on the initial printout. The first shop didn't do a thing to it. The automotive industry is full of such unscrupulous activities.
 
Well, there you have it. Couldn’t ask for two posters with much more knowledge and experience.

The tiles shown by Steve are available at any big box store, they are commonly know as VCT or vinyl composition tile, they will crack easily so when you drive up on top of them make sure they are square to each other or lift the car and drop it down on them.
 
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I like the idea of having brackets that bolt onto either end of the car to set up the strings. With the bumpers removed it shouldn't be terribly difficult to fab something up (if you have more fab skills than I). I would be a buyer for such a contraption if it was available, for a reasonable price, commercially. And the hub stands look really nice, but, they are probably something that's priced a bit out of my league. Same with turn plates. I'm more of a floor tile and grease guy, I like those.
Because I don't use strings I fabbed up a toe bar. It's simple and inexpensive, but it's a bit of a PITA to use. It's simply a long piece of aluminum angle, with a couple of uprights at 90', and a couple of L brackets to hold it up against the tires.
P1050340.JPG
It has an old depth gauge bolted to one of the uprights at a 90' angle, at a 10 inch height (because the tires I use are 20" in diameter).
P1050342.JPG
To use it I first scribe a line in the middle of my tires (sometimes a squirt of paint around the circumference of the tire will help define the line).
I use a very simple tool I made to scribe the line.
P1050343.JPG
Then I slide the bar under one end of the car and set it up against the front of the tires with one side of the upright that doesn't have the depth gauge lined up with the scribed line at the 10" high mark. Then I scramble over th the other side of the car, move the depth gauge in, or out, until the end lines up with the scribed line, and tighten it down a bit. Next, I slide the bar out, and lay it up against the back side of the tires, with the upright without the gauge, lined up again on the scribed line. Then, I run around to the other side and note how far I have to move the depth gauge to line it up with the scribed line. That distance is my toe setting. By using the depth gauge, theoretically at least, I should be able to get very precise measurements.
Of course if I need to make an adjustment I have to repeat the measurements again to verify everything, and that is a bit of a PITA, especially because I have to repeat the procedure on the opposite end of the car.
I suppose it would be much easier to use a toe boards that fit up to the outside of the tires, but those assume that your tires have a very consistent side wall, and that's something I'm not at all confident the tires I use have. And of course the wheels are not bent either. And, the measurements using toe boards are taken at the bottom of the tire so the toe you measure will vary with the camber you use. Change your camber and you need to figure what toe setting you want to use because it WILL be different. I think by scribing a line down the center of the tires you eliminate those variables. At least that's my story, and I'm sticking too it. (Besides, I was drunk when I thought this up so I'm not responsible. 🥴)
BTW - I welcome any sober critique of the methodology, I'm always open to learn new and better ways to do things. :)
 
In the early 1980s, I built a giant caliper using 3/4" rigid conduit, wood, and a few miscellaneous parts. With it, you could quickly measure toe in. I also made another contraption to measure the rear tracking in addition to the rear toe in. I recently ran across the caliper jaws that attach to the conduit in my basement. Unfortunately, the conduit was used for another project long ago so I'll need to make a run to Home Depot if I want to check my toe in.
 
One thing I should have noted. I typically don't use strings doing alignments on my car. Instead I use toe plates. These are very simple and easy to use. However, they don't give you a reference for centerline and therefore, unless you have some reference, you can't set the rear thrust angle or center the steering wheel.

I have techniques for both of these and once its done the process is quick and easy.

 
Steve Hoelscher said:
One thing I should have noted. I typically don't use strings doing alignments on my car. Instead I use toe plates. These are very simple and easy to use. However, they don't give you a reference for centerline and therefore, unless you have some reference, you can't set the rear thrust angle or center the steering wheel.

I have techniques for both of these and once its done the process is quick and easy.

Click to expand...
I made a set of those, they are simple but I just don’t much care for them. They do suffer all the negatives you have stated So they are difficult to use if you are starting from a wide variety of unknowns with new parts.
 
Steve Hoelscher said:
One thing I should have noted. I typically don't use strings doing alignments on my car. Instead I use toe plates. These are very simple and easy to use. However, they don't give you a reference for centerline and therefore, unless you have some reference, you can't set the rear thrust angle or center the steering wheel.

I have techniques for both of these and once its done the process is quick and easy.

Click to expand...
I have those plates and find them easy to use but like you said, no reference to centerline. I have set up a plumb line from the measured midpoint of the rear control arm plate and the front crossmember jacking plate then used that to try and get center. Only thing is, the tape measures are a lot further apart than the tire diameter. How much toe in do you dial in with the tape measures and the plates? Thanks.
 
MikeHynes said:
I like the idea of having brackets that bolt onto either end of the car to set up the strings. With the bumpers removed it shouldn't be terribly difficult to fab something up (if you have more fab skills than I). I would be a buyer for such a contraption if it was available, for a reasonable price, commercially. And the hub stands look really nice, but, they are probably something that's priced a bit out of my league. Same with turn plates. I'm more of a floor tile and grease guy, I like those.
Because I don't use strings I fabbed up a toe bar. It's simple and inexpensive, but it's a bit of a PITA to use. It's simply a long piece of aluminum angle, with a couple of uprights at 90', and a couple of L brackets to hold it up against the tires.
View attachment 34486
It has an old depth gauge bolted to one of the uprights at a 90' angle, at a 10 inch height (because the tires I use are 20" in diameter).
View attachment 34487
To use it I first scribe a line in the middle of my tires (sometimes a squirt of paint around the circumference of the tire will help define the line).
I use a very simple tool I made to scribe the line.
View attachment 34485
Then I slide the bar under one end of the car and set it up against the front of the tires with one side of the upright that doesn't have the depth gauge lined up with the scribed line at the 10" high mark. Then I scramble over th the other side of the car, move the depth gauge in, or out, until the end lines up with the scribed line, and tighten it down a bit. Next, I slide the bar out, and lay it up against the back side of the tires, with the upright without the gauge, lined up again on the scribed line. Then, I run around to the other side and note how far I have to move the depth gauge to line it up with the scribed line. That distance is my toe setting. By using the depth gauge, theoretically at least, I should be able to get very precise measurements.
Of course if I need to make an adjustment I have to repeat the measurements again to verify everything, and that is a bit of a PITA, especially because I have to repeat the procedure on the opposite end of the car.
I suppose it would be much easier to use a toe boards that fit up to the outside of the tires, but those assume that your tires have a very consistent side wall, and that's something I'm not at all confident the tires I use have. And of course the wheels are not bent either. And, the measurements using toe boards are taken at the bottom of the tire so the toe you measure will vary with the camber you use. Change your camber and you need to figure what toe setting you want to use because it WILL be different. I think by scribing a line down the center of the tires you eliminate those variables. At least that's my story, and I'm sticking too it. (Besides, I was drunk when I thought this up so I'm not responsible. 🥴)
BTW - I welcome any sober critique of the methodology, I'm always open to learn new and better ways to do things. :)
Click to expand...
Mike, your toe adjusting setup is very much like one my dad left behind. He spent his career in the automotive industry, including owning a small chain of service shops at one point. Unfortunately most of the tools and equipment he had disappeared over the years. But among the alignment related items were a toe gauge like the one you made (his looks to be a commercial product), a pair of cast iron pivot plates (sadly they were broken, badly rusted, incomplete, and unusable), a bubble type tire balancer (still works but I don't like the results), and a caster gauge that uses a bubble level (also broken and unusable) which clamps onto the center dust cap of old American cars. The "scribe" to mark the tire centerline for the toe gauge is a spring loaded 'hook' with a point and has a base that sits on the floor. The toe gauge and scribe were by far the simplest designs of them all and and they are the only items that still work. ;)
 
So I did the simple method this morning. I just used a board that's very straight and made it flush against the fronts and then the rears. At least the two toe measures are pretty consistent between the front and rear. I will get a true alignment later from a trusted shop and mechanic using a Hunter or further put time into the methods described above. Right now a better way at an alignment is not whats preventing my car from reaching 60 mph.

I took it out driving and it still shook in the front. I can tell there is something off with the steering rack, tie rods or the ball joints. I am tending to agree with Steve here.
Steve Hoelscher said:
First, its important to note that a severe shake isn't caused by an alignment issue. Shake is typically caused by loose, worn, bent or otherwise damaged parts. Any part (ball joint, tie rod end, control arm bushing, wheel bearing, etc...) that is used to control/locate the upright, if loose or worn will enhance a vibration or shake as it will allow the oscillating frequency more amplitude. Therefore, the first thing to do is carefully inspect all of the suspension components to identify any slop and fix that first. Also check the hub and wheels for runout, and the wheels for balance.
Click to expand...

The wheel shook like crazy and not just rotated but left to right as well. I could also hear a bit of a cluck from that general area with each change of direction. I think it might be internal to the rack.

Perhaps I should create a new thread as this is clearly a debate on proper alignment methods and not "whats wrong with my steering rack?"
 
Rodger said:
I have those plates and find them easy to use but like you said, no reference to centerline. I have set up a plumb line from the measured midpoint of the rear control arm plate and the front crossmember jacking plate then used that to try and get center. Only thing is, the tape measures are a lot further apart than the tire diameter. How much toe in do you dial in with the tape measures and the plates? Thanks.
Click to expand...

For a street car I typically run 1/8th inch total toe-in.
 
AKimball92 said:
So I did the simple method this morning. I just used a board that's very straight and made it flush against the fronts and then the rears. At least the two toe measures are pretty consistent between the front and rear. I will get a true alignment later from a trusted shop and mechanic using a Hunter or further put time into the methods described above. Right now a better way at an alignment is not whats preventing my car from reaching 60 mph.

I took it out driving and it still shook in the front. I can tell there is something off with the steering rack, tie rods or the ball joints. I am tending to agree with Steve here.


The wheel shook like crazy and not just rotated but left to right as well. I could also hear a bit of a cluck from that general area with each change of direction. I think it might be internal to the rack.

Perhaps I should create a new thread as this is clearly a debate on proper alignment methods and not "whats wrong with my steering rack?"
Click to expand...

Bad rack bushing, and/or, rack mounting bushings. While your there check the tie rod ends and ball joints. Also the radius arm bushings.

A slightly out of round, or out of balance, tire can wreak havoc with a group of even lightly worn front end parts.
 
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