74_5.0L_Z

I'll have to measure that tomorrow (or this weekend). I'm getting ready to go to bed. I have to be back at work at 1 am. I'm on third shift all week until we get Atlantis off the pad.

I just came in from the garage. Since I had the car up and the springs removed, I decided to measure the motion ratios of the front and rear suspension. I did this as follows: 1. Jack and level the car. 2. Remove springs and reinstall strut. 3. Let strut go to full droop and perform following measurements. ---a. Measure from ground to center of hub. ---b. Measure length of shock tube to line on bump stop. 4. Jack wheel up 1/2 and perform following measurements: ---a. Measure from ground to center of hub. ---b. Measure length of shock tube to line on bump stop. 5. Repeat step 4 seven times to get measurements through the range of travel. 6. Graph shock measurements versus hub measurements. 7. Fit regression line and get slope (inches of shock travel/inch of hub travel). For the rear, I came up with a motion ratio of 0.882. For the front, I came up with a motion ratio of 0.904. The suspension ratios at the center of the tire contact patch are related to the ratio at the center of the hub by a constant that is equal to one for wheels that have a zero offset. My suspension is modified as follows: Front: Stock length lower control arms (fitted with inboard spherical bearings) Shortened strut to fit Koni 8610-1149 insert. Lower Control arm pivot point moved up 3/4" and out 1/4". Top of strut tower moved back ~3/4" 1" bump steer spacer Ground Control camber plates. Rear: Custom rear control arm adjusted 1/4" longer than stock Eccentric camber bushings adjusted equally to maximum negative camber. Shortened strut to fit Koni 8610-1437race insert. Ground Control camber plates. Though my suspension is fairly heavily modified, none of the modifications will have a huge affect on the motion ratios.

Thanks for the replies. I think I am going to do two things: First, I think I'll lower the car an additional 1/2" to gain some more rear droop travel. Second, I'm going to install some stiffer springs. I've been wanting to do this for a while, but I needed to wait until I had some decent rear struts. Currently, I have 250 lb/in springs in the rear and 200 lb/in in the front with a 1" front sway bar and no rear sway bar. I now have 8610-1149 front struts and 8610-1437race rear struts. I just need to decide which springs to get. I plan to go through all the math and pick the springs as suggested in chapter 16 of Milliken's RCVD.

I have completed sectioning my rear struts and installing the Koni 8610-1437race inserts. I ended up taking 2.25" out of the housing and installing a 1.5" spacer below the insert. At the same time, I got rid of the stock upper spring isolators and installed Ground Control camber plates. I finished putting the car back together on Saturday and discovered that I had virtually no droop travel with the back of the car at 6.5" (measured at horizontal portion at the back of the rocker panel and a 245/45/16 tire). So, to gain some droop travel, I lowered the car so that the back of the rocker panel is at 5.625" an the front is at 5.25". I now have 1" of droop travel without me in the car. The control arms are almost level with the ground and the front angle upward to the wheel. I was a little concerned that this would not be enough, but not so concerned that it prevented me from running in an autocross on Sunday;). I was a bit afraid that I might experience a snap oversteer situation, but much to my surprise that was far from the case. The car performed very well. In fact, it went pretty much anywhere that I pointed it. While I am very happy with how the car performed in an autocross, I have lingering concerns that the limited droop travel might be insufficient for a track event. How much droop travel are you track gurus running?

Putting the rod end in double shear would definitely be a whole bunch simpler. I dig simple.

The rod ends that I'm using in my current rear control arms are Aurora XAM10-T which have a 3/4" shank and a 5/8" ball. For axial loads they are rated at ~40,000 lb. Aurora suggests that the rod ends are good for 10% of that in the orientation we use them. I'm toying with the idea of using a ball joint on the A-arm portion. To do so I would have to modify the rear strut. We'll see...

The angle between the strut housing and the end link for the sway bar would be less than 20 degrees. If the sway bar were applying 200 lbs of force at its end, the force applied perpendicular to the strut (bending force) will be equal to 200 lb x sin (20 degrees) = 68 lbs. This torque would be proportional to the amount of roll and would only be present in turns. Mounting sway bar end linnk will cause a bending moment in the strut.

The strut tube is behind the axle shaft. So without modifying the strut, the rear rod end is below (but inboard of) the strut tube. I like having the fixed point on the A-arm below the strut tube so that adjustment to toe will have a minimal affect on camber. So, the spacing between the rod ends has not changed.

I like the first example because it is simpler and uses fewer rod ends. It is exactly what I envision. As far as the anti-sway bar goes, I don't use a rear sway bar. If I did, I would rather attach upward to the strut housing rather than down to the control arm. I assume that the connection between the toe link and A-arm is a spherical bearing and that it is free to rotate.

You will not get any binding as long as the spindle pin is parallel to the axis of control arm rotation. So lengthening the track shouldn't be a problem. The issue that might occur is having enough adjustment at the top of the strut to compensate for camber. Adding 50 mm per side to the length of your lower control arms will give you about 6.5 degees of negative camber. I don't think my Ground Control camber plates can compensate for that. This does sound like the topic for a new thread.

My car is not set-up as a drag car. I mostly autocross it, but I have had it to the drag strip. My best so far is a 12.42 @ 113mph. The engine is from a 1989 mustang. The engine came from a junkyard and the only thing that I have done are some bolt-on modifications. Edelbrock 60379 Performer 5.0 Heads Cobra Intake 1.7 FMS roller rocker arms Crower 15511 cam 24 lb/hr injectors C & L 73 mm Mass Air Meter 65 mm Throttle body I have never touched the bottom end and I know that it has at least 150,000 miles on it. All that being said, I have a 331 stroker on the engine stand just waiting for me to finish it.

Tholt, Your conclusion is what I came up with. The magnitude of the deflection is less than I assumed (that's why I did the calculations and spreadsheet). What the spreadsheet also says is that if the control arm cannot flex, the top of the strut will try to deflect 0.026" for a 0.3 degree toe in condition (0.3 degrees is equivalent to 1/8" toe in and a 24" tire). In reality, the strut will be much stiffer than the control arm, so a majority of the deflection will occur in the control arm. The ratio of the torsional stiffness of the control arm to strut will determine force applied to by the control arm to the strut. If the control arm has a torsional stiffness of 1000 ft-lb/degree, a significant side load will be applied to the strut. If the control arm has zero torsional stiffness(as in an A-arm toe link), then no side load is applied to the strut. As you observed, much (but not all) of the strut deflection due to splindle pin angle can be mitigated by careful alignment of the strut. By this I mean that after a toe adjustment, the strut must be shimmed forward or aft to minimize the deflection. As an example, if the toe is set at 0.3 degrees, the top of the strut will move backward 0.026" with the control arm horizontal, and will vary from 0.021" to 0.026" to 0.021" as the strut goes through its full range of motion. 0.026" is equivalent to 0.070 degrees of control arm twist. So given 1000 ft-lb/degree, the torque will be 0.070 x 1000 = 70 ft-lbs. The bearings inside the strut are approximately 16" above the connection to the control arm, so the side load on the bearings will be approximately 70 ft-lb*(12in/ft)/16in=52.5 lbs. Given the same conditions as listed above: If the strut is shimmed backward 0.021" after toe alignment, the variation can reduced to 0 to 0.005 to 0 as the strut goes through its range of motion. The maximum twist on the control arm is reduced to 0.0118 degrees and the strut side load will be reduced to 0.0118/0.070 x 52.5 = 8.85 lbs. Now assume the worst case with the toe is set at 0.3 degrees as above. Instead of shimming the control arm to correct direction, assume that the strut has an intial misalignment of 0.125". The twist in the control arm increases to 0.48 degrees. The side load on the strut now increases to 0.480/0.070 x 52.5 = 360 lbs:shock:. If we must use the H-arm strut lower control arm, we need to be really careful to shim the strut forward or back to minimize the control arm deflection and strut side loads. These problems completely go away with the A-arm toe lnk type lower control arm. Dan

Having the toe rod in compression won't be a problem as long as it is not too slender. I believe that the correct location of the hard point is below the strut tube. Having it there decouples the camber and toe adjustment. One thing that I want to explore is the length of the toe rod and its affect on roll steer. I have the fixture fom the construction of my old control arms. It will not be hard to modify it to make some of these. I expect to have some made within a month.

Jon, That is the exact design that I had in mind.

Jon, If you read my post immediately above, then you will see that we had the same eureka moment. Dude, get out of my head:mrgreen:

Flexicoker, What you have for an upper rear control arm is precisely what we need for our lower control arms. In our case, however I think the rigid point of the control arm needs to be in the rear below the axis of the strut tube, and the toe link in the front. By doing it that way, we can decouple the toe and camber adjustments. You also brought up a good point about not using rod ends at the wheel end of the control arms. What I would really like is a ball joint below the bottom of the strut tube and the toe link in the front.

I have had great luck with the control arms that I built. They are light and strong. My control arms, the stock control arms, and the ones sold by AZC are all examples of an H-arm strut (Milliken pg 641). The other option would be an A-arm and toe link strut. Each has their advantage and neither is meant to resist the twisting moment applied to the rear suspension when the brakes are applied (That function is performed by the strut). The H-arm strut has a limitation that is described by Milliken, "...the inner bushing pivots must be perpendicular to the axis of motion of the strut at all times or bending of the strut will occur." What this means is that as the control arm rotates about an axis, and the end that attaches to the strut follows the arc of a circle. This is true for all rigid parts of the control arm. With our control arms (H-arm), the entire control arm is rigid and the bottom of the strut is rigidly captured. The strut tube is (supposedly) perpendicular to axis of the spindle pin. So, if the axis of the spindle pin is parallel to the axis of the inner pivot, then the strut will always be perpendicular to the axis of rotation and no binding will occur. Now lets try a mental experiment. Let us adjust the heim in the front to get some toe-in. We have now turned the axis of the spindle pin so that it is no longer parallel to the axis of the inner pivots. This rotates the strut housing by a small amount and because the strut tube is angled away from the center of the hub, the top of the strut will try to rotate toward the back of the car. Well guess what: The top of the strut is captured by the bearing in your camber plates. You just put your strut in a bind. If you have rubber isolators and bushings you will probably get away with this. The rubber will compress before the strut bends. If you have spherical metal bearings everywhere, you will see evidence of the strut binding (springs hitting threaded collars). Interestingly, those cheesy aluminum/delrin eccentric bushings don't cause the same problem because the axis of the spindle pin and axis of rotation stay parallel. Now for the other option: What are the advantages of the A-arm toe link strut? The A-arm, like the H-arm is constrained to rotate about an axis fixed to the chassis. The A-arm however only has one point forced to follow an arc. That rigid point connects to the strut and forces the attach point to follow the same arc. The link between the strut and A-arm is spherical and as such has two degrees of freedom. The connection is free to rotate about the axis of the spindle pin and to rotate about the axis if the strut housing. We need an extra constraint to control rotation about the axis of the strut housing. We need a toe link to do this. This is the important part: The toe link should only control the rotation of the strut about its axis. The toe link MUST only add one constraint. To accomplish this both ends of the tie link must be free to rotate in all planes, both ends must be heim joints. Allowing the toe link to rotate freely allows the strut to rotate about the rigid end of the control arm and prevents binding. If either end is constrained to stay in plane (clevis connection), then we are back to a H-arm and its limitations. Every control arm that I have seen made for a Z of this type was made wrong. So lets try the same mental exercise with the A-arm toe link strut. We adjust to toe link to add some toe-in. We'll use the toe link in the front and the rigid link in the back. The spindle pin is again rotated so that it is not parallel to the axis of the inner bushings, and the top strut tube tries to moved slight back on an arc, but it is constrained at the top by the camber bearing. What happens? The whole strut rotates around the pivot at the rigid point on the control arm. As the strut compresses, the strut houing tilts further and further forward to keep the axis of the strut housing aligned with the bearings at the rigid end of the control arm and the camber plate. Because the toe link is not constrained, the strut housing is not in a bind and the control arm sees no torque. So, after all of this I have come to a couple of conclusions: 1. If you have an H-arm set-up, keep the axis of the spindle pin parallel to axis of the inner pivot bushings. 2. I will only adjust the toe of an H-arm set-up using the inner bushings. 3. I am going to build a set of A-arm toelink control arms so that I and have more adjustment possiblility without binding. Damn it, I used to be satisfied with my control arms. Oh well, back to the drawing board.

Actually, you've got that backwards. AN uses a 37 degree flare, and SAE uses 45 degree. Either way, If the flares were the issue you'd have visible leakage. Did you bench bleed the master cylinder?

Thanks John, I ordered the gland nuts from Truechoice today ($19.95 each).

OK, The new struts arrived today, and I have some more questions: First, I think I need to acquire some gland nuts. The struts that I removed from the rear were the old Koni sports (8641-1032). The gland nuts from those sat around the top of the strut insert and acted to center the insert in the housing. I assumed that koni would use the same gland nut for the 8610-1437, but it appears that I am wrong. Second, the box had a bag of parts. Some I recognize and some I do not. The ones that I recognize are the four nuts and rod end spacers. The ones that I do not recognize are two large OD steel rings, and two slotted plastic discs. The purpose of these last items is not immediately obvious. They were not included with my 8610-1149 struts that I put in the front a few years ago. Any help will be appreciated.

Thanks for the replies. I had to deal with the alignment issue when I did the front struts. For that I did as John suggested and made a mandrel to assure squareness and concentricity. I still have the mandrel and will use it for the rear. I guess my real concern was with losing too much droop travel in the rear. I have read somewhere on here that insufficient rear droop travel can create a snap oversteer situation. I obviously want to avoid that. Ideally what I'm hoping for is a very light preload of the spring at full droop. With my current set-up, The springs are unseated at full droop, and I have to guide them onto their upper perch when I lower the car off the stands. If all else fails, I'll come up with some droop limiters that are set at the point where the spring uncouples.

johnc put together a great write-up about sectioning struts about three years ago in the following thread: http://forums.hybridz.org/showthread.php?t=85960&highlight=section I followed his directions to the letter for the front struts, and everything worked perfectly. I am in the process of sectioning my rear struts for Koni 8610-1437race inserts, and I have a question regarding his write-up concerning the rear struts. Here are the instructions for the rear from the original write-up: The problem that I am having is this: The write-up suggests shortening the rear housing by 2.25" and then using a spacer below the insert of 2.25". The unmodified length of my housing is 16.75". If I remove 2.25", the inside length will be 14.5". From the Koni catalog the length of the 8610-1437race housing (Dimension A) is 13.07 inches. Also they suggest that the housing length is 0.04 to 0.16" shorter than Dimension A. Using 13" for the desired inside length (13.07 - 0.07). If I section my strut housing 2.25" and subtract 13", I get (14.5 - 13)= 1.5. So, here are my choices. 1. I can section the rear housing by 2.25" and use a 1.5" spacer below the strut. 2. I can section the rear strut housing 1.5" and use a 2.25" spacer below the insert. 3. I can section the housing some dimension in the middle and make up the difference with an appropriate spacer. johnc (and others), What is your suggestion? Have I made an error in my math?

When I was preparing the tubing in my cage I did as Johnc suggested. I would soak a rag or paper towels in solvent, and push / pull it through the tube until it came out clean. This worked well to remove the cutting oil and chips that accumulated during tube notching process. If you are using DOM mild steel or 4130 tubing, then there is going to be a thin coating of mill scale (inside and out) that cannot be wiped off with a rag and solvent. This coating needs to be removed in all areas that are going to be welded. To do that I used 80 grit paper, and then acetone.