Thread: Project Sebring GT Spyder

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The upper link is unchanged from the original design. It still uses the ¾” Spohn joints and ¾” cross bolts. Since there is only one upper link, I wanted to make it extra strong. The upper link mount on the frame is also unchanged. Both the upper and lower frame mounts have serrations in .100 increments. That’s probably a lot finer than I actually need. I also have some threaded holes in the back wall of the upper mount. Once I figure out where it needs to be for the best anti-squat, I can bolt on some boxing plates. The upper slots will be trying to stretch and open up since they are under tension. The boxing plates should help stop this. That and the upper link mount is 3/8” thick plate in the slots.









This is the brace that I added to support the upper link mount. I plated the trans tunnel for extra strength and carried the mount over to the frame. The lower part of the mount is also gusseted to the floor pan for extra support.





According to my 3-link spreadsheet, my stuff is way overbuilt. The safety factor is in the teens for both the upper and lower links.

My Monza pro stock race car had a 3 link rear------that upper link has a lot of effect on going straight ahead--------lots of nice work/welding

Thanks Jerry. That means a lot coming from someone with your experience.

OK, I’m behind on updates yet again. I do have a couple of pretty good excuses, though. Not long after making my last post my back started acting up again. It gives me trouble pretty much all the time, but it was pretty bad this time, forcing me to sleep in my recliner, since trying to lay in bed was too painful. Had to go back to the doctor and get some new meds. They seem to have worked, along with some physical therapy and I’m doing much better. Of course, then I came down with some kind of virus ( not covid ) that took a several days to shake.

Just as all this was behind me, my 83 year old mother fell and hit her head just before Thanksgiving. Broke her wrist, too. The head injury resulted in a small bleed in her brain. Luckily the bleeding sealed itself off and she didn’t need surgery. She did have to take a ride in a helicopter, though. Looked like it might be bad for a while. My wife and I have been taking turns sitting with her due to the difficulty she has with the cast on her wrist. Just before Christmas, the neurosurgeon basically released her, so she is definitely on the mend.

Because of my extended family, the holidays at this time of year take up most of several weekends. So, getting at lot of shop time is iffy at best. Since the first of the year, I have been slowly getting back to work on the car, but that may slow down again because my grandson needs help getting his old truck running. He just got his license and is chomping at the bit to get his truck going.

I think I can make a few updates with things I was able to get done before all this stuff broke loose, though.

The front suspension was pretty much mocked up before powder coat, but there were still a few odd jobs that needed to be sorted for final assembly. I’m using QA1 low friction ball joints and the tapered part of the studs were a little too long. The taper has full engagement in the spindle socket, but stuck up above the spindle, preventing the nut from tightening up. I made some thick spacer washers to take up that space. This doesn’t bother me since I have installed stock replacement ball joints that came with spacers in the box for the same reason.

The QA1 ball joints are very low friction. They are rebuildable and adjustable The tapered studs are available in 3 different lengths in most applications so that the suspension geometry can be fine tuned. I sealed them up with Prothane polyurethane boots.



Just like the rear suspension, I drilled the control arms and installed grease zerks. These poly bushings will get the same silicone grease as the rear bushings. Between the new bushings and low friction ball joints, the control arms move very free now. It’s far cry from the original setup. The old rubber bushings were so stiff that I could jack the whole frame up (with no springs installed) just from the tension in the bushings!

The front got the same type of adjustable Ride Tech coilovers as the rear, just a shorter length. I will attempt to run them upside down, too, but that can wait until I install the springs. I may not have enough clearance on the upper mount for the spring if they are inverted.



I also finished up the shock tower braces. I knew when I built them that they would need more support. The diagonal braces tie into the rack mount. The cross brace had to have the dip to clear the upper radiator hose. I made them all removeable to make engine service easier.

Coming together very nicely, looks great and should work even better!

Looks nice, very sturdy looking suspension.

Very nice work and sorry to hear about your mother. It's nice to hear she is healing up now. Those head injuries can go south real fast. I like the zerk additions on the control arms. I need to do that to the ones on my 40 when I replace the rubber bushings in them. Just add another thing to the already long list.

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Thanks guys. Mom is getting back to her old feisty self and is in an arm brace now instead of a cast. She chased us back home a week or so ago.

With the suspension hung on the car, it was time to get the alignment specs roughed in.

This is the old caster/camber gage that I used. It attaches with magnets so I had to swap the good rotors out for some old iron parts I had. The Baer rotors use an aluminum hub and the magnet obviously wouldn’t stick.



I modified the adjustment setup on this car so that I could use shims instead of the old pinch bolt sliding setup of the original Mustang II. The pinch bolt setup is a pain in the butt to get right and it has been known to slip over time. Like many GM cars and trucks, I built it so that adding shims increases negative camber. There is enough space to get more camber than I will ever need. The shim conversion has another advantage, too. Should I ever decide to track or auto-X the car, I can make up a race shim pack that can be slipped in at the track to dial in more negative camber. After the race, I can simply go back to the street shim pack with no need to do an alignment.

While I’m listing the mods I made to the front, I should also show the anti-dive I added to the upper control arms. The original setup on this car had none at all. I only added about 4 ½*, but any at all should be better than nothing.











The control arm mounts are also adjustable for height. By adding shims under the mounts, I can raise them a total of about an inch. This will change the camber gain by altering the angle of the upper CA should this ever become an issue. Raising the pivot point will decrease camber gain. This can also be used to alter the front roll center height. In case you don’t know, the roll center geometry is a very complicated set of angles formed by the upper and lower CA’s and where they intersect. The geometry at rest is fairly simple. Where it gets complicated is what happens when the suspension moves. I originally tried modeling this on a table with simple sticks, but that was an exercise in futility. I wound up buying a computer program that does it. With the program, I can literally model several control arm relationships in less time than it would take to draw one setup out by hand and I can see how the roll center moves as the suspension rolls or moves through it’s travel.

I’m also using Wilwood Pro Spindles. They have a longer upper leg than stock MII parts. Normally, this would have increased camber gain a good bit, but since I had to raise the inner CA pivots to do the shim alignment conversion, the longer leg gets me a smaller amount of additional camber gain.

Very nice work! That's a great idea on the way to mount your UCA's. I may have to steal your idea and adapt it to my UCA's on my 40. When I was setting the suspension up on it I thought that it could possibly move/slip over time.

Ditto on what Ryan said. I'm trying to get my grandson to do something like what you've done to his 66 Mustang when he gets ready to rebuild it.

NTFDAY - At least do the Shelby drop on that Mustang. Lowers the car about an inch and improves geometry. Shelby's team came up with it for the GT350. I read about it back when I was considering building a GT350 clone. As I recall, it only requires redrilling a couple of holes for the upper control arm mounts.

40 -Feel free to copy it, but I can't take credit for the idea. I saw something similar many years ago.

I made what I call “caster wedges” to set the gross caster and camber. I roughed them out on the bandsaw and fine tuned them on the mill. I was able to get pretty close with these and I only needed a few small shims to get the caster and camber where I wanted it. I wound up with 6* of positive caster and about 3/8* of negative camber. I think that those numbers will be a good starting point. I wanted a good amount of caster to give the car a good “center pull” on the highway and help the electric steering return to center after a turn.






Unfortunately, if I want to add any more caster, I will need to build offset upper control arms (or lower CA’s) that move the ball joint locations. There is no more clearance between the old spring pockets and the upper control arm to move it more. I really wanted to have the ability to get as much as 9*. Some of the Cobra guys have reported using 8 or 9 degrees with good results. I’ll save that project for a later date if it’s needed.

The original MII specs call for ¾ to about 1 ½ degree of positive caster, so I have approximately 5-6 times more than stock. Hopefully, that will be enough to overcome the internal drag of the electric steering unit, which is considerable. With many of the electric steering conversions I’ve read about, the drivers complain about the steering not wanting to return to center. Along with the increased caster, I’ve also switched to faster ratio steering box. This should give the return to center force generated by the caster maximum leverage against the EPS and I also just like the quicker steering. The old stock manual rack was 4 turns lock to lock. The new one is 3. The rack is mounted on solid aluminum bushings. There is no rubber or polyurethane anywhere in the steering, so the response should be razor sharp.

Very nice! Those wedges are awesome! I need to get one of those milling devices.

On the UCA, can you use these? I have SPC uppers on my Camaro and love them.

https://www.summitracing.com/parts/s...xoCQ28QAvD_BwE

I once thought about getting these for my 40 but really don't know if they are necessary for it. I don't plan to drive it nearly as hard as I do the Camaro.
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40, I wish I could use those. The UCA's on my car have to have a good bow in them to clear the old spring pockets, but that doesn't mean that I couldn't incorporate the adjustment features of those into some new ones. There may even be some already available that do what I want.

As to the mill, I would be lost without it. I've come to really depend on my machine tools.

During the initial build, I also fabbed up an adjustable steering rack mount so that I could adjust bump steer. You adjust it by using shims and it adjusts both forward and backwards as well as vertically. The MII front end has some bump steer when stock and as you dial in more caster, the steering arms move higher. This generally makes bump steer worse. At least, that proved very true on my car. I just wasn’t quite prepared for how bad it actually was.





Bump steer adjustment was the last alignment I tackled. At this time, I don’t have an actual bump steer gauge (as in the type that uses a dial indicator), but was able to rig up a laser setup that got me very close. The setup is not my idea. I first saw it on a YouTube video and it looked like it should work. A laser pointer is attached to the hub or wheel pointing forward. A mirror is positioned 5 times the tire radius to reflect the laser almost straight back on itself. A target is fixed on the hub near the laser and marked with a sharpie where the dot falls. The suspension is then jacked through it’s complete travel. Since the laser and target are moving up and down together, the laser dot only moves left or right from the starting point (lower control arm level). If the dot moves away from the centerline of the car, you have toe out. If it moves toward the center, you have toe in. Since the laser travels 10 times the wheel radius to get back to the target, any indicated lateral movement is 10 times what actually happens at the tread.

My rigged up tool consisted of a piece of heavy angle iron drilled to fit over one wheel stud. This formed a shelf that I clamped a heavy cast iron weight that I had laying around. The laser pointer was in a magnetic torpedo level. The target was just a piece of scrap aluminum clamped to a section of scrap angle iron. The mirror was an old Chevy truck door mirror that was stuck back on the shelf. It was sitting on a couple of milk crates. Definitely a bodge, as a Brit would say, but it did work just fine.





I should also add that I wasn’t concerned, at this point, with exact numbers. All I wanted was to get the bump steer acceptable for initial driving. I was just looking for minimal toe change through the entire suspension travel. I have 6 inches of total travel available (3 up and 3 down) with the body off the chassis, but I doubt I can use all of the compression travel. I might be able to use around 2 inches up before the tire hits the fender. I’ll double check that after the body is back on and if it happens, I can add a bump stop to the shock. The shock does stop the suspension in full droop before the upper control arm contacts the frame or the ball joint runs out of angular travel.