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Thanks for sharing all the info Mike. I've been mulling over a gear change and maybe doing a whole "pumpkin" so I could drop and swap. One of the plans was to do as you did and use a Ally pinion gear bearing mount. I hadn't read of the distance change but it makes perfect sense once I read it! So again. THANKS!
Your welcome. Glad I can help.
FWIW - I'm leaning toward the Yukon aluminum chunk. It's reasonably priced and has through bolts on the diff carrier bearings as opposed to just being threaded into the aluminum. Supposed to good for something like 800 HP! They are supposed to save 20 lbs over a cast iron unit.
What I would really like is a NASCAR style cast steel drop out. They are lighter than the cast iron parts, but not as light as the aluminum pieces. They're supposed to be the strongest regular carriers that you can get, but they are big $$$$. I've read that they turn up used from NASCAR teams, but wouldn't have a clue as to how to find one.
How about Racingjunk? I recall Dave Severson used to talk about stuff he'd found there, and they list a YUKON nodular iron unit, ready to go - https://www.racingjunk.com/Rear-Ends...=8&from=searchQuote:
Originally Posted by Hotrod46
Thanks. I didn't know about that site. I keep an eye on it.
I swapped over to 31 spline axles, too since I needed new ones for the shortened housing anyway. The axles I bought were from Quick Performance. Nothing special. They were just regular cut-to-fit axles that they cut for me. I was able to order them with the correct hub diameter for the SVT brake rotors.
The axles came with studs already pressed in, but I had to change them out. I wasn’t comfortable with the amount of lug nut engagement that I had with the aluminum wheels I’m running. The new studs are from Moroso. I was not impressed with the Chinese bearings that the axles came with, either. I’m glad that I ordered them with loose bearings for me to press on. I needed a bearing spacer to get past the thick caliper mount and had to install that before the bearings went on. I went with Federal Mogul bearings from my local parts store.
https://i.imgur.com/BY34j7h.jpg
https://i.imgur.com/5ZPsC9D.jpg
This is the axle after powder coating and reassembly.
https://i.imgur.com/rXMnQtM.jpg
I've bought a number of parts off Racing Junk, no problems with anything from there but I like to research the seller before making any deals! Over the years I bought a couple "N" center sections off the site, along with a Doug Nash 5 speed for parts. Just like any other site, it's still a "buyer beware" place, but when you know what you're looking for and how to confirm the parts being sold match the description it seems to be as trustworthy as any of them!Quote:
Originally Posted by Hotrod46
Here are a few more pictures of the Cobra SVT brake conversion I did. I started out with a fabricated two piece steel bracket that was bolted together, but eventually carved one piece brackets out of 6061 aluminum. The new brackets weigh about half of what the steel ones did.
https://i.imgur.com/GHIbSLm.jpg
https://i.imgur.com/R997eNL.jpg
https://i.imgur.com/zOFOv0Y.jpg
I think I should mention that it probably looks like I have the rotors on the wrong side. All of the slotted rotors I’ve seen have the slots slanting backwards at the top. However, I’m running Baer brakes in the front and they have directional, curved vane rotors with slots. Baer has the slots slanting forward at the top. Even though the rotors where clearly marked right and left, it looked different enough to make me question whether it was right. I looked at a Baer produced installation video and they make it a point to say that the forward slant is correct for their rotors. Since the rear rotors I’m using have non-directional vanes, I decided to swap them around to match the fronts.
I just recently found out that Baer makes a rear disc kit that appears to be basically the same thing I built! I originally got the idea from a Mustang site. They were talking upgrading Mustang brakes and it sounded good, but the SVT caliper brackets wouldn’t fit on the Explorer axle I was using then. So, I came up with my own brackets. Interesting to me that Baer felt it was a good enough upgrade to sell it under their name. That also explains why their tech knew exactly which master cylinder to recommend when I told him I was using SVT brakes.
J. Robinson, on his ’32 build thread, recently commented about how fabricators that build off the top of their head, often make problems for themselves that don’t show up right away. Well, that’s the same way I build, no drawings, just an idea in my head and I sometimes have those same types of issues. I ran into one while reassembling the rear suspension.
During the thrash to get the chassis to powder coat, I realized after I had the rear suspension torn down that I had forgotten to do the rear shock mounts. No problem, I thought, I’ll just measure and “quesstimate” where they should go. Well, I missed it by about a half an inch. I didn’t have the actual shocks I was going to use and went by an old pair I had under the bench. Bad idea and the new shocks were going to be too close to the Watts link mounts.
I came up with a few fixes. One, I could cut the existing mount off and move it, but that would have destroyed a large section of nice powder coat. I had them welded on very well.
Two, I could move the shocks to the rear of the mount and just run them in single shear. That might have worked if I had built the mount heavier, but I didn’t. It just had 3/16” thick ears and with the shock mounted behind, it put most of the load on a single ear, even if I tied the mount together with a spacer. Not good enough for me since the upper mount will be hidden when the body goes back on. Inspecting it will be difficult and I wanted to make sure it didn't fail.
The solution I went with was to move the shocks to the rear of the mount and add a third, bolt-on ear to put the mount back in double shear.
I started out locating and drilling 3/8” holes through the frame. This is how I make sure that I keep stuff like this square. I take an old piece of tubing or sometimes wood and drill a hole square to the surface. I clamp that on and use it as a drill guide. Works pretty good and is way better than trying to free hand that hole on the other side of the tubing.
https://i.imgur.com/BEdipWE.jpg
I made some crush sleeves and welded them in. This was just a “fusion” weld and took minimal heat.
https://i.imgur.com/8cY1t2a.jpg
https://i.imgur.com/Pyf4QIb.jpg
https://i.imgur.com/Ys30Wv2.jpg
After a lick of paint, it was almost like it never even happened.
https://i.imgur.com/qYHz8be.jpg
Here is the finished fix.
https://i.imgur.com/SqLcOaC.jpg
https://i.imgur.com/9Yj3IrJ.jpg
I've worked with some of the best engineers and designers, they have fixes too! Nice job!!
Good save Mike.
A great idea, great approach and great execution! Triple win!
That's clever.
Thanks guys.
Nice thinking, I've done a lot of cutting and welding on my frame since it was " finished ". A little paint you forget all about it .
After repairing the upper shock mounts, I needed lower mounts to match. These didn’t pose the problem that the uppers did, since I hadn’t built them yet. That was a stroke of luck since they had to be farther back to match the uppers.
Because they had to be so far behind the axle, mounting them in double shear would have taken a lot of bracing. I decided to mount these in single shear and just build them heavy enough to take the load.
The mounts wrap around and bolt to the lower link brackets. The main 5/8” bolts that hold the links also go through the shock mounts. This way as long as the links are attached, the shock mounts are too. A couple of 3/8” grade 8 bolts also go through the rear to stabilize them and allow moving the link position without the mounts coming off.
The mounts themselves are machined from solid bar with a 5/8” threads. I’m using a bolt right now but may swap over to a stud for maximum thread support. I counterbored the threads so that the weight will be supported by the full diameter of the unthreaded portion of the bolt and not just flexing on the root of the threads.
The mounts are a little longer than I wanted, but that’s the way it goes sometimes.
The shocks are gas filled parts by Ride Tech with a little over 6” of travel. The gas charge is why they are able to be mounted upside down. This reduces unsprung weight a little and allows easier access to the rebound adjustment. It would be very difficult to reach if they were mounted the other way.
https://i.imgur.com/phIergv.jpg
The shortened tap is what you do on a Sunday afternoon when you don’t have a bottoming tap, but you have two taper taps.
https://i.imgur.com/RDaWFTO.jpg
https://i.imgur.com/JIgWBqz.jpg
I do it because I'm cheap and can, been doing for so long I now have a whole set of bottom taps. LOL!Quote:
Originally Posted by Hotrod46
Or if you snap the end off a tap: voila, it's a perfect candidate to become a bottoming tap! Just grind it down, you'll use it eventually.
During the redo, I changed the way the Watts link brackets attached. This is how they looked originally.
https://i.imgur.com/lCgDG1q.jpg
I pulled them in closer to the axle tubes and raised them. The old system was more adjustable, but that adjustment wasn’t really usable if you ran the exhaust out the back of the car. The new setup had to have link bars with a dogleg in them. Building these wasn’t an issue now that I have a decent tubing bender. The left link was fairly simple, but the right link had to go over the exhaust pipe. While they look radically different, they both hit the same points in space. I built a temporary jig off of the left link and used that to build the right link. Because of the dogleg, the pivot on one end had to be non-swiveling, otherwise the link would just flop around, but it also needed to be able to move forward and back as the axle moved. For that, I used some Energy Suspension universal poly bushings and installed grease fittings. The other end uses heim joints. The Watts rocker (or propeller) is the same.
https://i.imgur.com/IkThctL.jpg
https://i.imgur.com/5wmh3mb.jpg
The new axle brackets
https://i.imgur.com/xLGG4fl.jpg
I have several poly bushings on this car and I’m fitting all of them with grease zerks. I bought a new grease gun that I filled with silicone grease with PTFE (Teflon). This stuff is called Super Grease and looks exactly like the grease that comes with most ploy bushings. Hopefully, by being able to give them a shot of grease occasionally, I can keep them moving free and avoid the poly bushing groan and moan. Here’s a link to the manufacturer’s page:
https://www.super-lube.com/silicone-...-syncolon-ptfe
I’m going to use this grease to lube the carb linkage that I built, too. It’s got a broad temp range and is supposed to be virtually impervious to water. It comes in standard 14 oz grease gun tubes.
The lower axle links changed, too. I moved the auxiliary air bags from the rearend to the lower link. The air bags are just for extra load carrying. Since I intend to do some long distance trips in this car, I will never know exactly how much weight I will be hauling. I have right at 3” of suspension travel in both directions, but I don’t want to use any of it up when loaded. The coilovers will still do most of the work. The air bags only come into play when the car is loaded. I will adjust the coilovers for a small amount of rear sag with no air. This will insure that the bags always have a little air in them to prevent them from being pinched. This is the way that GM and some other manufacturers did their supplemental air suspension. Because the lower links will be carrying some side loading, I built them out of heavier wall 1 ½” tubing. The bags are Firestone 7012’s, They will carry 1000 lbs each at 100 PSI. Mounted like they are, the shocks stop them from over extending and the frame bump stops keep them from compressing too far.
https://i.imgur.com/Fgyc6eZ.jpg
https://i.imgur.com/hGcfuGu.jpg
https://i.imgur.com/Lutq4xc.jpg
The front joint on the lower links is a Ride Tech R-joint. This is a little smaller than the Spohn joints I was using. I made this change because I had to cut some off the bottom of the front link mounts. After I lowered the car, they hung down too far. I shortened them one inch. The smaller R-joint allowed me to keep most of the original adjustment that I had built in. The axle end of the link has poly bushings. Like the Watts links, it had to have a non-swiveling bushing to keep it from turning.
https://i.imgur.com/1FUSMAd.jpg
https://i.imgur.com/PQ3SUor.jpg
Mounting the bags on the links actually reduces the unsprung weight a small amount.
The air suspension will be auto leveling. I am using a GM level sensor. These came on luxury cars from the 70’s up through the 90’s and they are a little bigger than a pack of cigarettes. The nice thing about them is that they are pretty much a stand alone deal. All of the electronics are in the case with the sensor. A couple of relays, a small compressor and some small solenoid valves are all you need extra. There is no air tank. The compressor just adds air straight to the bags when it’s needed. I used this same system on my T-bucket for almost 10 years with no issues. That car used the bags only with no other springs.
The compressor is a Viar 100, which is a motorcycle size unit. The valves are 1/8” industrial control valves. 1/8” is plenty big enough for this system. My intent is to hard pipe the valves to the bag inlets. This is the way my T was done and it could sit for days without leaking down very much.
This is the sensor on the car. All the crazy arrows are there so I can keep up with up and down. The sensor will work in a couple of positions, but there is a correct orientation. The control scheme opens the down valve for a few seconds before starting the compressor so that the compressor doesn’t have to start under load. So, the sensor has to be installed right or the operation will be backwards. I learned this the hard way on my T.:rolleyes:
https://i.imgur.com/UH1t4Zd.jpg
https://i.imgur.com/tUa3WHt.jpg
https://i.imgur.com/Umnb6ta.jpg
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.
https://i.imgur.com/gmOr73M.jpg
https://i.imgur.com/okWOIFh.jpg
https://i.imgur.com/qjRoDjt.jpg
https://i.imgur.com/MzyoeKp.jpg
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.
https://i.imgur.com/UXwFcsd.jpg
https://i.imgur.com/KPN6ShV.jpg?1
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.
https://i.imgur.com/5VnD2in.jpg
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.
https://i.imgur.com/kRv8p25.jpg
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.
https://i.imgur.com/duwP00O.jpg
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. :LOL:
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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.
https://i.imgur.com/cDtJLNh.jpg
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.
https://i.imgur.com/WY1azSq.jpg
https://i.imgur.com/c1hZN15.jpg
https://i.imgur.com/shkM8BY.jpg
https://i.imgur.com/KJptMom.jpg
https://i.imgur.com/kDPbeSL.jpg
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.
https://i.imgur.com/9otO8Xp.jpg
https://i.imgur.com/fjdo72R.jpg
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. :LOL:
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. :LOL:
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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.
https://i.imgur.com/QbIXtj5.jpg
https://i.imgur.com/oLBuARS.jpg
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.
https://i.imgur.com/gcfBpEs.jpg
https://i.imgur.com/TjhfeD4.jpg?1
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.
I started out by centering the rack and setting the toe. I pulled the clamps on the rack boots and slid them back so that I could measure the location of the inner tie rod ends. This allowed me to find the true center of rack travel. You can count the turns lock to lock and estimate center, but if the rack teeth are off, you won’t actually be on center. Everything has to be in the same position every time you check it or your results won’t be consistent. I checked the toe every time by laying a straight edge on the rotor and measuring to the frame rails. The toe has to be reset after every adjustment.
There are several charts on line that show how to interpret the toe changes and how to correct it. In my case, I had to raise the rack and move it forward I will say that I was very surprised to see the laser dot move well over 2” toe out the first time I compressed the suspension. That would be over ¼” toe change at the tread! I actually reran that test a couple of times just to see if it was repeatable. Unfortunately, it was. The toe change in droop wasn’t much better, either. Eventually, I was able to get it reduced, but it still wasn’t great.
The charts were telling me that my tie rods were too long. Now I am using 5/8” shorter control arms, but I had just enough thread travel available in the outer tie rod ends to compensate for that. Since this suspension is built completely out of aftermarket parts, the answer must be an incompatibility in the conglomeration of non stock components and altered geometry. After thinking this over for quite a while, I decided to shorten the tie rods and move the steering arms inboard. Luckily, the Wilwood spindles have simple bolt-on arms. The outer tie rod ends were just about bottomed out in the the threads, so I reasoned that if this didn’t work, I could go back and still have plenty of thread engagement.
I kept adding spacers under the arms, cutting a little off the tie rod and rechecking the toe change. Every time I cut a little off, the bump steer curve got better. Finally, after lopping a full inch off, the toe change curve was just about perfect. I had practically zero change, at the tread, in the first inch of travel increasing to about .015 in the second inch. The final inch brought to total change to around .025. That is less than 1/32 of an inch in 3” of travel. This was both in compression and droop, but there was a price to pay for this.
Moving the steering arms in greatly reduced the amount of Ackerman. In fact, I wound up with almost zero Ackerman. This bothered me so I had to call full stop and do some more research and that research really didn’t give me a definitive answer to my questions. I spent a bunch of time looking through the various suspension books that I have and checking out any articles I could find on the internet. As well as other forums.
Now let me say to start, I understand the basic principle of Ackerman. In a nutshell, it allows the inside tire to make a tighter radius than the outside tire so that each tire can follow the radius of a turn without sliding, but it seems that even in published articles, there is no real consensus as to whether it’s actually needed for anything but extremely low speed in a modern car. It was originally invented to keep buggies and wagons (horse drawn) from cutting ruts in soft dirt when turning and side loading fragile wooden wheels. Because early cars were just self-propelled buggies, it transitioned into the automobile era. Over the years cars have apparently been built with “correct” Ackerman of varying amounts, zero Ackerman and even anti-Ackerman.
Supposedly, some sports cars and Formula One cars deliberately use weird Ackerman setups to generate a high slip angle on the inside tire, which, as I understand it, is supposed to make the car turn in better. Essentially, this acts as a turning brake to literally drag the front end into a curve (no, I’m not making this up). I know I have definitely seen factory front steer cars that appear to have zero or even anti-Ackerman. The reason generally given for this is because it’s difficult to get the proper steering arm angles on a front steer car without hitting the tire or wheel, especially with wide tires.
Then there is the situation with pickups, which admittedly are not usually considered high performance vehicles. They are available in various wheelbases, from short bed standard cabs all the way up to long bed quad cabs. As far as I know, they all use the same spindle, which means only one of those wheelbases could possibly have anything close to correct Ackerman. From what I could gather, since a tire will generate some amount of slip angle at anything above low speed, Ackerman is just not considered critical anymore.
In the end, I decided to just give it a try. I’m convinced it’s not going to make the car uncontrollable or dangerous, but it will, most likely, have some degree of tire scrub in a parking lot. Of course, so do a lot factory cars designed by credentialed engineers.
If it turns out to be a situation I don’t like, plan B will be a custom rack. It will have to be built wider (by 2”) between the centers of the inner tie rod ends while fitting a standard Fox body Mustang mount. Flaming River builds custom racks, but I imagine it won’t be cheap. Unfortunately, this is the kind of issue you can run into when you get too far from stock stuff. Suspension geometry is a complex interaction of many parts and this suspension literally does not have a single part from a stock MII except for the spindle bearing nuts. Some kind of issue like this is just to be expected, but at least this one can be corrected fairly easily, but expensively, if needed.
These are the aluminum spacers I machined to move the arms in.
https://i.imgur.com/6YUw3wA.jpg
Mike, I really appreciate your explanations of the thought processes you go through, your talents and the solutions! I predict that for this one, at some point you'll overhear some guy talking to his buddy or his girlfriend at a cruise or show, saying "Look at this, the guy put his wheel spacers on the wrong side!" The things you hear when parking lot "experts" are "explaining" things....:HMMM::rolleyes::LOL:
I'll agree and echo Mr. Spears thoughts in the first sentence. But, now I'll have to sit and be patient for you to take it for a ride and then give us a report on your findings. Ackerman =YES? or NO? You've got so many nice features built into this chassis, should be a blast to drive.
Thanks folks. I really appreciate the words of confidence.
I will report back on this, good or bad. I've put too much time, money and effort into this thing to just live with something that doesn't work.
BTW - I may have already figured out a way to "fix" this without a custom rack. It would involve machining extensions for the rack main shaft to space the inner tie rod ends out 1" on each side. I'm sure this wouldn't be as simple as it sounds, but I think it's doable and a lot cheaper than buying a custom rack. That's a nice little thinking problem for a later date. Gotta finish this thing first. Debugging (which is ALWAYS required) can come later.