Dave29...Try taking one of the bolts out of the UPPER, CENTER link. In other words, temporarily disconnect it. Fold it up out of the way. I AM NOT SUGGESTING THAT YOU DRIVE THE CAR THIS WAY!!! Now, with the upper, center link disconnected, jump up and down on the rear. Has ANY of the binding diminished? I think you have created what effectively amounts to two different-lengths of UPPER links. Re-read my first post. You can't mix different arcs (lengths) on the SAME plane. What ye say? DD
hotroddon...I agree with what you say, and as you'll see in my last post, I would never suggest DRIVING the car like this. My point is that the shackles have been designed into this suspension (mistakenly) as LOCATING and PIVOT points. This suspension needs to be re-designed so that the shackles ONLY serve the purpose of what shackles are designed to do. Extending forward from the axle centerline like they are, and in relation to the LOWER control arms, the shackles have become locating points about which the axle TRIES to rotate as it travels up or down. The "entire frame flexing" is a distinct probability, and is most likely why something has not broken yet. DD
I think I would get the car on a lift and check everything over,if you haven't already. Sounds like maybe the frame is ''hinging'' somewhere if the door gaps are changing going down the road. I'd also check king pins,tie rods,steering box play and u-joints and every single suspension mounting point. While the car is on the ground I would have someone shake the steering wheel back and forth to see if something is moving or flexing that shouldn't be. What does the steering shaft consist of? I didn't see any pics of the whole thing. May not be a design problem,could just be something worn out.
The short lower links, headed up hill towards the front cause it to want to oversteer. When it does, it compresses the outside rear suspension even further which in turn causes more rear steer. A vicious cycle. Some redesign is in order. Also the little tabs for the upper link welded to the cast housing will fail, probably at an inconvenient time.
You got WAY to many leaves in that spring !!! 5 to 7 is more than enough. Add shocks also. That upper control arm welded to that housing is not a good idea the way it is done even if the center section is a forging and not cast. The entire rear suspension needs to be redone as far as I'm concerned.
^^^ Listen to him, he does this kind of stuff for a living. Do you know what wall thickness the 2X3 tubing is? It sounds like it might be thin wall tubing & that may be contributing to the flex (changing door gaps indicates flex). Some thing screwy is going on, a car that light on a 2X3 frame should not have any flex during normal driving.
Too much confusion on this thread. I stopped reading. 1. the clevis ends on the rear suspension must go. They are binding up and causing the links to act like springs, loading and unloading in lateral force. Put rod ends here. 2. the three link rear is a great choice, but a panhard or watts link is mandatory. Panhard is easiest. 3. cross steer isn't mandatory to have a panhard, but it sure makes one behave better. Add one. There is a risk of binding between the rear shackles and any 3 or 4 link type suspension, but it's minimal. Your biggest issue right now is the clevis ends. And yes, ElPalacko knows his ****. (but so do I)
Are the lower suspension links horizontal when the car is on the ground? With the lower links pointing up hill like in pictures, during suspension travel the axle will want to push the axle back. That change in axle position fore and aft will put the rear spring in a bind, you are trying to push the spring, it doesn't like that. Lower link attachments to the frame in single shear! Nut welded to frame as attachment point! Very bad ideas. Will work for a while, but metal fatigue is in your future, failure is almost guaranteed.
I am re-reading all statements and suggestions. Wondering now which direction to take to make this a safe ride. I can't get out to the garage until Thursday night. All members observations and suggestions are very appreciated and not p***ed off lightly. I want this roadster to be safe at any speed. Not sure the thickness of the sq. tubing. The lower links point upward and slightly outward toward the frame rail when the car is on the ground. I will perform as many tasks as suggested and post results. I'm pissed off now.
Too many leaves in rear spring ,Take a few out and definately add shocks ,Thats my setup ,I think you have too much rebouund with the rear spring ,Also rear spring needs to be greased.....
I got a Vette rear on my t-bucket w/ the same problem you having. I still have to take out a few springs which was suggested to me. I will I be doing that after the first of the year. Also I dropped the air presser in my tires to about 15 front / 18 lb rear and that alone help out a lot. Good Luck and keep us posted
please get rid of the clevis's-they are not made to be a pivoting joint! The only bearing surface ends up being the body of the clevis and the bolt itself.Use them only on the non- pivoting end of a hairpin type radius rod.even then they are not made to take any side load
Don't get too mad or frustrated with it. Suspension set up is one of the hardest aspects of a car to get right. Some people have the best intentions with creative suspension design but fall short in execution. I have friends that have had their cars completed for 10 years and they are still trying different springs, shocks, tire pressure, and alignment to get them riding perfect. Make a change, see how it responds. Make another change, etc. DO NOT make a wholesale change of everything listed, you won't know what fixed it and what you wasted time and money to fix. Start with the Safety concerns.
The C3 vettes had either 7 or 9 leaf springs if I recall correctly. More leaves of thinner stock is better, or easier to remove one or two leaves from. Weaker shocks often help too.
what kinda car is this on? i agree with most that has been said... i think a couple of your major problems are: -no rear shocks ...this will do strange things to a light car you never dreamed of..especially with some egg shaped repop tires -no front panhard in a cross steer ...i have heard people say if everything is proper you don't need one...im not an engineer but i still say ********...i got the misfortune of driving two hotrods without ...white knuckle at best...it makes the car twitchy the steering wheel reacts different all the time easy to over and under steer -clevis reasons already stated - rear panhard ...i'm not sold on those for what i do...but for your application might not hurt, i would probably do a triangled top link like already stated also -spring in front of rear...my experiance with that style of set up seems to make the car feel choppy like a short wheel base ,without being there i cant say for sure , but in a roadster i usally take every other leaf out ,it may benifit ..maybe not. but if its to stiff you might as well weld the rear solid to the frame - i hate z'd frames that are spelled with an L make sure it is gusseted well - are all your 3 links on the same pivot? -what is your caster set at in the front, what is the toe? my guess is that just shocks, an alignment, and a front panhard rod will change your car 100% for the better
Good morning just got back from the Indy trade show and caught this post. So here is my take on the issue. First going back to the initial post question, You must install shock absorbers on the rear axle. Much of your problem is the failure to control the spring action with some kind of dampener..It seems that you have determined the this is a rear end issue not a front end issue so lets start there first. The second step is to determine if you have a rear steer issue on the vertical movement axis of the rear axle. To check for the change in wheel base, set the ch***is at ride height on jack stands or blocks, place a floor jack under the rear pumpkin and remove the rear tires. This will give you the ability to watch the action of the rear axle as you raise or lower the axle to represent hitting a bump or drop in the road surface. Disconnect the center upper control arm link. The rear axle still is connected in a 4 link set up by the spring but because the spring is flexible both by stretching as well being able to twist on the lateral axis it does not serve as a positive linkage but slow manipulation will give you an idea of what action is taking place as your car runs down the road. If there is a high degree of offset frontward or rearward you will experience a rear steer that become more and more noticeable as the speed of the vehicle increases. You can accurately measure this by dropping a carpenters plumb bob line from the center of both ends of the axle at rest and compare the locating point movement as the axle is moved up or down. If you are getting an offset forward or rearward of center within 2-3 inches of travel you have an issue with control arm length. What is happening is the arc operation distance created a lengthening of the spring under compression does not match the arc of rotation distance change of the lower control arm. The two operations will try to balance themselves and the axle will steer right or left based upon the favoring components rotation of the rear axle.. Reattach the upper link and repeat the test to see if the same off set is smaller or larger. If the offset is smaller than the link is helpful, if the off set is larger then the link is incorrectly angled and the operational arcs of the upper and lower links are not in the same arc path, this top link is actually creating the problem. Try this test first and report your findings.
The simplest fix I can see for the geometry would be to cut the shackle mounts down and hang the spring off 2 double heims at each end (one set on each side of the spring eye). This effectively "divorces" the spring form trying to locate the axle. Cut the mount off the center section of the housing and add 2 mounts to the axle tubes right where they join the cast center. Build a "V" upper link to tie into the existing ch***is bracket. Change all the clevises to heims and mount in double shear (2 plates to sandwich the heim). And ABSOLUTELY add shocks...
Replying to thirty-two. The lower end links are at 10 degree angle tilting up toward the front of the car when the car is on the ground. The center link is at a 15 degree angle. Caster appears to be 8 degrees positive, using an angle finder. Toe is approx. 1/8”, using a plumb bob and tape measure. Heading out to the garage right now and perform **** SPADAROS’s suggestions. I’ve made so many measurements the last few days. Front hairpin distance, from rear mount to back of front axle is 33 ½” on driver’s side and 33 5/8” on p*** side. I know one thing. I’m sure learning a lot about ch***is design. Reading a lot of threads on the HAMB plus purchased a couple of books on the subject. I really appreciate all the help.
Might help a few of us, if a change is registered when you improve a...that's one[1] feature of the suspension. Let us know. Many of these are the usual-suspects.
Somebody went to a lot of hard work fabricating this setup. The biggest problem is the rear spring in front of the rear axle. Ford moved the spring from the top of the axle to the back of the axle for better handling. You are kind of driving an old Ford Bronco (65) with a short wheel base. They were unsafe on bumpy roads. Ford never named a vehicle more accurately. This set up has shortened your wheel base. You can add all kinds of bars, remove bars and add shocks but the spring should be behind the axle. The top of the spring is way up in the air and this makes it a long level arm to twist the frame when you hit a bump. The brackets welded onto the axle housing for the shackles are long and create another long lever arm which multiples the force on the high spring cross member. **** will probably come up with a good solution and easy fix.
Raised ch***is to ride height & removed rear wheels. Disconnected the center upper control arm link. I had to raise the pumpkin to free it. Removed the bolt & noticed threads were worn where it contacts inside the rod end. Also notice in the attached images the dimples on the center control arm link and spring mounting pad. When I lowered the jack, the axle came to rest on the lower rear wheel housing. Also note that the bracket attached to axle would hit the square brace that supports the gas tank & battery. Look how close the positive battery cable is on the p*** side. Several wks ago I removed some of the lower wheel housing sheet metal after jacking up the car. I did not disconnect the center upper control arm link at that time so I thought I had removed enough metal. Jacking up the axle on the p*** side caused ½-¾ rearward axle movement. With the center link attached & jacking it up, the rear moved back ¼. Jacking up the driver side caused the axle on the p*** side to move rearward from center 3/8 - ½. Attaching the center link and performing the same task, caused the p***. Side to move ¼ to the rear. The center upper control arm is preventing the rear axle to drop by limiting its travel. Im concerned about suspension when it rebounds after hitting a bump with the center link attached. What is the function of the center link, besides adjusting the pinion angle and preventing the axle from hitting the outer wheel housing or cutting the pos. battery cable?
Checking the Hamb at lunch and saw you did a little experimenting. By now you must understand why your car gets a little unstable at high speed bump. The upper link is doing you some favor keeping everything in some alignment but the culprit is the short arc of the lower control rods in relationship to the upper spring hanger. Because the short links swing in such a small arc the spring twists and skews the rear axle. The upper link tries to locate this but due to the fact that it pivots it still alows the axle to **** and initate a rear steer. A possible cure is to double the lenght of the lower control rod and recheck the offset with the longer arm.
Still reviewing my options. I would like to go to a triangulated 4-link if possible and keep the buggy spring. If I keep a similar set up that is on the car now, getting rid of the clevis ends and changing the rod end mounts from a single shear mount to a double shear, I need to install a panard bar. Only thing is, there is no place to attach it. The frame stops ahead of the rear end. The upper bar on the triangulated 4-link would only be 13" long. The lower bars would be somewhere around 20" long. Not sure if the bars would be too short. I’ve seen a few 4-link set ups on muscle cars and some are only 15-18” long. Still sorting out interference issues, brake line, on driver side & gas line on p***. side. I’m new to this. I want to remove a few leaves from the rear spring pack but I need to fab. up a leaf spring spreader to ***ist me in this process. Been reading on how to make one. In order to install rear shocks, the frame would have to be extended to the rear to install a cross brace.
Wow... This thread contains an awful load of misinformation from well- intentioned people obviously not schooled in suspension design. I think you've discovered that you need to get the suspension linkage geometry sorted out before you even think about spring rate or shocks. Short links swing through short arcs, resulting in more fore-aft movement and steering of the rear axle for a given amount of vertical travel. Your current setup is badly bound up. I'd suggest you pay close attention to posts # 49, 50 and 55. Relocate your link pickup points to reduce rear steer effects as much as possible, set it up so it steers into the corner when the body rolls, not to the outside. Drop the front end of the lower links. The "heim end shackles" is a great idea that will eliminate much of the spring- induced binding. Some sort of provision for lateral location of the rear end is necessary- panhard bar, triangulated upper link, looks like you don't have room for a watts link. Shocks are a must. I'd also suggest picking up a book on suspension design, by some one like Herb Adams. Edit: This would be a good choice, one of my faves: http://www.amazon.com/How-Make-Your...=sr_1_9?s=books&ie=UTF8&qid=1292895182&sr=1-9 And there are a lot of companies out there selling poorly engineered kits to unsuspecting consumers.
Removed 3 leaves from the rear spring after making a spring spreader. Learned a lot from that experience. Definite suspension bind from upper center link. Been leaning toward installing a 4-link, with panard bar, instead of a triangulated 4 link due to simplicity. Got a question concerning clevis and rod ends on ladder bar setups. Previous posts on my roadster’s set up stated get rid of the clevis and install rod ends due to safety issues. Why do some ladder bar manufacturers, such as Pete and Jakes, use clevis to attach the bar to the rear bracket? I’ve seen other use rod ends. Can someone tell me why clevis are used to attach bars (links) to the rear end? I’ve seen them used on “traditional “ set up too. Educate me.
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