Its very very very very........hard to tell as the quality of the picture is crap, BUT!!!: I saved and made the picture a little lighter as my screen makes everything a lot darker than it is. Bottom line is Imma Dick! it aint no leaf and evrybodys being right.....BUT me!
If this were a thread about suspension design, I would tell you about instant center and anti-squat. But it isn't. I would be more worried about the fact it is under the scrub line, and be very suspicious from there on out.
To answer your original question, rear 4 bars are not normally level to the ground or parallel with each other. The fact that the bottom bar in the picture runs downhill aft looking forward is odd looking though. I agree with the others, the forward mount looks pretty low and more pictures will help..
If you're are lookin' to buy that T it would be good to get more pics. To me from that pic the back looks to low makin' the four bar angle worse. Smokey
The picture only shows the bottom of the L/R , but NO they aren't level . Depends on how you set the 4 link up . RetroJim
There's been a few decent discussions on rear suspensions this year. I agree that the car posted looks a bit off, well silly, really. Sometimes it's hard to get your head around what others do or why. Do a search. there's some top flight people on here giving good input now and then. Are you building something or just askin?
Look up instant center, in that pic I would guess the instant center is behind the car and fairly high up. A good rule of thumb for a 4 link is the lower bar level with ground, upper bar down in front some. 4 bar suspensions are both same angle and approx. level. I won't claim to be a suspension expert but I have done a lot of studying on them. You are seeing a lot of hot rods, etc being built obviously by people that have not done even fundamental design theory reading and understanding of why things are certain ways.
Here's a really simplifiied and brief description of rear suspensions and theories. A 4 link, or 4 bar as the street rod guys call em, is just what it indicates. 4 separate bars, boxes or rods locating the rear axle. Both bars equal and even to the ground even using solid or semi solid mounts would control only up n down travel. A Panhard bar or track locator would then be employed to control side to side movement. By dropping the top bars the expected action is to plant the rear tires under more severe load conditions by using leverage from a point ahead of the rear axle. That point is refered to as an instant center that's calculated by the intersect point of the upper and lower bar angles. The leverage is imparted by the torque or twisting forces of the rear axle when the load is increased. Looking at the driver's side, the pinion forward, the twist is best described as the pinion rolling straight up into the car. With the bars installed it can't roll and therefore the tires go down with a force greater than the weight of the car, and those forces are controlled by the length of the instant center or the distance from the axle centerline. What does complicate this action is the 2nd force imparted on the axle again applied through by multiplied torque, wants to lift the right rear tire up off of the surface. Looking at the rear of the car the axle twists counter-clockwise under load. In normal driving conditions creating this leverage point is not as critical as ride quality and predictable handling. All of that above relates to equal length parallel 4 link bars and as is widely known there's other forms of rear axle locating hardware that's similar. Unequal length bars used in a triangulated mounting design can eliminate the need for Panhard or track locating bars. The angles of the bars can be set to handle side to side movement and that design is especially preferred where space is limited. There's no hard rules as to the angle of the bars speaking in really broad terms. Obviously what you've posted is not only unatractive but has other forces against it. As that bar straightens out the wheelbase has to get longer. Simple geometry tells us that using the axle centerline and the mounting point ahead of it, as you bring that bar down at the axle the arc of that travel will take over and try to push the axle back. If it's mounted solid like on a buggy spring or combined with short top bars then binding is unavoidable. There's a shit load of info related to this and like I started out saying here this is a simple overview. There's wishbones, watts links, Panhard bars, track locators, spherical rod ends, rubber or urethane bushings, and let's not forget 3 links. There's a few keywords for ya to search things out. Much of this applies to more than cars like that posted. It applies to drag racers, OEM rear suspensions like GM's 3 and 4 bar designs, and aftermarket chassis designed for several applications. This should be enough for you to dig around here as well as general 'net search. The info is endless and is as varied as peoples opinions as to what's best. Have fun learning this stuff. It's pretty rewarding when you 'get it' and it always helps.
It looks like the front mount of the rear bar would be a great speed bump scaper. Front mount looks too low, but with out seeing what the person is doing who know's. I am learning 1st hand how screwed up a car can be you buy .. dont assume anything. Everything I assumed was wrong and now I am have a new chassis built, I surrendered, it won.
Thanks all! I've also been reading Brian Angus' "How To Build A Hotrod Frame" thread. I wondered about Watts links as well, but I figured that they weren't used for aesthetic reasons on an early-style car with a rear suspension that's easily seen. The earliest hot rod that I know of with a Watts link was a factory Thunderbolt that was modified by the owner/builder with coilovers when it was new. I'm sure the concept is way older than that but I wonder what era they might have first been used in a hot rod?
To add to Highlanders excellent description, you also have to think about the fact that the lower links are taking ALL the "push" from the rear tires/axle and transmitting that force into the frame, which makes the car move forward. With those bars angled down that far, the forward force is also pushing the chassis down toward the ground (compressing the rear spring), with the resultant reaction being the tires get lifted and go into wheel hop. Yes, the lower links should be level with the ground or close to it. You will see the links run downhill in some drag applications to anticipate the rise on launch, but no where near as far as the ones in your picture. As far as the watts link for the rear; it has some advantages. Unlike a panhard bar, the length is irrelevant as long as the geometry is correct, so it works well with a narrow chassis. The watts is much more complex to install, and needs a much lower mounting point off the frame than an equal height panhard bar.
I'm sure the history of the Watts Link can be traced easy enough. It's been used recently by an OEM, (Ford/Mercury full size I think) but even produced and developed for mass production the same downfall exists in my view, it's ugly. Panhard bars like to be as long as possible, and the more travel the rear suspension has the more critical that length is. Once again the arc of the travel from the solid point (frame) to the axle can impart side to side movement. Basically a short Panhard bar in a long travel rear suspension is not a good idea. As a point of interest Packard saw fit to install a shock absorber on the end of their Panhard bars starting in the late 30s. This would dampen side to side movements that are inevitable with long leaf springs. It's also a good looking part.
Dodge is another one that used the watts link lately, on the Durango. I saw an axle from a late model Lincoln, I guess, at a friend's shop the other day. It had the watts link butterfly up front on the forehead of the pumpkin, above the pinion yoke. It was really compact and not at all hard to look at. I think that is a way to package one where appearance is a concern.
I find that rear suspension geometry to be basic until somebody tries to explain it and for some reason people will ignore a simple design and try to build a complex structure with lots of angles and moving devices. Why is that? Why hasn't anybody considered the 'rear steer' when postulating about the sustension stuff in the rpu? Lots of theory and design issues that apply to going straight, but nobody seems to have thought about what goes on when he goes around a corner. Esp if there is a little hill and a crown in the highway. It'll pucker your asshole up, i think.
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