OK, I'm not understanding why you think a coil spring doesn't wear out and lose tension? Coilovers, as well. ALL springs will lose height over time.
I know they do but with the leverage lowering blocks put on leaf springs, along with them riding flat front the get go, leaf springs would lose height and tension much faster, wouldn't they? Also when the coils were out they're a lot cheaper to replace.
I fail to see how lowering blocks 'put leverage' on leaf springs. The spring is attached to the axle in exactly the same manner with or without blocks, just separated by a bit more distance. The weight the springs are subject to does not change with lowering blocks.
Im not 100% on it but, the block is like an arm. Kind of like a block of wood. The taller it is the easier it is to push over. The higher the block, the easier it is for the axle torque to turn the spring into an S shape
No, I know straight up and straight down a block doesn't make a difference. But there's more of a chance for spring wrap the taller the block is. Maybe I'm overthinking it but still the cost comes into play and if I can eliminate that possibility, that seems like the best way to go. There are a bunch of threads on Posies and Ch***is Eng. and I'm sure other companies springs inverting in just a few months/miles. Since mine's my daily driver, the miles add up fast. If I do have to replace springs on a regular, or even not so regular basis, I'd rather spend $70/pr. over $400/pr.
You are correct about the leverage when consider axle housing rotation.....however, that can fairly easily be dealt with by an inexpensive link. In the old days there were ‘traction bars’ below the spring. That would not work for you, wanting the car to sit low. Leaf sprung Ford Explorers have short links to control axle wrap above the spring from a bracket on the housing to the frame rail. If you have the opportunity to look under one, you’ll see what I mean. At a ‘pick a part’ I think those would be very low cost to buy.
See how the car sits right now... this is how I'm trying to keep it. This is between 6 and 7 inches lower than stock. I'm using 3" blocks and the spring perches I had made have 1" of drop built in. Heres a pic of my scrub line as well. Both pics are with the "new" springs I put in, which according to my buddy were sagged 2 -3". Even if I got 4" dropped springs, I'd need 1 to 2" blocks which I don't think would get my u-bolts above the rim. Here's a pic of the springs I pulled, and what I'm trying to avoid having ever happen again. Now that's not showing the negative arch that it had because it's on a lift but the rear sat exactly where it sits now, with no 3" blocks
You could have a spring shop make U bolts that are ‘squared’ rather than U and run them upwards. It would require a different ‘plate’ , shaped more like a muffler clamp. And you would shorten the U bolts and eliminate excess threads.
That's not a bad idea. The spring shop local to me however is outrageous and wants to charge almost $90 for four u-bolts. I cant imagine what they would charge for custom plates as well
I guess technically I could get another set of Spring perches and another set of Spring plates and just weld them together and to the top of the axle and use four bolts.
The upper 'plates' could be made from rectangular tube......1" W x4" D x (approx) 5"L for example. A hole could be sawed in the center, then the box cut lengthwise in half to make two clamps.....just like the bottom of a muffler clamp, only larger. You would need two such ***emblies to have four clamps....two per side...one for each U bolt.
Actually, The spring perches would be ideal, being pre-made and inexpensive....if the pads are long enough to allow the U bolt to p*** through a hole drilled in their ends.
I ask all dealers/manufacturers about their wall thickness. Sure you can find cheap deals out there, but what are you REALLY getting. Most of the eBay specials are cheap thin walled Chinese steel. Sent from my iPhone using The H.A.M.B. mobile app
Can't tell from your pics, but are your brackets below the frame? If so I've seen them moved inboard and brackets fit to the inside of the frame up higher. That could move the spring up, reduce your spacer block thickness, and help your scrub line
Dunno why you couldn't blacksmith squared-off u-bolts with use of oxy acetylene torch, a BFH and some sort of improvised anvil...just modify what you have
So as far as the upper links go, should they be perfectly parallel with the lower links? I've read a ton of things saying that for street use, the bars should be parallel but in all the diagrams I've seen, it says that they should point at an angle so that they intersect at a point between the center of the vehicle and the front bumper, which of course would make them not be parallel.
If upper and lower links are all parallel, that is a “parallel four bar design”, actually a five link because that setup requires a track bar of some sort, either Panhard or Watts link or a diagonal link. The “triangulated four bar” eliminates the need for the additional lateral control link because the horizontally angled upper links do double duty, controlling axle housing rotational forces and lateral movement.
Oh. Sorry....I misinterpreted the comment. I think the question you have is related to “instant center” geometry of the control arms and is not something I feel I understand well enough to offer ***istance. That is an area that, for me, requires more study in books devoted to suspension theory and design. Books on that subject are readily available. In fact, I have such books on hand, but have not done the required reading on that particular element of design. Guess I better dig into them....
That could be part of a reason many people choose to utilize a parallel 4 link system, as they are much easier to visualize and set up over a triangulated link setup, and also, although it needs a centering device like a panhard bar or watts link behind the rear end, allows for more clearance which could be useful when dealing with a car floor, driveshaft, exhaust, etc since they are typically mounted outboard of the frame. You would still need to make spring coil spring pockets on the frame and axle, (unless you went with coilovers), and a panhard bar, but that would probably be easier in the long run than a tri 4 link. If I was trying to go extremely low without air suspension, I would be looking at a parallel 4 link with a panhard bar and coilovers. a triangulated 4 link in a static suspension car seems like an unnecessary amount of work and takes away a lot of useful space, in my opinion, even in my truck with a raised bed floor, the upper triangulated bars require a lot of space and limit options of exhaust, gas tank, etc.
While I was under the car measuring, I came up with 24.5" from the front leaf spring mount to directly under the axle (4" straight down from the axle tube to account for the brackets). I also came up with exactly 18" from the frame to the front facing side of the axle tube, right next to the center section. 60% of the lower bars is 14.5" so as long as my upper frame/axle link brackets are 1.75" long I'm exactly in the "rule of thumb" zone. If my upper links need to be pointing down towards the front, I'll need to lengthen them and mount the axle tabs on top of the tubes, which will throw the 60% rule out the window. I did some research and I found that a '70 Chevelle convertible with an 8 cyl is almost the exact weight (curb, front and rear) as my hardtop. Rockauto has the springs for $50 or so a pair
Umm No! A spring has the same rating [lbs/in] for it's whole life. It only loses it's set [or height] Regardless of it's shape. It doesn't sag over time, but over cycles [or oscillations] sort of like a pendulum slowly swinging towards vertical. If a spring is bent beyond it's point of yield ,it will stay in the new shape [just like bending steel] Lowering blocks don't change the vertical load on the spring at all. There is a slight increase in leverage causing pinion torque reaction upwards , but the increase in axle thrust leverage counteracts this by trying to point the pinion downwards. This can cause oscillations [axle tramp] but a simple 3rd link running forward off the top centre of the diff will remedy this
The pinion torque is what I meant when I mentioned leverage. Also, if the spring starts out flat, wouldn't the leverage from the block/pinion be multiplied that much more over a positive arch in the spring? Check out the multiple posies and ch***is eng threads where people use their lowered leaf springs and most of them end up inverted within a few months. Is that due to leverage wearing things out faster or or crummy springs? I dont know but I'd rather not find out by spending $4 to $600 on leaf springs just to turn around and spend $500 or so on a link setup when I could've just done that in the first place. If I had money to burn it would be no problem to experiment but I kinda wanna get it right the first time. I realize people have been using blocks, dearching springs, reversing eyes and doing all kinds of stuff for years but that doesn't mean there isn't a better way.
The pinion torque is constant to the distance of the pinion contact to the axle centreline It never changes unless a larger diameter crown wheel is used [ but that only changes axle torque, because the torque comes from the pinion ] Due to mechanical gearing ,the axle thrust forward trying to propel the car forward is greater than pinion torque reaction. So in theory the diff tries to nose down if lowering blocks are used [due to increased leverage distance] This nose down at***ude tries to created lift at the footprint [pivoting around the front spring eye] And Accelerating forces applied at the mounting pad with resistance at the front spring eye cause the leaf to try and shorten. So it bends in an "S" shape. Manufacturers shorten the front half of the spring to help control torque [the overall length is for stiffness] Simple "traction override bars" like early Shelby Mustangs or OEM Ford Cortinas will address this issue without compromising ride quality [just get the pinion angles correct] If a spring inverts itself in a few months it is made from the wrong spring steel or the rating was wrong. I have never in the history of cars known this to happen to OEM springs from the factory. After 61 years my old 57 Chevy only settled 1/2" [***uming the ch***is rails were level, where I measured it] I pulled the springs apart, and reset the mainleaf in a hydraulic press ,using chalk marks on the ground for reference then re-aasembled them
Dont get me wrong...the springs I put in are from a '53 two door sedan but they still have positive arch. It's just the replacement lowering springs that are inverting right away. Once I do my notch I MAY do the u-bolt flip we were talking about earlier in the thread, at least until these springs wear out. I'm not buying new lowered leaf springs though. When these springs are done for, if I keep them that long, I'm going with the 4 link. The first order of business is front disc brakes and getting the '54 lower control arms and uprights on
Springs don't wear out! They slowly lose their set [or load height] They can simply be re-set again to restore the desired height. You could get a spring "smithy" to reverse eye the main arch [flip it over then re-arch it back the other way] This would allow some arch but still have a lowered spring. AND Get an extra front 1/2 leaf added to control torque ,without changing the height/stiffness [this is an old road-racing trick] In an old cruiser , I would much rather have the simplicity and reliability of leafsprings than some re-engineered 4 bar kit that will eventually flog-out all the bushings. Your springs are from 1953! [65 years old] and you're worried about them sagging in a few months. I would rather trust them old ones [re-set] than some new "trailer springs"
I hope they dont sag in a few months but if I cant get the u bolts flipped my rear may get torn off before the springs do wear out
Well guys, even if I flip my u-bolts I still won't be above the scrub line because I'm still using the factory shock mount plate. Does the very bottom leaf actually provide any support for the pack at all or just add a bit of height? I could pull that one and it would help tuck things up a bit
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