I have been looking for a 28-31 model a roadster to buy for the past year or so. I ended up pulling the trigger on a 28' roadster with a brookville body. The car is about 80% complete and does run and drive to a point. I knew that the suspension needed some attention because the previous owner had installed air shocks on the rear. After my first trip around the block it is painfully apparent that the rear suspension is far from set up right. The P.O said the rear is a 37 banjo center with 40' bells and axles. The shackle brackets welded to the axles looks like possibly a speedway part. the first thing i notice is that the spring eye / shackle end is pretty much touching the axle tube and obviously doesn't have room to pivot because even if it did clear the axle tube, it would bind into the bracket welded to the tube. from my rough measurements i believe that the shackle eyes on the axle are spaced at about 48.5" center to center. the spring appears to be a factory ford part as i see some leaf wear on the main leaf. obviously some of the leafs have been removed to attempt to lower the rear. i counted 7 leafs but of the 7 leafs, 2 are short leafs from the top of the pack, flipped below. #1 air shocks, brackets and lines have got to go. #2 id like to use a reverse eye main leaf to get it a tad lower. #3 im assuming i need to remove the axle tube shackle brackets. i'm thinking maybe buying mounts that attach to the backing plates (house of fab member here) sells some. now for the photos! Am i way off on my thinking? as it currently sits i can stand in the back and the rear suspension doesn't move at all. After i get the spring set up i can think about tube shocks for dampening. thoughts on tube shock application to use here?
I would weld the shock mounts all the way, not just tacked, change the shackle mounts so the shackles clear. When you get the shackle brackets high enough you may find that the shackles interfere with the wheel cylinders.Mine did
sorry for the confusion. the last photo is from House of fab showing the brackets they offer. their example shows them installed on a parallel spring rear. Those are the brackets i am considering.
The House of Fab brackets look good. I think my spring eyes are about 48.5 too. I edited my first post
You simply cannot use air shocks on car that has almost no weight on the rear. I say that as they require some air pressure to last. So, it will ride like a brick. My question is why he chose them? Did he remove too many leaves and the car settled too much, or was he trying to keep the shackles from hitting because he built the brackets incorrectly? Yes, those shackle brackets won't work. Either way...start over. It took tons of time to get the rear of my 32 to ride extremely nice. I worked on the spring leaves before I ever put shocks on. Got it so it feel OK by jumping on the rear spreader, then looked for soft tube shocks. After the car was out in real world driving, I ended up messing with leaves again, due to bottoming out occasionally with 2 people, or with a full 20 gallon tank.
Are those shocks all the way compressed at rest? They look huge. I bet if you removed the shocks and took it around the block it would be bouncy but not bound up. I'd rip those off and whip em in the woods first thing.
Yes, weld the shock mounts and remove the leaf spring mounting pads. Remove and modify the rear spring mounts to sit higher above the axle so that there will be clearance for the shackles to move with the suspension movement. Make sure that the mounts are the proper distance apart center to center for your spring (not sure what that measurement should be). Then with a reversed eye main leaf and tube shocks you should be good to go.
I'd like to remove the add on shock mounts (gold brackets) and go back to the ford lower shock mount shown in photo 2 and 3.
Hack everything off, keep the bolt on shock mounts and install the House of Fab parts, that will help get the correct geoemetry on the spring shackles. Using the House of Fab parts will cause other problems. To properly install an A spring on axle you should always need to stretch the spring to install, at this point the shackles should almost flat. You could also CAREFULLY diss-assemble the spring, install the main and then CAREFULLY re-assemble the spring pack. Once weight is on the suspension you should end up with shackles that are approximately 45 degrees to ensure proper spring travel. Since you are essentially converting your 40 axle into a spring over A Axle, the new mounts may likely interfere with the backing plates, read on here for "putting hydraulic brakes on an A axle". you will see that in every case when using model A spring over axle (above axle mounts), the spring shackle will interfere with the brakes cylinder. In most cases the builder will have to re-drill and clearance the backing plates to clock the wheel cylinder away from the spring shackles.
Chappy, Sorry man, but your spring geometry is wrong, Your spring is completely bound and you have no suspension travel. Any spring travel will require the end eyes of the spring to travel outwards, your system is completely blocking the spring travel. Optimal set-up will have the spring shackles at 45 degrees in a loaded state. Your shackles are at almost 90 degrees when the eyes come in contact with the spring mount.
Springs must have room too move. The shackle should hang close to 45* with room to move too about 90*down when a bump loads the spring. Bump makes the spring get longer,by having the shackles at a bout 45*,it self centers the axle to keep side shake out of the frame===ture at both ends of cars with this type spring design............................that's the way they should work. Some poorly built rods have shackles hanging closer to 90*but still have room for shackle to move=in that case,they must use a panhard bar to center the frame over the axle.........
Yep. It wouldn't be difficult to correct, but you'll have to cut off the existing mounts and fabricate new mounts that relocate the top shackle pin an inch or 2 towards the backing plate (that will establish the proper 45* shackle angle), and also leaves room for the shackle to swing out as the spring compresses.
Chappy; I'm thinking you got some work to do before Spring driving season... "aren't ya glad you posted that pic"? ...but..everything happens for a reason. Your car will ride so much better. I'm wondering that if you ran it long enough like this, that maybe the spring eye would break off.
Thanks jrblack, I agree that it is less than optimal...and it is on the list of get to eventually... there are other items to get to as well... on a brighter(?) Note, that spring has never compressed enough to cause the shackle to touch the mount bracket. (See virgin paint in pic below) I did not build this car and am finding and repairing issues as I drive and enjoy it. In about 24 month we will be moving and the new place will actually have some room to work and I will probably blow this thing apart and change it up a bit. Thanks again Chappy
It is a shame that the original builder of the car didn't just leave the stock 1940 mounts on the axle and relocate the spring cross member. You wouldn't need to deal with any part of this conversation
You need to look for the contact spot higher up. It simply has to be hitting...unless it is never driven. .
I agree, it should be something on the fix list, I would be concerned about the dust building up on top of the axle. You spring may not be rubbing the axle, I would bet the 1/4" plate is wearing groove into your spring eye and vise-versa. I would guess that the dust is a nice blend of Paint, Primer and metal shavings.
so it sounds like the House of Fab brackets may be the ticket.. That may present an issue with the backing plate/ hydraulic cyl. bleeder.
Yes, I would start there. I have not heard of anyone having problems with the House of Fab brackets. just something to look at. Keep tinkering, researching and reading, the answers to every problem are out there somewhere.
Ugggg... you guys suck!... not really, I appreciate the feed back and assistance... I knew I should have just gone to work today instead of crawling around under the car. I did find out why the spring eye never touched the mount plate. I may be blowing it apart sooner than I wanted to... . I have spent the last year getting the steering, braking, wheel bearings and carburation right I haven't even made it to the back of the car yet. [Anyone looking to pick up some side work? I really dont have the space to do this project right now] Chappy
cobra51addict....something to consider is to have the main spring leaf shortened. I'm almost positive the spring mounts on my stock Model A reared are 49.5" center-to-center. While the spring is being shortened, or if you buy a "short" spring from Posies, you could also go to a reversed eye to lower the car. I had St. Louis Spring shorten and reverse roll the eyes on my spring when I needed to position the shackle mounts closer together on a 8" Ford than they are on a stock Model A banjo. I built my own mounts, similar to Chappy444's mounts, but I used two parallel curved brackets coming up from the rearend rather than just one thicker bracket. Chappy444... in your last photo it appears your wishbone mount would be hitting the underside of the main leaf with very little suspension compression. If it's working though, good for you! Maybe it's just an optical, photo angle trick that makes it look closer than it really is. Believe me, I'm not picking at your car. Lynn
Looks like your spring is too long to me. Shackle should be at a 45 degree angle at normal ride height. I'd contact someone like Posie and give them your spring perch c/c measurement and have them, at least, make you a new main leaf.
It looks like Millworks has a product as well. https://www.millworkshotrod.com/col...r-spring-perches-fits-ford-and-lincoln-brakes
Most of my observations have been well addressed by others, but I think there a couple of other aspects that bear consideration. You stated that the spring is "pretty much touching" the axle housing. In the picture it appears that it is touching. I assume the car was not jacked up to take the pictures, in which case things would be even worse. When you have two people on board, and a full gas tank, it will be worse. Apparently you have zero bump capability with any normal loading, i.e., effectively no spring. The 45 degree shackle angle is a well used rule-of-thumb, but should be verified. One shortcoming of the "A" spring is that the "eye" moves laterally in "bump" almost as much as it moves up. This is accommodated more easily with longer shackles with regards to shackle angle change, but enough lateral clearence must be provided regardless. Note that with a fairly flat spring, there is much less change in shackle angle. If the spring eye is reversed, you will lose maybe 1 to 1.5" clearence between the banjo and the center spring mounting hardware; be sure to consider this. A consequence of the 45 degree shackle angle is that there is a horizontal load on the spring perch equal in magnitude to the corner weight of the car. Your picture is not clear in this regards, but it appears the shackle support bracket is an ungusseted flat plate, with bending stress (due to the forementioned horizontal load) at the base in the weak direction. Attached is a sketch comparing stress levels in two loaded plates, oriented in line with and transverse to the load. With the plate dimensions as noted, the stress level varies by a factor of 4! The design shown in Chappy444's posting (disregarding the vertical shackle), appears superior regarding stress distribution. With the full length spring, you may not be able to fit this arrangement. The House of Fab arrangement may be fine, but I would want them to advise the vertical load rating with 45 degree shackle angle, with consideration of the bent plate thickness, and the high tension that will be in the bolting, to absorb the moment from the load. I'd also be concerned about load on the backing plate bolt lugs, which hopefully House of Fab has considered in their design, if they are marketing them for this specific application.
Desmodromic thanks for the insite. I had similar thoughts in my head regarding the bracket deflection. This weekend i will start removal of the air shocks and try and get some additional photos of the overall setup. Without a doubt, the current setup is incorrect in several details. Thanks for the insite!
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