Howdy, y’all Hope everyone is looking forward to the holiday weekend. I know I am! I recently “finished” my Av8 (sorry, banger bros. I still haunt the monthly meet). After taking it for a few spins (and rebuilding the trans. Thanks for all the input on that) I noticed the suspension is too softly sprung in the front. I really love my stance, carb is level, caster is good, etc. Is there any rule of thumb for stiffening the leafs without adding a lot of height? Should I go with more longer leaves, or shorter ones? I read a thread where you can fashion a “progressive” leaf pack by placing shorter springs in between longer ones so that the suspension rides softly until is encounters a large bump, and then takes up that load with the rest of the pack. Any help is always appreciated.
That's a very nice car. The antenna isn't my style, but the rest looks great. There were several front springs built for the A's with differing number of leaves - assuming you have an original spring. But in any case, how many leaves do you have now? And does the main leaf have reversed eyes?
By"too softly sprung", I am assuming you are blowing through the suspension travel and hitting the bump stops often during regular driving, correct? You are not experiencing excessive bouncing or hopping, which would indicate a dampening issue. The simplest way to increase the spring rate is to add full length leaves to the pack. However, this will increase your ride height and spring pack thickness, which may be undesirable. Another option is to replace the leaves with leaves made from a thicker material. Again, this may increase your ride height and pack thickness, depending on how the spring is designed. A third option would be to move over to a parabolic leaf, but that could get expensive quickly. If you are interested, read up on Leaf Spring Design. The math is fairly straight forward if you have a mechanical background. It will help you shed light on what needs to be done in order to stay within your parameters. A good spring shop will also be able to help. https://www.brighthubengineering.com/machine-design/45183-laminated-leaf-spring-design-procedure/
Thanks for the kind words. The antenna doesn’t do anything except fill the hole where the rumble seat step went. I know it’s not for everyone! I have a reversed eye front spring that I bought loose at a swap meet. I then added the leaves from my old pack. It’s 10 altogether, now.
I thought about that, but I really need to limit travel. I didn’t get into too many specifics, but I’m bottoming out on HUGE bumps. Puttering around town is no problem, but around here we have epic potholes, and road construction constantly. Stuff that makes your cringe when you hit it.
10 leafs is a pretty substantial spring already. is there very little arch to it? I have 7 or 8 on most my cars
Yeah, I think the reversed eye I bought was pretty tired by the time I got it, and my original pack had seen some miles, as well. I like the earlier suggestion of using thicker leaves to stiffen without adding height, but rearching the ones I have is also something to consider. In the meantime, I think I’ll add some longer springs to prevent bottoming out. Solid plan?
Spring clamps will stiffen the springs without changing the ride height. I use to do it all the time on parallel rear leaf but I don't see why it wouldn't help in your situation. https://www.summitracing.com/parts/SLF-00250?rrec=true
10 leaves is a lot! It should hold up a BBC. Something else is wrong. Maybe the leaves have lost their temper?
Are the roads that bad in Chicago? 10 leaves seems like a lot. Is something funky with the spring length / shackle perch / shackle angle that is causing the spring to lose effectiveness? Some pictures of your current spring pack would help us know what you are dealing with. Is there some way of incorporating a progressive bump stop in there to deal with the chewed up roads?
Yes, some portions are that bad. They’ll come in, and scoop out the top layer of street, and leave it like that without any signs for weeks. You’ll be driving along in traffic, so you can’t even anticipate hitting a hole, and suddenly the car in front of you drops 6in. It really is awful. I don’t think most people would even believe. Here are some pics. The worst of it is my front pulley has licked my tie rod. Can’t go any lower on the steering unless I go under the bones. Can’t raise the engine due to other fitment issues further down the line. Easiest, and I think best way is to raise/stiffen the suspension.
The angles all look good, and nothing looks out of place. Either you are driving it like an off-roader or you just need to move. Maybe another second leaf would help.
I see, my straight axle vehicles, even though they didn’t bottom out, are pretty violent when hitting a chuck/pot hole. Heck still racks my nerves in my DD. Lol
Would be nice one of these days, but I’m wedded to the city in more ways than one. I don’t think I bomb around town too recklessly, but in the event it can’t be avoided I would like to have just a wee bit less suspension movement in front. Thanks for taking a look. Maybe add a bump stop to the bottom of the u bolt bracket?
I think a bump stop will just give you and the car a pounding when the axle hits it . Heavier , meaning thicker leaves are your answer . The friction shocks aren’t progressive like hydraulic shocks are . The further a hydraulic shock goes the harder it gets , usually . You could install tube shocks with small coil overs on it , usually much cheaper and easier than replacing the entire leaf .
Ford incorporated a rubber bumper insert into the lower spring clamp, I think beginning in 32. It should bolt right onto your car. Basically the same part you already have but with a hole in the middle for the bumper to wedge through.
The angles do look good on the shackles. You have more distance than I do between the ubolts and axle and mine does not hit and it has 7 leafs and a reversed eye main. The long leaves are the ones that control spring rate, you have enough of them, with a spring pack like that it should ride like a truck, so they must be no good. A bumper is still going to let it hit. I would get a complete new spring and adjust from there. Why is your tie rod on top of the bones? Are you running 32-34 spindles?
The u bolts aren’t hitting the axle, my crank pulley is hitting my tie rod. I haven’t measured, but it’s probably less than three inches between the two. I don’t think three inches of suspension travel is unheard of. Obviously could be less tho. The tie rod is on top of the bones on a stock Model A, but I had my axle dropped, and stretched, and am running ‘37 Willys tie rods, now. I’m running stock spindles, but do have ‘32 spring perches since I kept the mechanical brakes.
Get rid of the friction shocks. Once they break loose the resistance is less so the dampening goes away rather than maintaining. Ford Houdalie would be my choice, some are adjustable, late 30's early 40's.
Most don’t grasp the seriousness of the roads out in Chicago and the burbs. Seen seewer lids remove over 2” of oil pan sump. Completely remove the rh. Ft. Control arm, spindle spring and control arms. These holes should not be underestimated. They are vicious and cruel and act without feeling and will steal your junk any chance the get. These are not to be underestimated. On me and my buddies cars we used 1/4 aluminum plate12”X24” as skid plates. This is real stuff folks.
Over the years I've done a lot of rebuilding of spring packs to get ride height, stance, and ride where I wanted it. And always because my budget required me to figure it out, instead of just buying something new and hoping it worked. I've found that longer leafs do indeed stiffen the ride, but also discovered that longer leafs need to be equal, or thicker than what you took out. A thicker leaf does more to stiffen the suspension, than going longer. So if you can find a thicker leaf, even if it's longer than you need, you can cut it to the length you want, and replace a thinner leaf with the thicker one. Of course you'll need to also find a leaf the correct width! I cut them on my bandsaw, and then use a belt sander, or angle grinder to smooth, and round the cut ends. They cut surprisingly easy. I tossed all the leafs in my spring pack on the '39 Chev in my avatar, as it had 9 thin leafs and sat high, but was mushy. I replaced them with 4 thick, flatter leafs cut and fitted to the set to get the stance, and ride I needed for my build. I had donor packs that were off the front of a '58 Chevy truck axle, and they worked great.
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