I am restoring/modifying a 78 F-250 2WD P/U and I want to lower it to improve handling. Since it is a restoration, shorter front springs (up to 2") would be great as they would do very little to the original look. The reduced spring length should reduce axle (wheel) travel due to the reduced clearance between the axle and bump stop rubber. Cutting and re-shaping the bump stop would recover only about one inch of travel. The fabricated drop axles would be technically superior but are clearly non-stock and visible. I would really like to get thoughts and experience on the use of the shorter (and stiffer) front coil springs for moderately lower ride height.

 

If you are talking about buying shorter springs, then you can do that, but be aware the alignment will be off. I'm not sure if your truck uses ball joints or kingpins, but the compensation would have to be made in there.

If you mean just cutting the coils down, that's a different story, and most people would put that under the stupid/dangerous category.

 

I won't be cutting the existing springs. I'm hoping to get some real data on the existing springs so I can design the modified (stiffer) suspension with an added sway bar. The truck uses kingpins and I'm aware that the change will affect the alignment, but this can be handled. The real concern is what I feel will be a real reduction in wheel travel with the shorter springs and how this will affect handling on the road and mild off-road work.

 

Why would cutting springs be stupid? You have to know how much to cut, and cutting them will make them stiffer, but what is wrong with it? The biggest issue when cutting the spring is reshaping the end. If you don't have a rosebud tip, you won't have any luck. You can purchase shorter springs for a fair price (roughly $100) but like they said, your alignment will change.

I like the dropped beams...they don't look that different from stock and once the tires are on are nearly invisible.

Kenny

 

Actually shortening the springs will be OK, BUT I'll still be left with 371 #/in springs. They will not get stiffer as a result of shortening. Since dropping the suspension with shorter springs is actually dropping the pivot points of the twin I-beams without changing the position of the bump stop or the kingpin at the other end, the spring rate will have to increase to limit the axle/wheel travel to the reduced available travel. Otherwise, the axle will beat the living heck out of the bump stop and the frame. I layed the suspension out and for a 1 1/2" drop, the spring rate will have to increase to 532 #/in (with a 5/8" reduction in bump stop height) and will produce 1 3/4 degrees of negative camber. A 2" drop will need a 666 #/in spring rate and produce 2.4 degrees of negative camber with the same bump stop surgery. While I will use some negative camber, I would like to keep it around 1/2 degree so alignment will have to be corrected. Then I plan to add a sway bar and this will have to be designed to work with the stiffer springs.
The alternative is the drop axles that allow the use of the original or stiffer springs without other mods. They are not forged steel beams, but rather welded steel fabrications and therefore appear non-stock. But since they are welded fabrications, it follows that welded tabs can be added to mount sway bar end link mounts. I understand that the original I-beams are not readily weldable either as a result of alloy content or carbon content (carbon equivalence), so the end link brackets will have to be bolted on
And I would still like to hear from more people with experience dropping the suspensions for enhanced handling performance using either procedure. I am to old to enjoy cut and try modifications.

 

I used Moog CC-844 springs which have a 630 lb./in. rating.The top coil is different (made for 80-up F-350).I cut the top 3 coils off which gave about 3'' drop (from stock).I can't remember,but I think it ended up with 2 deg. negative camber,before I bent the I-beams. I don't know where it was to start with.Hope this helps.

 

Good input. My layout and calcs would predict more negative camber for a 3" drop. About 4 degrees. How did you regain your wheel travel? The 3" drop should have closed up the gap between the bump stop rubber and the I-beam significantly. My layout showed only a 1/2-3/4" gap with the stock bump stop at a 2" drop. If you had clearance, then I really need to re-think my layout.

 

I will respectfully disagree with you...shortening springs does increase their rate. You can actually calculate it as long as you know the original rate and how "long" the spring is (some formulas use # of coils and diameter but all coil springs are torsion bars, just wound up). The shorter the spring (in length), the more force it will take to "twist" the bar the same amount. Coil springs twist as they compress ala torsion bars.

As for travel, you are stuck unless you notch the frame, and I don't think I would do that in front. I also know that the 78 F150's (I know, you are using a 250) had the most "drop" for a stock kingpin beam. I could have used one on my 81 F150 and gained 1" of drop but it would have decreased my suspension width a little (I don't remember the exact number, but not excessive, would have looked normal). You could replace the bump stop with delrin or something similar. Run it about 1/4 inch thick...it would be a little padding but not much, it would still hit like a hammer just not the steel on steel hit.

At one point I dropped mine 2 inches with springs (81 f150). Yes I gained roughly 1.5 degrees of camber per inch of drop. The good thing was I had + camber to start with, thus I ended with a little too much street camber but the tires wore better and the handling improved. I also cut my bump stops to roughly 1 inch tall in order to gain back some travel. A hand wood saw worked best for this then I smoothed them off with a 40 grit disk on the button grinder.

Good luck with the project! I am sure it will look great when you are finished!

(random thought) Kenny

 

On the first point, I think we have a semantics issue. Spring rate should be constant throughout the compression until it reaches its stacked length. The spring rate calc is a function of G (modulus of rigidity); d (wire dia); D (mean coil dia) and n (number of active coils). No lengths or compression is involved. Spring LOAD, however, does increase with compression. In my case, it increases by 371# for every inch of compression.
Thanks for the input on the I-beam drop. This means that none of the other truck years in the 73-79 series will offer an option in achieving more drop to accomodate the shorter spring and still give me useful wheel travel (assumming they would interchange). Any problems with the shorter bump stops? Like bone jarring axle stops? Overall, were you happy with the improvements in handling with the 2" drop and shortened bump stops. Did you change springs or cut off the OEM springs? If you changed-what did you use? Thanks for any help.

 

OK...Semantics aside, we agree on the spring issue!

I really didn't notice a difference in bottoming when I shortened the bump stops. Yes I noticed it bottomed more often due to the shorter travel but the harshness was roughly the same.

I was very happy with the increased camber and how it went from chewing up front tires in 15,000 miles to 35,000 out of the last set (replaced due to age and mods, not worn out). It improved the handling quite a bit on my setup (though it is still a pickup...I don't use it for handling, for that I have my Pantera). I didn't lower the rear at that time but have since changed all the suspension and am quite happy.

Now I run 3" drop DJM beams with the 90's style ball joints/spindles. In the back I used a bell tech 4" shackle and hanger setup. There is no way to get 2" of drop without changing the spring eyes with shackles alone. If you used the drop hanger alone, it will give you about 2.5 inches of drop (it raises the mount point 5", thus since the axle is roughly mounted 1/2 way you gain half the rise). The hanger alone will help the leaf spring geometry for handling (gets it closer to level) compared to stock and not as much with the shackles.

I also rebuilt everything on the suspension and it had factory front and rear sway bars. It is really hard to compare now to then because I also changed from Load range c 235/75/15's on 15*8's to XL 255/45/18's on 18*9.5's. It is much better than it used to be but I am not finished yet! I am going to drop the front another 1" by cutting the spring...I like a little nose down attitude.

Kenny

 

Thanks for the time and info. It's the first good tech info I've gotten from the site in six months. You're experience suggests that ultimately I'll end up with the DJM drop axles anyway, but I'll probably go through the shortened spring exercise first. I'm planning on the 4" drop in the rear and trying to adjust attitude with the tires. I'm gonna try new rims on the original steelies to maintain some appearance of stock-at least from the side.

 

wow you thought that out really well, here is another thought. Put a big enough swaybar on it with almost no play in the bushings and you won't have to worry about hitting your bumpstops. You can then run softer springs than you would have originally. I have done this to a 52 ford truck and my 77 trans am. they both rode well and handled very nice. there is one company that makes drop i beams that look original, if i can remember the name i will put it in here.

 

I had to start thinking it out-it cost too much to keep doing it over. I did this routinely on sports cars but this is the first time on truck suspensions. I never played with the twin I-beams before. A sway bar doesn't do anything in straight line driving so bottoming in this mode is all on the springs and shocks. In cornering, the bar will try to keep the body level amd minimize suspension changes and it's success depends on the bar's diameter and the length of the arms. Bottom line is that vertical suspension movement is all in the spring design. The shocks are pretty much limited to damping and to a limited degree, restricting the rapidity of the suspension movement. But I will be adding a sway bar after I decide on the drop and the required spring rate to avoid knocking a notch in the frame rail. The bar design will be based on the stiffness of the spring and a stiffer spring demands a bigger bar otherwise it's just added weight along for the ride.
And if you have a reference for a drop axle other than DJM, I would really like to have it. Choices are good!

 

SRD4X4--Forgot to ask. How did the truck ride with the 660#/in springs? Was it noticebly harsher than the stock springs. I'm guessing that those springs are maybe twice as stiff as the OEM's. I like to comfort of a taut suspension, but would like to keep my kidneys in place.

 

You can check around but the DJM's are sold through summit racing and are the cheapest ones around. I paid $389 with free shipping for mine. One beam was machined just a hair too big for the ball joint and they (DJM) shipped a replacement pronto. They also have a lifetime warranty, no questions asked, just keep your receipt.

AIM makes a good beam but they take pot shots at the DJM beams that are blatantly false. It made me shy away from them (I like my companies with morals).

I don't think Belltech makes one for the kingpin style front ends.

What is nice about the drop beams is the stock shocks still work as designed. None of the geometry is changed when looking at the radius arms, shock and springs. I will say I had a little trouble with the stock sway bar, I could not get it to bolt on the perch without hitting the drag link/tie rod. I figured out the cure was to move the front mount further forward...low and behold there were predrilled mounts for it on the stock frame (about a 1 inch move). Stock sway is 1 inch, the biggest I have seen it 1.25 and I might be moving that direction soon.

Kenny