After 31 years, I fear the coils in the front of my F-100 may have given into gravity; But I don't know how much. All I know is that I need an extra 2" up front now that I installed a new set of 32" tires...

Is there some kind of reference that I can consult that might shed some light on how far my front suspension may or may not have sagged over the years? The rear is looking good, but it has some helper springs installed to mitigate any apparent sagging. The front, for all I know could be OK, but I have no baseline to go from to determine if I need a new set of STOCK springs or a set of 2" lift springs.

Need a little help here...

 

Check some of the alignment specs in the books. The have ride height measurements with respect to model/GVWR.

 

My 74 has the same problem. Besides being able to see that the front looks too low, it affects the steering in such a way as to cause a pretty good case of oversteer at highway speeds. I need to either order a new pair of stocks or find the equivilants in a newer model donor at the parts yard. At least that's what I have narrowed it down to and I hope that that is the problem. I have replaced the radius arm bushings, the front shocks, the rag joint, and rebuilt the power steering box (swapped from a 78 model) and it still likes to try and drive off the road with the slightest over correction. On a smooth surface straightaway, it feels really solid - no pulls or wobbles but really gets dicey when on a shoulderless section of highway (like a bridge or overpass) right next to a couple big rigs and then hit a pothole or something. A couple of hair raising swerves before settling back down if you are not real careful. I am hoping that a new pair of coils and a good check up at the alignment shop will smooth it out. Kingpins seem to be pretty solid but if all else fails I may have to get them replaced as well. I have also thought of trying to find a front sway bar setup that will work - I think the camper specials had them?

Sorry kind of got sidetracked there - if you search this forum, I think I remember a posting about spring hieght specs while compressed. I'll try and find the post I am thinking of tomorrow and will post a link if I find it.

 

Ok, this is a PITA, but it really works.

What we need to know is what you have now, bad or good doesn't matter.

We need your current spring rate (lbs/in) and the free length and the static length.
Rate can be computed by wire diameter but this is not the method to use on worn out springs, IMO (yours are, we just don't know how bad!) So....

Set a dial indicator under the crossmember, in the center of the front suspension pivots. Now put a know weight on the center of the hood, right over the center below (be close, you don't have to be perfect), a couple of 80lb sand bags or a big friend is fine also (know the weight don't trust the label). Now you have some deflection with a known weight divided by two springs. Do the math to see what your spring rate is.


Now if you measure your spring length in and out of the truck, you say for example: My old POS springs are 500# an inch, and compressed from 12" to 10" loaded, so now I need some new springs that are the same rate but 2" longer free length. (In this simplified example you also fiqured out the corner weights are 1000 lbs on the front.)

Here is the fun part, you get to try to find some stock springs that will have a rate you like (softer or harder or the same) AND have the right free length to put you at the right ride height you want when installed (because you fiqured out the corner weight). This will require the spring MFG catalog or a nice guy at the spring house who either help you with your specs or will let you go measure the stock with calipers and compute the rates (see: google search "coil spring rate calculator")

If all that is making you run for asprin and a beer, the other option is trial and error. Go buy a set for the next heavier engine combo and see what you get.

Re: oversteer... I like some negative camber (1/2 degree or so), I think Ford for calls out for some positive.

 

Just let us know the ride height with a tape measure.

To top of the wheelwell is good enough.

With truck empty <> At the rear : From top of frame to ground is 24.8"

The truck should have come with G's to L 78's.
What Gvwr do you have ?

What does a 35" translate to?

 

GVWR is 4600#

Measurements:

* 30.5" from the ground, vertical to the bottom lip of the fender.

* 37" from ground, vertical to inner fender well. Measurement taken from behind the driver's side drag link.

* 10" from ground, vertical to the bottom of the "spring bolt" (large bolt that goes up through the I-beam and into the base of the spring.)

* 16.5" from the ground, vertical to the bottom of the frame (taken from behind the driver's shock absorber).

I hope this helps...

 

Here's one other option that may better address your question than my previous reply: if someone has a set of replacement stock springs for your application where you can walk in and see them and you don't mind taking one of yours out.... stand your old spring up next to the new one, see they have the same number of turns and wire diameter (which they should), the free length difference will be how much your ride height will change in the front. GL

 

What does this mean?

 

The 78 part is the % of the side wall to the tread.

if your thread is L = 8.35"'s the side wall is 78% of that or 6.435"'s.


This gives you the tire height thus affecting the truck height..

I don't know what tire the 35" is considered

Tires went from 70's > 78's > 75's on 15" rims

Now you can get 17" rims with 60's or 50's tires.

ie:
H = 8.25
G = 8.05
F= 7.75
E = 7.50

I'll see if I can find my saved tire site.

 

Yeah, I was thinking the same thing - Dennis you are usually so clear and to the point but I didn't understand that at all. You mention at the rear for the ride height measurement but we are talking about the front coils - did you mean at the rear of the front wheel?

You getting drunk before getting online now?? (I'm kidding of course - keep up the good work!)

EDIT - OK you replied while I was typing what a coincidence - that helps a little but still a little vague. Is L or G a tread width designation that we are unfamiliar with here in the US? The designation used that I am familiar with is the number of millimeters of width to the percentage of sidewall height such as 235 70R15 tires have 235millimeter tread width and 70% of that is the sidewall height or ~165mm. The R stands for Radial

 

Will these solve my problem?:

Ebay auction#: 7912154818

 

Yeah, I was thinking the same thing - Dennis you are usually so clear and to the point but I didn't understand that at all. You mention at the rear for the ride height measurement but we are talking about the front coils - did you mean at the rear of the front wheel?


They don't mention the front.






Sorry,

235 = L

225 = J

215 = H

205 = G

 

How about looking at www.rockauto.com for a 75 - 77 highboy application ?

I'm going there now.

What company does the label on that box say?

I wouldn't take a chance with E-Bay

EDIT:

Here is what I found.

http://www.clubfte.com/users/mil1ion...ings2504x4.JPG

 

According to an old book of mine it looks like the ride height between the spring seat lower surface and the front I-Beam should be about 3.5" on an F100. If you mess with the spring height it will throw off caster and camber badly on these vehicles.

 

OK, I went and talked to our local "Spring Expert" regarding this issue. Having been in the spring-business for 36 years, and having a big shop catering to all things "springgy," this guy has obviously seen just about everything re: springs...

His contention was that the Ford I-beam suspensions RARELY sag in the front (a bonus for Ford truck owners). If they do sag, it is a minimal amount compared to the other brands of trucks out there. He said that even new springs installed in old trucks rarely net more than 1/2" in the rise of the suspension, so therefore, unless one has a broken spring, he almost never need to put springs in the older Ford trucks.

That being said, he admitted that he has a supplier who can custom-wind springs for these trucks to give them a bit more height, but the REAL question was whether or not a competent alignment shop could get things squared up again. So I then headed off to the local expert alignment shop where they said they COULD align a raised I-beam truck, so long as it was not raised more than an inch. Even then its dicey...

So, I'm still not sure how much my front end has sagged (if at all), and am quickly finding out that the venerable I-beam front end is a PAIN to moderately raise easily.