Friday, February 5, 2010

Front suspension

Since I put the truck together the ride of the front suspension has been unacceptable. I had originally used what was marketed as a 3 inch drop spring. I have used a lot of these springs in the past and had no issues with them whatsoever, but this particular set was way too stiff for my old bones.

Now, a little mechanical theory. A car's suspension can compress to absorb bumps. You average family car might have say 5 inches of bounce before the suspension bottoms out. During normal use, that is plenty and the suspension rarely, if never, bottoms out.

Now, these springs are made 3 inches shorter than the stock ones, to give the desired 3 inch lowering. The issue becomes that our original 5 inches of suspension bounce now becomes only 2 inches since you're now 3 inches lower. This causes the shocks to bottom out and the suspension snubbers to touch pretty often during even routine driving.

What I did today was to switch the existing 3 inch drop coil springs out for a pair of 2 inch springs. But, you say, this will raise the truck up one inch from where it used to sit ! Well, I have the solution to that too.

3 inch springs on the left, 2 inch on the right...




Hmm, there is much more than 1 inch difference between the two...



To counteract the taller spring and again achieve my lowered ride height, I also installed drop spindles. These are the cast iron pieces that your wheel and brake bolt on to. They interchange with the stock ones, but the machined pin for the wheel hub is made 2.5 inches higher onto the casting giving 2.5 inches of drop. This does not affect the ride of the truck in any way. The additional 2.5 inches of drop are effectively free since they don't shorten our suspension range of motion.

Here is the stock one...



Here is the 2.5 inch lowered one...



Notice the big pin sticking out of the spindle is much higher on the one in the second picture. That's your drop right there.

After changing the parts, a test drive confirmed that the truck now rides like it should. There is no more harshness or bottoming out. Surprisingly, I removed a 3 inch drop spring and replaced it with a 2 inch drop spring PLUS a 2.5 inch spindle and the end result is about the same ride height. Obviously, according to the numbers I should be 1.5 inches lower than before, but it's not, yet. After driving it a while the new springs should settle slightly and give me a little more drop.

3 comments:

  1. Brian M from CalgaryFebruary 6, 2010 at 8:11 AM

    Hi Kevin
    Thanks for your useful information again. Very helpful. Wondering if you had the time to go into a little detail as to what you did and what you used for the rear suspension on your truck.
    I find it interesting and inspiring following your projects.
    Brian

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  2. Brian,

    The rear suspension is the one area of this project that I didn't do too well on documenting.

    I replaced the bushings on the rear trailing arms with urethane units from Energy Suspension. The coil springs are 5inch drop units from Early Classic Enterprises. The rear end is a 3.08 gear unit from a 72 Suburban. It's a straight bolt in to these earlier trucks giving you 5 lug wheel bolt pattern and much bigger brakes.

    I also used Early Classic Enterprises shock relocator kit with KYB shocks and a Super Track Bar kit.

    Basically, it's the rear 5 inch drop deluxe kit that Early Classic Enterprises sells.

    Any more questions, just ask and I will do my best to answer and supply any pictures I might have.

    ReplyDelete
  3. hey kevin, this is beebster from the 67-72 forums. I am not a big fan of "lowering" trucks but this one looks beautiful and has me changing my mind on a slight 3/5 lowering of mine.
    i'm lovin this blog!

    beeb

    ReplyDelete