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T-Bucket Suspension Spring Rates

18K views 12 replies 7 participants last post by  Youngster 
#1 ·
Like to know what is the most efficient spring rates for both ends of a 2000lb. T-Bucket?
 
#3 ·
I would think they'll work. I'm building a V8 bug and I'm thinking of using these as well. They're rated at 700 lbs., I'm thinking each? But they're meant for the back or front. As you know the back of a vw bug or buggy is the heaviest part of the car and vw's bugs / buggies weight about 1,700 - 2,000 lbs. For $50 or so bucks I'm thinking it's worth the try. If nothing else I'll just slap on another pair and double it up. ;)
 
#9 ·
Think of what "spring rate" means: The weight it takes to depress the spring 1". Then you go from there through these steps: 1. Measure the weight the completed T-Bucket on a front and rear wheel. 2. Set the ride height you want. 3. Install the coil over mounts so the coil over will be near mid range (slightly more up travel than down). 4. Determine how much it must be compressed to fit the mounts. 5. Compute the spring rate you need. For example, your rear wheel weight is 400 pounds (800# total on rear axle) and you need to depress your coil over 2 3/4", then a 150# spring weight will get you very close (funny how NAIRB got 140 rate). Think of it like this: The first 150# compresses the spring 1", the second 150#s compresses another inch, and the remaining 100#s compresses another 2/3", which gets you close enough.

Trees
 
#10 · (Edited)
trees said:
Think of what "spring rate" means: The weight it takes to depress the spring 1". Then you go from there through these steps: 1. Measure the weight the completed T-Bucket on a front and rear wheel. 2. Set the ride height you want. 3. Install the coil over mounts so the coil over will be near mid range (slightly more up travel than down). 4. Determine how much it must be compressed to fit the mounts. 5. Compute the spring rate you need. For example, your rear wheel weight is 400 pounds (800# total on rear axle) and you need to depress your coil over 2 3/4", then a 150# spring weight will get you very close (funny how NAIRB got 140 rate). Think of it like this: The first 150# compresses the spring 1", the second 150#s compresses another inch, and the remaining 100#s compresses another 2/3", which gets you close enough.

Trees
Trees is absolutely right!!!

It's hard to believe how many people cannot grasp this concept. Most coil over springs are linear in rates, meaning that if it's a 200 lb/in spring, it flat takes 200 lbs of force to compress it 1 inch, 400 lbs to compress 2" and so on.

I've always explained it like this. Choose a shock with a mounted length that approximately matches your approximate mounting points at ride height, mock up the rear axle to achieve the desired rake and frame height, build your mounts with respect to the shocks mounted length and then pick a spring that will carry the vehicle at that height.

The job of the shocks are to dampen the ride.

The job of the coil over spring is to carry the car and keep the shock within it's specified stroke range.

Too many people think they can achieve whatever ride height to whatever they want by simply adjusting the spanner nut, and they fail to realize that you can't be running around and topping or bottoming out the shocks. The spanner nut is there to get the shock into it's correct height. If you have to unwind the spring to the bottom to achieve ride height,the spring is too heavy!! If you have to crank it all the way up, it's too weak!

Sometimes it takes a little finessing and fine tuning to get the ride just how you like it. I've had customers that had to swap springs, but not everybody knows exactly what their car will weigh until they have finished the build.

I had one customer that had a trailing arm car with coils. He was trying to use some sort of junk yard spring, and it rode like a wagon. I estimated his car weight, did a little math and sent him a couple of 5", 170 lb coil springs, and the guy was so happy he couldn't see straight. It's common sense most of the time. A spring is a spring, unless it's a variable rate spring, and they aren't used that often in a rod.

I do believe that larger diameter, taller springs give the best ride, but there isn't always room for such large springs in alot of hot rods.
 
#11 ·
T-bucket suspension spring rates

NAIRB..When I set up the rear of the A coupe, I made up a set of struts to set the ride heigth of the coil overs at 12.5''. When the car was assembled I figured it to weigh 2650# give or take 75#. Using the formula in Speedways catalog, I ordered the coil overs with 200# springs. When I had the car weighed it was 2745#. I didn't weigh it front and back, just total weight. After sorting out the front end, it rode and handled very well with no bottoming out of the shocks.

My question to you is, was this the way to chose the coil overs or did I just get lucky?
 
#12 ·
That is the correct way to do it, and a 200 pound spring in a light model A sounds about right. We use a 225 pound spring in the Speedway all steel 32 roadster.

Some guys prefer a stiffer spring, particularly if the car sees some strip action. If you stand the car up on the back wheels, you have the entire car weight on the rear springs!!!!
 
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