i need help on my 29 roadster its a (glass) full fendered rod. what coilover spring rate would you use.
It has been a while now, but...I think I had 210 lb. springs on mine, but, they were a bit stiff...the ride sucketh... I am going to try 180's now...I have been warned against variable rate springs, also...I have a chart for determining this, somewhere...speedway has one in their catalog, don't they?
depends on the length , and the angle.....my last 2 model a's ( 28 sedan on 32 rails....and my current 28 coupe highboy on a rails...) both used a 200 pound spring and a short shock ....the shortest qa1 coilover in the speedway book...the sedan could have used a little more ....the coupe is pretty good....just installed a pair of the same spring weight but longer shock on a customers a coupe highboy....helped it a ton.... brandon
I have a 3000 pound 32 3 window rear shocks QA1s @ 20 degrees .I have 300 pound springs they provide a firm ride .Blaine
This is much easier to figure than you realize. The spring makers have charts but they don't explain how they get the numbers. Here's the basic idea..... You need X amount of suspension travel, overall. Let's say 6 inches to make the math easier. (most use much less) The shocks will be 6" longer fully extended, than fully compressed. The recommended ride height places the shock in a position where it is compressed 2", leaving 4" for compression and 2" for extension. Still with me? OK. Now let's say that your car weighs 800 lbs. on the rear axle. (not wheels. The weight of the axle, wheels and tires is under the spring, not over.) To get the right compression of 2" on the installed spring, so that you hit the desired ride height, you need a spring that will compress 2" under the weight of your car. Sping rates are stated in 1" increments. With these numbers, you will need a 200 lb. spring. That means that 2 springs will compress 1" under 400 lbs. and 2" under 800 lbs. There are variables to consider. Say you have very little available suspension travel. You can increase spring rate to reduce travel in normal conditions at the expense of ride quality. Most street cars use only about 2" of available travel. They still need an inch above and below that, but it's the 2" in the middle that matters. Here's a cheat. Let's say I want a heavier spring, but I don't want it to hold the car too high because I don't have the weight to compress it down to where I want it. That's where the installed length of the spring comes in. Use the adjustment collars to preload the spring and you get the 1st inch mechanically and then you only go beyond the 2nd inch of compression under heavier use. Again, ride quality will be more harsh, but handling might improve. Experiment and be prepared to buy 2 or 3 sets of springs. And keep in mind that lean in the shock/spring will reduce it's mechanical advantage and net travel. Never lean them more than about 30 degrees.
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