So I broke two stock model A rear ends after swapping out my stock engine for a 153 ci four banger and a t5 trans. runs great. I swapped out a narrowed 9inch and installed with a universal street rod kit. ladder bars,pan hard bar, coil overs,brackets, etc. Everything works ok but the rear springs are way too stiff. Ive got a bumpy asphalt road to my house and by the time I get there Im ready for a barf bag. Ive tried adjusting the compression and rebound and it seems to be a little softer but still way too harsh for me. Cant seem to get a straight answer from so cal as to what the spring rate for these shocks as shipped were. just wondering if anybody has experienced this or what spring rate do you think it should be. I believe they ardran brand. Im not sure of the spelling but.Im punning a two door sedan weighs like 2660 lbs. Any thoughts.
I'm not sure what shocks you've got but when I talked to SoCal a few years ago, they said they used 250# shocks in the rear of their 32 Roadster.
Shock placement and installed angles can make a huge difference, but if your current springs are 250#/" it is no wonder the rear is stiff. My 26 coupe weighs 2550#, 1250# on the rear. Shocks @18 degrees. I run 140#/" springs on my coilovers. One spring removed on the front. Rides real nice. I have 150 #/" springs in my 27 roadster. A little stiffer than the coupe but still rides good.
Springs are easy enough to check. Get you a digital scale and a couple steel plates to spread the load across the whole scale. Slide the scale under a heavy car or truck with said vehicle jacked up. Use a couple rulers to measure with. Zero out the scale with plates and spring setting on scale. Lower the vehicle down till the spring is compressed 1", read the scale. It should be in the 250 lb area if the spring rate is 250. All springs are rated the same way, X amount of weight, for every 1" of compression. If you was to go 2" down, the scale would read 500 lb for a 250 spring rate. Once you know the rate and the angle they are mounted, do the math from the charts above. You can also measure using a hydraulic press and a scale. Something else to consider, if you are using a heavy rear axle and tires, the actual weight the springs are carrying will be much less the what the scales under the tires is reading. If you could place the scales between the springs and axle housings, you could measure the actual weight of the body. The unsprung weight, such as brakes, axle, driveline, tires and wheels, is controlled by the shocks and some by the springs, but not totally by either one. USE CAUTION!
You can actually do the same thing with an arbore press and a scale. I have even seen guys do it with a common bathroom scale and hit pretty damned close. Any spring shop should be able to measure the spring rate for you and most towns of any size have several spring shops. I cannot imagine that SoCal does not know what spring rate their street rod kits have, it should actually be printed in the literature or invoice that came with the kit.
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