I'm sort of confused about spring rates as they apply to hot rods. I understand the measurement but I am confused as to what rate I should use in the rear with rod as light as my 27 T Tudor build. I am trying to use coil spring suspension.
Have some experience w/ coil over shock type, Speedway has a big selection and a chart w/ suggestion's. I bought Carrera springs at Behlings Circle Track, Butler Wi. The rate you use changes w/ angle of shock, believe 30 deg is recommended standard, car came with a verticle rear shock setup on my 29 Highboy and ended up w/ #100 for comfort (had #180) when driving home after purchase, at 50 miles, stopped let the tires down, had 36 psi, was knocking my fillings loose, changed springs next, still a POS for comfort, but got it good as it could be. From what I remember from reading/research and your shocks are on an angle #120 might be a good starting point, hopefully a ch***is expert on here will jump in and give you a better guess on rate
There are probably guys on here that can give you a good estimate based on experience. Since I have never had a T bucket, I would start by having the car weighed. If you know any circle track guys they will know who has scales. You can also go to the local commercial scales (junk yard etc.) and weigh the front back, and whole car. (The two ends should equal the total car weight.) You can calculate spring rates with math and geometry but you will likely be happiest with springs that will just hold the car up. The weight of the car should compress the spring approximately 1/2 of it's unloaded, installed length. My guess would be that you could be looking at 90 or even 80 pounds/inch of compression.
I will throw my 2cents in and say 120 pounds or so. The one thing I would recommend is get a good set. I love American coil overs and for a few reasons. The first time I bought a set was over 20 years ago and new to using the coil over setup. I blew the spring rate and had a **** ride . I called them and asked a few more questions and then they corrected me on my rate figures. They exchanged the spring I had for the one I needed no questions asked and no cost, wow who does that! The coil overs are still on the car and ride great. The first being a great company standing behind there product and quality of ride and product. I also would say its warranty and no BS and lifetime you own the product I believe. Then of course it's made in the great USA and look great. On a short wheelbase low weight car as such it will be a challenge to dial in both performance and quality ride . So I recommend a lighter rate
In the center chart above, anyone want to hazard a guess why the front and rear spring rates recommended are so much different when the actual weight on the wheels is the same? I'm guessing it's some sort of compensation for the engine, but if there's only 1200 lbs on the front end and the same 1200 lbs over the rear wheels (an ideal 50/50 wt distro) why does the front end need so much stronger springs? Gary
Me too..I did call QA1 and asked what I should use for 50/50 and was told start with the same spring rate all around..
Gary, My guess would be heavier springs on front due to weight transfer under braking. We could also talk about polar moment of inertia and center of gravity, but I don't want to.
The stiffer end of the car will slide out first when cornering aggressively, if the front is stiffer the car will slide the front wheels, what racers( that go around corners) call understeer or pushing witch is a lot more predictable than oversteer or "loose" when the tail p***es the nose!
The front springs on an upper and lower A arm suspension are working on a lever being the lower arm. The back springs are not. Also if your springs lower to half the unloaded amount you will bottom out those springs just getting out of the driveway. Ideally you want the spring to compress about 20% loaded
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