Let's create a Thread with details about rear coil-overs Coil-Over rate: Year: Make: Model: Weight: Details: ex. fenderless, full fendered, engine, trans etc.. This could help many of us looking for best ride quality on our cars Thank you in advance.
This is a dangerously misleading idea! You should be asking the wheel rate. The spring rate is a factor of motion ratio [eg: laid over, or moved inboard etc etc] Plus you need to know the sprung rate vs unsprung rate [not total corner weight] A good example is a Road Race Camaro with a 1.5 motion ratio [a 650 lb/in spring = 288 lb/in wheel rate] But in a Mustang with a 2.0 motion ratio [a 1150 lb/in spring = 287.5 lb/in wheel rate] I've seen many Chevy guys try and copy Ford set ups and result in a stiff understeering pig The spring rate ÷ Motion ratio² = Wheel Rate On a lightweight car like a T-Bucket with the rear springs directly over the axles [and vertical] you want a spring rate of about 70 lb/in and a 5" spring load [it compresses 5" for normal ride height] This means each spring is supporting 350 lbs sprung weight [850 lbs rear weight including 150 lbs unsprung weight would be normal for a T-bucket]
I had a copy of wheel rate calculation chart (?) and other suspension data however I'm unable to locate. Kerrynzl would know a lot more about this than me.
@Kerrynzl thanks for that. I don't know of a spring that compresses 5 inches to ride height on a T, though. I can try to measure what I've got, but it was just an eyeball out of the local yard. BTW, it is a coil with separate shock, not coilover. 850 rear weight, unknown unsprung (50 olds, plus part of the arms). The charts show a low end of 95lb/in. I might try to find a 70# spring, but I'd guess it's going to be pretty rare.
Try here https://f-o-a.com/shop/viper-2-5-inch-id-spring-16-inch-length/ I like their numbering system Viper parts numbering system is as follows… (We’ll use part number 3x14x450 as our example.) 1. The first number shows the inner diameter size. (3 denotes a 3” inner diameter spring, 2.5 denotes a 2.5″ inner diameter spring) 2. The second set of numbers shows the springs free length. (14 denotes a 14” long spring) 3. The third set of numbers denotes the spring rate in pounds. (450 denotes a 450 lb per inch spring rate) So our example of a 3x14x450 is a 14” long spring with a spring rate of 450lb and an ID of 3”. 70# is the bottom of their chart on the 2.5x16 Mike
@AccurateMike thanks, they are trying to appeal to the tape measure guys there! Unfortunately, I've got a 3" inner. 2.5" won't fit over the locators. I tried a 10" length and it's 125# lightest. 12" and 14" are 100. 16" does offer a 75#, but i fear it's too long. Cutting it would increase the rate, IIRC. I have saved the link and can call. Currently have some Kia Rio rears. I trimmed off the pigtail on one end and they are pretty good. IIRC, installed is 11". When I climb in and bounce around, they do move, which is a big improvement on the ones it had! The old ones were big stiff boogers.
A lot of examples the springs need compressing 2 to 3" to install ,then the weight of the car takes up the difference One correction... The suspension needs to compress 5" [not necessarily the spring] If it was a Ford Falcon/Mustang front the spring load would be 2-1/2" because of the 2:1 motion ratio The 5" is just a guideline [rule of thumb] to guess the frequency for the street .Too many go too stiff [most road racing cars are approx 3" load] load is the point of equilibrium between suspension stiffness and sprung weight, and frequency is relative to speed. As an experiment go and jack up a leaf spring car [at the front hanger] and measure how much the car lifts before the wheel comes off the ground.
Well, I measured a 9" ride height, but didn't jack up the rear with the shock removed, so I can do that later. If I remember, the arms aren't exactly smooth in full range of motion. Instead, I cleaned up the garage, bolted up the mirrors and took it out since it's nice! In the background with snow on top is Humphreys Peak, the highest mountain in Arizona. Elevation of 12,633 feet, near Flagstaff.
Only one car with coilovers. 1937 Austin A8 2350 lbs. QA1 coilovers with 150 lb. springs Ladder bars and coilovers with panhard bar rear suspension. Need to also state shock angle as it has a big affect on spring rate. Mine on my Austin are straight up, but angled give a softer ride with an equal rated spring.
spring angle is part of the motion ratio equation. A very good example is the 4 x laid over coilovers mounted inboard on a Jag IRS
Everything I have is off topic. Can I be excused from class? This could be a very useful thread but as has been stated, it's not simple.
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