I have a little '31 chevy hot rod here that needs a little updating. Its got coil spring suspension in it out of a fox body mustang, but it sits WAY too low. so instead of screwing around with coil springs and spacers and trial fitting and all that crap, I figured we could just put a set of adjustable coil overs in it. OK, that said, where do I start with determining spring rate so I look like I know what I'm talking about when I call to order some. Thanks in advance!
Call the techs at QA-1 and they will do the math and give you the part numbers. FYI, Get the ball bearing spacer plates. Then order from Summitt.
Mitch, I am not sure that you can raise/lower one with coil overs and not sacrifice the ride characteristics. I’m no expert, just thinking out loud….
Make sure you have the weight taken at each wheel before you start searching. Without that they will be guessing.
You want the shocks roughly centered in their travel. Set the car at desired ride height. Measure the distance between the centerline of the mounting holes. Hopefully there is an off the shelf shock that works for this dimension. Scale the car to get individual wheel weights. Call someone and buy shocks and springs. Install and adjust to final ride height. Having them nuts on centered in their travel isn't super important IMO. Close is close enough. You would prefer the shocks to not be the limiting component in the suspension though. Like say the lower control arm hits the frame before the shock bottoms or something.
Couple of questions! Can you change the spring pockets! With the springs you have if yoe move the upper or lower pocket 2 inches closer it will raise the rear of the car 2 inches + or -. With that said it seems the springs you have are to heavy. I have a 32 coupe(glass) the car is 2400 LBS. I use springs from a vega (Deuce Roadster,RIP recommened them) My spring pockets are 10.5 inches apart inside with rubber insulators top and bottom, It rides great! If interested I can get all the parts numbers tomorrow. Pete
A 'new' rod shop in Campbell finished a very slick '29 roadster, O.T. independent susp., front & rear. Coil overs on all 4. Owner thought the car rode 'stiff', but was going to the NATS. He called 3 days later; Jim, the rod shop owner was 'shocked' to hear the stiff coil overs in front tore the bracket right off the frame, passenger side: Shop owner paid large $$$ to get the roadster trailered back to his shop, from K.C., Mo back to Campbell, CA. Car owner's wife was shaken, car skidded a long way before it stopped. Tore the R.F. fender off, too. They flew back on a plane.
Springs of an impossibly high rate are a common mistake. I have met a few "pro builders" that think that spring rate is synonymous with the corner weight of the vehicle. They swear up-and-down that it is. Don't even try to talk to them about spring angle on an independent setup, or even a right axle. For perspective, under a 2400lb roadster, with a 60/40 weight bias, they would put 720in.-lb. springs on each corner in the front, and 480in.-lb. springs on each corner in the back. With that, they get ZERO suspension action, but hey, hot rods are supposed to ride rough, right?! I have had people scream at me that I most certainly did not have 200lb. springs on all four corners of my Jeep. They were right, though. I realized that after being screamed at that the rears were 180lb.
You might also check the total available suspension travel before you get too far into it. If there’s very limited travel, it’s very difficult to achieve a proper ride or handling. Covering that up with stiff springs isn’t the answer. Things have to able to move without binding, and proper stops should be included.
Not entirerly sure if we are talking ifs or rear end. I'm not going to post a picture, go to Instagram Kugelkomponents to see what they have redesigned for a better ride. Their description : This is our “Continental” IFS system that we are installing on this 32 Ford Roadster. We’ve done a couple of these set ups now, and it’s proven that moving the lower shock location inward gives you an even smoother ride and more travel in the suspension. With less angle on shock, you’ll use a lighter spring rate, hence a smoother ride and the mechanical advantage it has for more travel. Also, the best oil filled shocks by @qa1motorsports Also we use a cross shaft and shims for camber/castor alignment on upper arm to make adjustments super easy.
Tilting a shock absorber, or a coil over, inward at the top increases travel measured at the shaft. As an added bonus, it adds roll stability. Tilting it makes it the hypotenuse of the triangle, instead of a straight line. A 10-inch dead-vertical shock moving 3-inches is exactly that. A 10-inch shock, tilted 15-degrees off of vertical moves 3.106-inches. Tip that to 25-degrees and that 3-inches telegraphs to 3.991-inches. The more you tilt them, the longer the shock body can be, and the taller the spring. This will allow you to run a softer spring, with more preload at ride-height, rather than a stiffer one. This can put a shock body in the optimal position in its stroke, too.
I would see that suspension straight into the scrap bin. Rack and Pinion solid mounted to the chassis with a straight axle is one major no-no. Cantilevered (single shear) upper coil-over mounts is another bad situation. Not to mention all the spiderweb non-sense. The hand-fabricated caliper mounts also look suspect at best.
first off, you don't want to measure weight under the wheels... you want to measure the weight with the tires on the ground... with a scale measure the weight the springs need to hold and how long the spring needs to be...so, we all know that coil springs are measured @ 1'' compression so lets say that your weight is 1000 lbs... divide by 2, 500 lbs a side... so lets say your ride height need a 10'' loaded measure ment... this is where most get screwed up... an 11' 500lb spring will hold the car at 10'' but will need 1000 lb of force to move down 1''... way too stifff, right?? so you drop to a 250lb spring....now you need a 12'' spring , but now , you have a spring the has double the travel... 2'' up and 2'' down at 1000 lb force.... so if you have a car that can use more travel, you get a 200 lb spring.. you now need a 13'' spring.. 500 lbs will compress the spring about 3'',... so your ride will be at 10'', but now you 6'' up/ down travel, there's a whole bunch more ways to get the best ride, carry the weight, and not get to Gout... things like main and tender combos... so using the same weights and measures.. you could do some thing like a 100 over a 250... get you more travel...but.... that more getting in long travel off road stuff... that being said.. if the spring rate is right... you can raise or lower a car with out changing the ride, by adjusting the collar on the shock...
The thread is 18 months old. The suspension stiffness and load is easy to calculate if people simply help themselves by gathering some information. Otherwise they fall foul of some phone jockey "expert" that will machine gun them with an endless supply of parts from their shelves to try [at a cost] You need sprung weight or weight minus unsprung weight [ by weighing the wheels with the suspension disconnected ] Spring length at desired ride height. Motion ratio Or you can simply go on the internet an read "war stories" about what works for others.[based on "feel"]
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