Howdy all, long time listener, first time caller. I'm building a 1935 Studebaker Commander, all steel, modified stock frame, Jag IRS, 351W with an AOD. I just mounted a TCI '34 Ford front suspension with coilovers (it was the closest to the correct frame and track width). My Stude is long in the nose, much more so than mainstream brands of the era: the front cross member is about 13" forward of the crank pully on my 351. From TCI, the front end came with 400# coilovers. When I put on my front fenders and grill surround on, the nose is jacked way up with the coilovers fully released, I'm getting zero compression on the springs. Even when I put my 200# self on the front axel with the sheet metal, I'm getting no compression, I can bounce it up and down a little, but not much. The lower control arms are at a downward angle and the bottom of the grill is about 11 inches off the ground. I pulled the coilovers out and made spacer bars to level the lower arms and get the stance I'm after; my "ideal" distance from the lower mount to the upper shock mount is about 11.25", so I need to find coilovers which will hit that mark with the weight of the car. I think the engine being back significantly from the front axle line is complicating the issue and shifting the center of balance. I have a '34 Ford (all steel 350/350) with a nice stance (same front suspension) and swapped the coilovers just to make sure it wasn't the springs, and my Stude nose stayed up in the air. Does anyone have any suggestions on how to determine the appropriate spring rate so that I can get the correct ride height and handling response without just trying a bunch of different spring weights? Thanks - Ryan
Get the front of the car on a set of scales with you and passenger in the seat. It needs to be in " as driven condition " to pick spring rates. Once you know the weight on the tires, subtract the unsprung weight, ( anything below the springs ). Divide the remaining weight in half since each spring will hold half the weight, then figure how much compression of the springs you will need for the ride height you want. Ideally you want to use 2/3 of the travel for compression, 1/3 for extension. Spring rates are listed as 100 lbs for every 1" of compression. 400 lb spring compress 4" with 400 lbs on them. Coil over springs are rated in free length. If the spring is compressed by the ride hight adjuster, the compression hight will not be linear to the 100 lb/ 1' ratio. Look here, https://nefariousracing.shop/coilov...f4pA0q5WwQU9POhXBE7BjJueNC_dIgbQ2WosJ4fk9cyt6
'35 Stude?, I'm in! ... Commander or President? Still have the orig front end parts, if so, I'm interested. PM me. Marcus...
@Ryan Skiles You need to corner weigh the vehicle, then corner weigh the wheels again with the suspension disconnected Subtract the unsprung weight to get the sprung weight. Once you know that, you can figure out the wheel rate / frequency [usually between 5:1 and 7:1 on most street driven cars] eg: an evenly balanced 3600 lb car would have 900 lbs per corner , Minus 100 lbs unsprung weight = 800 lbs sprung weight. A comfortable car would be 7:1 ,so you need a wheel rate of 114 lbs/in [stiffness at the wheel] Because all springs are not directly on top of the wheel but mounted inboard we need the motion ratio [even macpherson struts are 1.11:1 or greater due to the angle] most old Fords [Falcons & Mustangs] have a motion ratio of 2:1 [or 0.5 depending on your method of math] most old Chevys [Camaros] have a motion ratio of 1.5:1 [or 0.66] The motion ratio must be "squared" mathematically because there are TWO factors involved 1: The force due to leverage, so 100 lbs force on a 2:1 leverage requires 200 lbs resistance] 2: The distance due to leverage, so 1" travel on a 2:1 leverage moves the spring 1/2"] so 200 lbs x 1" = 400lbs x 1/2" to get 114 lbs/in wheel rate on a Ford requires a 455 lb/in spring [2:1 motion ratio] to get 114 lbs/in wheel rate on a Chevy requires a 256 lb/in spring [1.5:1 motion ratio] To calculate ride height you actually need to factor the Free height to Loaded height. The above example with 7:1 frequency means the spring needs to be 7" longer divided by the motion ratio. On a Ford that is 7" ÷ 2 so you add 3-1/2" to the spring load height On a Chevy that is 7" ÷ 1.5 so you add 4-2/3" to the spring load height [yes the softer Chevy springs compress more because they are further outboard] This also explains why we need spring compressors to install them [softer springs have more load over static height] please note : The frequency method I describe above is a generalized rule of thumb. There is a lot [more like a shitload] more math involved, especially for race cars. Now one last thing "the biggest mistake with suspension, is the wrong choice of springs" and most people usually "over spring" the suspension.[too stiff]
-------- Thanks to both you and @Joe H for the education, looks like I'll need to sharpen my pencil and get the old slide rule moving I'm still in bare frame build stage, I can mock up all the major components but that obviously won't get me close enough to final weight so this may be a 'future me' problem for later this summer. I appreciate the information and it'll help once I'm further along.
Commander St. Regis (dual side mounts and a bustle trunk) No joy on any original components, I pulled the body from south of Chicago about 20 years ago and it had a '53 Chevy crossmember and 10 bolt under it with no engine or tranny. I've done a bunch of builds between then and now but '25 is the year of the Studebaker for me.
SDC &/or ASC member? '35 is favorite yr of wife & myself. Resto-rod type build? Marcus... Have a '25 chassis/cowl awaiting speedster-izing. Among others...
----- Back in 2004 I found the listing on 'old car trader' with a single picture, It was the car I always wanted, but didn't know what it was. I was in Spokane, it was south of Chicago, my trailer was near Eugene Oregon.... I ended up driving close to 7,000 miles round trip in 10 days to pick up the body and have been holding onto it ever since. I was active military at the time so it's been shuffled around with me until after I retired. The intent is what I would consider a mild custom, 3" chop (I will never chop another 4 door so long as I live). 351W, AOD, IFS/ IRS, 4 wheel disc, nothing else too wild. I think I put it off because I didn't want to screw it up, but it's past time.
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