My first 40 and some suspension tech/ questions (1 Viewer)

Joined
Sep 19, 2020
Messages
5
Location
Redwood City, California
Hey all,

Left the 4runner gang and traded for a '73 40 series. Who wouldn't accept that trade?

The 2nd previous owner converted the 40 to SOA with a 4ish" lift with some god awful 3 pack leaf springs and es9k procomp shocks. Let's just say your grandpas old John Deere tractor rides better than this.

I want to lower the cruiser by about 2" so I'm looking at either the OME dakar springs or Dobinsons. I know I can't go wrong with either or, but I had a few tech questions regarding the spring lengths. I will also be changing the front shackle angle (right now it is angled forward like " / " and I plan to correcting the angle and face it toward the rear like " \ "
Curb weight for the 40 is 3960 lbs measured yesterday. I'm running 39" KM3s with allied beadlocks, so about ~100lbs per tire
So just around 3500lbs sprung weight. That's a quick assumption so don't flame me for not being accurate. Anyways with those numbers I'm thinking of getting the medium duty OME springs, part # CS001F and CS001R with rates of 350 ft/lbs and 300/450 ft/lbs respectively. I was unable to find the flat spring length on any catalog or website but I need that measurement for finding the correct hangar distance from front hanger to shackle hanger.
The formula is: Flat spring lenth - SIN(desired angle x shackle length) = hangar distance. So the question IS: does anyone know the flat spring lengths of those OME springs, and not the eye to eye measurement, but the actual length of the spring in a flat plane.

Once I get the correct springs I'll be looking into correctly valved shocks. Im debating between bilstein 5100 or Fox 2.0s. Anyone got a recommended valving/shim stack for this car?

Any and all comments are appreciated. Thank you.
 
Joined
Sep 20, 2004
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Assuming a SR was done by your description of shackle angle,
Your spring mounts may not have factory spacing. FWIW most of the aftermarket replacement springs, lifted or not, yield less than desirable shackle angles when installed on not stock suspensions. Thats said, If you are not willing to move the hangers to get longer springs then put some shackles that you wanna use on it held at the max angle before spring wrap hits frame and measure the straight line distance from lower(empty) shackle hole to the fixed front hanger center, thats the flat line, max lineal distance of spring before it inverts, thats where your bumps want to stop uptravel, a little past ( 1/2 ") won't hurt but I leave that for bump stop compression. I agree with the rating of spring you picked, get the lowest pressure, 11.5" travel , 5125 bilsteins( theres 2 pressure offerings). I would determine the flat line distance you need for optimal shackle angle at full stuff and reset shackle to wanted angle at ride heigth, take that eye to eye ( center front hanger to lower shckle hole) measurement as well, with those 2 number you can compare to springs offered and see if any yield the needed measurements. IMO you will find all do not. Custom length with custom center pin location gets you proper shackle angle and you can get 3 or so inches wb.
 
Joined
Sep 19, 2020
Messages
5
Location
Redwood City, California
Assuming a SR was done by your description of shackle angle
Thanks for the info peesalot, and yes I should have been more clear in the original post, the previous owner performed a SR
I do plan to redo the shackle angle in the front with the new springs and aim for a better angle between 60* and 45*.
I would love the run custom springs but I can't fork out $1500+ for leaf springs right now, and I plan to link the car down the road anyways, I just need something that's not a bucking bronco right now.
I'll take your method of measurement into consideration when I start rewelding new shackle hangers.

Thanks
 
Joined
Mar 11, 2020
Messages
21
Location
SF Bay Area, Ca-NorCal
I've run Foxies on a FJ Cruiser and just thought they are overrated but couldn't pass up a great deal. I've since run Billies on our T4R. I would look towards Kings if you are looking to spend the money on Foxies. (Both of which are rebuildable/reshimmable/restable-can't really go wrong with Billies either).

With that said. My newly acquired 1970 Fj40 has an OME medium duty suspension. I'm just across the SM Bridge if you would like to take a drive. I work in SL or you could travel a little farther to Dublin/SR. The suspension was recently replaced with less than 500 mi so it's not quite broke in but it is my DD with 31" tires @31psi.

Hope this helps

-J
 

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