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  View original topic: Another cut and turn question (or two), but different than most
mbjeeper Wed Jan 13, 2021 1:51 pm

I have a few questions about cutting and turning a VW (ball joint) beam to lift a car.
I have cut and turned several beams in my younger days, and I know the process just fine.
My questions relate to raising the front of a full body car 1 1/2-2" without destroying the ride. I am doing this primarily for tire clearance for all terrain tires, and the car will see only very mild off road use, if any.
My questions are;
First, since the leaves are anchored in the center with the grub screws, and the trailing arms slide onto the ends of the leaves, why does simply rotating the pivot (either by cutting and turning or welding in adjusters) increase the stiffness of the front end and preload the leaves?
Wouldn't moving the anchor point of the springs in the center simply rotate the leaf pack, turn the trailing arms down, and increase travel, but maintain the same ride? I mean, inside the tube, the leaves don't know where they are anchored in the center. Why would rotating the anchor point a few degrees up or down make a difference in the preload?
Obviously it does, so what is it that I am missing?
Question 2;
I have never cut and turned just one tube. I have heard that it will raise or lower, but have less negative effect on the ride quality. Like I said, I don't really need an increase in stiffness, I just want the height.
Does this work, and will it last? It seems to me that this type of lift might sag fairly soon, as one set of leaves would seem to be doing all the work. Is this correct? I know someone out there has done it. How did it work out? is there a preference of which tube to cut and turn?
My goal is to maintain a decent ride with this car, increase the ride height 1 1/2-2", and be able to run a larger tire.
I have had Bajas and buggies in the past (the distant past, I am afraid) and they were used off road, and I wanted the additional stiffness for the terrain, but on this car, I want a nearly stock ride with the height increase.
Ideally, a set of 2" lift spindles would solve my problem, but no one makes them, and I'd rather not if I can achieve the lift and ride another way.
I do not want to go with the available 3-3 1/2" lift spindles because I don't want to have to go through all of the mods I have to do to lift the rear that much, and 3" is more than I want or need anyway.
Last question;
I always cut and turned for maximum effect, like a 1/2" or so.
How much would I want to turn to get the 1 1/2- 2" and not too stiff a ride? I'm thinking 3/16" might do it.
The car will be heavy, relatively speaking. It's a '70 convertible, all stock fenders and bumpers, with the spare up front, tools, a little additional bracing for a skid plate to protect the apron, and I am a big, big boy.
I'd certainly appreciate the benefit of your experiences .
Thanks,
Greg
@14 air coolers

dustymojave Wed Jan 13, 2021 6:23 pm

mbjeeper wrote: I have a few questions about cutting and turning a VW (ball joint) beam to lift a car.
I have cut and turned several beams in my younger days, and I know the process just fine.
My questions relate to raising the front of a full body car 1 1/2-2" without destroying the ride. I am doing this primarily for tire clearance for all terrain tires, and the car will see only very mild off road use, if any.
My questions are;
First, since the leaves are anchored in the center with the grub screws, and the trailing arms slide onto the ends of the leaves, why does simply rotating the pivot (either by cutting and turning or welding in adjusters) increase the stiffness of the front end and preload the leaves?
Wouldn't moving the anchor point of the springs in the center simply rotate the leaf pack, turn the trailing arms down, and increase travel, but maintain the same ride? I mean, inside the tube, the leaves don't know where they are anchored in the center. Why would rotating the anchor point a few degrees up or down make a difference in the preload?
Obviously it does, so what is it that I am missing?
Question 2;
I have never cut and turned just one tube. I have heard that it will raise or lower, but have less negative effect on the ride quality. Like I said, I don't really need an increase in stiffness, I just want the height.
Does this work, and will it last? It seems to me that this type of lift might sag fairly soon, as one set of leaves would seem to be doing all the work. Is this correct? I know someone out there has done it. How did it work out? is there a preference of which tube to cut and turn?
My goal is to maintain a decent ride with this car, increase the ride height 1 1/2-2", and be able to run a larger tire.
I have had Bajas and buggies in the past (the distant past, I am afraid) and they were used off road, and I wanted the additional stiffness for the terrain, but on this car, I want a nearly stock ride with the height increase.
Ideally, a set of 2" lift spindles would solve my problem, but no one makes them, and I'd rather not if I can achieve the lift and ride another way.
I do not want to go with the available 3-3 1/2" lift spindles because I don't want to have to go through all of the mods I have to do to lift the rear that much, and 3" is more than I want or need anyway.
Last question;
I always cut and turned for maximum effect, like a 1/2" or so.
How much would I want to turn to get the 1 1/2- 2" and not too stiff a ride? I'm thinking 3/16" might do it.
The car will be heavy, relatively speaking. It's a '70 convertible, all stock fenders and bumpers, with the spare up front, tools, a little additional bracing for a skid plate to protect the apron, and I am a big, big boy.
I'd certainly appreciate the benefit of your experiences .
Thanks,
Greg
@14 air coolers

#1 When the front torsion anchor is rotated to raise the front ride height, the ride gets stiffer in some respects. The actual spring rate is not changed. BUT the angle of the arms makes for a stiffer ride at low speed. At stock ride height, the arms are relatively level from spindle to torsion bar. Vertical movement of the car is pushing along the arm, instead of rotating the arms. It's like when you pick up a little kid by the hands, if the kid holds their arms straight down at their sides, you can pick them up, but if their arms go out of straight down, then they fall. Same sort of deal. But going forward fast, the arms are pushed backward and thus up. The ride gets smoother.

#2 My Hi Jumper in my avatar got the upper tube rotated 5/16". The lower tube wasn't rotated. It worked fine.

Rotating both torsions 1/2" is a LOT!!! 3/16 to 1/4" would probably be good for what you want. But adjusters would allow you to ...adjust the ride height.

Another issue not considered above is that lifting a vehicle to clear bigger tires is a not sound engineering. When you hit a bump, then the tires won't clear. This is a fallacy of the lifted pickup poser crowd. Lift it so the bigger tires clear when it's sitting still... OK if you just want it to look cool when it's parked. But doesn't make sense if you want to use the thing.

DHale_510 Wed Jan 13, 2021 6:37 pm

Rotation does not increase the spring rate. If the result limits the down travel that may feel like increased rate but is harshness from the bottoming or topping out of the suspension.
Stock spring rate is about 25 or 39#/" per spring pack. It varies so maybe just measure what you have. Then figure just how much weight you want to suspend and go from there. The real trick is to figure how much rotation gives an inch or two. As you know, 1/2" on both tubes puts you at the top of the travel and that's pretty harsh, although since it tops out the suspension it is not likely the same as 1/2" twice equals 4" of rise. There is no easy answer like 3/16" because the weight of the car and driver are important in the calculation.
You basically are running stock loads, maybe 800#, and stock travel, maybe 8", and maybe the torsions are twisted halfway at rest and you want them at maybe 1/4 at rest. Measure the rest point with the front unloaded, then drop the car and add your weight and measure the change and figure your new point form there, maybe double the twist.
If you just cut one tube and do not run the suspension at either full droop or full extension you will nor change stiffness. If you remove the center screw on one tube you will halve the stiffness but turn the open spring pack into a swaybar, not likely your goal here.
The springs work together so there is no variable rate, they simply work together until you hit a limit stop. They likely will not "sag" until they have been hammered a bunch from hitting the limits.
Then if you ever change to longer arms for more travel you get to start all over with a nonlinear spring rate calculation....
Converting to adjustable fancy coilovers and through rods gives you all the adjustments you ask for plus easy change of spring rates...
Dennis

mbjeeper Thu Jan 14, 2021 8:14 am

Thank you both very much for the replies. It gives me some things to consider.
I guess with this car I'm going to be a poser, the only real reason to raise the car is to get an all terrain tire, probably a 205/75R15 General Grabber AT or similar, and have a little fender clearance for them. Dirt roads and snow.
Suspension travel isn't really the reason for raising the car.
If I want to go offroad seriously I'll take Jeeps or my buggy.
I have been considering installing the sway away style adjusters in both torsions, and ultimately that's probably what I will do, setting the neutral position in them maybe 1/8"-3/16 above the factory grub screw setting.
Again, thanks for the replies.
Greg

mr_bill Fri Jan 15, 2021 4:25 pm

[size=18]CLASS 11 cars, cut-n-turn 9/16" with good results with "stock" fuel tank & spare tire under the hood!!
/size]







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