I was "approached" in another thread about WHY torsion bar lifts cause rough rides. It was stated that "the keys let you raise the front w/o added stress " which is completely not true. My goal with this thread is not to "call anyone out" but to simply make my case and participate in a CIVIL conversation about the technical aspects of lifting with torsion bars. Let me state that I am NOT the creator of torsion bar lifts...hell I've only owned my LMM for 8 months. Most of my knowledge came from this site along with my own observations of my own truck. I am a weekend racer and an engineer by day. I've designed suspension systems from the ground up. My experience is mostly with road race cars.
I have to start by giving Nor-Cal Nick the most credit as he states perfectly WHY torsion bar lifts cause a rough ride in the thread below. Read it....understand it.
http://www.dieselplace.com/forum/showpost.php?p=1641068&postcount=7
To summarize, the "rough ride" everyone complains about is from the shocks and/or upper control arms running out of droop travel. What happens is that when you hit a dip in the road you run out of droop travel and the chassis is tugged towards the earth. The strange thing is that it feels just like a vehicle that is sprung too stiffly. Which leads to the wrong assumption that tighting the torsion bar adjusting bolt actually "tightens" the torsion bars and makes them stiffer. This is just wrong....wrong....wrong. Of course I can jump up and down untill I'm blue in the face, but that won't make you believe me. On to the theory.
The first thing you have to undertsand is that torsion bars are just coil springs that are straitened out and are twisted instead of bent. So they act just the same. Lets use a coil spring in our example and then bridge the gap to our torsion bars. Lets say we have a 500 lb/in spring and we put it on a car that has 1000 lb per corner. Assuming that the spring is in line with the wheel for simplicities sake we will have to compress that spring 2" for the chassis to settle out. 1000 lb's = 1000 lb's. Lets say you want to lift the vehicle 1", so you add a 1" spacer on top of the spring. The spring is not going to compress any more than it already is because you have added no more weight, you've simply changed the installed height of the spring.
Now lets jump over to torsion bars, the twisting motion on the bar is exactly the same as the compression of a coil spring. You are bending a spring only in different directions. By twisting the torsion bar with the adjusting bolt you are simply changing the preload on the spring, not adding any more weight. So when we "crank" on our torsion bars we are not adding any more weight or twisting the bar any more than stock.....we are simply changing the installed "height" of the spring. You could paint a strait line on the bar and crank the bar any where you like (without hitting the droop or bump stop) and the line would still be strait.
Older trucks (02-05ish) came with softer bars, and it turns out they don't have enough travel left in the stock keys to level most trucks. So along came "indexed" keys, or more simply put the hex hole in the key is rotated slightly to the arm that rests on the adjusting bolt. These came off the 1500 trucks, you could even use a Ford key that was indexed even further. The newer trucks have slightly stiffer torsion bars so the keys were not rotated as far in stock form. I personally had plenty of bolt to crank the suspension untill I bottomed out the stock shocks. I then added shock extension and could still bottom out the upper arms on the stops. I might have run out of room if I had used the cognito upper arms. I was able to get within 1/2" of level with nothing more than shock extensions and a wrench.
I would also like to touch on tire wear and alignment. Any time you change the ride height you HAVE to re-align the truck, the toe will be way off. I did a study of the "bump steer" which is a measurement of how much the toe changes as the wheel travels up and down. Would you believe that we get almost a full 2" of toe change from full droop to full compression. That's right, we worry about 1/16" of an inch of toe adjustment wearing tires too much and the stock suspension can go a full 1" out or in from our initial adjustment. I'll post a link to my thread later. No torsion bar lift kit is going to address this problem. You're caster and camber settings will also change as well. On my truck the caster and camber didn't change enough for me to worry about it. I went slightly negative on the camber and lost just a little castor. If you try to set the castor back to stock and get close to zero camber you may start to run out of adjustment. Cognito upper control arms may help with this a little, but it's my understanding that the upper ball joint angle was the only change from stock. Key's and shock extensions won't do a darn thing.
On the subject of worn out suspension components. Any time you run a ball joint at or near it's limit of travel there can be more wear. I don't personally think the mild 2" of lift that most of us run is anything to worry about. I believe that the type of driving you do has way more to do with it than anything else. The cognito upper arms do put the upper ball joints back closer to stock angles, but the tie-rods are still left to fend for themselfs. I think we can all agree that the tie-rods are weak to begin with.
As a pure ancedotal reference I tried driving my truck with the upper control arm set with 3/4" of clearance to the stop and it rode like crap. I added the shock extensions and it smoothed right out, proving to me that indeed the droop travel limitation was causing my rough ride.
I have to start by giving Nor-Cal Nick the most credit as he states perfectly WHY torsion bar lifts cause a rough ride in the thread below. Read it....understand it.
http://www.dieselplace.com/forum/showpost.php?p=1641068&postcount=7
To summarize, the "rough ride" everyone complains about is from the shocks and/or upper control arms running out of droop travel. What happens is that when you hit a dip in the road you run out of droop travel and the chassis is tugged towards the earth. The strange thing is that it feels just like a vehicle that is sprung too stiffly. Which leads to the wrong assumption that tighting the torsion bar adjusting bolt actually "tightens" the torsion bars and makes them stiffer. This is just wrong....wrong....wrong. Of course I can jump up and down untill I'm blue in the face, but that won't make you believe me. On to the theory.
The first thing you have to undertsand is that torsion bars are just coil springs that are straitened out and are twisted instead of bent. So they act just the same. Lets use a coil spring in our example and then bridge the gap to our torsion bars. Lets say we have a 500 lb/in spring and we put it on a car that has 1000 lb per corner. Assuming that the spring is in line with the wheel for simplicities sake we will have to compress that spring 2" for the chassis to settle out. 1000 lb's = 1000 lb's. Lets say you want to lift the vehicle 1", so you add a 1" spacer on top of the spring. The spring is not going to compress any more than it already is because you have added no more weight, you've simply changed the installed height of the spring.
Now lets jump over to torsion bars, the twisting motion on the bar is exactly the same as the compression of a coil spring. You are bending a spring only in different directions. By twisting the torsion bar with the adjusting bolt you are simply changing the preload on the spring, not adding any more weight. So when we "crank" on our torsion bars we are not adding any more weight or twisting the bar any more than stock.....we are simply changing the installed "height" of the spring. You could paint a strait line on the bar and crank the bar any where you like (without hitting the droop or bump stop) and the line would still be strait.
Older trucks (02-05ish) came with softer bars, and it turns out they don't have enough travel left in the stock keys to level most trucks. So along came "indexed" keys, or more simply put the hex hole in the key is rotated slightly to the arm that rests on the adjusting bolt. These came off the 1500 trucks, you could even use a Ford key that was indexed even further. The newer trucks have slightly stiffer torsion bars so the keys were not rotated as far in stock form. I personally had plenty of bolt to crank the suspension untill I bottomed out the stock shocks. I then added shock extension and could still bottom out the upper arms on the stops. I might have run out of room if I had used the cognito upper arms. I was able to get within 1/2" of level with nothing more than shock extensions and a wrench.
I would also like to touch on tire wear and alignment. Any time you change the ride height you HAVE to re-align the truck, the toe will be way off. I did a study of the "bump steer" which is a measurement of how much the toe changes as the wheel travels up and down. Would you believe that we get almost a full 2" of toe change from full droop to full compression. That's right, we worry about 1/16" of an inch of toe adjustment wearing tires too much and the stock suspension can go a full 1" out or in from our initial adjustment. I'll post a link to my thread later. No torsion bar lift kit is going to address this problem. You're caster and camber settings will also change as well. On my truck the caster and camber didn't change enough for me to worry about it. I went slightly negative on the camber and lost just a little castor. If you try to set the castor back to stock and get close to zero camber you may start to run out of adjustment. Cognito upper control arms may help with this a little, but it's my understanding that the upper ball joint angle was the only change from stock. Key's and shock extensions won't do a darn thing.
On the subject of worn out suspension components. Any time you run a ball joint at or near it's limit of travel there can be more wear. I don't personally think the mild 2" of lift that most of us run is anything to worry about. I believe that the type of driving you do has way more to do with it than anything else. The cognito upper arms do put the upper ball joints back closer to stock angles, but the tie-rods are still left to fend for themselfs. I think we can all agree that the tie-rods are weak to begin with.
As a pure ancedotal reference I tried driving my truck with the upper control arm set with 3/4" of clearance to the stop and it rode like crap. I added the shock extensions and it smoothed right out, proving to me that indeed the droop travel limitation was causing my rough ride.
