how much stiffer will the ride be after a torsion lift?

[LCbruiser2000]

Hello All

I have a stock 100 with 285/75/16 BFGoodrich tires.

I'm gonna go in a few weeks for a torsion adjustment, maybe an inch to an inch and a half. When I told my mechanic he's like "you know it's gonna make it real stiff up there"

The ride is already much different from the michelins to the bfg's...
and i like it.

how stiff are we talking?

Thanks everyone

 

[2000UZJ]

Spring rate will not change, stiffness is related to the thickness of the torsion bar. I guess in a very small degree it will change. As you crank the front end it pulls the wheels inward, and puts the suspension arms at a more vertical position. When you hit a bump they will have to push outwards before they can compress. That will be the only thing that changed in your ride. And you probably won't notice it.

 

[rusty_tlc]

I like it, it almost eliminated the front dig on hard corners.

 

[Anthony.L]

Fire your mechanic, he's an idiot. Cranking torsion bars don't effect the ride quality, at least anything noticeable while driving. The thickness of the torsion bars is what changes the stiffness, hence why aftermarket bars are larger diameter than stock.

 

[rusty_tlc]

Fire your mechanic, he's an idiot. Cranking torsion bars don't effect the ride quality, at least anything noticeable while driving. The thickness of the torsion bars is what changes the stiffness, hence why aftermarket bars are larger diameter than stock.

I'm having a tough time getting my arms around that one. I can understand if you re-index that the ride wouldn't change, but if you crank the torsion bars to get more lift you are changing the tension on them, which certainly must change the ride quality.

 

[jgray]

I went from a stock ride to cranked factory tbars (nearly maxed out) to aftermarket tbars. Each change I made has changed ride quality. I've collected parts and added items as needed during my build process. I originally cranked tbars to accommodate larger tires and match the lift from new coil springs when I installed aftermarket coils, shocks and diff drop. I added the aftermarket tbars after installing a heavier aftermarket front bumper. The stock suspension rides soft and cushy. After you start doing suspension mods the ride does stiffen up a bit and give a sportier ride with better handling and less body roll around turns. I have heavier 3" lift coils waiting to be installed after I install a heavier aftermarket bumper (these also affect ride quality). If you are unsure what will work best for your build I would recommend calling someone like Slee Offroad, Just Differentials, Metal Tech or another shop that specializes in Land Cruisers and they can help you sort out what you should order.

If you are just adjusting your tbars you can do this easily yourself. It helps to get familiar with your vehicle and see how these things work. I'd recommend buying yourself a breaker bar and picking up a 30MM socket and doing this yourself. Crank (tighten) them a few times on each side and measure. Lots of threads on here about adjusting tbars and also replacing them.

 

[rove_mcanus]

I'm having a tough time getting my arms around that one. I can understand if you re-index that the ride wouldn't change, but if you crank the torsion bars to get more lift you are changing the tension on them, which certainly must change the ride quality.

You are correct.

The spring rate varies depending on the force applied to it. A torsion bar sitting on the shed floor has a zero spring rate.

Newtonian law state that for every action there is an equal and opposite reaction. So in theory (i havent tested it )if you apply 200 foot pounds of torque to a torsion bar, the spring back rate will also be 200 foot pounds.

As for affecting ride quality, well that is largely subjective because we all have different ideas of quality. However technically speaking if you adjust a torsion bar up, without adding an equivalent amount of weight to the vehicle then it most definately will have an effect on the way it rides.

 

[pfran42]

EDIT: Disregard the following post. I got it all wrong and Dennis and petrotk40 helped straighten me out

Spring rate definitely changes when you tighten the Anchor Arm Adjusting Bolts in order to achieve lift.

As the AAAB is tightened, it becomes progressively harder to tighten the bolt and the ride becomes firmer.

If you want to increase lift but maintain spring rate you could do the following:

• Adjust the AAAB in order to achieve desired ride characteristics
• Mark the AAAB where in comes out of the Anchor Arm Swivel on the Anchor Arm
• Loosen the AAAB until the Torsion Bar Spring is completely relaxed with zero load
• Slide torsion bar forward and out of the Torque Arm
• Re-index by advancing the Torsion Bar Spring 1 or 2 splines
• Driver side: clock-wise (from perspective of facing the front of vehicle)
• Passenger side: counter clock-wise (from perspective of facing the front of vehicle)
• Tighten AAAB to previously made mark
• Measure distance from center of wheel to fender
• Repeat procedure to gain additional height

Sure, you will probably need to do some final tightening in order to get the same amount of lift on both wheels but this way you are doing as much as possible to preserve desired spring rate.

Somebody chime in if you can find a real flaw in my theory. And yes I know that as the Lower Suspension Arm rotates further down past even plane with the horizon, the more leverage it takes to put it in motion.

 

[MoJ]

Spring rate definitely changes when you tighten the Anchor Arm Adjusting Bolts in order to achieve lift.

As the AAAB is tightened, it becomes progressively harder to tighten the bolt and the ride becomes firmer.

If you want to increase lift but maintain spring rate you could do the following:

• Adjust the AAAB in order to achieve desired ride characteristics
• Mark the AAAB where in comes out of the Anchor Arm Swivel on the Anchor Arm
• Loosen the AAAB until the Torsion Bar Spring is completely relaxed with zero load
• Slide torsion bar forward and out of the Torque Arm
• Re-index by advancing the Torsion Bar Spring 1 or 2 splines
• Driver side: clock-wise (from perspective of facing the front of vehicle)
• Passenger side:counter clock-wise (from perspective of facing the front of vehicle)
• Tighten AAAB to previously made mark
• Measure distance from center of wheel to fender
• Repeat procedure to gain additional height

Sure, you will probably need to do some final tightening in order to get the same amount of lift on both wheels but this way you are doing as much as possible to preserve desired spring rate.

Somebody chime in if you can find a real flaw in my theory. And yes I know that as the Lower Suspension Arm rotates further down past even plane with the horizon, the more leverage it takes to put it in motion.

Makes sense to me. You're essentially changing the starting point of adjustment while keeping nearly the same spring rate. Otherwise, yes, simply further twisting a torsion spring (bar), ceteris paribus, will increase the spring rate and impact the ride.

 

[OregonLC]

So just to clarify the terminology, the spring rate doesn't change as you make the adjustment, however the total spring force does. The rate is the amount of force increase per degree of deflection.

Upgrading to an OME t-bar would indeed being changing to a different spring rate as each degree of deflection would be met with an increase in force per unit.

So yes, your buoyancy point changes but the spring rate does not. I will say that with 866 springs and OME t-bars, the front remains the most compliant part of the system.

 

[petrotk40]

Pfran, wouldnt reindexing and cranking the bolt will have the same effect on the ride. The bars will have to be at the same tension in order to lift the vehicle to the same height

 

[pfran42]

EDIT: Disregard the following post. I got it all wrong and Dennis and petrotk40 helped straighten me out

So just to clarify the terminology, the spring rate doesn't change as you make the adjustment, however the total spring force does. The rate is the amount of force increase per degree of deflection.

Upgrading to an OME t-bar would indeed being changing to a different spring rate as each degree of deflection would be met with an increase in force per unit.

So yes, your buoyancy point changes but the spring rate does not. I will say that with 866 springs and OME t-bars, the front remains the most compliant part of the system.

Maybe I didn't do a good enough job of explaining and I may be totally off on this but it here goes...

With, say a rear spring you have a traditional spring rate. Force X causes it to move distance Y. When you reach the end of the spring and it is 100% compressed, that's it, no more travel. To gain lift you need spacers or longer springs. You also can't adjust the rate at which the rear springs push back against a load imposed on it.

The torsion bar does not operate like this. Forget about indexing for a minute. If you solely tighten the Anchor Arm Adjusting Bolt, not only are you "winding up" the Torsion Bar Spring, but you are doing so with enough torque that it's only way of fighting back is lifting the front end. Basically you added preload. Keep in mind there is no "stopper" like there is on a traditional rear spring. If the spring rate was not progressive then theoretically you could keep on cranking indefinitely (limited only by AAAB length) because the Torsion Bar spring would never be stressed to the point of failure. We all know that is impossible and that enough torque on a TB would snap it in half. That is further evidence of a progressive spring rate. At zero load you can turn the AAAB with your fingers, half way through the threads, you need to switch from a normal ratchet to an extended one. You wouldn't need to do this if it was constant rate spring. Vehicle weight has nothing to do with this either. With the vehicle firmly planted (on a stock rust-free LC), you can get a good 3-4 360 degree rotations in on the AAAB before you feel it getting more difficult. This is because you are increasing the amount of force with which the Torsion Bar Spring wants to push back. As you add more turns to the AAAB, it gets progressively more difficult.

It is true that adding to the diameter of the Torsion Bar Spring will increase the spring rate

In all honesty, I know next to nothing about this stuff. This is how I am rationalizing my experience with having OEM TBs, and then going to OME. I have noticed that you can have 1.5" of lift in two very different feeling ways depending on how you adjust the AAAB, Indexing or a combination of the two. Maybe I am just using the incorrect terminology to describe what I have experienced.

Pfran, wouldnt reindexing and cranking the bolt will have the same effect on the ride. The bars will have to be at the same tension in order to lift the vehicle to the same height

I would say no.

Think of it like this:

You have a piece of rubber the size and shape of a hotdog. This is your torsion bar. At 10 ounces of rotational torque (weight of the vehicle) it rotates 1/4 turn but then hits a state of buoyancy. Also at that 10 oz level of torque, it has squishy feeling of 5 (not too firm, not too soft). Now because of the leverage gained by the anchor arm I can further twist that hotdog shaped piece of rubber another 1/4 turn. This winds up the rubber and it becomes harder to keep increasing the torque. Now because I have 1/2 of a turn on the rubber hotdog, I achieve lift because there is no other place for the tension to go. This higher tension on the rubber hotdog also causes it not to be as pliant and as a result it has a squishy feeling of 3 (more on the firm side)

Now if all I want to do is raise the vehicle, I can rotate the rubber hotdog "starting point" in a manner in which 10 oz load rotates the hotdog 1/4 of a turn and it finds it's buoyancy point just as in the above example, just at a higher point to begin with.

Sorry for the rubber hotdog example. This is how I was picturing the components when I started thinking about it.

 

[pfran42]

The more I think about it the more I tend to agree with Dennis and petrotk40. However, maybe what I am experiencing has something to do with force angles (if there is such a term):

EDIT: I think I have it figured out now....The torsion bar is always stronger than the weight of the vehicle. So as the vehicle is raised/lowered it finds it's point of buoyancy and its constant spring rate along with it. Indexing only helps if you are at the end of your adjusting range and need more threads. The changes I have noticed in suspension feel must have something to do with the drawing I posted. At no lift it appears that it takes less vertical force to cycle the suspension vs that same vertical force applied on a lifted suspension (assuming torsion bar springs are the same for both scenarios). Thanks for helping me clear this up!

 

[OregonLC]

A progressive spring is one that increases its rate as the deflection increases. That is if a 10% deflection yields 100 lbs of spring force a 20% deflection might yield 250 lbs, a 30% deflection a 400 lbs force, etc. The increase is not linear but is progressively increasing. Some specially wound coil springs and all multi-plate leaf springs are progressive.

A linear spring is one that has a constant rate as the deflection increases. In the same example, if a 10% deflection yielded 100 lbs, a 20% would yield 200 lbs, 30% would be 300 lbs, etc. It would be a linear relationship between deflection and spring force. Some coil springs and (I believe) all torsion bar springs are linear.

The above, of course, applies only to the point at which the spring begins to fail.

Back to the OP, because the t-bars are linear, there is no more spring force applied at the static position; you've simply shifted the neutral point. Because the rate at which the spring force increases remains constant the shock/spring relationship remains unchanged and the ride should be unchanged. Suspension geometry, however, may alter the leverage the vehicle has on the spring.

Lastly to the OP, two items to remember: 1) the LC wants to have 3/4" forward rake or it will start pulling under power, and 2) remember to get an alignment after you find the new position you're happy with.

 

[OregonLC]

The more I think about it the more I tend to agree with Dennis. However maybe what I am experiencing has something to do with force angles (if there is such a term):

Please tell me you don't have a white board in your living room!

 

[hoser]

A coil spring is the same as a torsion bar, only wound into a coil. Cranking the T-bar is basically the same as adding a spring spacer to a coil spring, granted you are operating between the bumpstop and the maximum extension allowed by the shock. Obviously a t-bar doesn't bottom out like a coil spring can.

If the shocks/extension were maxed out at rest/ride height, then the t-bar could be wound up to "pre-load" and make the ride harsher but nobody really runs their suspension like that.

A difference in ride quality will occur mostly because of a difference in suspension geometry as pfran has illustrated above.

 

[2000UZJ]

If the shocks/extension were maxed out at rest/ride height, then the t-bar could be wound up to "pre-load" and make the ride harsher but nobody really runs their suspension like that.

A difference in ride quality will occur mostly because of a difference in suspension geometry as pfran has illustrated above

Thanks for posting this...i'll add my experience if you dont mind. When I replaced my torsion bars I cranked them all the way when I finished, didn't take measurements, just cranked until the bolt stopped. The front end bounced everywhere, there was NO give.

I would say I had a 3" lift. But was far from drivable.

 

[hoser]

Haha, okay, maybe I should've said, "nobody runs their suspension like that for VERY LONG."

 

[2000UZJ]

Haha, okay, maybe I should've said, "nobody runs their suspension like that for VERY LONG."

Yeah, down the driveway, a four letter word and reversed back up. I thought I fawked everything up

 

[LCbruiser2000]

the diagram rocks!

good work!

The more I think about it the more I tend to agree with Dennis and petrotk40. However, maybe what I am experiencing has something to do with force angles (if there is such a term):

EDIT: I think I have it figured out now....The torsion bar is always stronger than the weight of the vehicle. So as the vehicle is raised/lowered it finds it's point of buoyancy and its constant spring rate along with it. Indexing only helps if you are at the end of your adjusting range and need more threads. The changes I have noticed in suspension feel must have something to do with the drawing I posted. At no lift it appears that it takes less vertical force to cycle the suspension vs that same vertical force applied on a lifted suspension (assuming torsion bar springs are the same for both scenarios). Thanks for helping me clear this up!