Questions for people with LC torsion bars and springs in an LX

[thebeedeegee]

I'm about to put the Land Cruiser TB's in my LX, I installed the rear LC springs today. Prior to this I added a TJM bumper and my pressures were just slightly high. I was able to get them back in spec, but the driver side AHC torsion bar is pretty close to maxed out, and the passenger side is about halfway or more. Since I added a rear bumper with single swing out (around 175 lbs) I decided to install the LC springs in the rear and go ahead an upgrade the front torsion bars as well. My truck drove great before, the comfort settings all seemed to work, but I worry about off roading with the front and rear bumper, and I would like to add a winch eventually as well.

After the spring change I noticed the drop from N to L took way longer than before, same with going from N to H. I guess its fighting those stiff springs. Will I be able to get the pressures in spec in the front with the LC torsion bars or will they be too stiff?

Can I just throw them in set the preload and start looking at pressures? Can you get the pressures close to spec with the LC bars?

I plan to make sure I get 1" of rake between front and back. I'd like to not lift it much above stock if possible. The springs brought the rear up about 1/2" from what they were with the OEM springs.

What is the optimal droop I should be aiming for with the new torsion bars in?

 

[suprarx7nut]

You can definitely get pressures in spec, that's no problem.

I would switch back to LX torsion bars. You may need to reindex them. The torsion bars are different by 25-40%. Unless that TJM bumper and winch weigh a combined 600-1000+ lbs, the LC springs are overkill at standard heights. It's just waaaaay more mechanical spring than you need. You can adjust the LX bar to hold plenty, from what I've read.

I'm running a front bumper (Dissent, aluminum with steel bull bar) and a 12.5 Come Up Winch. Running the factory LX T-bars, just cranked up 5 turns or so. My pressures are actually too low and I need to back off the T-bars.

On droop, I can't offer first hand insight other than I'd aim for a very modest sensor lift. 19.75" wheel center to fender is stock, so maybe aim for 20.25. That's plenty close to OEM that you're not going to ruin anything and you'll avoid falling down the rabbit hole on needed ancillary items to support a tiny bit extra lift (shock extenders, sway bar links, UCAs, diff drop, etc...).

 

[LXKevin]

What is the ride like pre LC TB's ?

 

[thebeedeegee]

I haven't installed them yet, I had just read on here it was better to go that route if you had an aging AHC system and a bumper in the front. My pressures were in spec in the front with the bumper, but it took about 5 turns and my driver side didn't have much adjustment left.

I figured by upgrading the springs and bars I could add some weight carrying capacity and help my AHC last longer

 

[thebeedeegee]

You can definitely get pressures in spec, that's no problem.

I would switch back to LX torsion bars. You may need to reindex them. The torsion bars are different by 25-40%. Unless that TJM bumper and winch weigh a combined 600-1000+ lbs, the LC springs are overkill at standard heights. It's just waaaaay more mechanical spring than you need. You can adjust the LX bar to hold plenty, from what I've read.

I'm running a front bumper (Dissent, aluminum with steel bull bar) and a 12.5 Come Up Winch. Running the factory LX T-bars, just cranked up 5 turns or so. My pressures are actually too low and I need to back off the T-bars.

On droop, I can't offer first hand insight other than I'd aim for a very modest sensor lift. 19.75" wheel center to fender is stock, so maybe aim for 20.25. That's plenty close to OEM that you're not going to ruin anything and you'll avoid falling down the rabbit hole on needed ancillary items to support a tiny bit extra lift (shock extenders, sway bar links, UCAs, diff drop, etc...).

So if I swap to the LC torsion bars I basically won't get any of the dampening effects (comfort to sport?) My bumper up front probably weighs 130 lbs, rear is probably 175 with the tire. Loaded with family and gear is probably and extra 600 lbs

So I should just reindex the TB's? I haven't checked my rear pressures with the LC springs in the rear but they were out before

 

[suprarx7nut]

So if I swap to the LC torsion bars I basically won't get any of the dampening effects (comfort to sport?) My bumper up front probably weighs 130 lbs, rear is probably 175 with the tire. Loaded with family and gear is probably and extra 600 lbs

To a large extent, yes. You'll diminish the AHC system's ability to provide all it's benefits of a highly dynamic spring and damper system. It'll work fine, but you'd be taking the system out of balance from where it was designed to work and narrowing the window of what it can control.

So I should just reindex the TB's? I haven't checked my rear pressures with the LC springs in the rear but they were out before

For the front, I would only index the T-bars when you run out of thread. If you haven't run out of thread and you're in spec, preferably at the low end of the spec, then leave it alone. If you run out of thread, time to re-index one spline.

For the rear, the progression of springs is something like this:

OEM 100 LX
OEM 100 LX plus spacers
King Springs
King Springs plus spacers
80 series LX
80 Series LC (Unsure on this one)
100 Series LC

You jumped a handful of steps all at once by installing the LC springs. It'll probably be ok, but not ideal. Again, keep in mind the springs are different by ~25-40% from AHC to non. That means you'd need to add that much weight per axle for the swap to make sense. That's like 1000 lbs per axle. You're nowhere near that much added weight.

This is all about neutral pressures. If you can post your current state equipment, current neutral ride heights, planned future weight additions and current pressures, we can better assist.

 

[thebeedeegee]

Here are my pressures last time I adjusted. At that point I only had a front bumper. My driver side bar maybe had half inch to 3/4" of thread left to adjust after this adjustment.

Since this point I added the rear steel bumper and swingout

I'd like to eventually add a winch up front, a modest sensor lift so I don't have to mess with a diff drop, and extend the life of the system before having to buy new globes.

 

[suprarx7nut]

On the front things look great. You're before the middle of spec. I doubt you'll need to even reindex.

On the rear, I think we need updated info. That rear bumper situation will change a lot. If you haven't already, maybe remove the factory spare tire holder if it's no longer in use. That's good for some weight.

Do you have pressures of the rear after rear bumper and spring install?

 

[thebeedeegee]

On the front things look great. You're before the middle of spec. I doubt you'll need to even reindex.

On the rear, I think we need updated info. That rear bumper situation will change a lot. If you haven't already, maybe remove the factory spare tire holder if it's no longer in use. That's good for some weight.

Do you have pressures of the rear after rear bumper and spring install?

Unfortunately I didn't get pressures after the bumper and before springs. I've started to just reindex the stock bars and get pressures tonight. I'll update with what I find d

 

[thebeedeegee]

What is the ride like pre LC TB's ?

Just re read your question.

It was fine, everything seemed to work great I was just worried about the rear pressures being high already and then adding that rear bumper. I also knew one of my TB's was near maxed out even though pressures were in spec up front. And if I added a winch I figured they would be out....I didn't consider re indexing though.

 

[LXKevin]

Just re read your question.

It was fine, everything seemed to work great I was just worried about the rear pressures being high already and then adding that rear bumper. I also knew one of my TB's was near maxed out even though pressures were in spec up front. And if I added a winch I figured they would be out....I didn't consider re indexing though.

Seems you are on the right track. Good luck

 

[thebeedeegee]

Well, my old PC s*** the bed so I couldn't get pressures, and apparently I installed the driver and passenger side rear springs on the wrong side because the passenger side is 1" higher than the driver. I'll deal with that tomorrow.

I did get the fronts even at 19 5/8" and 19 3/4" hub to fender. Good enough for me.

Also found play in the driver side wheel. Either inner tie rod or bearings. I have very little play at 12 and 6, but maybe an 1/8" at 9 and 3. Doesn't look like the outer tie rod is moving, must be the inner.

 

[suprarx7nut]

Well, my old PC s*** the bed so I couldn't get pressures, and apparently I installed the driver and passenger side rear springs on the wrong side because the passenger side is 1" higher than the driver. I'll deal with that tomorrow.

I did get the fronts even at 19 5/8" and 19 3/4" hub to fender. Good enough for me.

Also found play in the driver side wheel. Either inner tie rod or bearings. I have very little play at 12 and 6, but maybe an 1/8" at 9 and 3. Doesn't look like the outer tie rod is moving, must be the inner.

In my case, my front heights leaned to one side and it was more visible in the rear. Correcting the front heights to match each other solved most my weird side to side lean in the rear. Might be something to try before swapping coils unless you can verify they're off before removal.

 

[LXKevin]

Well, my old PC s*** the bed so I couldn't get pressures, and apparently I installed the driver and passenger side rear springs on the wrong side because the passenger side is 1" higher than the driver. I'll deal with that tomorrow.

I did get the fronts even at 19 5/8" and 19 3/4" hub to fender. Good enough for me.

Also found play in the driver side wheel. Either inner tie rod or bearings. I have very little play at 12 and 6, but maybe an 1/8" at 9 and 3. Doesn't look like the outer tie rod is moving, must be the inner.

Did you drive the truck after indexing the TB's? Are those LC springs new or used? Have you checked your rack bushings?

Sucks abt. the PC defecation - u really need the TS data to play the AHC game. Good Luck

 

[Moridinbg]

When re-indexing the torsion bars, don't you just add preload? Which is different than fitting a spring with a higher spring rate, which is what is needed for added weight?
I had maxed out my driver side torsion bar after the bumper and winch. I now have a tent and planned an extended tank and rear carrier with 2 spare tyres.
I am wondering if I should go for a thicker torsion bars...

 

[Shortpencils]

When re-indexing the torsion bars, don't you just add preload?

Yes.

Which is different than fitting a spring with a higher spring rate, which is what is needed for added weight?

Yes.

I am wondering if I should go for a thicker torsion bars...

Yes.

 

[thebeedeegee]

Yes.

Yes.

Yes.

With just a bumper I'd be riding on only the torsion bars essentially correct?

How much weight would need to be up front to justify the land cruiser bars with the AHC system?

It seems like if you set the preload with the weaker AHC torsion bars it wouldn't absorb a bump as well as the LC torsion bar, esecially when worn or the truck is loaded. So the AHC pressures would be good during normal circumstances, but could be way out of spec offroad or carrying a lot of weight since the older weaker bars could be overwhelmed.

On the other hand if you set pressures within spec using the LC bars, it seems like if you hit a bump that went past what the AHC could dampen you hit that stiff torsion bar and it would jolt you a lot harder.

Is there any advantage to using the LC bars with AHC still intact?

 

[suprarx7nut]

1. With just a bumper I'd be riding on only the torsion bars essentially correct?

2. How much weight would need to be up front to justify the land cruiser bars with the AHC system?

3. It seems like if you set the preload with the weaker AHC torsion bars it wouldn't absorb a bump as well as the LC torsion bar, esecially when worn or the truck is loaded.
3a. So the AHC pressures would be good during normal circumstances, but could be way out of spec offroad or carrying a lot of weight since the older weaker bars could be overwhelmed.

4. On the other hand if you set pressures within spec using the LC bars, it seems like if you hit a bump that went past what the AHC could dampen you hit that stiff torsion bar and it would jolt you a lot harder.

5. Is there any advantage to using the LC bars with AHC still intact?

Here's my take. Numbered your q's so I can follow along.

1. Not sure what you mean here. I think the answer is no.

2. See the figures below. That's with AHC holding 40% of the weight. With my over-simplified math, it would make sense to switch to LC bars if you add about half of 1122 lbs. So call it 566 lbs. A steel bumper should be ~100 lbs and the winch, another 100. You've got 350lbs to go before the LC bars make more sense than the LX bars in my mind. If you could find an aftermarket LX torsion bar (similar to how King makes the beefy LX rear springs) that would be ideal. To my knowledge, no such product exists. I think this is because you can get away with cranking the torsion bars (adding preload) in most cases.

3. Shock absorbing is not handled by the springs in either case. The globes do that regardless of the bar/spring used. Higher spring rates *should* be used with more powerful shock absorbers. Since we can't control the shocks (globes) in this case, I believe you're best off staying as close to OEM spring rate as possible.
3a. I think you're correct here, but I don't think it matters at the relatively low weight additions common to even built rigs. If you add 400 lbs to the rear alone, that's an increase of ~25% and well within what Toyota designed the rig to occasionally handle with all OEM equipment.

4. Not sure here. I suspect the LC bars would be slightly more harsh, but I can speak from experience there.

5. Yes, definitely. AHC does a long list of things. Acting as a spring is only one of those things.

 

[thebeedeegee]

Here's my take. Numbered your q's so I can follow along.

1. Not sure what you mean here. I think the answer is no.

2. See the figures below. That's with AHC holding 40% of the weight. With my over-simplified math, it would make sense to switch to LC bars if you add about half of 1122 lbs. So call it 566 lbs. A steel bumper should be ~100 lbs and the winch, another 100. You've got 350lbs to go before the LC bars make more sense than the LX bars in my mind. If you could find an aftermarket LX torsion bar (similar to how King makes the beefy LX rear springs) that would be ideal. To my knowledge, no such product exists. I think this is because you can get away with cranking the torsion bars (adding preload) in most cases.
View attachment 2520139

3. Shock absorbing is not handled by the springs in either case. The globes do that regardless of the bar/spring used. Higher spring rates *should* be used with more powerful shock absorbers. Since we can't control the shocks (globes) in this case, I believe you're best off staying as close to OEM spring rate as possible.
3a. I think you're correct here, but I don't think it matters at the relatively low weight additions common to even built rigs. If you add 400 lbs to the rear alone, that's an increase of ~25% and well within what Toyota designed the rig to occasionally handle with all OEM equipment.

4. Not sure here. I suspect the LC bars would be slightly more harsh, but I can speak from experience there.

5. Yes, definitely. AHC does a long list of things. Acting as a spring is only one of those things.

Thanks for the response, trying to think through suspension changes makes my head hurt sometimes.

As for #1 I just meant if I replaced the LX bars with LC ones would they be so stiff the AHC wouldn't support any of the truck weight anymore, but I see now that's not true and I think I understand now how that'd work. I'd basically have to set the land cruiser bars a lot "looser" per se to get the pressures in range.

So thinking through that it seems like the only advantage I would have by adding LC bars right now is that I would have a larger range of adjustment available with a bumper and winch since my LX AHC bars are near maxed out. It seems like if I kept re-indexing them eventually they would just wear to the point that the extra weight and height couldn't be supported anymore right?

Would another benefit possibly be the ability to support the truck if the AHC failed on the trail? If I had the LC bars in and the AHC failed completely I should be able to crank them to support pretty much all of the weight of the truck back to near stock height to get home I would think. Sure, it would probably ride like crap but it wouldn't be on the bump stops

 

[suprarx7nut]

Thanks for the response, trying to think through suspension changes makes my head hurt sometimes.

As for #1 I just meant if I replaced the LX bars with LC ones would they be so stiff the AHC wouldn't support any of the truck weight anymore, but I see now that's not true and I think I understand now how that'd work. I'd basically have to set the land cruiser bars a lot "looser" per se to get the pressures in range.

So thinking through that it seems like the only advantage I would have by adding LC bars right now is that I would have a larger range of adjustment available with a bumper and winch since my LX AHC bars are near maxed out.

1. It seems like if I kept re-indexing them eventually they would just wear to the point that the extra weight and height couldn't be supported anymore right?

2. Would another benefit possibly be the ability to support the truck if the AHC failed on the trail? If I had the LC bars in and the AHC failed completely I should be able to crank them to support pretty much all of the weight of the truck back to near stock height to get home I would think. Sure, it would probably ride like crap but it wouldn't be on the bump stops

1. I'm confident in saying you would never wear the bars out. Spring degradation like that occurs over a very long time and to a small degree.

2. Yes. That's a good point. The LC bars could be setup to provide improved trail reliability (assuming you carry a 30mm wrench on the trail with you) at the expense of having a non-ideal spring rate.