AHC lift, couple quick questions

[BamaLX470]

I've been doing alot of reading the past month on the 100 series. I'm coming from a Jeep Wrangler and wanted to move into something a bit more comfy. After looking around, I've settled on doing the AHC lift. I like the functionality, stock appeal, I don't really have a need to rip it out and start over, plus I don't want to sink thousands into this car like I did the Jeep. I just have a couple questions to round everything out before I start anything. I don't offroad but anymore besides back roads and the occasional woods trail.

With the sensor lift, I can gain about 2" lift up front and 1.75" in the rear. Would I be able to run 285/75/18 or 295/70/18 Toyo AT 2's comfortably?

With the Japan 4x4 AHC spacers, do these add any lift or do they just compress the shock so you have better up/down travel?

Lastly, it appears that a BIOR diff drop and 30mm rear spacers help smooth things out. I can crank the torsion bars for a tad more lift and to level the pressure in the system? I don't want a rake since I don't tow anything. I like a nice level stance with the front maybe a bit higher than the rear. Coming from a Jeep with evenly split travel (5 up/5 down), I want to make sure I have everything planned out to provide the best ride and have a good balance of travel.

Thank you!

 

[ihadmail]

The Japan 4x4 spacers only bring the hydraulic shock back within it's operational limit so that you have full up/down travel again.

Cranking the torsion bars will not get you more lift, it will simply return the AHC pressures to an acceptable range.

Hope this helps you out some.

 

[BamaLX470]

The Japan 4x4 spacers only bring the hydraulic shock back within it's operational limit so that you have full up/down travel again.

Cranking the torsion bars will not get you more lift, it will simply return the AHC pressures to an acceptable range.

Hope this helps you out some.

Thank you! I was getting confused with everything.

 

[jLB]

Start with Christo's post here:

315/75r16 = 15mm larger​

Then start working your way some of these threads:

What is the largest tire I can fit with no lift?
Which size tire?
Need help choosing wheels and tires size.
Best AT Tire size for OEM 18'' Wheels?
Largest 18" Wheel / Tire Combo?
Yet another tire and lift question​

 

[bhicks]

The Japan 4x4 spacers only bring the hydraulic shock back within it's operational limit so that you have full up/down travel again.

Cranking the torsion bars will not get you more lift, it will simply return the AHC pressures to an acceptable range.

Hope this helps you out some.

X2 on what he just said

 

[2001LC]

No rake or negative (rear lower) may make vehicle wonder on HWY.

 

[mgoblue]

Are the Japan4x4's necessary if the torsion bars are adjusted accordingly?

 

[ihadmail]

Are the Japan4x4's necessary if the torsion bars are adjusted accordingly?

They accomplish different things.

The torsion bars bring pressure in spec.

The spacers return the lost travel of the shock.

Neither of those will affect the opposite.

 

[Ramathorn15]

The Japan 4x4 spacers only bring the hydraulic shock back within it's operational limit so that you have full up/down travel again.

Cranking the torsion bars will not get you more lift, it will simply return the AHC pressures to an acceptable range.

Hope this helps you out some.

Excuse my ignorance, but how would the spacer cause the travel to return to normal?

My thought process is; if I set my AHC to the H position, it extends the "shock" but the travel of the shock does not change. It will still extend and compress the same amount as if I was in N. The only difference is the starting point being a more compressed state in the N vs the H position.

So if you adjust the height sensors to get an inch or so of lift, when you add the AHC spacers, it only brings the shock closer to the original N position pressure and length wise but does not change the overall travel of the shock itself. It would however give you an additional inch (or however long the spacer is) of down travel but you would lose the same amount in up travel. Esentially, you are just shifting the same length of travel in favor of downward travel.

Is this not factual? What am I missing?

 

[ihadmail]

Excuse my ignorance, but how would the spacer cause the travel to return to normal?

My thought process is; if I set my AHC to the H position, it extends the "shock" but the travel of the shock does not change. It will still extend and compress the same amount as if I was in N. The only difference is the starting point being a more compressed state in the N vs the H position.

So if you adjust the height sensors to get an inch or so of lift, when you add the AHC spacers, it only brings the shock closer to the original N position pressure and length wise but does not change the overall travel of the shock itself. It would however give you an additional inch (or however long the spacer is) of down travel but you would lose the same amount in up travel. Esentially, you are just shifting the same length of travel in favor of downward travel.

Is this not factual? What am I missing?

Everything I've read about the sensor lift shows that the shocks will bottom out on down travel if the spacers aren't installed. By performing the lift the new N height is the old H height. This extends the shock to much more near its limit, reducing the down travel available. I'm sure a pavement queen would hardly notice the lack of down travel, so one could consider the spacers optional.

 

[Ramathorn15]

Everything I've read about the sensor lift shows that the shocks will bottom out on down travel if the spacers aren't installed. By performing the lift the new N height is the old H height. This extends the shock to much more near its limit, reducing the down travel available. I'm sure a pavement queen would hardly notice the lack of down travel, so one could consider the spacers optional.

Okay, this makes sense. By adding the spacer, you shift the travel to allow more downward travel, as not to reach the full extension of the shock. You do however loose the same amount gained in downward in upward travel so your shock would bottom out at the top sooner than normal. Really adds no off-road benefit but instead prevents reaching full extension when going over large bumps.

 

[BamaLX470]

Start with Christo's post here:

315/75r16 = 15mm larger​

Then start working your way some of these threads:

What is the largest tire I can fit with no lift?
Which size tire?
Need help choosing wheels and tires size.
Best AT Tire size for OEM 18'' Wheels?
Largest 18" Wheel / Tire Combo?
Yet another tire and lift question​

Thank you! I've read most of those but haven't seen too many people running a 285/75/18. I have seen the 295's and I think I'll go with those since they're a bit smaller and wider. If they rub, I don't mind getting spacers. I would just prefer to not get a 315 because those are too wide for my taste.

Everything I've read about the sensor lift shows that the shocks will bottom out on down travel if the spacers aren't installed. By performing the lift the new N height is the old H height. This extends the shock to much more near its limit, reducing the down travel available. I'm sure a pavement queen would hardly notice the lack of down travel, so one could consider the spacers optional.

This is what's interesting to me. Coming from Jeep's, people that really understand suspension focus on uptravel. Better road manners, better offroad, better all around. So with the AHC shock maxed out in the H position, it has plenty of uptravel but very little down travel if I'm understanding this right.

 

[bozncsurf]

the spacers should bring the comfort of your "daily driving ride" back to stock after being lifted. Ride in high / H and its stiff, ride in normal / N and its back to factory smooth. the spacer should remove the pressure and stress on the extended shocks.

i think?

ask member PADDO.

 

[Ramathorn15]

Thank you! I've read most of those but haven't seen too many people running a 285/75/18. I have seen the 295's and I think I'll go with those since they're a bit smaller and wider. If they rub, I don't mind getting spacers. I would just prefer to not get a 315 because those are too wide for my taste.



This is what's interesting to me. Coming from Jeep's, people that really understand suspension focus on uptravel. Better road manners, better offroad, better all around. So with the AHC shock maxed out in the H position, it has plenty of uptravel but very little down travel if I'm understanding this right.

That is correct. If you put the spacers on, you lose some up travel in exchange for more down travel.

 

[Ramathorn15]

the spacers should bring the comfort of your "daily driving ride" back to stock after being lifted. Ride in high / H and its stiff, ride in normal / N and its back to factory smooth. the spacer should remove the pressure and stress on the extended shocks.

i think?

ask member PADDO.

Not sure about this alone. If you don't add spring spacers and crank the torsions, the pressure on the shocks will remain the same with or without the shock spacers after adjusting the height sensors to get lift.

In order to lift by adjusting the height sensors and maintain stock ride is to add coil spring spacers, crank the torsion bars, and get the pressures back to where they were in the stock N position. The shock spacers acts only to shift (not add or remove) shock travel downward so you get similar downtravel to when in the stock N position and thus prevent overextending the shock.

The reason you truck feels more stiff in the stock H position is because the pressures in the shocks shoots up because of the lack of help from the stock set torsions and coils. It also increase the angle of your control arms making it feel more harsh.

 

[ihadmail]

Okay, this makes sense. By adding the spacer, you shift the travel to allow more downward travel, as not to reach the full extension of the shock. You do however loose the same amount gained in downward in upward travel so your shock would bottom out at the top sooner than normal. Really adds no off-road benefit but instead prevents reaching full extension when going over large bumps.

It's really just returning the shock piston to its original position in its total travel pre lift. So if N was 50% of total travel pre lift, it would now become 75% total travel (measured from the bottom) post lift. The spacer simply moves the piston back to 50% of travel post lift. I hope that makes more sense than my first attempt to explain it. You aren't gaining any additional up or down travel by installing the spacers, simply repositioning the piston back to its previous point in the travel. You would need a new hydraulic shock with a larger amount of total travel to achieve more up or down travel over stock.

The difference in ride quality in N vs H is due to the larger pressure required to push the weight of the truck up when in high. More pressure means more resistance to dampening (compression).

 

[Ramathorn15]

It's really just returning the shock piston to its original position in its total travel pre lift. So if N was 50% of total travel pre lift, it would now become 75% total travel (measured from the bottom) post lift. The spacer simply moves the piston back to 50% of travel post lift. I hope that makes more sense than my first attempt to explain it. You aren't gaining any additional up or down travel by installing the spacers, simply repositioning the piston back to its previous point in the travel. You would need a new hydraulic shock with a larger amount of total travel to achieve more up or down travel over stock.

The difference in ride quality in N vs H is due to the larger pressure required to push the weight of the truck up when in high. More pressure means more resistance to dampening (compression).

Yeah, were on the same page.

 

[Ramathorn15]

Let me propose this... and this is what I intend to do.

My AHC pressures are pretty close to the factory recommended so I plan to:

1. add LC coil springs (they are stiffer since no AHC to take some of the weight) and that should reduce my rear pressure
2. Adjust rear height sensor until the rear pressure is inline with stock.
3. Adjust front height sensors until I achieve the proper rake.
4. Crank the torsion bars until I get the right pressure in the front
5. Add the Slee overide
6. Put 295/70/18 on it

I think this should add a bit of height, maybe an 1", and allow the tires to not rub on normal driving. Then when I go offroad, I can use the override to stay in H mode for the extent of the off-roading.

This is all in my head right now and I don't believe it has been done so I can't say for sure if it will work well.

 

[bozncsurf]

Not sure about this alone. If you don't add spring spacers and crank the torsions, the pressure on the shocks will remain the same with or without the shock spacers after adjusting the height sensors to get lift.

In order to lift by adjusting the height sensors and maintain stock ride is to add coil spring spacers, crank the torsion bars, and get the pressures back to where they were in the stock N position. The shock spacers acts only to shift (not add or remove) shock travel downward so you get similar downtravel to when in the stock N position and thus prevent overextending the shock.

The reason you truck feels more stiff in the stock H position is because the pressures in the shocks shoots up because of the lack of help from the stock set torsions and coils. It also increase the angle of your control arms making it feel more harsh.

Thanks for the insight

Probably should've included that my wife's DD is an 05 LX with:
-ahc sensor lift
-bior diff drop
-slee 30mm rear coil spacers
-front torsion bar adjustment
-techstream neutral pressure verified
-slee ahc override (only used off-road)

The only area I have not addressed is the shocks

Let's face it .. We are really just lifting the truck and trying to "trick" it into thinking its stock or "N"

My comment was trying to simply state that the shock spacers will bring it back closer to stock specs (and closer to stock travel) ... however other members are questionable to the benefits associated with the front shock spacer (due to its length I suppose)

Anyway - you guys sound like you've got it all figured out. Just post your findings / experiences / pictures for us to enjoy.

 

[bozncsurf]

You're definitely on the right track.. And the ahc lift has been done many times by mud members

Just wanted to point out that one member attempted to use stock non-ahc rear coil springs from a 100 and found them to be too stiff / incompatible with a non-rear loaded cruiser with stock bumper.

The stock 100 springs will likely work with a cruiser that has rear cargo drawers or an off-road bumper / tire carrier

Good luck - excited to see what you come up with.