Stock 100 t-bars and springs on my LX470

[offroadkid]

I installed my sliders last night and will be installing my Slee rear bumper tonight after work.

My question is am I going to be able to drive home after the install with my AHC with stock springs or is it going to be upset and "wig-out"?

I have the stock LC100 springs and t-bars in the garage, but I don't think I will have time to install them after installing the bumper before I need to leave work to come home.

Would it be a better ideal if I install them first and then add the Slee bumper?

 

[Ramathorn15]

You will be fine. I wouldn't recommend installing the stock t-bars or springs. You're probably netting 100 lbs in the rear and the AHC is fully capable of handling that, plus a good bit more. I would eventually look into either king springs or spacers for the rear. Get techstream if you don't already have it and check your pressures to see how far off you are. Go from there.

 

[offroadkid]

I have a screenshot with the Techstream of before installing my sliders last night. I didn't think about it but removing the rear bumper and trailer hitch will lose some of the weight the bumper will add. Not really sure how to decipher the pressure readings.

 

[Ramathorn15]

Your front is 7.0 and rear is 6.9 assuming you took that photo after going from L to N.

You may be at 7.3 or a little more in the rear after the bumper install. You should install everything you plan on installing, take a reading, then determine what you need to do to get back to stock. Likely, you can probably get away with 30mm spacer in the rear and some adjustment of the T-bar.

keep in mind, the AHC is a strong system and has the ability to tow per toyota's specs.

 

[Ramathorn15]

You can find the stock pressure ranges here: AHC Neutral pressures, help me read them!

 

[ihadmail]

Your front pressures are high, you need to adjust your torsion bars to lower those pressures. Tighten the 30mm bolts on the rear of each torsion bar, start with 2-3 turns on each and check your neutral pressures again after going for a short drive.

Your rear pressures are a little high but not bad. Rear spring spacers will lower that pressure around .4 mpa.

With no front bumper you're better off staying with the LX torsion bars.

I'm running the Dissent front bumper with a Smittybilt x20 12k winch and 2" front lift. My LX torsion bars were easily adjusted to get good static pressure readings. The LX bars are not strong enough to handle all of that weight dynamically, while driving, I get a lot of dipping in the front when slowing/stopping and the AHC constantly having to re-level the front. I have a set of LC torsion bars now and will be installing them soon. Sadly this system is too intricate to simply throw them on and dial in static pressures to FSM spec on the heavier bars. It's going to take some adjusting, driving, monitoring, adjusting to get a pressure that the AHC likes while still maintaining the good soft ride that I had before beginning to mess with things on the truck.

The rear 100 series springs are the stiffest of the OEM rear springs and will be too stiff even with a rear bumper.

Rear springs in order from lightest to heaviest are: OEM LX, King Springs, 80 Series LC/LX (there are multiple versions of these each with slightly different spring rates), 100 series LC.

I tried the 80 series rears with sliders, Gamiviti roof rack and 3" of sensor lift. They were way too strong still. With the same accessories, 2" of lift and new OEM LX springs with 30mm spacers my pressures are still high but I have no issues going into H mode.

Once I finalize my drawer system and install a Dissent rear bumper I will revisit the 80 series springs. If that doesn't work out I will drop down to the King Springs and if needed trim packers/spacers.

 

[Ramathorn15]

4-5 turns is a lot. Each turn of the bolt is ~0.2mpa. So 4-5 turns in would drop you down to 6-6.2 mpa and the factory range is 6.8-6.9 You likely just need a half turn. I used white nail polish to mark a line down the side of the bolt onto the platform it rests on. That way you can see exactly how may turns you've done.

 

[ihadmail]

4-5 turns is a lot. Each turn of the bolt is ~0.2mpa. So 4-5 turns in would drop you down to 6-6.2 mpa and the factory range is 6.8-6.9 You likely just need a half turn. I used white nail polish to mark a line down the side of the bolt onto the platform it rests on. That way you can see exactly how may turns you've done.

Thanks for the correction there. Just woke up after only two hours sleep following a 12 hour night shift. I edited my original post.

Paddo has stated multiple places that an aged system, almost always, prefers the low end of the front pressure spec from the FSM and the rear prefers the low end or slightly even lower. The FSM values are a good starting point then each individual system should be fine tuned for optimum ride and performance.

 

[offroadkid]

Thanks for all the info and replies!

I know I post about it earlier but I still don't really have a grasp on it.

Got the bumper on after work and drove it home no problem!

 

[Ramathorn15]

Now go read your pressures again to see what the change was. Report back.

 

[offroadkid]

Now go read your pressures again to see what the change was. Report back.

Tomorrow at work I'll pull it in the shop on flat ground and post my readings!

 

[offroadkid]

Okay, this is sliders, roof top tent and Slee rear bumper. With stock AHC t-bars and springs.

 

[ihadmail]

Seeing those numbers I would try to adjust the torsion bars and wait patiently for the results of the King springs in the rear.

 

[offroadkid]

I put the LC100 torsion bars and rear springs on and it feels fine, I think it will now be able to handle a loaded rig!

I connected my Techstream to look at my neutral pressures after the springs and torsion bars were put on and now I'm way below specs!

Do I need to try and get it back to specs at factory height or is this going to be my new readings with the stiffer springs on?

Do I need to adjust my level sensors now and that will fix it?

 

[ihadmail]

You may be able to get the front pressures in spec by loosening the torsion bar adjustment, ride will most likely be horrible though.

You would have to raise the rear 6+ inches to raise the rear pressure back into spec, most likely add a few hundred pounds of rear cargo full time also.

Good luck with this setup, the harsh ride and extremely low pressures are why it's not used by most of us.

 

[DirtDawg]

Also your comfort adjustment in this setup will pretty much not work. It's like 80% spring 20% shock.

 

[PADDO]

There is nothing wrong with hybridizing your system to suit your needs - desirable actually, but this configuration is heavily skewed towards mechanical spring to the detriment of the hydraulic/pneumatic damping. You'll need significant permanent loading to get some semblance of factory spring/hydraulic balance and damping performance back. Factory pressure readings aren't really that relevant anymore for this combination so I wouldn't bother chasing numbers but if you choose to then try using pressure gauges on the front and rear hydraulic circuits for accurate readings. Its my experience that Techstream pressure results can be suspect initially when you do significant changes to the system, others have read pressures that don't seem to correlate with what's actually happening too. By all means adjust TBs to try and find the best damping but if it rides fine to you then that's all that matters.

 

[offroadkid]

Update!

Tonight I installed my new coil springs from King Springs in Australia and loosened the front stock LC 100 t-bars until I achieved 6.9 MPa in the front, and the rear is at 5.8 MPa!

Rig has an ARB deluxe bumper with 10K WARN winch, sliders, Slee rear bumper with dual swing-outs, and a James Baroud Evasion XXL roof top tent.

The ride home was smooth again and no bottoming out of the rear shocks. Also the system now quickly changes between height modes as it used to before the rear stock LC100 coil springs and front stock LC100 t-bars were in. The rear coil springs from the stock LC100 were way too tall and these King Springs are designed for AHC equipped vehicles.

BIG THANKS to everyone who has replied to my posts with information and input!

I'm smiling!!

 

[Ramathorn15]

Good to hear. I have the king springs in mine but no rear bumper yet (waiting on dissent). It's rough when unloaded but feels awesome once loaded with gear and the tent. I'm excited to get the bumper and finally be in constant smooth like before.

 

[bozncsurf]

Update!

Tonight I installed my new coil springs from King Springs in Australia and loosened the front stock LC 100 t-bars until I achieved 6.9 MPa in the front, and the rear is at 5.8 MPa!

Rig has an ARB deluxe bumper with 10K WARN winch, sliders, Slee rear bumper with dual swing-outs, and a James Baroud Evasion XXL roof top tent.

The ride home was smooth again and no bottoming out of the rear shocks. Also the system now quickly changes between height modes as it used to before the rear stock LC100 coil springs and front stock LC100 t-bars were in. The rear coil springs from the stock LC100 were way too tall and these King Springs are designed for AHC equipped vehicles.

I'm smiling!!

Can we see a picture of this beast!

Sounds awesome.

Really great info in this thread - thanks to everyone who has contributed to it.