Springs to help rear AHC Pressure (4 Viewers)

[01BluLX]

Is there a thread or any collection of information that explains options for rear springs to help high rear AHC pressures? I've looked over the ones that I can find, but there doesn't seem to be a real consensus on how much each option lowers the pressure. My rear pressure is a little high at 7.4. I have drawers with tools/camping gear, otherwise stock. 265k on my truck, and the rear coils are original as far as I know. I have globes on order, although that won't change the pressures from my understanding.

I still need to adjust my torsion bars to get the front in spec, but I'm just looking for some input on what to do with the rear. Spacers, OEM LX coils, Kings, AHC LC coils, non-AHC LC coils? Too many options...

 

[Jcreme]

I can't answer your question, but the front will take load off of the rear. Get the front right before you make decisions about the rear.

Also, (and I'm just thinking out loud) it's pretty typical to need to replace springs on a 20+ year old car of any kind. I wonder how many people have gone to heavier springs, when their root problem was actually worn out springs. That said, I have no problem getting my '99 into spec pressure.

 

[hoser]

King and 30mm rear spring spacers. Adjust rear height sensor to get desired pressure, which could be stock or slightly lower. Then adjust front end height to compliment rear height. Lastly, adjust t-bars to get proper front pressure.

 

[01BluLX]

King and 30mm rear spring spacers. Adjust rear height sensor to get desired pressure, which could be stock or slightly lower. Then adjust front end height to compliment rear height. Lastly, adjust t-bars to get proper front pressure.

From what I've been reading the Kings sound like they might be too stiff, not sure though. Do you have personal experience with them?
I worry that if I went that route, my pressure would drop too low and end up with a bouncy ride... but that can be resolved by adjusting the height sensor?

 

[hoser]

No, I don't have the Kings personally but people sometimes say they aren't enough. It's the next spring up, there is no in-between except maybe an LX570 spring. In any case, no doubt, you can get your rear pressure in spec with them, it's just a matter of adjusting the rear height sensor (and hence ride height). If you are inflexible about ride height, then it'll get a little more tricky and you'll need various spring spacer/trim packers on hand to fine tune.

You can even drop the rear ride height now and get the rear pressure in spec. If happy with the ride quality/load capacity and only unhappy about the drop in ride height, you can just get 30mm spacers... and again adjust rear ride height 30mm higher and the pressure will be in spec.

 

[GTV]

I use Kings. Since they are identical height put a 10-15mm spacer on the drivers side to square it up. Adding or subtracting spacers didn’t change the pressures much for me.

 

[01BluLX]

I use Kings. Since they are identical height put a 10-15mm spacer on the drivers side to square it up. Adding or subtracting spacers didn’t change the pressures much for me.

What kind of extra weight do you have on your rig? Bumpers, sliders, etc?

 

[01BluLX]

No, I don't have the Kings personally but people sometimes say they aren't enough. It's the next spring up, there is no in-between except maybe an LX570 spring. In any case, no doubt, you can get your rear pressure in spec with them, it's just a matter of adjusting the rear height sensor (and hence ride height). If you are inflexible about ride height, then it'll get a little more tricky and you'll need various spring spacer/trim packers on hand to fine tune.

You can even drop the rear ride height now and get the rear pressure in spec. If happy with the ride quality/load capacity and only unhappy about the drop in ride height, you can just get 30mm spacers... and again adjust rear ride height 30mm higher and the pressure will be in spec.

I am willing to adjust the ride hight if needed, but would like to keep it as close to stock as possible and would prefer to only go up. Correct me if I'm wrong but if I go with the Kings and find the pressures to be too low I would have to raise the ride hight right?

 

[95Fantasma80]

Yes, it's one of the main preventative maintenance items I did for AHC along with changing fluid. I replaced the rear springs with new OEM stock springs. With a healthy AHC system I don't think you need to do anything additional for a bit added weight.

 

[01BluLX]

Yes, it's one of the main preventative maintenance items I did for AHC along with changing fluid. I replaced the rear springs with new OEM stock springs. With a healthy AHC system I don't think you need to do anything additional for a bit added weight.

Did you read your AHC pressures before and after replacing them with stock springs? Curious to know how much it changed.

 

[x8o8drifter]

Hyperco makes custom springs.
Might be worth a shot to hit them up.

Slight thread jack...
So I cant for the life of me find the answer.
Does anyone actually have the stock spring rates? Cant imagine the AHC and Non AHC springs are the same rate.
I can find ones somebody tested and gave info for on the 80 series but nothing anywhere on the net for the 100s.
And lots of info on the aftermarket stuff like OME but nothing for the stockers. You would think that info would be easy to find so people can make an informed decision on how much more stiff than stock they need.

 

[GTV]

What kind of extra weight do you have on your rig? Bumpers, sliders, etc?

Sliders, skids, drawers, 40g tank, bike rack.

Stock spring rates are posted in this forum.

 

[David310]

Check out this post by @LndXrsr:

Post in thread 'The ABCs of AHC - How to Measure, Flush, and Adjust all in one place'

May 29, 2020

AHC Mods:

Rear pressure adjustments in order of magnitude:
- Adding/removing weight over rear axle: ~1.0MPa/210lbs
- Rear sensor lift 1": +0.6MPa
- New OEM AHC springs (95 lb/in): -0-0.3MPa depending on how worn the current springs are
- 30mm spring spacers: -0.3-0.6MPa reduction
- King KTRS-79 Springs (130lb/in): -3.0MPa reduction
- OEM 100-series non-AHC or 80-series springs (170lb/in) -or- LX450 springs (150lb/in): YMMV, >3MPa reduction likely


Lifts:
- Sensor lift - adjust all three sensors to add variable static ride height, typically 0-2.5" before limiting droop travel...

• LndXrsr

• 

The benefit of having too many rear spring options is that it provides the flexibility to adapt to different scenarios. Is your ride static or dynamic? If static, select the most appropriate spring rate, if dynamic, go with air bags. I have gone from new LX470 springs, LC AHC springs with and without 30mm spacers, to new LC non AHC springs. I also have airbags to assist with towing an M1102 trailer. The best recommendation(based on your weight) would be to go with LC AHC springs. If pressures are still too high, you can either lower the ride height a bit to relieve pressure or add 30mm spacers. If pressures are too low, you can raise ride height a bit until springs settle.

It’s a balancing act until you get everything dialed in. I like my pressures on the lower end (not a daily driver) which will make for a bouncy ride but feels great once loaded.