Long Travel AHC (2 Viewers)

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Probably no surprise, but I've been a big proponent oh AHC. Damping always dialed in regardless of load. Large fluid volumes and remote accumulator damper that stays cool with extended off-road travels. Actively pressurized for long term performance and durability. Combined with unique traits of adjustable height, load handling, and multi-rate springs for anti-brake dive and handling, there's a lot going for it.

But where does it come up short? Suspension travel due to shock length. Because length dictates maximum suspension droop of the suspension, it has until now limited travel to the stock 9" front and 10" rear. An area where aftermarket suspensions has a clear advantage.

This thread is about keeping all the goodness of AHC, while extending travel (droop) to 10.5" (+1.5") front and 11" (+1") rear.

Before anyone gets too excited, know that this is not an easy job and does require a certain amount patience, fabrication, and tools. It's also a great time to refresh the shocks, fluid, and maybe accumulators. I'm $1400 in parts all between the sales and sourcing OEM accumulators from Japan. A comparative steal.

1655869898611.png
 
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Joined
Apr 27, 2011
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San Diego

Front Axle - 4 out of 5 banana job (fabrication and tools)​

Special tools: spring compressor, press, grinder

Parts:
- LC OEM spacer (10mm).
- Tundra 1/2" leveling spacer (7mm)
- Polaris RZR 3/8" x 24 thread x 1.75" long wheel studs set
- 8x 3/8" x 25 TPI nuts
- DBF17T Durobumps Front Bump Stops
- AHC fluid
- Might as well replace the front stock AHC shock while in there

The front axle recipe follows the same formula identified with using the LC OEM 10mm shock spacer. Expanding on this idea, by adding another 7mm worth of spacer, for a 17mm stack. The bit more travel is twice as much work than just dropping in the stock LC spacer, as it requires full disassembly of the coilover, longer shock mount studs, and grinding the AHC hydraulic fitting. Grinding is necessary as the hydraulic brackets now sit within the coilover bucket, instead of above. Needs lateral clearance as the coilover moves side to side when cycling.

Steps:
1) Depressurize AHC system by bleeding the front accumulators. Bleed twice.
2) Remove AHC line from top of shock
3) Remove shock
4) Mark all components and note alignment and orientation. Dissemble coilover with spring compressors.
5) Press out stock studs (could probably hammer it out and use a nut to pull in new studs, in place of a press)
6) Replace with longer wheel studs (Polaris RZR wheel studs that are easily sourced drop right in. They are standard, but I can live with that, as it's incredibly hard to source a proper metric stud that's long enough)
1655879328062.png

7) Grind the AHC retention bracket (coilover side) to the edge of the nut; spray paint
1655880143420.png

8) Grind AHC line bracket (car side) to the edges of the bolt hole; spray paint
1655880153041.png

9) Re-assemble coilover, making sure all elements are in alignment
10) Stack 2x spacers on coilover
11) Re-assemble suspension
12) Install Durobump in the rear position

Part of the trick is to make sure the shock doesn't become the full compression limiter as this has the potential to damage the shock. Granted I've not gone full send and completely jumped my car, but I've definitely driven it hard. From the witness marks of my shock piston, looks like like there's more travel to be had and 17mm of spacers should work fine. The Durobump is added insurance, and should make for a good bump stop upgrade for more aggressive driving.
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Joined
Apr 27, 2011
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7,152
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San Diego

Rear Axle - 4.5 out of 5 banana job (fabrication and PITA to remove/install rear shock)​

Special tools: Long or offset 14mm box wrench , press, grinder or band saw, welder, lots of patience

Parts:
- New AHC rear shock
- AHC fluid

1655948944129.png


The rear axle recipe is custom fabrication to extend the shock. As the rear motion ratio between shock and suspension travel is 1:1, it's about re-locating the lower eyelet by 1". 1" isn't really a magic number, but based on my assessment it was a reasonable balance between maximizing droop while still keeping the shock safe under full compression such that it doesn't take the full impact of being the first or primary bump limiter. I could see maybe expanding this to 1.5" for someone that's willing to be more aggressive or lower the frame bump stop accordingly.

I checked the witness marks and there seems to be lots of clearance potential, at least for my driving style, and airbags minimally at 5PSI.
1655949974511.png



Easiest way in my mind was to lop off the partial eyelet on a new shock so it becomes a standoff bracket, take the harvested eyelet off the old shock, and burn them together. There potential to modify the axle side lower shock mount by relocating that higher, but I figured it was cheaper, easier, and reversible if I modified the shock.

Steps:
1) Depressurize AHC system by bleeding the rear accumulators. Bleed twice.
2) Remove AHC line from top of shock (2x 12mm bolts). This is going to be an exercise in patience.
3) Remove lower shock bolt
4) Remove sway bar link at top nut
5) Remove upper shock nut. More patience. Fortunately the LX shock piston is keyed. Unfortunately working from the inside of the frame with an boxed offset wrench turns only 30 degrees at a time.
6) Remove shock
7) Mark all components and note alignment and orientation. Dissemble coilover.
8) Press out lower bushing of both new and old shock
9) Cut full eyelet off old shock
10) Measure twice, and cut new shock eyelet to work as standoff to old eyelet hoop
11) Fabricate inner ring support with 1/4" steel
1655950242152.png

12) Burn it all together, minimizing heat going into the shock body (undercut and need another cover pass here)
1655950281212.png

13) Spray paint
14) Press new bushing in
15) Reinstall
16) Check brake line length, may need to bend some locating brackets to get more slack
18) Optionally shim frame bump stop down (I used a 1/4" shim). I may remove these as I shake things down, to maximize travel.
1655950037200.png

19) Optionally shim sway bar end link down 1/4"
 
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Joined
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Why and what this mod enables​

I've always been a proponent of less lift and bigger tires. Keeps better suspension geometry and brings real clearance under the rear diff. With AHC, there is the ability to sensor lift. However, there is still a balance to maintain between useful sensor lift, and too much given stock travel. The 100-series guys have a rule of thumb to keep ~2.5" droop travel when sensor lifting.

The progression is to tackle bigger obstacles and drive faster in the rough. Translation - More clearance and compression travel. This mod opens the door to larger useful sensor lifts. Lifts that total 6"+ over stock when paired with large 35 in tires. 7" if AHC engages auto Extra-High mode. I mention 35s, as IMO, tires are integral to overall suspension performance, especially when aired down, and maybe worthwhile to tackle ahead of this type of suspension mod.

Clearance and Articulation for Crawling​

AHC already lifts 2"+, and when combined with 35s, is a solid 4"+ lift. Any sensor lift is gravy on top. Yet too much sensor lift, and it starts eating up suspension travel in droop. Droop travel is important so it doesn't feel pegged. That pegged out feeling also means little articulation, and articulation is key to crawling.

In the stock AHC setup, the front has 9" total travel, with normal ride height splitting 3.5" compression to 5.5" droop travel. Rear, 10", 4.125" compression, 5.875" droop. The stock setup keeps a big travel bias in droop, and why it feels so good and slinky. In AHC high, still keeps a solid 3.5" in droop, front and rear.

Challenge comes when sensor lifting aggressively. For example, a 1.5" sensor lift leaves only about 2" droop travel F and R in high. Sensor lift higher, and it's pegged out, stiff legged, with no articulation. Remember the 100-series communities learned 2.5" droop rule of thumb?

AHC long travel brings back droop travel, and a slinky functional AHC high position. In my case, I sensor lifted 1.5" F and 1" R. AHC high with 35s, is now a substantial 5.5" more clearance than stock. While still having 3.5" of plush droop travel and articulation.

More Compression/Bump Travel and Clearance for High Speed Baja Running​

As mentioned earlier, stock AHC Normal ride height keeps relatively little compression travel with 3.5"F and 4.125"R. Higher speed desert running can benefit from more compression travel. Though it's just as important to keep even more droop travel. AHC long travel gets the best of both worlds. With 1.5" F and 1" R more overall travel, and a matched sensor lift by the same numbers respectively, there's now 5"F compression travel and 5.125" R compression travel at Normal AHC height. While keeping great 5.5" F and 5.875" R droop travel.

I don't need to rely on AHC high as much, which is a compromise as it lowers to normal height at ~20MPH. Using 4Lo expands AHC high to ~50MPH, but gearing isn't as suited to higher speed running. Gotta keep up with those pesky Ford Raptors.

The expanded overall travel can pay-off in avoiding G-outs in both bump travel and larger jumps. With jumps, the suspension now has 10% more travel as it reaches out in full droop before landing to avoid bottoming out. Further upgraded with Durobump bumps stops in front, and low pressure airbags in rear.
 
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Testing full stuff and she'll still sit all the way down. Hard to test the rear as one side can stiff further when the axle is fully articulated. Seems like the shocks are well protected enough.

1656191831612.png


Armed with more droop travel, I was ready to dial in more sensor lift. Click a few buttons in the Techstream height offset utility, and I'm now at 1.75" F and 1.3" rear sensor lift.

New ride height in AHC normal from hub to fender: 20.5" and 22.125" R. From ground is 36.375" F and 38.12" R

AHC high position. Hub to fender: 22.75" F and 24.35" R. From ground to fender is 38.375" F and 40.5" R
1655870081660.png


Had to re-setup the hitch and WD tension as increased ride height relaxes the WD bars. About 2300lbs payload between the trailer tongue weight, mods, and people/vacation gear. I can tell the COG is raised and the car moves around on the road just a hint more, but she still hauls the 8k trailer with control and stability. The real test is off-road and I'll get a chance in a few weeks up in Big Bear.
1656192444501.png
 
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Joined
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Golden, CO
Pretty excited about this one. I’m really close to making the conventional swap. As you know @TeCKis300 the lack of travel moving fast off-road in N and Crawling in H with a standard sensor lift is incredibly limiting in experience.

I feel like I’m going to rip the shafts out of the shock bodies quite often.

AHC has so many incredible qualities as you mentioned. I really want it to work for my driving style…just not sure yet. Can’t wait to see you detail it out for us in one thread.
 
Joined
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Why were the studs in metric hard to find? The fact that needs to be 10mm instead of the common Toyota 12mm?

I couldn't source it in the couple days I was looking locally, even at a specialty industrial supply. Part of the trick is these are fine thread studs. I could find stock 30mm length, but couldn't find the 40mm length needed. Was about to grind down metric hex bolts but I questioned the strength. Amazon to the rescue.

The 3/8" studs couldn't have worked more beautifully. Pressed in like a glove (IIRC within .05mm), equivalent grade, perfect length, cheap to boot. The studs are practically a specialty part of the assembly and won't ever be replaced in the field so it's a non-issue in my mind.

Still, the hive mind has surprised me so I encourage if anyone can find a better metric option. Leading us to the next question:

I am also interested in the mm wide of knurl on the stock studs, and the length of knurl on stock studs.

Stock 10mm x 30mm stud. 10.5mm diameter and 6.5mm length knurl.

Need 40mm length.

1655947357895.png
 

linuxgod

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I couldn't source it in the couple days I was looking locally, even at a specialty industrial supply. Part of the trick is these are fine thread studs. I could find stock 30mm length, but couldn't find the 40mm length needed. Was about to grind down metric hex bolts but I questioned the strength. Amazon to the rescue.

The 3/8" studs couldn't have worked more beautifully. Pressed in like a glove (IIRC within .05mm), equivalent grade, perfect length, cheap to boot. The studs are practically a specialty part of the assembly and won't ever be replaced in the field so it's a non-issue in my mind.

Still, the hive mind has surprised me so I encourage if anyone can find a better metric option. Leading us to the next question:



Stock 10mm x 30mm stud. 10.5mm diameter and 6.5mm length knurl.

Need 40mm length.

View attachment 3040850
All that technical info in the first post and you guys are focused on a set of bolts

Once you’re willing to start grinding and cutting you’re a brave man. Bravo.
 

grinchy

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All that technical info in the first post and you guys are focused on a set of bolts

Once you’re willing to start grinding and cutting you’re a brave man. Bravo.
just curious. Spent a lot of time looking for and finding metric studs when looking for longer options for our hubs.
 
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Did someone do thicker spacers with built in studs recently or did I imagine it? I believe that person also had to grind down the AHC brackets. How much more travel do the shocks have in them?
 
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Joined
Apr 27, 2011
Messages
7,152
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Liking it! Did you happen to measure front shock length at full compression?

I have it sitting in my garage and will pull a number this weekend.

Did someone do thicker spacers with built in studs recently or did I imagine it? I believe that person also had to grind down the AHC brackets. How much more travel do the shocks have in them?

@1UZJ80N60 Yup, done more extreme and paired with long arms! I think we had him pegged for around 12" of front travel

 
Joined
Apr 27, 2011
Messages
7,152
Location
San Diego
Pretty excited about this one. I’m really close to making the conventional swap. As you know @TeCKis300 the lack of travel moving fast off-road in N and Crawling in H with a standard sensor lift is incredibly limiting in experience.

I feel like I’m going to rip the shafts out of the shock bodies quite often.

AHC has so many incredible qualities as you mentioned. I really want it to work for my driving style…just not sure yet. Can’t wait to see you detail it out for us in one thread.

Added more notes as to why in the write-up above here - Long Travel AHC - https://forum.ih8mud.com/threads/long-travel-ahc.1287237/post-14493235

Why and what this mod enables​

I've always been a proponent of less lift and bigger tires. Keeps better suspension geometry and brings real clearance under the rear diff. The progression is to tackle bigger obstacles and drive faster in the rough. Translation - More clearance and compression travel.

Clearance and Articulation for Crawling​

AHC already lifts 2"+, and when combined with 35s, is a solid 4"+ lift. Any sensor lift is gravy on top. Yet too much sensor lift, and it starts eating up suspension travel in droop. Droop travel is important so it doesn't feel pegged. That pegged out feeling also means little articulation, and articulation is key to crawling.

In the stock AHC setup, the front has 9" total travel, with normal ride height splitting 3.5" compression to 5.5" droop travel. Rear, 10", 4.125" compression, 5.875" droop. The stock setup keeps a big travel bias in droop, and why it feels so good and slinky. In AHC high, still keeps a solid 3.5" in droop, front and rear.

Challenge comes when sensor lifting aggressively. For example, a 1.5" sensor lift leaves only about 2" droop travel F and R in high. Sensor lift higher, and it's pegged out, stiff legged, with no articulation.

AHC long travel brings back droop travel, and a slinky functional AHC high position. In my case, I sensor lifted 1.5" F and 1" R. AHC high with 35s, is now a substantial 5.5" more clearance than stock. While still having 3.5" of plush droop travel and articulation.

More Compression/Bump Travel and Clearance for High Speed Baja Running​

As mentioned earlier, stock AHC Normal ride height keeps relatively little compression travel with 3.5"F and 4.125"R. Higher speed desert running can benefit from more compression travel. Though it's just as important to keep even more droop travel. AHC long travel gets the best of both worlds. With 1.5" F and 1" R more overall travel, and a matched sensor lift by the same numbers respectively, there's now 5"F compression travel and 5.125" R compression travel at Normal AHC height. While keeping great 5.5" F and 5.875" R droop travel.

I don't need to rely on AHC high as much, which is a compromise as it lowers to normal height at ~20MPH. Using 4Lo expands AHC high to ~50MPH, but gearing isn't as suited to higher speed running. Gotta keep up with those pesky Ford Raptors.

The expanded overall travel can pay-off in avoiding G-outs in both bump travel and larger jumps. With jumps, the suspension now has 10% more travel to avoid bottoming out. Further upgraded with Durobump bumps stops in front, and low pressure airbags in rear.

Wondering if that is the limiting experience you're looking to improve on?
 

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