elripster
Roll Me Over
Reged: 03/15/01
Posts: 2731
Loc: San Diego, CA, USA
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Numerous times, we've talked of air shocks on the front of an IFS Toy. In Theory, they would take advantage of Newton's Third Law: Every action has an equal and opposit reaction, to better distribute forces between the two wheels. I went through a few sets of shocks, took measurements, to be honest I was hoping to develope a kit and sell it. (School is to much to do and start a business) I have 'em on my truck and think this is the best mod I've done other than a locker.
Here's the skinny so far:
- Since I have a 4" lift(89 4runner), I'm using Gabriel HiJacker 729279 Air Shocks. If you have a stock height vehicle, you'd need a different model. Since stock you don't have much travel though, you wouldn't really be able to take full advantage of the mod. If you were to do a little fabbing and relocate your compression bump stops, go to a parts store and ask to see their shock catalog. Get measurements from your shocks, or go to the ORC site, there's some info there. In the back of the catalogs is the measurements and you can find a set that will fit.
- The stock shock mounts aren't very strong. In fact, when I first aired them up, they flexed quite a bit. To remedy this, I made some re-inforcing brackets. In case you are wondering if they are strong enough, well for those at the Jambo, remember the ride back from the Fisher Mountain Trail? Rember the endless whoops? I was one of the first people back. I bashed the shiznit out of it to see if the system would hold up. It did.
- I also made some blocks to expand the travel. It was easy, just used aluminum square. This is very strong, much more so than the Rockstomper kit. Also, the bumpstops are angled for square contact, something else you don't get with the Rockstomper kit. If you can cut and tap a hole, you can make these and save a buck! I don't have the measurements right now but I'll get 'em.
I originally started out taking measurements, etc... and at like 85 psi had like a 30% improvement. Later I pumped 'em up to 110-120 psi, I ended up loosening the T-bars like 18 turns. (Don't worry, there's TONS of bolt still protruding above the cams) I never got to quantify this increase but from just seat of the pants wheeling, it's night and day. Instead of the truck pitching and tossing like it used to, it actually articulates over the terrain. It's like riding on air. It uses all 12" of it's travel. It actually feels like it's pulling with the front for a change. I'm way stoked on this mod and highly recommend it. I would wager that this would put off a lot of SAS's.
Anyway, I gotta run. I'm sure you guys have questions I forgot to answer here so fire away. I don't have pics right right now of my truck in action and won't for a while and for that I apologize.
Frank.
[ September 25, 2002, 11:13 PM: Message edited by: elripster ]
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1994 4runner, 3.0, auto, 4.88's, 31's, BJ spacers, Coil spacers, air shocks, D-ring anchors, 4Crawler F/R swaybar discos.
www.sdori.com
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DirtyHarry
Toyota Moderator
Reged: 11/15/00
Posts: 4192
Loc: Rapid City/Albuquerque/Reno
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First the Supra LSD and now this! ![[Nerd]](graemlins/nerd.gif) Frank you are cranking out the good tech, keep up the good work!
I already cut my IFS out, so I can't take you up on your claim that this would put it off. That is a pretty bold statement, you must be really happy with the results.
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Harry Wagner
Harry Situations
4x4Wire's Toyota Section
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Brian894X4
Trail Leader
Reged: 05/14/01
Posts: 6767
Loc: Gresham, Oregon
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quote:
Originally posted by elripster:
Anyway, I gotta run. I'm sure you guys have questions I forgot to answer here so fire away. I don't have pics right right now of my truck in action and won't for a while and for that I apologize.
Frank.
I already SAS'd too, but it all sounds interesting. However, I'm a little confused on how it all works. I didn't exactly ace science. ![[Drunk]](graemlins/drunk.gif)
Do I understand correctly that the shocks are tied together?
[ September 25, 2002, 11:43 PM: Message edited by: Brian894X4 ]
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My Toyota/Expedition Website
Foreign & Military Toyotas - Expedition 4x4s
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Jeff the marmot
Trailriding Forum Moderator
Reged: 02/13/00
Posts: 4668
Loc: Thornton, Colorado
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Funny you bring this up now. It's good to hear that it works well.
Did you know that the 2003 4Runner will have cross-linked shocks? Toyota says it's the first application of this in a mid-SUV. Their abbreviation is X-REAS, which stands for diagonally-linked Relative Absorber System. Well, at least they didn't call it dia-reas. ![[Smile]](images/icons/smile.gif)
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Jeff
2000 4Runner SR5, supercharger, rear e-locker, ARB front locker, 285/75R16 MT/R's, custom bumpers & skids
2007 Tacoma double cab 4x4 - stock
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elripster
Roll Me Over
Reged: 03/15/01
Posts: 2731
Loc: San Diego, CA, USA
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As for putting off the SAS, that's only because, given the high stock spring rates even with a large travel window you get maybe 6" total before you lift a wheel. (Level ground, etc...) Or, you get the solid axle and flex like mad. There isn't a whole lot in between and what's there is kinda pricey. (Long travel kits and likes) This would put it off for those who reside in the middle ground or are cash strapped. Obviously, if you want the ultimate, a solid axle is the way to go for many reasons.
As for how it works. The air shocks share the same volume of air. That air is under pressure of course which takes load off of the torsion bars. Now, the shocks don't care if one is compressed and the other is extended, or both are even, it's about that given volume and resulting pressure. Where you lose the force required for traction is when one spring is bearing the majority of the weight. There is only a fixed amount of weight, what you take from one you give to the other wheel. By placing the load on the air shocks, which remember don't differentiate force based on their compression/extension, you help to remove the springs from the equation. The more you load the shock, the less you load the spring. Less loaded springs flex more for a given amount of load. Think of it like this, you take a spring at rest, push on it, it flexes. Now preload the spring and push on it again, it's much harder to flex. The shocks lessen the preload.
I could go into equations and the likes but this is already a long post so I figure maybe it's better not to.
Interesting thought, in theory, there isn't any reason I can think of that, within the IFS limits of travel(big caveate I know) there is no reason that it couldn't distribute the forces better than a solid axle. (Solid axles use statics and leverage where you sum the forces and torques. The result is a better distribution of forces even when one spring is severely compressed and the other extended.)
I hope more people try this as this mod is really in its infancy. There's a ton of room for improvement. The shocks are like 40$, a travel kit is another 40 or much less if you make your own. The brackets are a few dollars of steel. A person withthe tools could easily get away for less than 60$ and have some healthy flex...for a Toy with IFS.
I wonder how this would work with a long travel kit.........
Frank.
[ September 26, 2002, 01:29 AM: Message edited by: elripster ]
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1994 4runner, 3.0, auto, 4.88's, 31's, BJ spacers, Coil spacers, air shocks, D-ring anchors, 4Crawler F/R swaybar discos.
www.sdori.com
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elripster
Roll Me Over
Reged: 03/15/01
Posts: 2731
Loc: San Diego, CA, USA
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quote:
Originally posted by Jeff the marmot:
Funny you bring this up now. It's good to hear that it works well.
Did you know that the 2003 4Runner will have cross-linked shocks? Toyota says it's the first application of this in a mid-SUV. Their abbreviation is X-REAS, which stands for diagonally-linked Relative Absorber System. Well, at least they didn't call it dia-reas.
Yeah I saw that. I had thought of this last year in my physics class after doing a DOE on my truck for a final project. It's a good idea, it works. I only have mine linked across the front, I bet it works even better diagonally given that's what's going on when you cross up.
Also, these shocks really ride nice. The wheels seem to track the ground well, better than before.
There is more body lean, not much but a little. I'd use a sway bar with this set up.
Totally off subject, but didn't that Tercel Lars and others put the big wheels on look similar to the new 4runner?
Frank.
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1994 4runner, 3.0, auto, 4.88's, 31's, BJ spacers, Coil spacers, air shocks, D-ring anchors, 4Crawler F/R swaybar discos.
www.sdori.com
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Anonymous
Unregistered
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wut wuz the before shock?
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Wyatt
Roll Me Over
Reged: 11/24/99
Posts: 2543
Loc: Sellersburg, IN
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What about dampening on road? Don't you get any wierd funky butt-puckering oscillations (yawing)? ![[Wink]](images/icons/wink.gif)
It's been awhile since I had air shocks on my '65 Old Starfire, but I remember it hopped around like a horny bunny. ![[Big Grin]](images/icons/grin.gif)
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I'm your Huckleberry
96 4Runner LTD,S/C,headers,2.5 w/ 285's
89 4Runner SR5 V6,locked,33's
Wyatt's Toys
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aowRS
Body Damage is Cool
Reged: 08/02/01
Posts: 1024
Loc: Ellicott City, MD
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Frank,
I think your explorations are really commendable. I only have one concern with the setup: By relaxing the torsion bars and giving the air shocks some of the support duty, you are stressing two items not originally intended to support the weight of the frontend. While you strengthened the upper shock mount, I would double check the lower mount and possibly reinforce that, if not cannibalize the lower strut mount from a 3rd Gen. These were designed to take the brunt of the suspension duties, while your stock mounts were only spec'd to keep a fairly tame shock in position.
The other item is the shock itself - is it sold more as a "helper shock" for load carrying, or do you think it is up to the task of taking a portion of your frontend weight on a continual basis? I've seen these type shocks used on a friend's off-road project buggy, but the vehicle weighed maybe 500 lbs.
I think the idea is great - I would just strengthen the A-arm areas to mimmic the 3rd Gen. and check whether the shocks are able to cycle in the fashion you describe. I would assume that the majority of people use these to add weight-carrying capacity, and as such, probably lower the pressure when not needed. It would be nice to do away with the rigid T-bars completely.
Just some thoughts.
Andreas
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2001 4Runner SR5 4WD, Dorado Gold, 246,000 miles
2007 Volvo XC 90 AWD V6, Silver
1995 Porsche 993, Polar Silver
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Dandeman
Toyota Moderator
Reged: 04/27/00
Posts: 3726
Loc: Chapel Hill, NC
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I've been thinking about this for a long time, but plan to soon try the Gabriel air shocks on the rear of my 4Runner and crosslink them... and plan to use as follows.. The rear shock mounts are very beefy, so think they are up to the job.. that can be one of the concerns.
Since I already have an onboard 100psi air compressor I was going to install two electric air control valves for in cab control... one to pressurize, and the other to vent back down..
On road, I would leave them open (so no effect from crosslinking and vehicle will run at normal height) but off road where I really need to improve rear overhang clearance a bit, crank them up.. this is important as on our off roading (aka long trips), the back end is loaded down with extra weight..
not expecting any improvement in rear articulation limits (as limited by design, per investigation by Steve Schafer), but maybe some in range improvement.
hope to start on this soon....
One question elripster, I'm pretty sure I've read you can do this with the Gabriels, but can you confirm whether you can run them with zero air pressure.. I know you can't do this with air bags.. as they will get out of position and get ripped up...
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2000 4Runner,V6,Auto,31's, Sliders, Skids, On-Board Air, Air Shocks
Related Interests: Welding, Ham Radio, Road Tripping (Blue Highways), High End Video/Audio Systems
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