Break over angle improvement

[wfo9]

This thread is not for everyone.. I'll be clear upfront and admit the concept is sort of ridiculous for this truck.. but if being dumb and making things do what they are not suppose to be able to do interests you read on and contribute. If not... don't bother commenting please.

So.
I was out playing on trails the other day again in my 5th gen (it had been a while... I mostly play games with my solid axle truck these days. Anyway, same observations as before. The truck does amazing except for the getting caught on the gas tank skid and rear LCA brackets. Hardly anything else stops it on most reasonable obstacles.

Obviously, it still has limits, but I can look at something and think... this truck can do that... and I'm usually correct. But when I'm wrong.. it's always the gas tank skid or LCA mounts break over that stops it in dry conditions.

The work around is hitting it with a more aggressive angle of attack to shorten the effective wheelbase. But this gets sketchy and puts you in a lot of unstable scenarios if it is really steep... sometimes you just can't risk getting your wheelbase too far off the fall line.

So I've been trying to think of solutions again.

There seems to be 4 possible choices.

1. Run more lift
2. Run 37s...
3. Get the gas tank and lca mounts above the frame
4. Rig up something to raise the rear on demand (air bags...)

1. Is no good because the truck is already too tall with 3" of lift and 35s...
2. Seems like a ton of hacking the truck up plus tough on the CVs....and rear axle. 37s just won't really fit.

3. Would be great but very complex to execute.
Run a smaller tank. Inboard the rear LCA mounts inside the frame rails. Then install an aux tank to feed the main tank in the spare tire area or mount another one on the other side of the frame. This would introduce a ton of complexity.. but It got me thinking that the FJ tank could be a possible solution for part of the problem. The other benefit of this would be the possibility of running a gear driven crawl box in front T-Case at some point. which would be a total game changer in terms of capability and fun on rock trails....


4. Would be the easiest and least expensive thing to try. It would basically be an alternative to stacking rocks.. but would not be elegant or even safe if you left it on during a down hill scenario. Maybe worth a try...

Probably best to just leave it alone... but can't help but want that little extra as I feel it would be a game changer.

 

[honda250xtitan]

build your own LCA's, mount them inboard of the frame rails, or outside of them. whatever works i guess. I'm not sure how finicky the geometry is on a 4link solid axle setup though. i'm sure its nothing like screwing with the front end. but those LCA's aren't hard to duplicate with your own changes. its just two heims with a nut welded inside some tubing on both ends.

Mount fuel tank on your roof rack duh.

 

[LJ75 Driver]

I vote 37's... lol
But it's not my truck to take a body saw to.
If it was me, I'd look at raising the rear shocks up on top of the axle. Probly not too hard. It would just take a couple tabs and some creativity to make an upper mount on the frame rails.

 

[Jeremy556]

I vote 37's... lol
But it's not my truck to take a body saw to.
If it was me, I'd look at raising the rear shocks up on top of the axle. Probly not too hard. It would just take a couple tabs and some creativity to make an upper mount on the frame rails.

The stock shock mounts are in the best possible location. You move them on top of the axle and you will lose several inches of travel and lots of articulation. The top mounts are already above the rail right against the body, you can't raise the upper mounts without cutting into the body.

What hangs up are the frame side mounts of the LCAs, mostly. Going to take major surgery to improve that, including reduction of the fuel tank.
Now you might as well triangulate the 4 link, since you are moving around suspension mounts and the fuel tank, then you should probably stop and find a different donor vehicle than a 5th gen 4runner.

 

[LJ75 Driver]

Huh... makes more sense, guess I misread what he was getting hung on. Sounds like line selection is key.
But at the end of the day, these trucks aren't rock crawlers or mud boggers, Never will be.

 

[wfo9]

Huh... makes more sense, guess I misread what he was getting hung on. Sounds like line selection is key.
But at the end of the day, these trucks aren't rock crawlers or mud boggers, Never will be.

Yes, and I stated that clearly at the very beginning of this thread. This is not a topic for the budget or logical minded...


Line selection is always key.. but in these are being taken and the truck itself just does not have the clearance necessary. It's an inch or two away from making it every time.... I think there would be a magical increase in capability if those inches of break over clearance could be gained.


If there was a kit out there... to get more gas tank clearance and flatten out that portion of the belly... I would be all over it.. but taking on the task myself seems like the juice is not quite worth the squeeze at this point (maybe when I'm looking for a project with nothing else to do). But the airbag idea might be easy enough to try... Just not very elegant overall.. which kills my motivation to try it a bit.

 

[Jetboy]

I've been through 3 iterations of rear suspension. 4 if you count stock. The first was to swap in GX460 airbags. They're by far the best offroad of the options I've used. They highway manners were my issue, and I may go back to them eventually. The problem was mostly that with KDSS they need 2 channel air with self leveling side to side NOT self balancing of pressure. I built a wireless control unit that self balanced pressure. It didn't work properly so I used manual fill valves. That sucks too because it's not convenient.

It's a good route to go though for what you want if you want to get fancy with electronics to measure suspension height. If I had a donor GX460 that I could take the entire electronics package out of - I'd put them back in a heartbeat.

The benefit is that the air springs have more travel range than any coil that fits. They'd easily max out the extended travel shocks on both sides, so you can go as high as your shocks let you with the push of a button. And they have ridiculous soft flex with progressive spring rates. But shock tuning for highway ride was the downfall for me. I didn't like the highway ride. It was soft - but not comfortable.


I've also run air helper springs inside regular coils with a coil spacer. That was version 2. It worked okay - but the ride quality sucked worse than the air springs, only on the other side of the spectrum. It was always too stiff. Only when loaded down with a trailer or full of gear would the ride soften up a bit. The minimum air in the helpers makes the coil rates much stiffer. I put them in to run the Rubicon and I'm grateful I had them. The extra inches on demand were worth the $80 just for that trip.

I'm now on version 3 which is just Dobinson 2" lift coils and no air helpers. The ride is better than any of the air options on the highway. Offroad it's pretty good too. BUT no adjustability.

So my next thought was to use air/coil combo but separate the air from the coils. Either with small air springs or air shocks. I think the right air shocks might be just the ticket. The ones I've been looking at. They're from a GM z55 autoride suspension. Why I like them as a starting point is that they are very close in length to my extended travel Fox rear shocks, they have air adjust for ride height, AND - it could be cool to have electronic adjustable dampening on the fly. I can't seem to find much info about how they're adjusted by GM originally - I assume it's as simple as a voltage stepdown regulator. But it could be something complex, in which case I'd get the version without electronic dampening adjustments. The other major downside is that they're basically street shocks - so I'd guess you'd overheat them if you wanted to do any high speed desert type stuff.

 

[wfo9]

I've been through 3 iterations of rear suspension. 4 if you count stock. The first was to swap in GX460 airbags. They're by far the best offroad of the options I've used. They highway manners were my issue, and I may go back to them eventually. The problem was mostly that with KDSS they need 2 channel air with self leveling side to side NOT self balancing of pressure. I built a wireless control unit that self balanced pressure. It didn't work properly so I used manual fill valves. That sucks too because it's not convenient.

It's a good route to go though for what you want if you want to get fancy with electronics to measure suspension height. If I had a donor GX460 that I could take the entire electronics package out of - I'd put them back in a heartbeat.

The benefit is that the air springs have more travel range than any coil that fits. They'd easily max out the extended travel shocks on both sides, so you can go as high as your shocks let you with the push of a button. And they have ridiculous soft flex with progressive spring rates. But shock tuning for highway ride was the downfall for me. I didn't like the highway ride. It was soft - but not comfortable.


I've also run air helper springs inside regular coils with a coil spacer. That was version 2. It worked okay - but the ride quality sucked worse than the air springs, only on the other side of the spectrum. It was always too stiff. Only when loaded down with a trailer or full of gear would the ride soften up a bit. The minimum air in the helpers makes the coil rates much stiffer. I put them in to run the Rubicon and I'm grateful I had them. The extra inches on demand were worth the $80 just for that trip.

I'm now on version 3 which is just Dobinson 2" lift coils and no air helpers. The ride is better than any of the air options on the highway. Offroad it's pretty good too. BUT no adjustability.

So my next thought was to use air/coil combo but separate the air from the coils. Either with small air springs or air shocks. I think the right air shocks might be just the ticket. The ones I've been looking at. They're from a GM z55 autoride suspension. Why I like them as a starting point is that they are very close in length to my extended travel Fox rear shocks, they have air adjust for ride height, AND - it could be cool to have electronic adjustable dampening on the fly. I can't seem to find much info about how they're adjusted by GM originally - I assume it's as simple as a voltage stepdown regulator. But it could be something complex, in which case I'd get the version without electronic dampening adjustments. The other major downside is that they're basically street shocks - so I'd guess you'd overheat them if you wanted to do any high speed desert type stuff.

I'm pretty happy with my rear suspension overall. Would not mind a little more bump stop control, but that is all I can really complain about.

If I was to try airbags.. I would run them at 0 pressure and only bump them up to clear something when the weight is shifted back. I know there would most likely be problems though.

 

[rochmpr]

I would agree that the gas tank and LCA rock anchors caught me a lot this summer. I would think that relocating the gas tank to the spare tire location would free up a lot of space to reconfigure the rear links and inboard the lowers.

Again, with many things time, money and parts source / fabrication (especially of a relocated tank and components) was not an issue, I would just go the route of RSG and their SAS on 40's.

A short answer to the rock anchors would be a longer "ramp" to decrease the angle of the stock mount possible making it easier to slide over the rock / obstacle.

 

[Jetboy]

The problem is that you can't run them empty. They both pinch flat between the coils - and they don't stay put. The simple air helpers just kinda suck because they're a fixed shape and fixed volume. So when the spring extends they're not going with it and they move and will pull out of the air line if they're not fixed in place somehow.

And even if you do run them empty - they will be at approximately full shape. Since they have no volume adjustability - they're almost full anyway. So you'll get effectively a really stiff air bump that starts early into the compression stroke. And the ports are so small that if you leave the valves totally open - the orifice will still be a limitation.

If you were closer I'd just give you mine to try. I think you'd take them back out pretty quickly because of the unloaded ride quality.

There are other air springs that could fit inside the coils though with custom mounts. The size that would be a perfect fit are air springs for heavy truck driver's seats. But they're upside down! otherwise IIRC they'd be almost ideal in size. If you mounted them the way they're designed they'd fill up the folded over sleeve of the bag with dirt and wear out right away.

 

[wfo9]

The problem is that you can't run them empty. They both pinch flat between the coils - and they don't stay put. The simple air helpers just kinda suck because they're a fixed shape and fixed volume. So when the spring extends they're not going with it and they move and will pull out of the air line if they're not fixed in place somehow.

And even if you do run them empty - they will be at approximately full shape. Since they have no volume adjustability - they're almost full anyway. So you'll get effectively a really stiff air bump that starts early into the compression stroke. And the ports are so small that if you leave the valves totally open - the orifice will still be a limitation.

There are other air springs that could fit inside the coils though with custom mounts. The size that would be a perfect fit are air springs for heavy truck driver's seats. But they're upside down! otherwise IIRC they'd be almost ideal in size. If you mounted them the way they're designed they'd fill up the folded over sleeve of the bag with dirt and wear out right away.

Makes sense... I figured it would be clunky.... probably not going to bother.

Maybe back to the idea of some type of UHMW on the skids to allow actual sliding.

 

[Inv4drZm]

I think a 3-link setup would be best for our vehicles considering the gas tank is directly in the way on the driver's side. I've been thinking about converting my stock "semi-triangulated 4 link" design into a true 3-link. I think all that would be needed would be to beef up the mounts and the links, and delete the driver's side upper link. Would this not be a true 3-link? By deleting the driver's side upper link, and with my 1.5" body lift, I could raise the gas tank theoretically 1.5" as well. This would keep the stock link geometry, or you could mess around with the upper link length while you are there to tune in pinion angles and all the other stuff.

Haven't thought much about the lower link hangup issue. Hasn't been a big one for me, usually it just hits the skid and slides over.

 

[Swarty]

Not in reality.

I think a 3-link setup would be best for our vehicles considering the gas tank is directly in the way on the driver's side. I've been thinking about converting my stock "semi-triangulated 4 link" design into a true 3-link. I think all that would be needed would be to beef up the mounts and the links, and delete the driver's side upper link. Would this not be a true 3-link?

Sort of we currently have a 5 link with no real triangulation. A true 4 link or 3 link doesn't need a track bar. Also 4 link and 3 link don't share geometry design. What the engineer in me actually wants to do is create a watts linkage. Like the CRC kit they have for Jeeps.

 

[Jetboy]

Sort of we currently have a 5 link with no real triangulation. A true 4 link or 3 link doesn't need a track bar. Also 4 link and 3 link don't share geometry design. What the engineer in me actually wants to do is create a watts linkage. Like the CRC kit they have for Jeeps.

I've never seen one mounted with a horizontal plane like that. Interesting. My question is this: Is there any reason the watts link needs to be centered on the axle? Could it be mounted off center to either one side of the axle with asymetrical center link and link bars to compensate? Mounting on the side of the differential housing would be better than on top for clearance I think.

 

[Inv4drZm]

Sort of we currently have a 5 link with no real triangulation. A true 4 link or 3 link doesn't need a track bar. Also 4 link and 3 link don't share geometry design. What the engineer in me actually wants to do is create a watts linkage. Like the CRC kit they have for Jeeps.

How would a 3-link setup not need a trackbar? (same thing as a panhard bar correct?) How is the axle aligned side to side if it doesn't? Is the upper link triangulated more than what I am thinking in that setup?

 

[Jeffy]

Surprised nobody mentioned LCA skids.... Pic stolen from RCI's page

They don't help the low contact point, but they do help you slide over much easier. You can even fab something up with a much "smoother" angle and weld it on so there's no protruding bolt heads, that would help you slide right over anything.

Gas tank is a b*tch though... You can lift the tank a bit to get it closer to the body, especially if you've got a body lift. That's not too complicated but it is a lot of work and PITA

 

[83Mule]

Never seen the top of tank clearance as it sits.....there may be an inch already there? Then a 1 inch BL would get you 2'' to raise the tank. Maybe there is another factory tank that is close in volume and thinner in profile......

 

[wfo9]

Never seen the top of tank clearance as it sits.....there may be an inch already there? Then a 1 inch BL would get you 2'' to raise the tank. Maybe there is another factory tank that is close in volume and thinner in profile......

Last time looked I thought I saw the tank attached to some type of frame mounts. But I need to look again. Raining and nasty out and tuck is out of the garage....


I may have given up though as the skid would have to be completely customized to take advantage of any upward movement. I'll look tomorrow and report back.

I would consider a 1/2" body lift but no more.... Even an inch overall would make a big difference as that darn gas tank is the #1 problem for me overall. The LCA mounts are next... I do have the RCI skids on the mounts... The help a little but not much in terms of getting up and over... More gradual ramping would just make it worse. They mainly just protect and are required...You have to bash really hard and I don't like that.. I find just about any contact as being bad.. gradual slopes may help a little.. but with the gas tank it already in full contact...

I don't think most people realize how just a small amount of contact will stop you.. The worse part is the gas tank will often pivot the truck in sketchy ways.

 

[Swarty]

Your not that close on top.

I've never seen one mounted with a horizontal plane like that. Interesting. My question is this: Is there any reason the watts link needs to be centered on the axle? Could it be mounted off center to either one side of the axle with asymetrical center link and link bars to compensate? Mounting on the side of the differential housing would be better than on top for clearance I think.

Watts linkages are usually on the back in the car world. But to avoid damage the top is the right spot. You currently hit the bump stops well before the rear diff hits the frame. Asymmetric design gets squirrelly real fast and you would see no advantage over track/panhard bar.

 

[Inv4drZm]

Last time looked I thought I saw the tank attached to some type of frame mounts. But I need to look again. Raining and nasty out and tuck is out of the garage....


I may have given up though as the skid would have to be completely customized to take advantage of any upward movement. I'll look tomorrow and report back.

I would consider a 1/2" body lift but no more.... Even an inch overall would make a big difference as that darn gas tank is the #1 problem for me overall. The LCA mounts are next... I do have the RCI skids on the mounts... The help a little but not much in terms of getting up and over... More gradual ramping would just make it worse. They mainly just protect and are required...You have to bash really hard and I don't like that.. I find just about any contact as being bad.. gradual slopes may help a little.. but with the gas tank it already in full contact...

I don't think most people realize how just a small amount of contact will stop you.. The worse part is the gas tank will often pivot the truck in sketchy ways.

Take a look at the driver's side upper link, the frame side mount is only 1" above the tank, and maybe the link is closer at full droop. That is the biggest obstacle on the 4th gens and FJ's at least. The gas tank either needs to be pushed forward (may not be close to feasible), or the link mount needs to be moved or eliminated with a 3-link setup.

Our heavy trucks aren't helping with the obstacle contact issues. If they were light that would be less of a problem IMO.