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Ok so its an issue with their link geometry and not the actual DTD cantilever set up. I was always under the impression that because of packaging with the cantilever, their track bar was too short (and not flat enough at ride height) for the amount of travel that suspension produces and caused a lot of left to right motion.


As for the rear lower control arm, whats the benefit of inboarding it? Cant you produce the same result by mounting the frame side flush with the frame and moving the axle side up to just below the tube? You would have to solve some clearance issues with the body mount.
 

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Ok so its an issue with their link geometry and not the actual DTD cantilever set up. I was always under the impression that because of packaging with the cantilever, their track bar was too short (and not flat enough at ride height) for the amount of travel that suspension produces and caused a lot of left to right motion.


As for the rear lower control arm, whats the benefit of inboarding it? Cant you produce the same result by mounting the frame side flush with the frame and moving the axle side up to just below the tube? You would have to solve some clearance issues with the body mount.
I'm not sure about track bar length, but otherwise there's no problem with the cantilever setup on axle steer. The big down fall of the cantilever is that the mounts are really close together so there's a lot less roll stability (more sway-bar need than if they were far apart). Essentially it's the equivalent of an inboard coilover mount, which is far inferior to outboard coilovers.


As for lower control arms, you indeed want them flatter so raising both axle and frame together rather than just frame is a big step in the right direction. It's not the entire solution though. You really want the axle mounts to be much further apart than the frame mounts, which necessitates having the frame side inboard. You can envision how this helps prevent rear steer. If the frame sides are closer together than the axle sides, then during articulation the side that is extending has its axle side control arm bracket traveling inward closer to the plane in the front-to-back axis passing through the frame bracket. This motion counters the axle steer induced by having the control arm traveling down. On the other hand if the frame sides are further out than the axle, then during articulation the side that is extending has its axle side control arm bracket traveling even further away from the frame bracket which makes rear steer even worse.

Essentially, having the frame mounts closer together than the axle directly counters the imperfection of having control arms that aren't infinitely long, with regard to rear steer at least. This is the basis for a double triangulated suspension. Triangulated uppers prevent the side-to-side travel you get from a track bar, and triangulated lowers prevent rear steer (hence a single-triangulated suspension still has rear steer).
 

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That last post was helpful in understanding some of the concern. I still need to cycle the suspension extremes and see what the reality comes out to.

The EVO high clearance rear arms are both mounted outside the frame. They are almost straight front to back, so I see how at full droop it would pull the axle forward more than if it were inboard.

Edit: the track bar is the stock bar.

Another good point you made is how inboard the cantilever mounts to the axle. I wonder if there’s a way to fix this.

These are things that I didn’t know/understand before I bought the system. I wanted a kit instead of one off fabricating because my time is limited. I wanted to do the work myself, but didn’t want to go through the steep learning curve. A kit made sense, but I guess the learning curve is inevitable.

There’s just not a lot of info out there about JK Kits with coilovers and bypasses. I try to avoid that other site, but it has the most info out there. Take it all with a grain of salt.

So far I don’t have a lot of drive time on this setup, but it seems to handle pretty well. It’s predictable on the road, and I haven’t taken it off road yet. Getting bugs worked out of the Motech kit first.

I sure could have used a thread like this before I bought it. Not sure yet if that would have changed the outcome though.
 

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You don't see much info on coil overs and bypasses is because it is a total waste of money on most set ups and people buy coil overs and bypass shocks for the bling. Almost nobody with the EVO stuff actually does any tuning on the system to get the most out of the $10k you spent on it. "but its EVO tuned" Thats total marketing bullshit. Bypass shocks are sensitive to weight and up/down ratio as well as what you are going to do with it. Their valving is pretty generic as well. Ones I have opened were just a progressive stack. Most people that run their kits also run them too low and have an unbalanced up/down ratio where you are basically running on the bump stop zone and not really using the main compression zone. Running them at low lift height also means that most people do not have any preload in there set up to make the shocks more responsive.

One thing that would help the rear steer is moving the axle lower control arm mount up so it is more centered on the axle. This will flatten out the arm a bit and give you more clearance under the axle.
 

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I hear you that there's a lot of people just looking for the bling factor. I was afraid that there was so much in the market that caters to them, that's why I didn't get just a coil over kit. I don't like how the coil overs are at severe angles in the rear. That seemed like too much form over function for me.

I also agree with you that most people won't tune their suspension, and that's going to boil down to the fact that you cannot expect people to understand the complexities of shock tuning and what changes can do for the ride. There's not a dumbed down shock that will get people 90% of the way there. It takes a specialist or someone to dedicate serious time to understand it. I believe money spent on a pro tuning shocks is money well spent. I was so disappointed when I saw the bypass shocks that came in the lever kit. They are like toys!

The reason I wanted coil overs and bypass shocks is because I am coming from buggies back to Jeeps. I have had buggies the last 10 years, dabbled a little in racing and decided that I would rather have a jeep that can take the family for ice cream and can take me through the hammers. Having said that, I still want to be able to drive the thing like a buggy! I know it won't be a buggy, but still want it capable.

I looked at the Genright setup and if it would have been capable with UD 60's I would have gone that route. The deal breaker was that it's cost with the required axles was just too far over what I wanted to spend.

Back to the EVO high clearance arms, the lowers on the axle side are raised substantially over stock. But I'll take a look at raising them in line with the axle tube. I would be concerned that then the uppers would be too low.

For now, I just want to get this thing working well in the form that it's in, then work on the tweaking. Meanwhile I would like to get a clear understanding of it's downfalls and compromises so I can make plans for the next move.

Thanks for everyone's feedback and sorry OP for hijacking your thread!
 

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Sorry, BL?

Edit: Body Lift, got it.

It’s stacked washers welded together and painted real pretty. It’s about 5/8” and was needed for the engine. Nothing to do with the suspension.
Thanks - I did a body lift for my hemi swap as well. Ok thread hijack over :laughing:

Sent from my LG-H910 using Tapatalk
 

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Back to the EVO high clearance arms, the lowers on the axle side are raised substantially over stock. But I'll take a look at raising them in line with the axle tube. I would be concerned that then the uppers would be too low.
Honestly, I'd probably focus more on dialing anti-squat than worrying about rear steer. Do you know where your anti-squat is right now? I've never run the numbers seeing that I can't personally measure anything, but pictures of the Evo high-clearance rear long arm always looked to me like the instant center is way too far back leaving a very high anti-squat, possibly well above 100% which would be a big problem for good performance. I recently dropped from about 100% to around 80% and the difference is tremendous for highspeed desert use (wouldn't really even notice crawling, maybe a tiny bit less hop when spinning up ledges).
 

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Honestly, I'd probably focus more on dialing anti-squat than worrying about rear steer. Do you know where your anti-squat is right now? I've never run the numbers seeing that I can't personally measure anything, but pictures of the Evo high-clearance rear long arm always looked to me like the instant center is way too far back leaving a very high anti-squat, possibly well above 100% which would be a big problem for good performance. I recently dropped from about 100% to around 80% and the difference is tremendous for highspeed desert use (wouldn't really even notice crawling, maybe a tiny bit less hop when spinning up ledges).
Raising the axle side lower control arm should reduce the anti squat. EVO also uses a rather heavy coil rate that would reduce actual squat but I would think you might get some wheel hop with it.
 

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I hear you that there's a lot of people just looking for the bling factor. I was afraid that there was so much in the market that caters to them, that's why I didn't get just a coil over kit. I don't like how the coil overs are at severe angles in the rear. That seemed like too much form over function for me.

I also agree with you that most people won't tune their suspension, and that's going to boil down to the fact that you cannot expect people to understand the complexities of shock tuning and what changes can do for the ride. There's not a dumbed down shock that will get people 90% of the way there. It takes a specialist or someone to dedicate serious time to understand it. I believe money spent on a pro tuning shocks is money well spent. I was so disappointed when I saw the bypass shocks that came in the lever kit. They are like toys!

The reason I wanted coil overs and bypass shocks is because I am coming from buggies back to Jeeps. I have had buggies the last 10 years, dabbled a little in racing and decided that I would rather have a jeep that can take the family for ice cream and can take me through the hammers. Having said that, I still want to be able to drive the thing like a buggy! I know it won't be a buggy, but still want it capable.

I looked at the Genright setup and if it would have been capable with UD 60's I would have gone that route. The deal breaker was that it's cost with the required axles was just too far over what I wanted to spend.

Back to the EVO high clearance arms, the lowers on the axle side are raised substantially over stock. But I'll take a look at raising them in line with the axle tube. I would be concerned that then the uppers would be too low.

For now, I just want to get this thing working well in the form that it's in, then work on the tweaking. Meanwhile I would like to get a clear understanding of it's downfalls and compromises so I can make plans for the next move.

Thanks for everyone's feedback and sorry OP for hijacking your thread!
There really is no reason you can't use UD60's with the genright kit. Its simply a matter of a few axle bracket and if you can do all the welding and cutting on the frame then the axle should not be any big deal. I just finished up a 4 door with out boarded coil overs and a double triangulated rear long arm with a genright rear mounted tank.
 

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Im sorry but isnt the real issue here that short upper and not the lower?
In general, on a 4x4 (where the lower control arms are much closer to the axle center line than the uppers, something true in 4x4 but not necessarily all vehicles), the lowers set the wheel base which is what will affect rear steer, while the uppers set pinion angle through travel and consistency of the anti-squat through travel. Short uppers can be a big problem to those things, but won't really create rear steer, so long as it's true that the lowers are much closer to the axle tube than the uppers.
 

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In general, on a 4x4 (where the lower control arms are much closer to the axle center line than the uppers, something true in 4x4 but not necessarily all vehicles), the lowers set the wheel base which is what will affect rear steer, while the uppers set pinion angle through travel and consistency of the anti-squat through travel. Short uppers can be a big problem to those things, but won't really create rear steer, so long as it's true that the lowers are much closer to the axle tube than the uppers.
But with a 4 link like the one pictured, its hard for me visualize how the short uppers arent affecting the front to back motion of the axle?
 

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But with a 4 link like the one pictured, its hard for me visualize how the short uppers arent affecting the front to back motion of the axle?
Here are pictures that might help visualize how only the lower really matters for front-to-back motion. This graphic assumes the lower is literally at the center of the axle tube which is impossible, so the uppers do matter a little bit, but for any logical 4x4 build the lowers are way more important for wheel-base/front-to-back motion.

These are two totally arbitrary suspensions (not modeling the Evo suspension at all), one with logical upper/lower lengths, and one with uppers that are insanely short compared to the lower.

Here it is at "ride height" showing the pinion angle (depicted by the short vertical line above the axle tube) is the same as well as ride height:



And now we droop out the suspension. Because the lower links are the same length and at the axle tube, the wheel-base and front-to-back motion are precisely the same, only the pinion angle is screwed up due to the short upper links. The anti-squat is also shot through travel. But the wheel base is unaffected and the rear-steer is exactly the same between the two suspensions.



I'm not saying upper length doesn't matter, it's critical to have appropriately matched upper and lower links (usually uppers should be just a bit shorter than lowers, but it depends on the suspension design plan). It just doesn't much matter for wheel-base effects such as rear steer.
 

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On a JK axle both arms come into play and both have an affect on the pinion angle during articulation since the lower hangs down below the axle centerline by several inches.
The steep angle of the lowers is the real issue, the more angle you have at ride height the more rear steer you will have. Same thing with the track bar, the steeper the angle at ride height the more left/right axle shift you will have.
 
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