The one thing I still don't understand is why the GX550 E-KDSS which can disconnect both the front AND rear does worse than the 250 which can only do the front. But I’m not going to geek out over it and will just accept it.
Dan Edmunds take a deep dive on GX550 suspension
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Fort9378
SILVER Star
Because KDSS isn't a true disconnect. There's still linkage. Similar to how in wranglers the Rubicon electronic "disconnect" (basically SDM) does not allow as much flex as true, manually disconnected, swaybars. All of those linkages and things come at a cost. I bet if you had a GX or 250 and manually removed sway bars then the score would be higher than either of the systems. That being said though, the differences in RTI between them are negligible and in re-testing the numbers could be swapped. RTI isn't an exact science. More significant gaps (like compared the Bronco) are where RTI can be a better indicator.
Comparing to the 200 is different because they are totally different suspension setups.
TBF it is a miniscule difference when you actually look on the ramp. I bet if you retested with a different LC and/or GX you would end up with slightly different results. I also think it's such a small difference that it comes down to things like shock tuning and tire flex rather than some fixed mechanical design advantage for the LC.
I'm really only talking about the difference between 550 vs 250 or E-KDSS vs SDM, neither of which is a "true" disconnect.
Fort9378
SILVER Star
To add, if I remember right from the Edmunds video, the RTI score is just a function of what percentage of a vehicles wheelbase is on the ramp. Divide by 10 and you have the percentage. So you're dealing with a difference of 1.5% of 112in, or about 1.7in. That can be a difference in tires, suspension, or just how the driver did that run. It's close enough that it's basically a wash.
Fort9378
SILVER Star
Right, I'm tracking. I was just saying all that to say it's not as simple as "SDM is front and E-KDSS is front and rear". We don't know what cost all those linkages have individually to create the end product. The larger point was that the scores are so close that it's not really important regardless. They still both beat the heck out of the non-disconnected 250.
With AHC on the outgoing you can do a sensor lift (at least on the 200, I'm assuming the same with the 460). A small lift shouldn't mess with the sway bar too much as both sides rotate down. Not many folks extend swaybar connectors for a 2" lift.
With no AHC on the 550, you would need either compress the spring inside the strut for preload (and reduced ride quality) or insert a spacer between the strut top and the body which then increases droop and potentially impinges the CV.
I'd guess that the LC250 feels significantly softer on the very rough terrain. The KDSS system frees the sway bars at lower speeds, but there is still a significant hydraulic system friction that will make it harsher in mid-speed rough terrain. Plus side of KDSS is that it is more adjustable and seamless in on/off switching - for example it can lock down in cornering by a function of speed and steering angle the SDM can't lock and unlock without re-aligning. So something like a mogul set with a slalom would favor the eKDSS.
The choice to dis-link the front and rear KDSS circuits does make me question what the point of eKDSS is though. It's now a lot of plumbing and complexity that seems mostly unnecessary and could be done in a much simpler way with a center sway bar mounted hydraulic clutch on one or both bars to get the same effect.
I was surprised that it underperformed vs the lc200 and the LC250 (albeit very close). It tends to point to the coil springs, shock length, bumps, and possibly linkage bushings being the limiting factors in RTI. Might be a little consternation if the 4Runner offroad trims end up higher on the leaderboard.
The choice to dis-link the front and rear KDSS circuits does make me question what the point of eKDSS is though. It's now a lot of plumbing and complexity that seems mostly unnecessary and could be done in a much simpler way with a center sway bar mounted hydraulic clutch on one or both bars to get the same effect.
I was surprised that it underperformed vs the lc200 and the LC250 (albeit very close). It tends to point to the coil springs, shock length, bumps, and possibly linkage bushings being the limiting factors in RTI. Might be a little consternation if the 4Runner offroad trims end up higher on the leaderboard.
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There is no lag from fluid movement in the non-electronic 200 KDSS so I'm not sure why there would be speculation for it in the E-KDSS. Both resist same side roll but open for diagonal roll. The difference being E-KDSS has one more cylinder and electronic timing of activation for better control. If anything it should ride better than a bar tuned for all conditions.
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There is. That's likely why the 200 relies on a fluid flow velocity actuated shutter valve - it keeps the fluid from overheating. The heat is from friction. Functionally it acts as a form of motion damper.
Also the eKDSS is no longer hydraulically linked front to rear so there is no passive balance resisting roll as there was before. It's just electronically controlled independently front and rear sway bar disconnect mechanisms. It's a lot different from the old version in that respect. That's why I think it is strange and sort of poor engineering to have all the lines lead back to a central control unit with accumulators on the frame rail. Those functions could all be done locally within the front and rear pistons in a piggy back accumulator rather than needing all the extra feet of hydraulic lines that add a lot of flow resistance, heat, failure points, cost, etc. There's a better way to design it if that's all it is now.
If you're not cross linking them and don't need to worry about fluid cooling as much - they should just use a front and rear hydraulic mid-bar system like BMW does. Doesn't even need an accumulator if you engineer it with symmetrical fluid volumes in either direction of rotation. Just a shutter valve between the two sides. One on each sway bar. On and off electronics. And Bob's your uncle. Less cost and easy modular part to put on any configuration of the GA-F platform as they spec out the trims.
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From the perspective of a driver, there is no lag. KDSS works great. Unless you armchair the experience. Then it definitely sucks.
It's timed to the rear; keep the rear locked until it the calculated time in which it is predicted to contact the same obstacle the front experienced, thereby reducing unnecessary roll and resulting head-toss. So take the goodness of KDSS and make it better by keeping roll at bay more while still articulating when needed.
It does work well. I wish Toyota would offer it on the trucks in North America like it does overseas in the Hilux. I would prefer the older cross linked KDSS on my own vehicles. But does have limitations that a free sway bar does not. The LC200 KDSS closes the valves at medium speeds over rough terrain by design. So does the 150 series KDSS system. The LC250 will not. Hydraulic fluid has friction and heat limits that a mechanical disconnect doesn't. As good as KDSS is - it is not the same as a mechanical disconnect and there is a real difference in medium speed offroad comfort. KDSS falls a bit short in that condition.
Adding a data point.
Toyota Auto Body's Dakar GR300 still uses eKDSS.
Toyota Auto Body's Dakar GR300 still uses eKDSS.
Toyota also used a KDSS 4Runner in the Baja 1000. But I'm not sure it was because KDSS was the best option. (by that I mean best option for that specific type of terrain - it was a great option for marketing purposes to show how durable it is). The Dakar race vehicles they use to win don't share much of anything with the factory models. Not to mention no sway bars and IFS/IRS chassis. Probably closer to a Lexus IS AWD than it is to Land Cruiser.
The production car category, in which TLC competes, is a category where mass-produced vehicles must run in a configuration similar to that of production vehicles, except for the mandatory "safe driving" equipment such as roll cages, six-point seat belts, large-capacity fuel tanks, and fire extinguishers. Modifications to the structure and materials of the engine, body/frame, and other core areas of the vehicle are prohibited, placing emphasis on the true performance of the base production vehicle.
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My point was mostly that if you're going to race stock class, you'll probably take the stock model that's your halo offroad model even if it's not really the best for desert racing. In the case of the 4Runner, it probably would have been better with a non-KDSS model for the baja but Toyota ran a KDSS model anyway. Because the ultimate goal is marketing and it made for better marketing to use the same vehicle that you could complete the Rubicon and then go finish the Baja 1k. The same may be the case here - a non-kdss model might be better than kdss for desert racing all else equal, but they'd still go with the GR Sport model for marketing. I'm not sure how much suspension modification is allowed.The production car category, in which TLC competes, is a category where mass-produced vehicles must run in a configuration similar to that of production vehicles, except for the mandatory "safe driving" equipment such as roll cages, six-point seat belts, large-capacity fuel tanks, and fire extinguishers. Modifications to the structure and materials of the engine, body/frame, and other core areas of the vehicle are prohibited, placing emphasis on the true performance of the base production vehicle.
HOME | チームランドクルーザー [トヨタ車体]
TLCはトヨタグループの中核ボデーメーカー・トヨタ車体の自社チームで1995年からランドクルーザーでダカールラリー市販車部門に連続参戦しています。このウェブサイトはTLCの活動を中心に、ダカールラリーの関連情報をお届けします。
When they have freedom of choice to build the best performing desert race setup they don't use anti-roll bars at all. That's more like the Hilux race vehicles.
I'm a fan of KDSS. It has the flexibility to do a lot of stuff pretty well. Especially on-road handling. It's just not the ideal design for conditions that require high articulation speeds. It tends to be harsh in the mid range speeds on rough terrain. I don't know if the GX550 or LC300 has a published chart of the speed range where it will open the valves. My understanding from the media push is that it is open into higher speeds than the previous KDSS design, but I'm not sure what the speed limit is now.
It's wholly possible the RTI difference between the LC250 and GX550 is not in the anti-sway system. Both eKDSS and disconnecting sways functionally disengage the anti-roll subsystem.
It's then down to springs and spring rates.
The GX550 likely has higher spring rates, a fact supported by its increased capacities.
With the same architecture and suspension stroke, it's possible the GX550 is not maxing out its travel due to the higher spring rates, relative to the LC250. This is something we've seen in modified off-road rigs reaching for heavier aftermarket springs to support heavier overlanding loadouts. Often, it results in lower RTI and potentially compromised off-road performance. Taken to an extreme, it's the reason why HD trucks don't flex well for off-road work.
Soft and slinky with great damping capabilities is what makes for a solid off-road rig.
It's then down to springs and spring rates.
The GX550 likely has higher spring rates, a fact supported by its increased capacities.
With the same architecture and suspension stroke, it's possible the GX550 is not maxing out its travel due to the higher spring rates, relative to the LC250. This is something we've seen in modified off-road rigs reaching for heavier aftermarket springs to support heavier overlanding loadouts. Often, it results in lower RTI and potentially compromised off-road performance. Taken to an extreme, it's the reason why HD trucks don't flex well for off-road work.
Soft and slinky with great damping capabilities is what makes for a solid off-road rig.
after watching dan edmund's video, which was very thorough, it made me wonder a bit as he spun a rear tire on the GX, does the (heavy) battery pack in the back of the cruiser vs the (probably heavier?) motor of the GX throw more weight at the front end and possibly those variables affect RTI?
i know with my coiled 80 series (best ever wheeling suspension imho) the nearly perfect 51% to 49% front to rear weight balance allowed superior articulation.
i know with my coiled 80 series (best ever wheeling suspension imho) the nearly perfect 51% to 49% front to rear weight balance allowed superior articulation.
