LC200 305/65R18'S

[claymation]

Finally got her all done. Love the vehicle but something strange is happening when going down the highway and driving over bumps or "waves" in the road that make the vehicle rock forward and back. Seems like the vehicle is shifting right and left. Almost as if one right or left shock is binding or at least not allowing the same amount of movement as the other side. Any help will be much appreciated!

 

[Sac Cerevisiae]

Are your KDSS valves tightened back up?

 

[Tommy Dwyer]

^ This...check your KDSS valves.

 

[Sandroad]

If the KDSS valves are ok, consider lowering the front and putting a bit of rake back in. I have no experience myself, but I have read more than a few posts on both the 200 and 100 LCs that having the front high like yours appears to be can play havoc with handling.

 

[claymation]

Most of those pics make the front look higher than it is. I'll try and find a pic sitting level. Checking the KDSS valves tomorrow.

 

[bloc]

How much lift?

If your panhard bar is now angled it will force the rear axle sideways as it cycles up and down.

 

[TeCKis300]

I presume you lifted the truck what looks like a bit more than a couple inches?

What your feeling is the suspension cycling in a portion of its suspension stroke that causes lateral motions to the chassis and directional instability caused by toe steer.

The rear in particular, when lifting puts the panhard bar at a steeper angle. As the panhard bar cycles to allow the suspension to compress and extend, it is literally pushing and pulling the body side to side relative to the axle.

At the front end, the control arms are also at a steeper angle. As the suspension travels, the tire moves side to side more. Producing lateral instability. Lateral loads (i.e. turning) will results in odd jacking and compression forces upon the suspension. Complicate this with the steering rods also at steeper angles, now causes toe steer (tire steering ever so slightly) as the suspension cycles.

 

[claymation]

How much lift?

If your panhard bar is now angled it will force the rear axle sideways as it cycles up and down.

Its got the Icon 2.5 setup. Installed the front coilovers as they came which is set to 2.5 inches

 

[Tripledave]

If KDSS valves are tight, see post above about panhard. I had the same issue and Installation of an adjustable unit from Dobinsons, Tough Dog, or Total Chaos will eliminate most of what you're feeling. If not, post your alignment specs or PM me for mine which will also help.

 

[claymation]

I presume you lifted the truck what looks like a bit more than a couple inches?

What your feeling is the suspension cycling in a portion of its suspension stroke that causes lateral motions to the chassis and directional instability caused by toe steer.

The rear in particular, when lifting puts the panhard bar at a steeper angle. As the panhard bar cycles to allow the suspension to compress and extend, it is literally pushing and pulling the body side to side relative to the axle.
View attachment 2075843

At the front end, the control arms are also at a steeper angle. As the suspension travels, the tire moves side to side more. Producing lateral instability. Lateral loads (i.e. turning) will results in odd jacking and compression forces upon the suspension. Complicate this with the steering rods also at steeper angles, now causes toe steer (tire steering ever so slightly) as the suspension cycles.
View attachment 2075848

all good points but i've had at least 10 lifted 3/4 ton trucks over the years and never noticed it. You think it's just WAAAAY more noticable on the LC?

 

[claymation]

If KDSS valves are tight, see post above about panhard. I had the same issue and Installation of an adjustable unit from Dobinsons, Tough Dog, or Total Chaos will eliminate most of what you're feeling. If not, post your alignment specs or PM me for mine which will also help.

You think a poor alignment might be the cause? Funny cause the shop I paid to align the LC "lost" the spec sheet. You just might be on to something here...

 

[LC200TX]

I have the same tire size and a 2.5 lift with zero issues... KDSS?

 

[Tripledave]

You think a poor alignment might be the cause? Funny cause the shop I paid to align the LC "lost" the spec sheet. You just might be on to something here...

Sure wouldn't help. I had my rig aligned at Slee after they installed the lift. IMHO, alignment was perfect......Until tire wear and suspension settling. I had it re-aligned by a local shop once new tires/wheels were sorted to the same specs as when done at Slee and all was right again. Good luck sir, I'd still check the shutter valves on KDSS sooner than later however.

 

[RobW0]

Search on Nitrogen Shock Pressure. There was a post a while back about unequal pressure causing something like what you talk about. Think it was @Taco2Cruiser that talked about it.

 

[RobW0]

Here is the post. See if this sounds like what is happening?

page-6

 

[Chris Carrera]

I presume you lifted the truck what looks like a bit more than a couple inches?

What your feeling is the suspension cycling in a portion of its suspension stroke that causes lateral motions to the chassis and directional instability caused by toe steer.

The rear in particular, when lifting puts the panhard bar at a steeper angle. As the panhard bar cycles to allow the suspension to compress and extend, it is literally pushing and pulling the body side to side relative to the axle.
View attachment 2075843

I wish Delta would make their panhard riser for the 200 series....

Delta Vehicle Systems - FJ80/FZJ80 Panhard Lift Bracket - $250.00

Fix your rear end wiggle!

www.deltavs.com

 

[TeCKis300]

all good points but i've had at least 10 lifted 3/4 ton trucks over the years and never noticed it. You think it's just WAAAAY more noticable on the LC?

HD trucks use a different suspension architecture that don't have the same lateral issues with lift.

At the front, they usually use a solid front axle. With leaf springs and a lower radius arm type link to locate things laterally.

Same with rear, leaf springs and trailing arms to locate things laterally .

If you could describe the side to side motions a bit more and under what conditions, it could help with what to focus on.

You have guys here that say their lifted trucks handle well. It's all relative and people have different expectations. I can say even at stock ride height, with large amplitude suspension strokes, I can feel the rear in particular move around on account of the panhard architecture. Which is why even though I could do an easy minor lift with AHC, I prefer not to in order to keep the suspension geometry optimal for handling. I use to road race so I am more keyed into suspension motions. Perhaps you also are more in tune with what you're feeling.

@Chris Carrera is on the right track. A large lift in the rear done properly will have a relocated panhard point.

 

[Delta VS]

I wish Delta would make their panhard riser for the 200 series....

Delta Vehicle Systems - FJ80/FZJ80 Panhard Lift Bracket - $250.00

Fix your rear end wiggle!

www.deltavs.com

We are!

 

[claymation]

HD trucks use a different suspension architecture that don't have the same lateral issues with lift.

At the front, they usually use a solid front axle. With leaf springs and a lower radius arm type link to locate things laterally.

Same with rear, leaf springs and trailing arms to locate things laterally .

If you could describe the side to side motions a bit more and under what conditions, it could help with what to focus on.

You have guys here that say their lifted trucks handle well. It's all relative and people have different expectations. I can say even at stock ride height, with large amplitude suspension strokes, I can feel the rear in particular move around on account of the panhard architecture. Which is why even though I could do an easy minor lift with AHC, I prefer not to in order to keep the suspension geometry optimal for handling. I use to road race so I am more keyed into suspension motions. Perhaps you also are more in tune with what you're feeling.

@Chris Carrera is on the right track. A large lift in the rear done properly will have a relocated panhard point.

All good points, and yes I'm very sensitive to vibrations, alignment etc. All that was installed on the LC was the Icon Stage 1 suspension system which is simply front coilovers and rear shocks/coils. Best description I can think of is when traveling maybe 30 mph plus and when going over what I call waves (sections of overpass highways where the front two and rear two tires contact the elevation change at the same time) in the road the vehicle rocks back and forth as normal but with some lateral twisting or torquing. There is a spot on the hwy where I travel everyday that makes it super obvious.

I presume you lifted the truck what looks like a bit more than a couple inches?

What your feeling is the suspension cycling in a portion of its suspension stroke that causes lateral motions to the chassis and directional instability caused by toe steer.

The rear in particular, when lifting puts the panhard bar at a steeper angle. As the panhard bar cycles to allow the suspension to compress and extend, it is literally pushing and pulling the body side to side relative to the axle.
View attachment 2075843

At the front end, the control arms are also at a steeper angle. As the suspension travels, the tire moves side to side more. Producing lateral instability. Lateral loads (i.e. turning) will results in odd jacking and compression forces upon the suspension. Complicate this with the steering rods also at steeper angles, now causes toe steer (tire steering ever so slightly) as the suspension cycles.
View attachment 2075848

Excellent point. All that has been added is the Icon Stage 1 suspension sys. 2.5" in front and 2" in rear I believe. You think that's enough lift to cause this issue? Certainly not a big lift and I'm surprised to be having any trouble at all from installing a pretty basic system like this...

 

[claymation]