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90 K-5, 4" Lift, new bilsteins, still rocks and rolls!

fltplan

fltplan

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San Diego, CA
Okay, got this really nice K-5. It has a 4" lift with 305/70/16's. They appear small, but I don't want to change the gearing. Just put some new bilsteins all the way around. It drives okay around town, but on the highway it has a really bad roll back and forth with bumps that are not 90 degrees to my path. I think it's dangerous actually. I tow my 21' boat and the springs don't sag at all. Not a lot of tongue weight.

So, with small tires, big lift, what are my options? I'm considering respringing the back and or the front also. The problem appears to be coming from the back, not the front. Also considering a little taller tire for looks only (I know it raises it even more). I'm also considering lowering it one inch with all new springs. I like the height but don't mind going down a little.

My question is this. Do you think this rocking and rolling is normal regardless of the springs, because of the height and small tires or will it be fixed with new springs?

I only drive this thing back and forth to the Colorado River with light off roading. Less than 5k per year on the miles. Functionally it's the perfect vehichle. I really want it to drive good. If I can't solve the issue, I would have to get something like a Tahoe or Suburban, which I really don't want to.:D

River July 2010 007.JPG
 
BTW, the back springs are probably stock, as there are blocks back there. The front was re sprung with the lift prior to my purchase.
 
what load range tires are they.....pressure? what does the trailer weigh and what is the tongue weight you're setup to?
 
shovelbill80 said:
what load range tires are they.....pressure? what does the trailer weigh and what is the tongue weight you're setup to?
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Load range E with 35psi. I only tow the boat occasionally. Just down to the river at the beginning of season and back at the end of the year. It doesn't do the wag towing the boat, only when it's by itself. I believe the boat keeps the movment in the back to a minimum.

Before the shocks this thing was almost undrivable when towing, because of the bouncing around with the aft center of gravity on the trailer and all.
 
boat and trailer under 3k. tongue weight about 100#s. like I said, the issue is driving without the boat at highway speeds.
 
how's all the spring and shackle bushings? sway bar? u bolts tight?
the shocks job is to keep the tires on the ground, sounds like something else to me. what's the max pressure on the side of those tires, 80 psi?

ok...just for some info. if your trailer weighs in at 3K, your tongue "should" be between 300 and 450 lbs.
 
shovelbill80 said:
how's all the spring and shackle bushings? sway bar? u bolts tight?
the shocks job is to keep the tires on the ground, sounds like something else to me. what's the max pressure on the side of those tires, 80 psi?

ok...just for some info. if your trailer weighs in at 3K, your tongue "should" be between 300 and 450 lbs.
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that's interesting info on the trailer. wouldn't that tongue weight vary with the placement of the axles, dual or single? Or should they be placed where they need to to get the tongue at 10%. There's 505#'s hanging 18" off the back, so the tongue is probably a little light. It actually tows okay.

I will start checking all of the bushings, etc. do you believe that if it's all tight, a 4" lift with said tires should be okay?
 
i'm certainly not an advocate of towing with big lifts and tires.......but your trailer isn't very heavy, the lift isn't bad and you have a stiff tire. yes, the tongue should be betwixt 10% and 15%........but this isn't a towing thread so i'll stop there.

35 pounds would be max for most 33 or 35" X 15's, but you do need more air in those metric tires. can't use the door sticker. i'd start at 50 pounds front and rear and go from there.
 
fltplan said:
boat and trailer under 3k. tongue weight about 100#s. like I said, the issue is driving without the boat at highway speeds.
Click to expand...
without the boat AND trailer
or
with just the trailer and no boar?

I would consider going with an Atlas spring or even a TC 4" lift rear spring. Get rid of the blocks and old springs. BUT I wouldn't bet the farm that that's your problem :dunno:

Also sounds like too little tongue weight. I'd say that big ass outboard might actually be lifting the back of the blazer up some during the "bouncing".
 
I'd start with the spring bushings, sway bar bushings and even look at your body mount bushings. Mine is doing the same thing with roughly the same lift as yours. I have not towed our boat enough to really have an good feeling but towing it for a few miles down the road, I definitely noticed it back there. That was with 37" tires and 4" lift. I have since moved down to 35" tires.

I just switched to Bilsteins and my new rear leaf spring bushings will be in tomorrow. I also have some movement on my front sway bar bushings. Hopefully this will tighten things up but for now, mine is behaving very similar to yours. I don't think I would be comfortable yet pulling mine down the freeway until I can get the truck feeling much more solid.

With short wheelbase vehicles, you are going to feel the up and down bouncing. Lifting it will just make that feeling worse.

A few things to try: increase tire pressure and mess with the hitch height. It looks to be pretty parallel right now. Try dropping the ball an inch or so and see how it behaves. That can make a difference if you have too much or too little of tongue weight.

2010-10-10_13-45-24_422.jpg
 
Guys he is not having an issue while towing, he said its unloaded at highway speeds. Not even around town.

Springs would be the obvious answer but you need to check and make sure nothing is broken or loose in the rear of the truck. U bolts, center pins, shackles, spring bolts, any leaf springs, rivets loose, etc. Check over everything first.

Maybe have someone drive it at highway speeds while you watch it. See if you can see what is moving around back there
 
Yep, check your rear springs out. Mine are the stockers at stock height and I get some of those symptoms. Does it get worse when towing or loaded with stuff and people?

Mine gets kinda "wallowy" the more weight I have in the back and even unloaded it's got some sway in the rear.

However I've measured and the right rear spring is about an inch lower than the left rear spring. I think at 22 years and 201,000 miles my springs are just old and tired. New springs and bushings are my plan.

As far as the tire pressure - the psi doesn't matter floatation vs LT Metric. Driving around unladen you probably need less than 30psi. I've got 305/70R16 Load Range D muds on 16x8's and at 30psi they're actually slightly high right now with the outer edges of the shoulders not touching the ground. Need to do the chalk test and figure out what pressure I need.
When towing that boat I would add more psi, but not for around town. Mine had 55psi in each tire when I got the tires put on (thanks to the tire store) and it felt like I was driving on roller skates. Skittering all over, twitchy steering, just weird handling. I dropped the pressure to 30psi each and viola, drove like normal-ish.
 
fltplan, does it feel like the rear is swaying back/forth when acted on by another force, ie: road surface change, wind from a passing truck? If so, this is the side effect from having a tall SUV with tall tires. The bigger tires will effect the handling characteristics of the vehicle, mainly because it takes less pressure to run them to where they wear flat across the tread. This lower pressure makes the tire softer overall. And that will allow the taller body of the SUV to sway more prominently. And these trucks have the aerodynamics of a cardboard box so any cross wind and you'll definitely feel it.

Corrections:
1st thing is to make sure all the leaf spring bushings are good. Dry rotted, cracked, rubber bushings are no good. Replace with poly if needed, also get some greasable bolts.
2nd rid your truck of the lift blocks, these put leverage on the springs. If you're towing and you like the look of the truck the way it is, go with a proper sized lift rear spring instead of the shackle flip. This keeps the springs rear mounting point high up on the frame which will increase stability.
3rd you can go with a different set of wheels/tires. Not saying you need to go to a smaller size, but something in the same height but with a larger wheel diameter will decrease the soft sidewall height and feel less spongy on the road. And you'll also gain some higher air pressure because the actual tire itself is smaller. Both of these will make the truck feel more stable.

I hope this describes your issue and helps towards solving the problem.
 
Ok, it does this when the road changes, not wind or semi's passing or turning. Only on a regular road, so a bridge that has some rolling to it. It's terrible.

Towing the boat actually keeps it to a minimum, as it's got a little weight holding it down. I'm taking it down to a spring shop this afternoon to have one of the guys drive it and see what he thinks.

Anyone got a picture of a stock sway bar on the front? I wanna see if mine is there and if it's stock.
 
Usually with stiffer lift springs up front plus a sway bar and stock rear springs you'll get exactly what you're getting. The stiffness up front helps pitch the body over on uneven bumps, and the stock rears are quite a bit softer than pretty much any front lift springs.

Rene
 
tRustyK5 said:
Usually with stiffer lift springs up front plus a sway bar and stock rear springs you'll get exactly what you're getting. The stiffness up front helps pitch the body over on uneven bumps, and the stock rears are quite a bit softer than pretty much any front lift springs.

Rene
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that is the exact set up. I just looked and I do have the stock sway bar up front. the fronts do stop the rocking eventually, but it always comes from the back first.
 
if its there it will be bolted to the side of your Ubolt plates on top of the spring. It will be the only thing that bolts to that plate
 
fltplan said:
that is the exact set up. I just looked and I do have the stock sway bar up front. the fronts do stop the rocking eventually, but it always comes from the back first.
Click to expand...

Same setup here too......and mine acts similar to yours. Let us know how the spring shop visit turns out. My rubber bushings are SHOT in the rear for sure.
 
A lot of it is just due to being leaf sprung front and rear, solid axles front and rear, and having a short wheelbase. It will never carve a corner, or ride like an IFS or coil sprung rig will.

Rene
 
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