CBI rear bumper swing out 'death wobble'

[bartvonwolf]

Hey guys, so I have a 2016 Trail with the full CBI rear bumper. I can't complain about the build quality of the bumper and it looks good, but the damn death wobble I get with it on the hwy is just intolerable. I do not really see any option other than to deal with it, or move my spare back under the truck. But I now have larger than stock tires (285/70/R17). I just tried to fit the spare under the T4R and there is a bracket in the way that would need to be removed. I don't recall anything being attached to it, but I figured I would check with you all on here and see if and how you were able to fit larger than stock spares underneath. Did you guys who have done this have to trim anything?

Thanks,

Bart

 

[High_Country]

CBI bumper death wobble

I don't have a cbi rear bumper but something sounds amiss. Death wobble is generally caused by poor suspension geometry up front (inadequate caster among other things I believe). After installing the bumper do you have an 'ass low, nose high' stance? (I dated someone like that once).
Have you lifted the truck? How much?
Did you get new UCA's?
Have you had a recent alignment and is it 'in spec'?
What sort of shocks and springs are you running at all four corners?
Not an ANSWER to your question but necessary info for someone to help you out.

 

[mckennar]

Are you talking death wobble as in front suspension vibrations, or are you talking about the spare on the CBI rattling (or visibly shaking) on the highway?

If the latter, what has CBI said about this? Perhaps you have a slight rear suspension shake/tire imbalance you don't feel from the driver's seat?

 

[Dropzone]

So you added a rear bumper and now you have Death Wobble up front?
The death wobble would make more sense if you had knocked your front end out of whack after adding a winch and bumper up front.

I am thinking you lost some wheel weights and it is just coincental that it was about the time you added the rear bumper...

Contact Steve at CBI for recommendations

 

[weeeee]

I can somewhat understand what you're talking about. Across heavy washboards or uneven freeway surfaces I can definitely see/feel my rear tire carrier on the CBI rocking back and forth. Completely normal. I just change speed which usually stops the shaking (if its bad enough) or ignore it altogether.

 

[Jeremy556]

Assuming you are talking about seeing the spare tire moving, not actual steering death wobble...

Is the latch tight? Can you move the swingout by pushing on it while closed?

If you are just talking about the difference in movement between the body and the frame mounted bumper, you'll have to get used to it. You probably really wouldn't want a front bumper with hoops, you get to see those moving in comparison to the hood all the time.

 

[BlackWorksInc]

Assuming you are talking about seeing the spare tire moving, not actual steering death wobble...

Is the latch tight? Can you move the swingout by pushing on it while closed?

If you are just talking about the difference in movement between the body and the frame mounted bumper, you'll have to get used to it. You probably really wouldn't want a front bumper with hoops, you get to see those moving in comparison to the hood all the time.

Yeah, even with all new body mounts all around and everything nice and snug on my 4th gen that front bumper wiggles quite a bit on the washboards and such.

 

[bartvonwolf]

Sorry guys, I should have been more clear.

I have a 2016 Trail with only 15000 miles on it an Icon Stage 7 lift. I have the CBI bumper with my oversized spare mounted on back. At hwy speeds between 55-65 mph, on certain road surfaces I get a horrid shaking of the tire that makes the whole vehicle "wobble". I should not have used the term "death wobble". I know what that is when you are talking Jeep steering and this is not the case. This is 100% due to uneven concrete slab roads and weight of the spare on the swing out. I do not believe this is due to my suspension setup, but I am willing to pursue any solutions.

The issue I have with this is that for the price of these aftermarket accessories, I find this kind of problem completely unacceptable.

Thanks - Bart

 

[mo_mo]

Sorry guys, I should have been more clear.

I have a 2016 Trail with only 15000 miles on it an Icon Stage 7 lift. I have the CBI bumper with my oversized spare mounted on back. At hwy speeds between 55-65 mph, on certain road surfaces I get a horrid shaking of the tire that makes the whole vehicle "wobble". I should not have used the term "death wobble". I know what that is when you are talking Jeep steering and this is not the case. This is 100% due to uneven concrete slab roads and weight of the spare on the swing out. I do not believe this is due to my suspension setup, but I am willing to pursue any solutions.

The issue I have with this is that for the price of these aftermarket accessories, I find this kind of problem completely unacceptable.

Thanks - Bart

Tire shake or steering wheel shake? If the later then go back to small street tires that are balanced

 

[3wbdriver]

You may need to wiggle it some while raising it but apparently it will fit under there.

http://www.toyota-4runner.org/5th-g...e-spare-you-can-fit-under-toyota-4runner.html

 

[LawnDart]

Sorry guys, I should have been more clear.

I have a 2016 Trail with only 15000 miles on it an Icon Stage 7 lift. I have the CBI bumper with my oversized spare mounted on back. At hwy speeds between 55-65 mph, on certain road surfaces I get a horrid shaking of the tire that makes the whole vehicle "wobble". I should not have used the term "death wobble". I know what that is when you are talking Jeep steering and this is not the case. This is 100% due to uneven concrete slab roads and weight of the spare on the swing out. I do not believe this is due to my suspension setup, but I am willing to pursue any solutions.

The issue I have with this is that for the price of these aftermarket accessories, I find this kind of problem completely unacceptable.

Thanks - Bart

FIrst off I think you need to define the issue as you're being rather vague about describing exactly the problem. If you're complaining that the rear tire, aka 85+lbs of mass, can rock and and forth with uneven road surfaces? that's totally normal. Either accelerate or slow down to break that rhythm.

It seems to be less so on my dual swing arm. But you're mounting a big ass chunk of metal and rubber to a pivot point, this is going to happen. It's also much worse on other bumpers. My only suggestion is to make sure the actual tire carrier is mounted as low on the arm as you can make it. If it can scoot down a hole or two, that'll help a lot.

But what you're experiencing is mass + acceleration.

 

[BlackWorksInc]

FIrst off I think you need to define the issue as you're being rather vague about describing exactly the problem. If you're complaining that the rear tire, aka 85+lbs of mass, can rock and and forth with uneven road surfaces? that's totally normal. Either accelerate or slow down to break that rhythm.

It seems to be less so on my dual swing arm. But you're mounting a big ass chunk of metal and rubber to a pivot point, this is going to happen. It's also much worse on other bumpers. My only suggestion is to make sure the actual tire carrier is mounted as low on the arm as you can make it. If it can scoot down a hole or two, that'll help a lot.

But what you're experiencing is mass + acceleration.

But should it be moving enough to cause vibration in the vehicle? I would imagine that if the latch is adjusted correctly for tension your spare tire carrier should not move much; additionally doesn't CBI reinforce the tire carrier with angled supports to reduce that or is it just box tube standing on it's own?

 

[3wbdriver]

FIrst off I think you need to define the issue as you're being rather vague about describing exactly the problem. If you're complaining that the rear tire, aka 85+lbs of mass, can rock and and forth with uneven road surfaces? that's totally normal. Either accelerate or slow down to break that rhythm.

It seems to be less so on my dual swing arm. But you're mounting a big ass chunk of metal and rubber to a pivot point, this is going to happen. It's also much worse on other bumpers. My only suggestion is to make sure the actual tire carrier is mounted as low on the arm as you can make it. If it can scoot down a hole or two, that'll help a lot.

But what you're experiencing is mass + acceleration.

Agreed. I also have to wonder if both gas cans were full when it happened. That's another 70+ pounds of weight. And I see from the website the swing out is also offset back a few inches from the pivot point instead of just running straight across the anchor points. Probably necessary to clear the hatch, but it is a consideration. All that weight set that far back from the rear axle, plus whatever you may have loaded inside the rear cargo area is going to cause some movement on rough roads. How much lift do you have? Is the track bar at a down angle? If so the act of compressing the rear springs over bumps may be causing just enough side axle movement via the track bar to initiate the rear end wobble, which is then transferred through the sidewalls of the tires. I believe someone makes a drooped track bar for lifted rigs to offset this affect but I'm not certain. Blah blah blah, yada yada ya. I could go on but it's past my bedtime.

 

[Okki]

I'm still running stock size tires, but have had no issue pushing speed with the tire on the back.

Are you seeing a result of a balancing/alignment issue? that speed range and the larger, more aggressive tires, can easily result in a vibration that you are just seeing manifested in your rearview mirror. Cause --> Effect.

Also, More money does not always mean more awesome. With all the suspension goodies you have, you also need more tweaking and knowledge to gt it right (i.e. you CAN shoot a mosquito with a howitzer, but it's not as easy as it may sound).

Is the spare solidly mounted on the swingarm? it may seem that way because of gravity and weight, but just because you can't lift it, that does not mean that physics can't.

My first reaction would not be the bumper. If you take the spare off and drive the same speed, are you still getting the shakes? if so; than the spare is not the issue for sure.

Hope this gives you some things to consider and check.

Okki

 

[LawnDart]

The bumper WILL move back and forth along the long axis of the vehicle, so not right/left. I get this really bad (I have not tried it with my new dual swing arm) going up I5 to seattle. The roads are paved near Tacoma with a texture that causes some weird forward/back rocking that I have to either accelerate out of to break, or brake to break.

I'd also make sure the tire carrier is mounted as low as you can make it, and make sure the latch is snug. The latch should go tight for the last 70 percent, and really chunk in to place. The U-bolt will stretch over time.

Hopefully that resolves it. But I'd try driving over the same roads without the tire, just to see if you have a bigger problem going on, the tire could just be a visual indicator, and not the cause.

 

[JWaldz]

So there's been a little debate about CBI and their rear tire carrier "death wobble". My 3rd gen rear CBI had this and there was nothing I could do to get it to go away. Others didn't have any problems while some had some wobble, but in all mine was the worst out of the bunch. I even took a video of it. Awful feeling outside of the normal wobble a swing arm would have. Would shake the entire ass end of the truck.

<iframe width="560" height="315" src="https://www.youtube.com/embed/ulsWc3kDXy4" frameborder="0" allowfullscreen></iframe>

 

[cstraface]

I have a CBI hybrid rear on my 3rd gen too, and can definitely attest to the "death wobble". Always on highway above 40 mph. Some roads just feel like get that thing into a rhythm and it won't stop until the surface changes.

It feels like you have a couple linebackers bouncing up and down on your bumper. I'm honestly not sure if it's a design flaw though...you throw enough weight on top of your bumper with our coil spring suspension, and it's going to happen. It's like loading a trailer - you don't load all the weight in the tail. Same principle.

 

[wfo9]

Seems like a design flaw in the bumper... I have not heard of this complaint for shockworks or 4x4 labs owners....

 

[ECUDrummer]

Seems like a design flaw in the bumper... I have not heard of this complaint for shockworks or 4x4 labs owners....

I would hope it wouldn't be an issue w/ 4x4 labs, considering their rear swingout bumper is a good $2k more than CBI's.

 

[JSparky]

I would hope it wouldn't be an issue w/ 4x4 labs, considering their rear swingout bumper is a good $2k more than CBI's.

It shouldn't be an issue on a $1500 bumper either. I had to shoot up to Oakdale yesterday and took my fzj80. I've got a 37" spare on a 4x4labs bumper on that and had no issues cruising at 75mph. Some movement occasionally which I think is probably impossibe to avoid, but by no means is it wobbly. Everyone's torquing their tension latches right?