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terrible bouncing when brakes are applied


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#1 coolioni

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Posted 06 August 2010 - 10:56 AM

On my 720 4x4 king cab I am having a problem which I think is brake related.
When I hit the brakes lightly I am getting a terrible bouncing that seems to be coming from the front pasenger wheel, the shaking will start there, but end up shaking everything on the truck even down to the bed.
When I hit the brakes harder, the problem pretty much stops.
I brought it in to get looked at and I am being told that I need new lower ball joints and a idler arm.
I am also being told that I have a broken motor mount.
Does this correct or could it possibly be something else ?
BTW about 5000 miles ago I completely replaced all 4 brakes including calipers and a master cylinder.
Any ideas ?
Thanks!
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#2 izzo

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Posted 06 August 2010 - 10:58 AM

Not sure about your situation, my rear drums are warped and it shakes when i apply the brakes too tho :D
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#3 banzai510(hainz)

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Posted 06 August 2010 - 11:00 AM

brake disc made in China???????? warped already?
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#4 jefe de jefes

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Posted 06 August 2010 - 11:07 AM

Check for rotor warpage....
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#5 datzenmike

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Posted 06 August 2010 - 04:56 PM

Jack it up and inspect it yourself. With raised wheel pull out and push in on the bottom of the tire, now the top. There should be no in and out movement. Find the idler arm, it's bolted to the outside of the pass side frame and has a cross rod on the engine side and a tie rod going to the pass wheel on the other. It should only swing from side to side to turn the wheel. It should not be loose or able to move up or down. A badly worn idler can set up an oscillation in the steering when using the brakes or if hitting a bump known a a death wobble.

Get a length of 2x4 and pry against the motor and look at the motor mount. The rubber should move slightly and that's all.

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#6 I'm BLUE

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Posted 06 August 2010 - 06:08 PM

Jack it up and inspect it yourself. With raised wheel pull out and push in on the bottom of the tire, now the top. There should be no in and out movement. Find the idler arm, it's bolted to the outside of the pass side frame and has a cross rod on the engine side and a tie rod going to the pass wheel on the other. It should only swing from side to side to turn the wheel. It should not be loose or able to move up or down. A badly worn idler can set up an oscillation in the steering when using the brakes or if hitting a bump known a a death wobble.

Get a length of 2x4 and pry against the motor and look at the motor mount. The rubber should move slightly and that's all.


I will strongly agree with this ^^^ , currently over the last month my Tension Control Arm Bushings ( same idea ) have started to give me trouble ...... upon inspection they are split ( lightly ) on the passenger side ,,,,,,,,,, gonna replace whole set (4 as advised ) to be safe..........

I also have warped rotors ......... they are expensive cross drilled racing rotors that came with the car ,,,,,,,, you can usually feel the vibration back and forth through the steering wheel if it is in the front ( drums too in my experience ) , but if it feels like your whole front end is creeping or BOUNCING ,,,,,,,, then make sure to check what datzenmike said for sure ^^^ to say the least !!! :D .......... This can be very dangerous and costly !!!

By the way ,,,,,,, I have both of these issues on my 240z right now ,,,,,,, and both are easily identifiable from the other ( easy to tell which is which , rotors are just slightly warped ,,,,,,,,, bushings feel worse right now :mellow: )

A horrible motor mount or one that is that far damaged should be easy to spot , thing that does't make sense to me is it starts to go away upon harder braking ???

I am planning on upgrading to 300zx calipers/pads when I have the monies in the future , and have ordered the bushings for the tension control rod last week when I had monies to deal with it

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#7 ]2eDeYe

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Posted 06 August 2010 - 07:10 PM

A badly worn idler can set up an oscillation in the steering when using the brakes or if hitting a bump known a a death wobble.

Get a length of 2x4 and pry against the motor and look at the motor mount. The rubber should move slightly and that's all.


These are both fairly easy and cheap to to replace yourself if they are bad.
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#8 Paul G.

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Posted 06 August 2010 - 07:49 PM

A badly worn idler can set up an oscillation in the steering when using the brakes or if hitting a bump known a a death wobble.


OMG! I thought only the king and link pin bugs had that problem. Hitting angled train tracks at 45 mph would shake the car so bad you couldn't see clearly out the windshield. Hauling it down to about 25 mph was the only solution.

My Beach buggy front suspension is getting real close starting that. It's up to shudder, but unable to sustain oscillation yet. Posted Image

#9 datzenmike

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Posted 06 August 2010 - 09:03 PM

Many years ago a buddy had an old tow truck and it would do this randomly at highway speed or if you hit a bump. He always drove with both hands on the wheel. It would almost pull his arms off when it went. All you could do was jam the brakes and drop the speed to 25-30 while the wheel jumped back and forth. Once was enough for me. :lol:

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#10 coolioni

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Posted 07 August 2010 - 11:46 PM

Thanks for the replies.
I am going to get someone else to look at the truck for me.
He is telling me I need new lower ball joints, but I looked at my service records and I replaced them about 5000 miles ago. So I doubt that can be any of the problem.
1983 720 series Nissan King Cab 4x4 totally rebuilt Z24 engine. mechanicly totally rebuilt too.
Working on body next!

#11 ggzilla

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Posted 08 August 2010 - 08:11 AM

Most likely this is just what Mike says.

Warped brake rotors can cause this bouncing, not the car bouncing, but a strong vibration/shudder. It is a notorious problem on 1980s Mustangs and other compact Fords. But not dangerous -- the fact that is smooths out if you push harder, and that it still stops true and even (no pulling to one side) is not dangerous. We've had rigs that have done this for years, like my 5.0 Mustang that would start doing it soon after truing the rotors. Our 1994 Mazda-Ford pickup did it for a couple of years, too. Ford just put too small of brakes on these rigs. Maybe bad iron alloys too. So they warp. Going downhill at light brake pressures was the worst. I had a Honda that did this too.
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#12 datzenmike

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Posted 08 August 2010 - 08:36 AM

Speaking of brakes....I read something about the 'glue' that holds the pad material together. Sudden extreme heavy use where they get very hot and then let the car sit and some of the pad material transfers to and bonds to the rotor leaving a pad imprint on it. Next time the brakes are used the bad grips this imprint as it rotates past the caliper causing a vibration. The rotor will even wear unevenly with a high spot where there is transfer. This is especially true of new pads or on cars that never see severe use. Then one day there is a panic stop and there is transfer to the rotors while they are hot. The rotors can be lightly turned to remove this problem but it can return again. The cure is to take any new pads out on the highway and drop the speed suddenly and hard several/many times to get them good and hot to 'cure' them BUT do NOT stop, but keep driving them till cooled down to a normal warm temperature. If you stop even briefly there could be transfer, so keep moving. Supposedly the bonding material or 'glue' in the pads is better cured or dried out by the heat and this prevents it from happening in the future.

Make of it what you will, it was an interesting read and I wish I had saved it.

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