Uncontrolled tire bounce

[JohnnyPopper]

Last year I had installed some cheesy KYB shocks on my K10.

On several occasions, driving over some decent bumps in the road at about 30-40 mph, one of my rear tires would being bouncing uncontrollably, shaking the entire truck violently.

Slowing down cured the symptom obviously.

It was almost like the shock froze and the tire went into wild vertical oscillations.

Suspecting shock failure I replaced them with Bilsteins, symptoms go away. (yay! I joined the club!)

Last week it happened again, so l turn to the brain trust for help.

Any ideas or similar experiences? TIA!

[zieg85]

Death wobble... 

[JohnnyPopper]

I think a death wobble would be more horizontal in nature.

This was definitely vertical.

The 'death' part fits though, I thought the truck was going to go to pieces!

[Shifty]

Tires flat-spotted from sitting? 

[VileZambonie]

You sure it's the rear? Check tires balance, bearings, lugs etc

[JohnnyPopper]

Thanks for the replies!

No flat spot, driven almost daily.

Sure its the rear, the bed starts hopping wildly.

Balance is done regularly, bearings are 2 yrs old, lugs tight.

It seems that the right combo of speed and road surface triggers a violent reaction that is only cured by slowing down.

I suppose if it happens again, I can speed up?!?

[VileZambonie]

Sounds like DW to me and that it's probably happening in the front.

[Mr Diesel]

Last year I had installed some cheesy KYB shocks on my K10.

On several occasions, driving over some decent bumps in the road at about 30-40 mph, one of my rear tires would being bouncing uncontrollably, shaking the entire truck violently.


Suspecting shock failure I replaced them with Bilsteins, symptoms go away. (yay! I joined the club!)

Last week it happened again.

If you are confident in your initial assessment then you should pull both Bilsteins and compare them. Maybe another bad shock. Seems unlikely but even good brands have bad parts or early failures.

[JohnnyPopper]

What causes a DW?

Wouldn't the steering wheel shake as well?

It's like the shock freezes

[devildogmech]

IMHO, you are simply out driving the rebound capability of the shock. If it's a cheapo, you're gonna get cheapo performance. At 30mph a washboard road would be hard on any stock suspension. JMHO

[Shifty]

IMHO, you are simply out driving the rebound capability of the shock. If it's a cheapo, you're gonna get cheapo performance. At 30mph a washboard road would be hard on any stock suspension. JMHO

Actually, the better your shock, the worse a washboard will feel....the shock it responding with higher gas pressure (most good ones are dual-valve), making it even stiffer since it has no chance to disperse...olde oil-filled actually work better in this instance.

[JohnnyPopper]

Well, Poop!

I had KYB's on it when it seemed to freeze.

Can you explain rebound capability pls?

I thought joining the Bilstein Club would end this...

[Shifty]

Washboard ruts don't get defeated by shocks very well....the Bilstiens will make 97% of your driving more pleasurable....

[JohnnyPopper]

I think you're right.

Seems like speed, rut depth/duration, tire PSI, and load/lack of, contribute a condition where the tire is drawn into an oscillating frequency that can't be controlled without slowing down.

Glad to know my membership has some perks...

[VileZambonie]

What causes a DW?

Wouldn't the steering wheel shake as well?

It's like the shock freezes

With the tires on the ground and rear wheels chocked, have an assistant rock the steering wheel while you observe EVERYTHING.