Need Some Ideas/opinions

[KyRob]

My truck bounces at 45 mph. I never noticed it before I put new tires (Firestone Destination A/T 265's)on and raised the torsion bars. I then put the torsion bars back to spec and it still bounces. I then put on a complete new set of tires (Bridgestone Dueler 695's 245's which is the stock tire size) and the dang thing still bounces at 45. I had a 4 wheel alignment done and balanced on a load force balancer and it still bounces. Bounce can be felt more in the seat than the steering wheel and man does it aggravate me to no end. The original, worn out Good Year tires never did this that I noticed and I believe I would have noticed it cause they were on the truck a year and everyone who rides in the truck mentions it unless I go thru 45 quick like. Anyone have any ideas what could cause this? I can't believe it's the tires cause I find it hard to believe that 2 brand new sets would do the exact same thing. The truck is an 04 Sierra Xtra cab 4x4 with 5.3 373 gears. It is not a Z71 package.

 

Thanks for any ideas,

Rob

[tobias]

Does it happen on all roads?

[marko]

Does it happen on all roads?

 

Does it happen on smooth roads?

[KyRob]

Pretty much all roads that are smooth enough to tell it from the road surface.

 

Rob

[alaska511]

I have chased wierd speed related vibrations on many vehicles, and found a variety:

-driveline (u-joints and/or possibly bent driveline)

-bent rear axle shaft

-bent rim (still balances for some odd reason)

-broken leaf in spring pack

-broken shock or shock mount, blown shock

-hub bearings failing/failed

[no bull]

pull off and clean-up the mating surface where the hub and rotor meet. It is very possible some rusty metal got dislodged during the tire swap.

[Zembonez]

pull off and clean-up the mating surface where the hub and rotor meet. It is very possible some rusty metal got dislodged during the tire swap.

I have the Firestones on my Jeep and they are the smoothest AT tire I have ever ridden on... and I have had a LOT of AT tires. The Bridgestones and Firestones are made by the same folks... might even be the same carcass with a different tread mold. Might try another tire. Maybe your truck just doesn't like them.

 

EDIT: Make sure to drop the pressures down below 40psi. I run about 37 in mine and they are sweet.

[desrtrat]

hows your shocks dose the bounce go away after a while or all the time. may be getting flat spots when your parked

 

[marko]

Pretty much all roads that are smooth enough to tell it from the road surface.

 

Rob

 

Rob,

 

I hope you didn't take my question the wrong way. It was a dig at Daddy's question.

 

I wonder if your tire guy has any suggestions for you. It doesn't seem that the tires are out of round because they are only doing it at one speed.

 

An easy thing to try would be to unbolt two of the tires (fronts maybe) and re-mount them 180 degrees from where they are now.

 

(and no you lurking smartasses I don't mean inside-out ).

 

This will probably accomplish nothing and should eliminate any worry that it is in fact the tires.

 

 

Another thing I've experienced that does this kind of vibration is the driveshaft being 180 degrees out. Have you done anything to the driveline lately?

 

Last thing could be shocks. The mass of a larger tire can create added strain on a weak shock which you did not notice with smaller tires. Also a different tire pressure or tire stiffness will cause a tire to rebound more. If you turned up the torsion bars then turned them back down I would suspect a problem with a front shock.

 

Often you see a car with a bad shock driving down the road and a tire going up and down like a pogo stick. Once they start bouncing, the bouncing effect can be amplified if not properly dampened.

 

Take your shocks off at the lower mount, and try to compress them by hand. I bet you'll find one that is bad.

[KyRob]

Thanks for the replies guys, I appreciate them. I have planned on removing the rear drive shaft and taking off in 4 hi to see what happens. That should tell me if the drive shaft is out of balance though I doubt it as it is at this one speed the most noticeable. I have been giving the suspension some thought lately and now that you guys have mentioned it, I will check out the shocks as well. I have had 2 different places align and balance so I feel certain that part is OK as well. Guess I shouldn't worry about the little things but I do. The truck has 30,000 miles on it so it shouldn't be worn out yet by any means. I'll post when I solve the problem and if you think of anything else, post it up.

 

Thanks again for your thoughts,

Rob

[marko]

Thanks for the replies guys, I appreciate them. I have planned on removing the rear drive shaft and taking off in 4 hi to see what happens. That should tell me if the drive shaft is out of balance though I doubt it as it is at this one speed the most noticeable. I have been giving the suspension some thought lately and now that you guys have mentioned it, I will check out the shocks as well. I have had 2 different places align and balance so I feel certain that part is OK as well. Guess I shouldn't worry about the little things but I do. The truck has 30,000 miles on it so it shouldn't be worn out yet by any means. I'll post when I solve the problem and if you think of anything else, post it up.

 

Thanks again for your thoughts,

Rob

 

You'd be surprised. Shocks can "go" pretty much anytime. 'Specially the OEM ones.

[tobias]

Pretty much all roads that are smooth enough to tell it from the road surface.

 

Rob

 

Rob,

 

I hope you didn't take my question the wrong way. It was a dig at Daddy's question.

 

I wonder if your tire guy has any suggestions for you. It doesn't seem that the tires are out of round because they are only doing it at one speed.

 

An easy thing to try would be to unbolt two of the tires (fronts maybe) and re-mount them 180 degrees from where they are now.

 

(and no you lurking smartasses I don't mean inside-out ).

 

This will probably accomplish nothing and should eliminate any worry that it is in fact the tires.

 

 

Another thing I've experienced that does this kind of vibration is the driveshaft being 180 degrees out. Have you done anything to the driveline lately?

 

Last thing could be shocks. The mass of a larger tire can create added strain on a weak shock which you did not notice with smaller tires. Also a different tire pressure or tire stiffness will cause a tire to rebound more. If you turned up the torsion bars then turned them back down I would suspect a problem with a front shock.

 

Often you see a car with a bad shock driving down the road and a tire going up and down like a pogo stick. Once they start bouncing, the bouncing effect can be amplified if not properly dampened.

 

Take your shocks off at the lower mount, and try to compress them by hand. I bet you'll find one that is bad.

 

 

Why's it got to be like that, eh?

 

My question was designed to find out if it happened on all roads, not just smooth ones, intentinally. My thought was that it could in fact, be reaching a resonant frequency on certain roads at certain speeds. I didn't know if maybe he ostly drove the same interstate/highway/backroads everyday or what. The interstate might be "smooth" but still have characteristics that could create a resonant frequency. I've heard of many members having that problem on certain types of roads, not just bumpy ones.

 

Now, go wash your truck.

[marko]

Pretty much all roads that are smooth enough to tell it from the road surface.

 

Rob

 

Rob,

 

I hope you didn't take my question the wrong way. It was a dig at Daddy's question.

 

I wonder if your tire guy has any suggestions for you. It doesn't seem that the tires are out of round because they are only doing it at one speed.

 

An easy thing to try would be to unbolt two of the tires (fronts maybe) and re-mount them 180 degrees from where they are now.

 

(and no you lurking smartasses I don't mean inside-out ).

 

This will probably accomplish nothing and should eliminate any worry that it is in fact the tires.

 

 

Another thing I've experienced that does this kind of vibration is the driveshaft being 180 degrees out. Have you done anything to the driveline lately?

 

Last thing could be shocks. The mass of a larger tire can create added strain on a weak shock which you did not notice with smaller tires. Also a different tire pressure or tire stiffness will cause a tire to rebound more. If you turned up the torsion bars then turned them back down I would suspect a problem with a front shock.

 

Often you see a car with a bad shock driving down the road and a tire going up and down like a pogo stick. Once they start bouncing, the bouncing effect can be amplified if not properly dampened.

 

Take your shocks off at the lower mount, and try to compress them by hand. I bet you'll find one that is bad.

 

 

Why's it got to be like that, eh?

 

My question was designed to find out if it happened on all roads, not just smooth ones, intentinally. My thought was that it could in fact, be reaching a resonant frequency on certain roads at certain speeds. I didn't know if maybe he ostly drove the same interstate/highway/backroads everyday or what. The interstate might be "smooth" but still have characteristics that could create a resonant frequency. I've heard of many members having that problem on certain types of roads, not just bumpy ones.

 

Now, go wash your truck.

 

[marko]

Pretty much all roads that are smooth enough to tell it from the road surface.

 

Rob

 

Rob,

 

I hope you didn't take my question the wrong way. It was a dig at Daddy's question.

 

I wonder if your tire guy has any suggestions for you. It doesn't seem that the tires are out of round because they are only doing it at one speed.

 

An easy thing to try would be to unbolt two of the tires (fronts maybe) and re-mount them 180 degrees from where they are now.

 

(and no you lurking smartasses I don't mean inside-out ).

 

This will probably accomplish nothing and should eliminate any worry that it is in fact the tires.

 

 

Another thing I've experienced that does this kind of vibration is the driveshaft being 180 degrees out. Have you done anything to the driveline lately?

 

Last thing could be shocks. The mass of a larger tire can create added strain on a weak shock which you did not notice with smaller tires. Also a different tire pressure or tire stiffness will cause a tire to rebound more. If you turned up the torsion bars then turned them back down I would suspect a problem with a front shock.

 

Often you see a car with a bad shock driving down the road and a tire going up and down like a pogo stick. Once they start bouncing, the bouncing effect can be amplified if not properly dampened.

 

Take your shocks off at the lower mount, and try to compress them by hand. I bet you'll find one that is bad.

 

 

Why's it got to be like that, eh?

 

My question was designed to find out if it happened on all roads, not just smooth ones, intentinally. My thought was that it could in fact, be reaching a resonant frequency on certain roads at certain speeds. I didn't know if maybe he ostly drove the same interstate/highway/backroads everyday or what. The interstate might be "smooth" but still have characteristics that could create a resonant frequency. I've heard of many members having that problem on certain types of roads, not just bumpy ones.

 

Now, go wash your truck.

 

 

What if it only happened on bumpy roads?