bouncing

illmac77 · December 19, 2001

does anyone have a clue whaty might be causing this? cant figure this one out. between 44-46 mph is the only time it does it and is better worse on different roads.

Shaners · December 19, 2001

one of three things,

1) out of balance tire

2)out of round tire

3)broken belt in tire

I would tend to think it is a rear tire otherwise you'd feel it in the steering wheel.

illmac77 · December 19, 2001

shaners, the "bounce" only comes from the front end, the steering wheel does "bounce" at 45 mph but seems to go along with the front end and goes away after i pass 45, ive had my tires rotated and balance and the prob is still there. do you think it can be something else then the tires... or if it was the tires wouldnt the " bounce" at 45 mph change after i rotated them? im pretty much clueless on this one. i run my tires at 50 psi and i have cranked up the torsions bars but i tend to think this wouldnt affect it bouncing slightly at exactley 45 per say... can any one figure this one out?

HillHound · December 19, 2001

one of three things,

1) out of balance tire

2)out of round tire

3)broken belt in tire

I would tend to think it is a rear tire otherwise you'd feel it in the steering wheel.

I agree with Shaners. Probably a unbalanced or out of round tire. The other thing that comes to mind is maybe a bent or defective rim. I'd just take it in to a good tire shop and let a good tire or wheel mechanic take a look. ???

Shaners · December 19, 2001

It is possible you have a front shock going bad... bad I still think it is tire/wheel related.

Generally with a problem like this, if you feel it in the wheel it's in the front... if you feel it in the seat of your pants it's in the rear.

crazy53 · December 19, 2001

This may sound nuts but certain lanes on the hughway are beaten down by heavy trucks.Living near Boston with all the BIG DIG bs happening the freeways near overpasses and expansion joints are getting like whoopdie doos on dirt.The more they bounce up and down the more the pavement gets smashed.My Silverado is 2WD and got a wicked vibration in the wheel in theses areas.Once the big rigs settle down the pavement and my vibration smoothens out.

Smitty00Z71 · December 19, 2001

My 2000 has always bounced at 43mph, even with a different set of tires. I think this is a problem with most new Silverado's.

siume99 · December 19, 2001

1) out of balance tire

2)out of round tire

3)broken belt in tire

If it was tire related, wouldn't it continue as you increase speed (the faster you go, the more vibrations)? ??? I'm new to truck trouble shooting so I'm asking. I like the irregular road theory or suspension personally. It could just be a characteristic of the type of suspension and the weight of the truck. Does it behave the same with a load in the bed? When traffic is clear, try driving in the other lane, or down the center where there is no wheel ruts.

illmac77 · December 19, 2001

loaded or unloaded it still would have the bounce in it, when i had my tires rotated and balanced bout a month and a half ago i told sears what my problem was and they didnt find anything wrong with the tires ... i dont think they really checked it out that hard though... last night i dropped my air pressure from 50 psi to 46 and when i drove to and from work today on the same roads that it normally do the "bounce" dissappered. does this one make sense to anyone. do you guys think that the tires had to much air in them (to hard) and not absorbing enough? im still not convinced on the psi changing the problem, ill no for sure in the next few days

Shaners · December 20, 2001

illmac, if that works then stick with it.

I suppose it could be possible that the tires are too hard and are bouncing like rubber balls. But since it is speed related, I would think a slight out of balance condition would have to start the bounce.

I had a minor vibration in my wifes van and it took only 20 grams of weight to cure the problem.

your tires are bigger and heavier than teh stock tire and there is alot of rotational mass which is all "unsprung weight". I'd take it back to where you bought the tires and have them set the balancer to a finer adjustment. For you and me they balance our tires to the ounce. If it was their truck I guarantee it would be balanced to the 1/4 ounce. Also make sure they have the wheel centered perfectly on the machine so there is no up/down movement. The front wheel on my motorcycle is so sensative to out of balance conditions, I have to indicate the wheel in side to side and up and down before it can be balanced properly.

illmac77 · December 20, 2001

good point about them using ounce weights, i never thought about that,ill see if my current psi solves the prob. hopefully it does.

burgundyz71 · December 20, 2001

My truck did the same thing and shaners is right at least thats what mine was I got new tires and problem solved

95Yukon · December 20, 2001

Its probably a tire. Maybe 2 of them so when they rotated, it didnt help. When they check the balance (ask them to check them first before removing the old weights to rebalance them) this way you might find a clue as to wether it was the balance or not. Sometimes you can watch them do it, and if the machine reads 0.00 after the spin, it's balanced. The highest reading you should see is 0.3, which is those very small weights, about 1/2 inch long. Anything beyond that and you'll feel it. It doesn't take much at all. If any of them require a lot of weight, something is wrong with the tire. In that case, they might try breaking the bead and rotating the tire 180 degrees on the rim and try again. But if they just tear off the old weights and rebalance them you'll never know if they were off to begin with.

If a tire has an out of round condition, or runout, even if it balances out perfectly, you'll still feel a vibration. It's easy to find the centerpoint of an oblong object and balance it, but if you try to drive on it, theres a bounce. The only cure for that is to get new ones. Ask them to check for out of round and bent rims when they are balancing. If they open the hood to the balancer and spin the tire by hand, you can look along the top edge to a reference point of something behind it and see the smallest amount of "up and down" movement if there is any. You can also do this in the driveway with a jack if you want.

If all else fails, believe it or not, an out of balance rotor can cause a vibration, but this is rare. A lot of those things are "balanced" when they are made, if weight is needed, you'll see a round chunk of metal shoved into one of the fin openings on the outer edge. I had that happen once with a weight which came off a brake drum and it was driving me nuts trying to figure out what was causing it.

95Yukon · December 20, 2001

BTW, vibrations don't always increase with speed, it will get to a point where it cancels itself out so you can't feel it. At that point the tire is starting to wear itself out and putting stress on all the components it's connected to.

Hope you find the problem.