Why do my seats shake.I the tires balanced,still does it.

Either a bent rim, tire is out of balanced and tire is bad. Rotate the tires and see if it goes from the wheel to the seat. If you can feel it in the seat then it's a bad tire.

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If the rear is shaking you would fell it in the seat if the front is shaking it will be felt in the wheel. If tire has been balanced but still has a loap to it you will sill feel it. When they balance a tire, its in the air in the balance r not the ground. Both sides should be balanced, not just one.

Does the shake match tire rotation or drive shaft rotation speed? If it's at tire rotation speed,have the new tires been dynamically balanced on a brand name motorized balancer?Re balance them that way.If a wheel weight has come off you will have a shake.You can also rotate the tires from front to back and see if that helps.Also,brake rotors can be out of balance and even with a perfectly balanced tire,the rotor can throw the balance off.

Sound like out of balance tire or a separated tire or bearing but, the two most common causes are the ones. I suggest visit some tire shop and would like to have the tires inspected and balanced.

Some customers may comment on shaking/vibration in the steering wheel, floor or seat while driving at highway speeds (typically between 60-72 mph (96-115 km/h)) on smooth roads.

These specific vehicles may be sensitive to various rotating mass assemblies, especially if they are considered to be out-of-balance.

In order to correct this:
1. Visually inspect the tires and the wheels. Inspect for evidence of the following conditions and correct as necessary.
- Missing balance weights
- Bent rim flange
- Irregular tire wear
- Incomplete bead seating
- Tire irregularities
- Mud/ice build-up in wheel
- Stones in the tire tread

2. Set the tire pressure to 30 psi (205 kpa) COLD.

3. If the road test indicates a shake/vibration still exists, check the imbalance of each tire/wheel assembly on a known, calibrated, off-car dynamic balancer. If any assembly calls for more than 1/4 ounce on either rim flange, remove all balance weights and rebalance to as close to zero as possible.

Important: Some GM dealers may have a Hunter GSP9700 Road Force Balancer. This will simplify Step 5 by not requiring dial indicators. If a Hunter GSP9700 machine is available, it may also be used to measure the radial force of the tire/wheel assembly. A guideline here is 18 lbs or less.

4. While on the balancer, measure wheel runout. If radial or lateral runout exceeds .020 in (0.50 mm) for aluminum wheels (.030 in (0.76 mm) for steel wheels), replace the wheel.

5. After confirming wheel balance and wheel runout, if any changes were made, road test the vehicle again.

6. If the smooth road shake/vibration still exists:
Important: The completed worksheet must be attached to the hard copy of the repair order.

Record Radial Force Variation readings if you have access to Hunter GSP9700 Wheel Balance equipment. Use the worksheet shown in this bulletin to record the readings.

If one or more of the tires have RFV readings in excess of 18 lbs, match mount the tires to get below 18 lbs. Readings of 12 lbs. or less are preferable for critical customer concerns.

If the RFV can not be reduced to an acceptable level, replace the affected tire with one obtained locally.

The screened tire program is no longer in effect for Bridgestone/Firestone, Goodyear and Michelin. Low speed screened tires are available from Continental General only, and only for the Buick LeSabre.

Road test the vehicle to ensure the shake/vibration has been resolved.

7. Replace both lower control arms on vehicles built prior to the VIN breakpoints shown. The new lower control arms may provide an incremental improvement to the vehicle ride. Customers who have become "tuned in" to the shake condition may still feel some shake in the vehicle after the new lower control arms are installed.
Refer to Lower Control Arm Replacement, (refer to the Parts Information table below for SI document ID numbers).

Important: THE CONTROL ARMS SHOULD ONLY BE INSTALLED ON VEHICLES IF, AFTER THE TIRE AND WHEEL DIAGNOSIS AND REPAIRS HAVE BEEN PERFORMED, THE VIBRATION CONDITION STILL EXISTS.

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Most likely a tire/wheel balance issue. The weights that are used to balance the tires can sometimes fall off. Generally how far out of balance it is determines when and how bad it will shake. Unfortunately this is not fixable without a tire balancing machine, has to got to a tire shop.

Were the tires rotated or replaced recently? Most major tire shops will check the balance for you at little or no charge if you take it back to the shop where the work was done.

You can also try to identify the problem tire by rotating the front and rear tires one side at a time. For example, if the vibration is coming from the front, swap the front and rear passenger side tires and drive the vehicle again. If the vibration moves to the back it's most likely the (now) passenger side rear tire that's out of balance. If the is no change, try the driver's side tires.

Hope this helps!

Most likely the front tires need to balanced or are worn unevenly. Have all four tires rotated and balanced.

get your wheels tracked and balanced should sort it out

RF wheel out of balance probably - maybe lost a balance weight or tire close to failure (seperated belts) - rotate to rear (and rear to front) and see if shake moves with tire (steering stops shaking)....then you'll know...

Balance your tires, if you did not have that done with the rotation........check for proper tire pressure (with cold tires)

you may have got the tires balanced but i would bet that you have a bad belt in a tire this would not show up on a mechanical balancer. i would have them check the tires themselves... please rate this