Roger Kraus Racing Ent., Inc. 2896 Grove Way. Castro Valley, CA 94546 http://www.rogerkrausracing.com

What Causes Wheel Vibrations?

1. Wheels are not properly balanced. A proper balance job will usually require weights on the outside and inside on each wheel. The reason for this is as follows: wheel balance can be divided in two categories. Dynamic and Static. Dynamic problems will always cause a side to side vibration known as wheel shimmy. This will occur at speeds between 52 MPH to 65 MPH. Static balance problems usually occur at speeds above 70 MPH. Dynamic vibration problems always require weights inside and outside. Dynamic balance is always recommended.
2. Bent Wheels: If the wheels are not round, a vibration will usually occur. original equipment wheels have a tolerance of .028". Low quality aftermarket wheels use a tolerance of .045" and top quality wheels have a tolerance of less than .012". Lateral run out can also cause vibrations or wheel shimmy. Usually a wheel that has more than .050" run out ( lateral or out of round ) will cause vibrations to those sensitive enough.
3. Hubcentric Wheels: A hubcentric wheel is located on the center of the hub with about .003" to .012" clearance. With this design, a wheel is balanced on the same center hole that goes over the spindle hub. If the wheel is not centered on the hub, wheel vibrations will almost always be the result. Non hubcentric wheels must be balanced through the lug nut seats, this is not always successful. High quality wheels are always hubcentric in design.
4. Tire Quality: The simple fact is, cheap tires are not good and good tires are not cheap. Tire quality is very important on all cars and critical on foreign vehicles. lighter suspension designs are more sensitive to vibrations. There are tires made for American cars and foreign vehicles. Many tires are made for American cars and should never be used on foreign cars. Foreign car tires may be used on American cars if the load range is correct. A qualified tire dealer can help if you have questions. Lower quality tires have another problem which is LEAD PULL, better known as tire pull. Another problem is tire trueness. High quality tires are truer and maintain this quality longer.
5. Worn Suspension Parts: Worn suspension bushings, tie rod ends, track rods, ball joints, loose wheel bearings, steering rack and bent hubs can all contribute to vibration problems. It can be difficult to find service shops that can properly diagnose this problem. Have the mechanic show you the suspect parts, ask questions.
6. Brake Drum Balance: Many aftermarket drums and some discs can be out of balance from the factory. We have seen some drums that were 14 ounces out of balance. Correct this problem and usually vibrations will disappear. Most shops cannot properly diagnose this problem.
7. Out Of Round Tires: Common to less expensive tires. Old or nearly worn out tires tend to get out of round. If the tire has sufficient tread depth left, you can have them trued. If the tire brand is of low quality this may be a waste of time. Such tires will not maintain a round shape in use.
8. Flat Spotting: Tires that have been locked under braking. These tires ( usually the front ) will have an area of the tread scrubbed flat. If the tire has sufficient tread depth left, you can have the tires trued and re-balanced.
9. Worn Shocks: Worn shocks do not cause vibrations but contribute to uneven tire wear which does. If the vehicle has been driven with bad shocks for an extended period you may have scalloped tires. The only cure is new shocks and to true or replace the tires. A totally worn out shock will cause vibrations and must be replaced before further diagnosis can take place.
10. Alignment: It is very rare to have an alignment cure a vibration problem. However, bad alignment can cause uneven tire wear which will create an out of balance problem sooner than normal. Alignment should be checked yearly and tires balanced at 10,000 mile intervals. Occasionally alignment can cure vibration problems but it is rare.
11. Warped Rotors: Warped rotors or drums will cause a shimmy or pulse when the brakes are applied. Turning the rotors or drums will usually solve this problem. If the rotors or drums are close to minimum thickness the problem may reoccur.
12. Cracked Frame: This problem is very rare and usually easy to detect. The vehicle will exhibit very low frequency vibrations when major bumps are encountered. Check for cracked or broken welds at the front cross-member. This is fairly common on Corvettes up to 1984. Some early Mustangs have the same problem.
13. Drive Shaft: This problem can be hard to find and diagnose. To solve this problem it may be necessary to have the drive shaft checked for balance. U joints can also cause vibration problems.
14. Wheel Locks: If the wheel locks are heavier than the lug nut they replace, you may have vibrations. To test this theory, install the lug nuts in place of the locks and test drive. Quality shops can COUNTERBALANCE the wheels to correct for the additional weight from the locks.
15. Wheel Torque: If the wheel nuts are over-tightened, the hub or rotor may be distorted. Older VW bugs were notorious for having this problem. If this has occurred, it may require turning the rotors or drums.
16. Cracked Wheels: Not very common. We have seen this happen more often with steel wheels than any other type. There will usually be a grinding noise when cornering. This was more common during the 1970's on heavy American cars.
17. Wheel Offset & Width: If replacement wheels do not have the proper offset, vibrations will increase. If wider wheels are installed there is an tendency towards increased vibration.