|TECH TIP||Technical Index|
by Mike C. -
Wheel Shimmy Ė II
We began covering wheel shimmy last month by looking at the rotating assembly, which includes drums, rotors, wheels, and tires.
We finish this month with the other areas of consideration. Hope you were not kept in too much suspense.
Speaking of suspensions, that is next on the list to check. Worn suspensions will not tolerate any kind of wheel or tire runout, and will not respond well to bumps and minor road irregularities. Inferior parts can make a big difference and when I say inferior, I normally mean rubber bushings versus urethane. Iíll tell you like I feel Ė rebuild your suspension on whatever VW you have with urethane bushings. There is not enough of a harshness or noise difference to notice and you will be rewarded with a much stouter setup that will retain its rigidity over a much longer period of time and will give you better handling. Period. You Super Beetle owners will immediately notice the big difference after installing urethane control arm and stabilizer bar bushings. For Super Beetles, this is most often the cure for the aggravating shimmies no matter what else is done. To prove this, jack your Super Beetle up enough to get the wheels off the ground. Rock the tire and wheel back and forth. Kinda easy to do, isnít it? After rebuilding your suspension with the urethane bushings, try to rock the wheels. Canít do it now, can you? The difference will astound you. It makes you wonder how Supers ever held alignment and handled as well as they did with the stock rubber components. If your suspension hasnít been touched in five years or more, rebuild it, especially if it is your daily driver. Buses, Ghias, Squarebacks, and standard Beetles can get by with rubber bushings, but I wouldnít use anything but urethane on Super Beetles. Check for play in the steering box and get this corrected as well.
Now that you have the rolling stock running true and the suspension redone and tight, itís time to actually balance the rolling assemblies. If you can find a shop that spin-balances the tires while they are still mounted on the car, by all means use that one and donít do it any other way. This will take into account any out-of-balance condition of the brake drum or rotor, wheel, and tire. It is the most accurate and practical way to balance the assembly at once. Another way I like to have it done is to use a "bubble" type balancer. This is a method where you take the wheel and tire off the car and put it on this balancer and use the balancer like you would use a level when building your house. You can get a very good balance with this method provided the person doing the balancing knows what they are doing and the rest of your rotating assembly is well-balanced. However, this method is not used much anymore. You can purchase this type of balancer through J.C. Whitney for around $100. They are worth having, as you can do the work at home this way. The last method I know that is being used in most every tire shop is the computer balancer. I have had fits with getting a good balance with this method, but there are probably a few factors to consider. First, these machines donít spin the tires up to nearly the speed they will see when they are on the car. Next to consider is whether the machine is properly calibrated. Finally, does the person operate it know what they are doing? Is the rest of your rotating assembly well-balanced?
To eliminate the brake drums and wheels themselves from the balancing process, take them to Beazleyís in downtown Memphis, and these folks can balance anything that spins. This way, the tire will be the only factor to consider when you need to balance things. If the person balancing your tires puts a lot of weights on the rim, question the quality of the tire you are using or whether the rim itself is in good balance. A lot of older steel rims left the factories with quite a bit of imbalance. Most tires these days do not need a lot of weight to get them to balance. Usually 3 or 4 grams is all that is needed. If the wheels and drums or rotors are well-balanced to start with, you may not need any weight for a good balance, especially if the tires are of a good quality.
Ainít it nice to drive your VW now without having to report to the Center for Earthquake Studies that it was just your imbalance problem? That bratwurst burrito will go down a lot smoother as well!
Your VW Maniac &Tech Specialist,
Your VW Maniac and tech specialist,