Over the pages of this annual Performance Training Guide, we’ve covered the technical aspects of custom wheels and how to sell them. Now we’ll discuss the last part of the equation: mounting and balancing.
We won’t discuss how to mount and balance tires and wheels; you ought to know how to do that. But we do want to offer some insight on techniques and procedures to help you to diagnose ride problems and prevent them from occurring.
Before placing a tire/wheel assembly on a vehicle, inspect the drums and rotors. Clean all mounting surfaces so that your assembly fits flush against the vehicle. Also, remove any clips that may be on the wheel studs (Photo 1). Remember, the mounting pad on aftermarket wheels is flat; OE wheel mounting pads have pockets to allow those retention clips to recess into the mounting surface. You must remove these to ensure proper contact of the aftermarket wheel to the vehicle.
Now that the vehicle is ready, mount the tire on its wheel and then place on the balancer. While balancing (You are using a dynamic balancer, right?) check for repeatability before proceeding to the rest of the process. This will ensure that you don’t have an error in your balancing technique or an error in your balancer itself.
First, check the accuracy of your balance by pulling the wheel off the balancer, rotate it at least 90 degrees and then replace it, being sure to tighten it back up in a different position. Spin it up and check your measurements. If your reading is more than .25-ounce off from the previous reading, then a mounting error occurred.
Remember, most aftermarket wheels are lug centric and need to be balanced through the lug holes with a flange plate adapter, not through the centerbore. If you get inconsistent results, pay close attention to your technique, inspect the cones, flange plate, balancer shaft and the nut to make sure that they haven’t been damaged.
It is always a good idea to have a soft mat under the end of the balancer shaft so that the cones won’t fall onto the hard concrete floor if dropped. These are precision instruments, not just chunks of metal!
While the assembly is spinning on the balancer, watch for a hop (lateral) or side-to-side (radial) movement. If you see either of these, it would be a good idea to diagnose what is causing the excessive movement. If the balancer is calling for an excessive amount of weight, deflate and rotate the tire 180 degrees. Rebalance to see if the amount of weight called for is significantly less.
You may need to determine if the tire, wheel or both are out-of-round.
Using common items like a tire crayon and a stationary metal stand, we can determine which is the likely cause. First, place the mounted tire/wheel assembly on the balancer and tighten. Spin the assembly by hand (Photo 2), then use the crayon to gradually move close enough to almost cause a mark on the tire tread. Hold the crayon steady. Any high spot will show a mark.
Now, loosen the assembly, spin it 180 degrees on the shaft and retighten. Spin the assembly by hand once more and repeat the procedure, only this time move slightly off to one side of the previous mark (Photo 3). If the second crayon mark(s) is in the same place(s) as the first (indicating that the assembly is centered on the balancer properly), then mark the wheel on the rear flange to indicate the high spot area(s).
Break the tire from the rim and rotate 180 degrees. Re-inflate and repeat the above steps. If your crayon mark doesn’t hit a high spot, chances are that the high spot on the tire and any high spot on the wheel were matched up before.
No mark means the low spot on the tire is matched up with the high spot on the rim to form a more uniform assembly. This should greatly reduce vibration that causes ride comfort problems.
If you still have a high spot on the tire after rotating it, check the mark against the mark on the rear flange of the wheel. If they are near equal, break the tire off of the wheel and bolt the wheel onto the balancer by itself. Spin it up by hand and look for any run-out.
If you see movement where the crayon was marked on the rear flange, you may have an out-of-round wheel. The tolerance for a steel wheel is .030-inch (1/32-inch) and .020-inch (1/50-inch) for an aluminum wheel. Before rejecting a wheel, check the wheel to determine the exact amount of run-out using a dial indicator.
Caution: Dial indicators typically have a magnetic base. Do not attach one to your balancer or other electronic equipment as it could damage that equipment. A metal stand will make a good base to attach it to.
If the wheel is beyond these specs, call your supplier and get another wheel. If it is within specs, you may want to try another tire. Another tire may match the wheel better and balance without any problems.
One last tip. If you are getting ride complaints and are finding that the balance is off when you check it, the tires may have slipped on the rim after you balanced them. To find out, rebalance the assembly and then index the tire to the wheel with crayon mark on the back of the tire and wheel before letting the customer drive away.
If they return with a ride complaint, you will be able to tell if the tire has slipped on the wheel, creating an out-of-balance assembly. This is especially common on large trucks and SUVs and high horsepower cars. Indexing a tire to a wheel is quick and easy and can help you diagnose a problem without having to spend a great deal of time.
The common solution to this problem comes on the front end: Don’t over-lube beads and rim flanges when mounting tires.
Performance customers are your best asset. Keep the younger customers happy with outstanding products and after-sale service, and you have a serious life-long customer. The older, more upscale customers will appreciate your knowledge and service, and they will tell all of their friends.
The key is to be able to eliminate potential problems on the front end, and have ready solutions on the back-end.